small modular reactors final reportpdf

Small Modular Reactors

Disaster Mitigation Through Enabling TechnologiesIn Redundant Power Supplies

By:

Ted Bloch-Rubin

Kyle Corfman

Alison Cowley

Andrew Hinnenkamp

Tommy Ji

Thomas Noyes

Travis Wilson

Spring 2012

ENES489P: Hands On Systems Engineering Projects

Final Report

Abstract

Nuclear energy is a potentially affordable and safe alternative to coalstations in the United States. However, several technological, financial, and public polchallenges currently inhibit the widespread adoption of this technology. This report focuses onenabling technologies which can solve some of these challenges. Specifically, redundant DirectCurrent (DC) power supplies are explored which can be usedAccidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japanwhen flooding caused by an earthquakesupply onsite. Normally, nuclear plantsprovide electricity to ‘selfsystems. These systems include the massive pumps and infrastructure used to circulatemonitor coolant within thesituation as the core temperature increases unchecked.

In the Fukushima case, the earthquakeloss of power from the national gridsystems to relywere damaged shortly after the earthquake by flooding from the tsunamiunavailableresulting in a partial meltdown, radiation release, and extensive structural damage due tohydrogen explosions.

This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRstypically provide less than 300MW of power,constructed relatively quickly. Land use is much smaller than traditican be located underground within cities.adequate sensure that LOCA events do not occur even in tfocuses on redundant DC power suppliesvarious trade studies intended to optimize the cost and capabilities of these systems.

Abstract

Nuclear energy is a potentially affordable and safe alternative to coalations in the United States. However, several technological, financial, and public pol

challenges currently inhibit the widespread adoption of this technology. This report focuses onenabling technologies which can solve some of these challenges. Specifically, redundant DirectCurrent (DC) power supplies are explored which can be usedAccidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japanwhen flooding caused by an earthquakesupply onsite. Normally, nuclear plantsprovide electricity to ‘selfsystems. These systems include the massive pumps and infrastructure used to circulate

coolant within thesituation as the core temperature increases unchecked.

In the Fukushima case, the earthquakeloss of power from the national grid

to rely on DC power from the onsite redundant power supplies. These power supplieswere damaged shortly after the earthquake by flooding from the tsunamiunavailable. Without a meansresulting in a partial meltdown, radiation release, and extensive structural damage due tohydrogen explosions.

This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRstypically provide less than 300MW of power,constructed relatively quickly. Land use is much smaller than traditican be located underground within cities.adequate safeguards against LOCA events. Robust

that LOCA events do not occur even in tfocuses on redundant DC power suppliesvarious trade studies intended to optimize the cost and capabilities of these systems.


challenges currently inhibit the widespread adoption of this technology. This report focuses onenabling technologies which can solve some of these challenges. Specifically, redundant DirectCurrent (DC) power supplies are explored which can be usedAccidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japanwhen flooding caused by an earthquakesupply onsite. Normally, nuclear plantsprovide electricity to ‘self-sustain’ their operations and provide power to the critical plantsystems. These systems include the massive pumps and infrastructure used to circulate

coolant within the reactor core. A loss of this circulation could lead to an emergencysituation as the core temperature increases unchecked.

In the Fukushima case, the earthquakeloss of power from the national grid

on DC power from the onsite redundant power supplies. These power supplieswere damaged shortly after the earthquake by flooding from the tsunami

. Without a means to adequately circulate coolant, the core temperature increasedresulting in a partial meltdown, radiation release, and extensive structural damage due tohydrogen explosions.

This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRstypically provide less than 300MW of power,constructed relatively quickly. Land use is much smaller than traditican be located underground within cities.

afeguards against LOCA events. Robustthat LOCA events do not occur even in t

focuses on redundant DC power suppliesvarious trade studies intended to optimize the cost and capabilities of these systems.

Figure

Small Modular


challenges currently inhibit the widespread adoption of this technology. This report focuses onenabling technologies which can solve some of these challenges. Specifically, redundant DirectCurrent (DC) power supplies are explored which can be usedAccidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japanwhen flooding caused by an earthquake-generated tsunami disabled the redundant DC powersupply onsite. Normally, nuclear plants either ob

sustain’ their operations and provide power to the critical plantsystems. These systems include the massive pumps and infrastructure used to circulate

reactor core. A loss of this circulation could lead to an emergencysituation as the core temperature increases unchecked.

In the Fukushima case, the earthquake resulted in the nuclear plant being taken offlineloss of power from the national grid. The lack of external power caused


to adequately circulate coolant, the core temperature increasedresulting in a partial meltdown, radiation release, and extensive structural damage due to

This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRstypically provide less than 300MW of power,constructed relatively quickly. Land use is much smaller than traditican be located underground within cities. However, this vision will not be possible without

afeguards against LOCA events. Robustthat LOCA events do not occur even in t

focuses on redundant DC power supplies, the requirements and design of these systems, andvarious trade studies intended to optimize the cost and capabilities of these systems.

Figure 1: Babcock & Wilcox SMR Site Rendering


Page 1


challenges currently inhibit the widespread adoption of this technology. This report focuses onenabling technologies which can solve some of these challenges. Specifically, redundant DirectCurrent (DC) power supplies are explored which can be usedAccidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japan

generated tsunami disabled the redundant DC powereither obtain power from the national grid, or they


reactor core. A loss of this circulation could lead to an emergencysituation as the core temperature increases unchecked.

resulted in the nuclear plant being taken offlineThe lack of external power caused



This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRstypically provide less than 300MW of power, are cheaper than traditional reactorsconstructed relatively quickly. Land use is much smaller than traditi

However, this vision will not be possible withoutafeguards against LOCA events. Robust, redundant power supplies are needed to

that LOCA events do not occur even in the face of serious local disasters. This project, the requirements and design of these systems, and

various trade studies intended to optimize the cost and capabilities of these systems.

: Babcock & Wilcox SMR Site Rendering

Reactors


challenges currently inhibit the widespread adoption of this technology. This report focuses onenabling technologies which can solve some of these challenges. Specifically, redundant DirectCurrent (DC) power supplies are explored which can be used to prevent Loss of CoolantAccidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japan

generated tsunami disabled the redundant DC powertain power from the national grid, or they


reactor core. A loss of this circulation could lead to an emergency

resulted in the nuclear plant being taken offlineThe lack of external power caused



This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRsare cheaper than traditional reactors

constructed relatively quickly. Land use is much smaller than traditiHowever, this vision will not be possible without

redundant power supplies are needed tohe face of serious local disasters. This project

, the requirements and design of these systems, andvarious trade studies intended to optimize the cost and capabilities of these systems.

: Babcock & Wilcox SMR Site Rendering

Nuclear energy is a potentially affordable and safe alternative to coal-fired electric generatingations in the United States. However, several technological, financial, and public pol

challenges currently inhibit the widespread adoption of this technology. This report focuses onenabling technologies which can solve some of these challenges. Specifically, redundant Direct

to prevent Loss of CoolantAccidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japan




resulted in the nuclear plant being taken offlineThe lack of external power caused the critical plant

on DC power from the onsite redundant power supplies. These power supplieswere damaged shortly after the earthquake by flooding from the tsunami and were


This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRsare cheaper than traditional reactors

constructed relatively quickly. Land use is much smaller than traditional reactors and the sitesHowever, this vision will not be possible without



fired electric generatingations in the United States. However, several technological, financial, and public policy


to prevent Loss of CoolantAccidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japan


sustain’ their operations and provide power to the critical plantsystems. These systems include the massive pumps and infrastructure used to circulate and


resulted in the nuclear plant being taken offline and athe critical plant

on DC power from the onsite redundant power supplies. These power suppliesand were


This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRsare cheaper than traditional reactors, and can be

onal reactors and the sitesHowever, this vision will not be possible without



fired electric generating


Accidents (LOCA). A massive LOCA occurred at the Fukushima Daiichi nuclear plant in Japangenerated tsunami disabled the redundant DC power

tain power from the national grid, or they

andreactor core. A loss of this circulation could lead to an emergency

and a

on DC power from the onsite redundant power supplies. These power supplies

to adequately circulate coolant, the core temperature increased

This project envisions widespread adoption of Small Modular Reactor (SMR) technology. SMRsand can be

onal reactors and the sitesHowever, this vision will not be possible without


, the requirements and design of these systems, and


Page 2

Table of Contents

Abstract........................................................................................................................................... 1

Table of Contents............................................................................................................................ 2

Table of Figures............................................................................................................................... 3

Introduction and Problem Statement............................................................................................. 4

Proposed Solution........................................................................................................................... 5

Project Goals ............................................................................................................................... 5

Requirements.............................................................................................................................. 5

High Level Requirements......................................................................................................... 5

Low Level Requirements ......................................................................................................... 6

Battery System Requirements................................................................................................. 6

Traceability.............................................................................................................................. 7

Simplified Models of System Structure ...................................................................................... 8

Mechanical Systems................................................................................................................ 8

Reactor Core.......................................................................................................................... 10

Support Facilities Block Diagram .......................................................................................... 11

Safety Systems Block Diagram.............................................................................................. 11

Structure Diagram..................................................................................................................... 12

Requirements Diagram ............................................................................................................. 15

Use Cases: Textual Scenarios and Sequence Diagrams ............................................................ 16

Use Case 1: Normal Operation.............................................................................................. 16

Use Case 2: Plant Outages .................................................................................................... 17

Use Case 3: Response to Fukushima-Type Events................................................................. 20

Parametric Diagram .................................................................................................................. 27

Trade-off Analysis ..................................................................................................................... 28

Discharge Time versus Cost Tradeoff Analysis...................................................................... 31

Conclusion..................................................................................................................................... 37

References .................................................................................................................................... 38


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Table of Figures

Figure 1: Babcock & Wilcox SMR Site Rendering............................................................................ 1Figure 3: Power Plant System Block Diagram................................................................................. 8Figure 4: Reactor Mechanical Components.................................................................................... 9Figure 5: Reactor Mechanical Systems Block Diagram................................................................... 9Figure 6: Reactor Core Components Overview (left).................................................................... 10Figure 7: Reactor Core Block Diagram (right) ............................................................................... 10Figure 8: Support Facilities Block Diagram ................................................................................... 11Figure 9: Safety Systems Block Diagram....................................................................................... 12Figure 10: 3-Day Batteries Block Diagram .................................................................................... 12Figure 11: Key Single Line for two reactors .................................................................................. 13Figure 12: Systems powered by 24-hour batteries....................................................................... 13Figure 13: Systems powered by 72-hour batteries....................................................................... 14Figure 14: Battery System Requirements Diagram ...................................................................... 15Figure 15: Activity Diagram for Normal Operation...................................................................... 17Figure 16: Activity Diagram for Refueling and Maintenance ....................................................... 20Figure 17: Activity Diagram for Station Blackout.......................................................................... 23Figure 18: Activity Diagram of LOCA showing relative components ............................................ 25Figure 19: Sequence Diagram of LOCA ......................................................................................... 26Figure 20: Battery Load Parametric Diagram ............................................................................... 27Figure 21: Tradeoff Plot tracing battery capacity in kilowatts versus system cost in dollars. Non-inferior points are highlighted with red circles ............................................................................ 29Figure 22: Tradeoff plot tracing full-load battery efficiency (%) versus system cost. Importantnon-inferior points are highlighted via red circles........................................................................ 30Figure 23: Tradeoff plot tracing shipping weight in kilograms of the UPS system versus the totalcost. A previously identified point of interest is highlighted via a red circle ............................... 31Figure 24: 24-hour load discharge time versus cost analysis ....................................................... 34Figure 25: 72-hour load discharge time versus cost analysis ....................................................... 35Figure 26: Correlation between number of batteries, cost, and peukert number ..................... 36


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Introduction and Problem Statement

Dr. Magdi Ragheb, a nuclear engineering professor at the University of Illinois, stated inRestarting the Stalled USA Nuclear Renaissance that “The March 11, 2011 earthquake andtsunami Station Blackout accident at the Fukushima Daiichi site caused an unprecedentedcascading multiple failures event including fuel damage in both reactor cores and spent fuelstorage pools, and ensuing hydrogen explosions and fires associated with fission productsreleases.” Events such as this inhibit the widespread adoption of commercial nuclear power.

We envision a world where Small Modular Reactors (SMRs) are as common as gas stations, andare able to co-exist with their residential neighbors without any concern. SMRs are designed tobe cheap, require minimal land use (often underground), be easily scalable, and be very safe.These systems are closely integrated with the areas and neighborhoods to which they supplypower. Federal funding of advanced reactor concepts such as SMRs has recently increased, andmuch advancement has been made in reactor design and safety. However, the FukushimaDaiichi event reminds us of the consequences of Total Station Blackout (TSB) and Loss ofCoolant Accident (LOCA) events. During a TSB event, critical safety systems used to circulatecoolant throughout the reactor and monitor reactor systems no longer function. This results ina LOCA event. TSB/LOCA events can lead to the meltdown and structural damage of a reactor,and may also cause a release of harmful radiation.

It is imperative that redundant DC power supplies (batteries) are designed to ensureuninterrupted power during the TSB and LOCA event. This project focuses on two scenarios: 1)the supply of adequate DC power to operate all safety critical reactor systems for a period of 24hours, and 2) the supply of adequate DC power to operate a sub-set of critical reactor systemsfor a period of 72 hours and allow for the orderly shutdown of the reactor.

In succinct terms, our problem statement is thus:

When a Small Modular Reactor suffers a Total Station Blackout, a redundant DC power supplyof adequate capacity must be available to supply power to the reactor safety systems andpermit the orderly shutdown of the reactor.


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Proposed Solution

Project Goals

This project has several goals, including:

1. Analyze the efficiency of safety systems in response to catastrophic LOCA events.2. Optimize performance of the emergency safety systems, with a primary focus on the

redundant DC power supply (battery system).a. This system provides emergency 24-hour power to mitigate reactor damage

during the LOCA event.b. This system provides 72-hour power to allow for the orderly shutdown of the

reactor.3. Perform trade-off analyses to optimize the cost and efficiency of emergency battery

systems.4. Provide Bechtel (a manufacturer of SMRs) with the best vendor package that optimizes

cost, design, and performance of the battery system.5. Analyze the relationship between the optimal design and the implementation scheme

(economies of scale analysis).

Requirements

High Level Requirements

Requirements: Level 1

Prevent catastrophic failure

Maintain efficient performance

Ensure public safety in any disaster event


Prevent internal component failure

Protect against external threats

Maintain structural integrity


Able to respond to natural disasters

Able to respond to a loss of off-site power

Able to respond to a complete station blackout

Able to respond to a loss of coolant accident

Able to remove hydrogen build up (Hydrogen Recombiners)


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Able to contain spent fuel rods

Low Level Requirements


Prevent core temperature from rising above 1000oC

Prevent core pressure from rising above specified level

Prevent coolant leaks in both primary and secondary loops

Prevent radiation leaks from the core

All components must be water-tight

Facilities must be deeply embedded and have a low profile architecture to prevent movementduring seismic eventsContain spent fuel for 30+ days without external intervention

Support accident mitigation systems with DC power (batteries) for at least 72 hours

Isolate design basis safety functions from AC power, on or off site

Support plant monitoring and control for 7+ days with battery powerHydrogen build-up in reactor core must be less than 3% of core volume

Battery System Requirements


Provide sufficient redundancy, eliminate single points of failure, and allow isolation of a singledivision for testing/maintenanceBattery racks must be designed for some seismic zone and installed in a room with properventilation and ductingA single battery cannot be discharged to less than 50% of its capacityDC battery system must have a total discharge time greater than 1.5 times the requiredaccident mitigation time periodLifetime of battery must be greater than 10 yearsRecharge time for a single battery must be no more than 4 times its discharge timePeukert number minimized; optimum value is 1.05Cost of back-up battery system -- including system design cost, single battery costs shippingcosts and installation cost -- must be less than 5% of the total plant cost


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Traceability

Use Cases1.1 Normal Operations2.1 Normal Shutdown Procedures2.2 Maintenance and Refueling3.1 Natural Disaster3.2 Loss of Offsite Power3.3 Station Blackout3.4 Loss of Coolant Accident (LOCA)

RequirementsIdentifier

RequirementsTested

REC1 REC2 REC3 REC4 REC5 REC6 REC7 REC8

Use Cases 29 5 3 6 2 5 1 1 6

1.1 5 X X X X X

2.1 3 X X X

2.2 5 X X X X X

3.1 5 X X X X X

3.2 4 X X X X

3.3 3 X X X

3.4 4 X X X X


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Simplified Models of System Structure

Figure 2: Power Plant System Block Diagram

Mechanical Systems

The mechanical components are responsible for the main function of the reactor: transferringthe heat generated from the reactor core to the generators which convert it into electricity. Abasic diagram of the electric power generation cycle is shown in Figure 3. Heat is initiallytransferred from the reactor core to the water in the primary loop. The water in the secondaryloop is then vaporized by the primary loop and drives the steam turbine that generateselectricity. The steam is then condensed into water and directed back into the secondary loopfor the cycle to start over again. A simplified internal block diagram of the reactor core isshown in Figure 4.


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Figure 3: Reactor Mechanical Components

Figure 4: Reactor Mechanical Systems Block Diagram


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Reactor Core

Nuclear fission takes place within the reactor core. The main components of the reactor coreare shown in Figure 5 below. The control rod drive mechanisms control the amount ofexposure of the fuel rods in order to increase or decrease fission. Reactor coolant pumps feedwater in the primary loop over the fuel rods in order to transfer heat. As the temperature ofthe water increases, the pressurizer maintains a higher pressure in order to prevent the coolantfrom vaporizing. Heat is then transferred from the primary loop to the secondary loop, whichflows directly to the steam generators. A simplified internal block diagram is shown in Figure 6.

Figure 5: Reactor Core Components Overview (left)

Figure 6: Reactor Core Block Diagram (right)


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Support Facilities Block Diagram

The major support facilities consist of the land on which the plant is built, the buildings thathouse the core, generators, and all of the mechanical components, the coolant storage tanks,and the spent fuel pool for the used fuel rods. These facilities are shown in Figure 7 below withtheir basic requirements.

Figure 7: Support Facilities Block Diagram

Safety Systems Block Diagram

The safety systems are described by the block diagram in Figure 8 below. All of these featuresare included in the design of the plant in order to respond to any type of event described in theUse Cases. Many of these safety functions are design based, such as seismic attenuation, watertight compartments, and spent fuel containment, or passive safety systems, such as gravity-driven circulation of coolant and passive hydrogen recombiners. However, there is still a needfor some means of powering specific features within the plant, which is supplied by off-site ACpower during normal operation and by either on-site AC generators or DC batteries duringcertain events.


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Figure 8: Safety Systems Block Diagram

Structure Diagram

During the event of a station black-out, defined as the loss of both off-site and on-site ACpower, the DC battery system must be able to provide power to specific safety-related systemsthroughout the plant. These systems are described by the block diagram in Figure 9 below.

Figure 9: 3-Day Batteries Block Diagram


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Four divisions of batteries, Divisions A, B, C, and D, supply power to the plant safety relatedfunctions. These batteries are shown by a portion of the Key Single Line diagram in Figure 10.All four divisions supply power for the 24-hour loads, while only Divisions A, C, and D supplypower for the 72-hour loads.

Figure 10: Key Single Line for two reactors

During a station black-out scenario, the 24-hour batteries are automatically activated andprovide power to the plant immediately. Power is supplied directly to DC panelboards, whichsupply power to solenoid and motor operated valves, and to inverters, which supply power tothe AC panelboards. The AC panelboards then power the control room load, emergencylighting, nuclear instrumentation, reactor protection system, engineered safeguard system, andthe distributive control system. Two batteries supply power to each panelboard and inverter inorder to ensure that power will be supplied even in the event of a battery failure.

Figure 11: Systems powered by 24-hour batteries


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If AC power is not returned by the end of the 24-hour period, select divisions continue to run tosupport the control room load, emergency lighting, remote shut-down station, and post-accident monitoring system for a total of 72 hours. As with the 24-hour loads, the batteriessupply power directly to the DC panelboards and to the inverters. This power is then redirectedto the AC panelboards and the control room fan, as shown in Figure 12 below.

Figure 12: Systems powered by 72-hour batteries


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Requirements Diagram

The requirements diagram shown in Figure 13 below describes the constraints that apply toeach of the battery system requirements. Constraints were determined through the physicalrelationships that govern each of the systems involved.

Figure 13: Battery System Requirements Diagram


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Use Cases: Textual Scenarios and Sequence Diagrams

Use Case 1: Normal OperationDescription: Operating near nameplate capacity.Primary Actors: Residential loads, commercial loads, industrial loads, reactor operatorPre-conditions: High demand for power.Flow of Events:

1. Operator raises control rods to increase fission in response to increase in demand.2. Temperature of reactor core increases, which increases the temperature of the water in

the primary coolant loop.3. Pressurizer increases pressure in primary loop to prevent water from boiling.4. Heated primary coolant is pumped into a secondary heat exchanger.5. Conductive heat transfer occurs between heated primary coolant and lower pressure

secondary coolant evaporating it to steam.6. Secondary coolant (pressurized steam) is directed through a turbine driving an electrical

generator providing electricity for distribution.7. After passing through the turbine, secondary coolant is condensed back into a liquid.

Post-Conditions: Electricity is being generated that meets demand.Alternative Flow of Events:

1. Operator increases boric acid in reactor coolant system to decrease fission in responseto decrease in demand (no control rod adjustments are needed).

2. Heated primary coolant is pumped into a secondary heat exchanger.3. Conductive heat transfer occurs between heated primary coolant and lower pressure

secondary coolant evaporating it to steam.4. Secondary coolant (pressurized steam) is directed through a turbine driving an electrical

generator providing electricity for distribution.5. After passing through the turbine, secondary coolant is condensed back into a liquid.

Assumptions: Reactor is operating at specified temperature, pressure, and powerrequirements.New Requirements:

1. Monitor internal reactor conditions and rate of coolant flow.2. Operator maintains stable operating conditions in response to transients.3. Select appropriate control rod level based on expected load conditions.


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Figure 14: Activity Diagram for Normal Operation

Use Case 2: Plant OutagesScenario 1: Normal Shut-down ProceduresDescription: One or more reactors are shut down.Primary Actors: Reactor operator, nuclear engineers, instrumentation and controlsPre-conditions: Refueling, maintenance, testing or simulationFlow of Events:

1. Decrease power output of reactor by steadily lowering control rods into coolant untilreactor is in subcritical state.

2. Continue until control rods are completely inserted and a nuclear reaction can no longerbe sustained.

3. Ensure reactor cooling systems continually operate to remove heat from radioactivedecay.

4. Monitor reactor vessel temperature to maintain the integrity of fuel assemblies andprevent pressure from increasing.

5. Remove heat from primary cooling systems through heat exchangers connected tosecondary cooling loop.


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Post-Conditions: Reactor is in subcritical condition.Alternative Flow of Events:

1. Decrease power output of reactor by steadily lowering control rods into coolantuntil reactor is in subcritical state.

2. If reactor is not below shut-down margin (still in critical state), reactor operatoridentifies the need for emergency shut-down.

3. If manual emergency shut-down is not performed and conditions persist, passivesafety systems initiate emergency shut-down

4. Control rods are rapidly inserted into coolant to quickly stop reaction and reduceinternal temperature and pressure.

5. Ensure reactor cooling systems continually operate to remove heat from radioactivedecay.

6. Monitor reactor vessel temperature to maintain the integrity of fuel assemblies andprevent pressure from increasing.

7. Remove heat from primary cooling systems through heat exchangers connected tosecondary cooling loop.

Assumptions: Monitor systems accurately detect transient conditions, design basis event hasnot occurred and normal procedures can be usedNew Requirements:

1. Reactor Coolant Inventory and Purification System (RCIPS) removes decay heat.2. RCIPS provides a means for transferring fluids and gases to the radioactive waste

processing system.3. RCIPS maintains reactor coolant activity at the desired level by removing corrosion

and fission products.4. RCIPS provides reactor cooling system with pressure control.

Scenario 2: Refueling and MaintenanceDescription: One or more reactors are shut down to replace fuel rods and maintenance isperformed on components that can only be done when reactor is off-line.Primary Actors: Reactor operator, nuclear engineers, maintenance technicians, maintenanceequipment, spent fuel pool, timePre-conditions: Component failure or degradation, aging fuel rodsFlow of Events:

1. Normal shut-down procedures take place (see Scenario 1).2. Reactor vessel head is removed, control rod drive mechanisms are disassembled,

and upper internals are transferred to stand in refueling pool.a. Refueling supervisors ensure that reactor components (other than the vessel

head) stay in place.3. Spent fuel rods are removed, new fuel assemblies added, and fuel assemblies are

reorganized to optimize fuel consumption and power profile. Approximately 25%-40% of fuel assemblies are replaced.

4. Maintenance on the following components is performed: circulating water pumps,motor controlled valves, motor control center breaker, relay testing.


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5. Upper internals are reinstalled, control rod drive mechanisms are reassembled, andreactor vessel head is replaced.

6. Inspection of reactor coolant pump motor, reactor shield, and steam generator isperformed.

7. Reactor goes through start-up procedure and returns to normal operation.Post-Conditions: Reactor returns to critical state and fuel performance is optimized.Alternative Flow of Events:

1. Normal shut-down procedures take place (see Scenario 1).2. In addition to refueling, maintenance work and inspections must be performed on

the following components:a. Turbine and generator inspections and modificationsb. Circulating Water Pump, Condenser, Feedwater Pump and Heat Exchanger

workc. Reactor and reactor cooling system inspections and work on components

connected to the reactor cooling system that cannot be isolated duringnormal operations.

d. Electrical bus inspections, breaker and relay testing on major 4.16 and 6.9 KVbuses

e. Transformer inspections and cable testingf. Major safety system components, including ECCS, emergency condenser, and

reactant coolant pump3. Reactor goes through start-up procedure and returns to normal operation.

Assumptions: Maintenance and inspections are performed during allotted outage period,reactor returns to normal operating conditionsNew Requirements:

1. Schedule required maintenance to be performed during refueling outage.2. Optimize efficiency during outages to reduce total off-line time.


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Figure 15: Activity Diagram for Refueling and Maintenance

Use Case 3: Response to Fukushima-Type EventsScenario 1: Natural DisastersDescription: Structural integrity of containment building is affected by the occurrence of somenatural disaster, such as earthquake or flood.Primary Actors: Extreme weather conditions, seismic activity, maintenance workers, reactoroperatorPre-conditions: Some natural disaster occurs that is outside operating basisFlow of Events:

1. When some event occurs that is outside of operating basis (the condition for whichthe structure is design to resist and remain operational), the plant must shut downmanually by the operator.


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2. During safe shutdown, inspections and any necessary maintenance are performedcontainment structures to ensure safe operation.

3. Plant resumes normal operation once the threat of significant aftershocks haspassed.

Post-Conditions: Plant assumes normal operationAlternative Flow of Events: Additional design-basis events occur simultaneously with a naturaldisaster, including loss of off-site power, station blackout, or loss of coolant accident.Assumptions: All structures are designed to remain functional in the case of operating basiseventNew Requirements:

1. Sufficient inspections and maintenance are performed to containment structures toensure safe operation.

2. Equipment is sufficient to detect unsafe operating conditions.

Scenario 2: Loss of Off-site PowerDescription: On-site emergency diesel generators supply power to emergency safety systemsin the event that off-site AC power is lost.Primary Actors: Reactor operator, diesel generatorsPre-conditions: Loss of off-site AC powerFlow of Events:

1. Loss of off-site AC power causes diesel generators to activate.2. Passive safety systems which do not require power to function respond by shutting

down the plant.3. Diesel generators power design-basis safety functions, such as emergency pumps,

valves, fans, etc., to maintain a safe shut-down condition and support all accidentmitigation indefinitely.

4. Reactor Operator continually monitors reactor conditions during plant shut-downsuch as pressure, temperature, containment hydrogen levels, radiation levels, andvalve positions.

5. Diesel generators continue to function until off-site AC power is restore.Post-Conditions: Off-site AC power is restored and plant returns to normal operation.Alternative Flow of Events: Additional design-basis events occur simultaneously with loss ofoff-site AC power, including station blackout, loss of coolant accident or containment breach.Assumptions: Back-up generators are fully functioning and able to provide power indefinitely.New Requirements:

1. Diesel generators need to be refueled.2. Maintenance on Emergency Core Cooling System is performed to ensure proper

operation in a repeat event.3. Inspect reactor components for degradation or damage to ensure proper

performance.


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Scenario 3: Station Black-outDescription: Back-up battery system supplies power to emergency safety systems in the eventthat all AC power is lost, both off-site and on-site.Primary Actors: Reactor operator, maintenance workers, emergency responders, DC batterysystemPre-conditions: Loss of all AC power.Flow of Events:

1. Loss of both off-site and on-site AC power and back-up diesel generators are off-line.2. Passive safety systems which do not require power to function respond by shutting

down the plant.3. Safety-related back-up batteries power design-basis safety functions, such as

emergency pumps, valves, fans, etc., to maintain a safe shut-down condition andsupport all accident mitigation for up to 72 hours.

4. Battery system supports motors that power emergency makeup and cooling pumpsin the event of a design-basis accident.

5. Auxiliary Power Units inside reactor building recharge battery system towards end of72 hour period, if necessary.

6. Reactor Operator continually monitors reactor conditions during plant shut-downsuch as pressure, temperature, containment hydrogen levels, radiation levels, andvalve positions.

7. Battery systems continue to function until off-site and/or on-site AC power isrestored. Back-up diesel generators may be used to assist plant start-up.

Post-Conditions: Off-site and on-site AC power is restored and plant returns to normaloperation.Alternative Flow of Events: Additional design-basis events occur simultaneously with stationblackout, including loss of coolant accident or containment breach.Assumptions: Back-up batteries are fully charged and can power all necessary loads for up to72 hoursNew Requirements:

1. Battery systems need to be fully recharged.2. Maintenance on Emergency Core Cooling System is performed to ensure proper

operation in a repeat event.3. Inspect reactor components for degradation or damage to ensure proper

performance.


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Figure 16: Activity Diagram for Station Blackout

Scenario 4: Loss of Coolant Accident (LOCA)Description: : Loss of reactor coolant due to breaks in the reactor coolant pressure boundary,including breaks equivalent in size to a “double-ended” rupture of the largest pipe in thereactor coolant system.Primary Actors:Pre-conditions: Core temperature increases and cladding temperature rises, leading to cladswelling and blocking of coolant flow.Flow of Events:

1. Large break in one of the main reactor coolant pipes leads to rapid depressurization.The core continues to heat up, past 1,000 degrees.

2. The flow from the RCIPS and Accumulator tanks is redirected into the EmergencyCore Cooling System.


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3. Eventually the coolant pressure decreases to saturation pressure and the spring-loaded accumulator valves open, injecting water into the primary loop.

4. Steam builds in reactor head and Containment spray system controls pressure bysupplying spray flow to the pressurizer

5. After the steam pressure decreases, the ECCS water can flow into the lowerchamber of the reactor core

6. Fuel elements rupture due to elevated core temperature and release fissionproducts to the primary loop.

7. After significant depressurization, the low pressure injection system pumps water ata high flow rate into the cooling water system.

8. Steam is condensed by the containment spray system, collected in the containmentsump, and cooled in a heat exchanger for recirculation through the core.

9. No containment breach occurs and natural circulation continues to drive theemergency cooling water through the core.

Post-Conditions: Containment structure is intact, radioactive elements isolated in the primarycoolant system, and large break LOCA is mitigated.Alternative Flow of Events:

1. Pipes are broken, but the reactor remains pressurized. Primary system slowlydepressurizes.

2. Pressure drop is detected by automatic control systems. Automatic control systemsinsert the control rods and shutdown the fission power.

3. Water is pumped from the High Pressure Injection System into the reactor.4. Liquid in the reactor start to vaporize and steam starts to build up in the upper head

of the reactor, unable to escape.5. The steam generators eventually become void of liquid and only contain steam.6. Steam formed in the reactor core is condensed in the steam generator and flows

back into the core.7. The core goes through the process of “core uncover” where the core dries from top

to bottom.8. Steam passes from the core through the coolant circulation pumps and out along

the cold leg to the location of the break. Rapid depressurization occurs.9. Water in the core vaporizes and a mix of water and steam bubbles rewets the upper

part of the core.10. Due to the depressurization, the accumulator and Low Pressure Injection System

become activated to move the coolant.11. The core is rapidly and brought to a cold condition.

Assumptions: Cooling loop taken off the Emergency Core Cooling System and transferred backto the RCIPS, core temperature and steam pressure decreased to normal operating levelsNew Requirements:

1. Ruptured pipe is repaired.2. Control system used to analyze successful transfer of cooling system back to RCIPS.


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Figure 17: Activity Diagram of LOCA showing relative components


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Parametric Diagram

Figure 19 shows the parametric design of the back-up battery system. The diagram has threemain constraints: cost, 24-Hour Load, and 72-Hour Load. The total cost is the sum of the design,battery, installation, and shipping costs. The battery selection will primarily affect the batteryand shipping costs. The batteries have an inherent cost, but their weight will affect how muchthe shipping will be. The 24 and 72 hour loads are the desired performance of the batteries.This diagram then shows the main design decision we will have to make, a trade-off betweencost and capacity, setting up the trade-off analysis in the next section.

Figure 19: Battery Load Parametric Diagram


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Trade-off Analysis

The team performed a tradeoff analysis in order to choose the optimal uninterruptable powersupply (UPS) system for the proposed backup power design. In order to perform an adequatetradeoff analysis, important design metrics needed to be identified. These metrics are directlyrelated to the requirements laid out for the system. Many of the metrics identified areproperties/design specifications from the manufacturer of the UPS system. The metricsidentified for the analysis were: output power capacity, full load efficiency, system cost, batteryconstruction type, input/output voltage, lifespan, discharge time and shipping weight. It shouldbe noted that almost all commercially available UPS systems use the same construction type:deep-cycle, lead-acid construction. This battery type has a consistent lifespan, and for thisreason construction type and lifespan were not available for tradeoff analysis. Also, theinput/output voltage is defined by the onsite AC system as well as the equipment to bepowered. Therefore, only systems that fit within the prescribed input/output voltages wereconsidered, leaving this metric useless for tradeoff analysis.

Given that the backup battery system is constrained by a pre-defined budget of 5% of totalreactor budget, cost became the dominant tradeoff metric that all other properties wererelated to. Discharge time is also an important metric given that strict requirements existstipulating the UPS systems must remain online for at least 24-72 hours (depending on loadunit). It should be noted that the team was able to acquire price quotes for a range of APCbrand UPS systems. So, for the purpose of this report, the tradeoff analysis will be limited to arange of APC systems. The analysis can be expanded by including metrics from othercommercial systems once price quotes were obtained.

The first tradeoff plot presented tracks the total battery capacity of the UPS system versus thequoted price. The tradeoff plot is presented below in Figure 20:

Figure 20: Tradeoff Plot tracing battery capacity in kilowatts versus system cost in dollars. Non

The plot shows a general trend of increasing cost for increasing system capacity. However, twonon-inferior points stand out and are highlighted in the figure. The first non($17,461, 108 kW) stands out amongst the rest of its cluster providcapacity for moderate system cost. The model associated with this point is the APC MGE Galaxy5000 120 kVA, and as we will see this system performs well across a variety of tradeoff plots.The second nonpoint corresponds to a battery capacity of 720 kW at a cost of $99,849. It should be noted thatthis system is the same price as a similar model (same model family), but provides an additional80 kW.

The second tradeoff plot tracks the battery efficiency operating at full load with respect to totalUPS system cost. The tradeoff plot is shown below in

Tradeoff Plot tracing battery capacity in kilowatts versus system cost in dollars. Non

The plot shows a general trend of increasing cost for increasing system capacity. However, twoinferior points stand out and are highlighted in the figure. The first non

($17,461, 108 kW) stands out amongst the rest of its cluster providcapacity for moderate system cost. The model associated with this point is the APC MGE Galaxy5000 120 kVA, and as we will see this system performs well across a variety of tradeoff plots.The second non-inferior point represents thepoint corresponds to a battery capacity of 720 kW at a cost of $99,849. It should be noted thatthis system is the same price as a similar model (same model family), but provides an additional

econd tradeoff plot tracks the battery efficiency operating at full load with respect to totalUPS system cost. The tradeoff plot is shown below in



($17,461, 108 kW) stands out amongst the rest of its cluster providcapacity for moderate system cost. The model associated with this point is the APC MGE Galaxy5000 120 kVA, and as we will see this system performs well across a variety of tradeoff plots.

inferior point represents thepoint corresponds to a battery capacity of 720 kW at a cost of $99,849. It should be noted thatthis system is the same price as a similar model (same model family), but provides an additional


Small Modular

Tradeoff Plot tracing battery capacity in kilowatts versus system cost in dollars. Nonwith red circles



inferior point represents thepoint corresponds to a battery capacity of 720 kW at a cost of $99,849. It should be noted thatthis system is the same price as a similar model (same model family), but provides an additional



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Tradeoff Plot tracing battery capacity in kilowatts versus system cost in dollars. Nonwith red circles



inferior point represents the optimal system irrespective of cost/budget. Thispoint corresponds to a battery capacity of 720 kW at a cost of $99,849. It should be noted thatthis system is the same price as a similar model (same model family), but provides an additional

econd tradeoff plot tracks the battery efficiency operating at full load with respect to totalUPS system cost. The tradeoff plot is shown below in Figur

Reactors



($17,461, 108 kW) stands out amongst the rest of its cluster providing increased batterycapacity for moderate system cost. The model associated with this point is the APC MGE Galaxy5000 120 kVA, and as we will see this system performs well across a variety of tradeoff plots.

optimal system irrespective of cost/budget. Thispoint corresponds to a battery capacity of 720 kW at a cost of $99,849. It should be noted thatthis system is the same price as a similar model (same model family), but provides an additional

econd tradeoff plot tracks the battery efficiency operating at full load with respect to totalFigure 21:

Tradeoff Plot tracing battery capacity in kilowatts versus system cost in dollars. Non-inferior points are highlighted

The plot shows a general trend of increasing cost for increasing system capacity. However, twoinferior points stand out and are highlighted in the figure. The first non-inferior point

ing increased batterycapacity for moderate system cost. The model associated with this point is the APC MGE Galaxy5000 120 kVA, and as we will see this system performs well across a variety of tradeoff plots.


econd tradeoff plot tracks the battery efficiency operating at full load with respect to total

inferior points are highlighted

The plot shows a general trend of increasing cost for increasing system capacity. However, twoinferior point

ing increased batterycapacity for moderate system cost. The model associated with this point is the APC MGE Galaxy5000 120 kVA, and as we will see this system performs well across a variety of tradeoff plots.



inferior points are highlighted

The plot shows a general trend of increasing cost for increasing system capacity. However, two

capacity for moderate system cost. The model associated with this point is the APC MGE Galaxy5000 120 kVA, and as we will see this system performs well across a variety of tradeoff plots.



Figure

The plot shows an interesting trend regarding fullsystems show a broad range of fullefficiency begins to level off around 93the same nonGalaxy 5000 120kVA. It is useful to track nonin order to see how they perform on a variety of metrics. A new nonhighlighted given its superio$13,921. It is useful to note that the previously highlighted, budgetshow advantageous efficiency given its large total cost.

The final tradeoff curve tracesThe tradeoff curve is shown below in

e 21: Tradeoff plot tracing full

The plot shows an interesting trend regarding fullsystems show a broad range of fullefficiency begins to level off around 93the same non-inferior point highlighted in the Battery CapaciGalaxy 5000 120kVA. It is useful to track nonin order to see how they perform on a variety of metrics. A new nonhighlighted given its superio$13,921. It is useful to note that the previously highlighted, budgetshow advantageous efficiency given its large total cost.

The final tradeoff curve tracesThe tradeoff curve is shown below in

Tradeoff plot tracing full-load battery efficiency (%) versus system cost. Important non

The plot shows an interesting trend regarding fullsystems show a broad range of fullefficiency begins to level off around 93

inferior point highlighted in the Battery CapaciGalaxy 5000 120kVA. It is useful to track nonin order to see how they perform on a variety of metrics. A new nonhighlighted given its superior efficiency for a given price range: 96.4% efficiency at a cost of$13,921. It is useful to note that the previously highlighted, budgetshow advantageous efficiency given its large total cost.

The final tradeoff curve traces shipping weight of the UPS system with respect to system cost.The tradeoff curve is shown below in

Small Modular

load battery efficiency (%) versus system cost. Important nonhighlighted via red circles

The plot shows an interesting trend regarding fullsystems show a broad range of full-load efficiency: ~87efficiency begins to level off around 93-94%. The bottom

inferior point highlighted in the Battery CapaciGalaxy 5000 120kVA. It is useful to track nonin order to see how they perform on a variety of metrics. A new non

r efficiency for a given price range: 96.4% efficiency at a cost of$13,921. It is useful to note that the previously highlighted, budgetshow advantageous efficiency given its large total cost.

shipping weight of the UPS system with respect to system cost.The tradeoff curve is shown below in Figure


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The plot shows an interesting trend regarding full-load battery efficiency. Relative loload efficiency: ~87-96%. As price increases, the battery

94%. The bottominferior point highlighted in the Battery Capaci

Galaxy 5000 120kVA. It is useful to track non-inferior points over the full range of tradeoff plotsin order to see how they perform on a variety of metrics. A new non

r efficiency for a given price range: 96.4% efficiency at a cost of$13,921. It is useful to note that the previously highlighted, budgetshow advantageous efficiency given its large total cost.

shipping weight of the UPS system with respect to system cost.Figure 22:

Reactors


load battery efficiency. Relative lo-96%. As price increases, the battery

94%. The bottom-most highlighted point corresponds toinferior point highlighted in the Battery Capacity vs. Cost plot, the APC MGE

inferior points over the full range of tradeoff plotsin order to see how they perform on a variety of metrics. A new non

r efficiency for a given price range: 96.4% efficiency at a cost of$13,921. It is useful to note that the previously highlighted, budget-

shipping weight of the UPS system with respect to system cost.

load battery efficiency (%) versus system cost. Important non-inferior points are

load battery efficiency. Relative lo96%. As price increases, the battery

most highlighted point corresponds toty vs. Cost plot, the APC MGE

inferior points over the full range of tradeoff plotsin order to see how they perform on a variety of metrics. A new non-inferior point (top

r efficiency for a given price range: 96.4% efficiency at a cost of-irrespective point doesn’t


inferior points are

load battery efficiency. Relative low-cost96%. As price increases, the battery

most highlighted point corresponds toty vs. Cost plot, the APC MGE

inferior points over the full range of tradeoff plotsinferior point (top-most) is

r efficiency for a given price range: 96.4% efficiency at a cost ofirrespective point doesn’t


inferior points are

cost96%. As price increases, the battery

most highlighted point corresponds to

inferior points over the full range of tradeoff plotsmost) is

r efficiency for a given price range: 96.4% efficiency at a cost ofirrespective point doesn’t


Figure 22:

The purpose of identifying shipping weight as an important metric is due to the implications ithas on total UPS system cost. The system cost presented on the xplots is the raw quoted price from APC and does not include shipping costs. Shipping cost isdirectly proportional to the shipping weight and should be accounted for whentotal cost of ownership. The above plot illustrates that in general, the heavier the system, themore expensive the UPS system is. However, the previously identified nonMGE Galaxy 5000 120 kVA, also shows the lowest shikg.

Performing the tradeoff analysis allows the investigation of numerous UPS systemssimultaneously through graphical interpretation. As a result of this analysis, one UPS systemwas able to be identified abovegiven its cost. The APC Galaxy 5000 120 kVA UPS system is recommended as the optimal systemproviding backup power given the proposed emergency electrical layout. The system isexpandable to mtime is also an important metric to identify optimal UPS systems and will be explored in thenext section.

Discharge Time versus Cost Tradeoff Analysis

Determining the dischargewell as several other physical parameters of the battery itself. One of the major factors in

: Tradeoff plot tracing shipping weight in kilograms of the UPS system versus the total cost. A previously identified

The purpose of identifying shipping weight as an important metric is due to the implications ittotal UPS system cost. The system cost presented on the x

plots is the raw quoted price from APC and does not include shipping costs. Shipping cost isdirectly proportional to the shipping weight and should be accounted for whentotal cost of ownership. The above plot illustrates that in general, the heavier the system, themore expensive the UPS system is. However, the previously identified nonMGE Galaxy 5000 120 kVA, also shows the lowest shi

Performing the tradeoff analysis allows the investigation of numerous UPS systemssimultaneously through graphical interpretation. As a result of this analysis, one UPS systemwas able to be identified abovegiven its cost. The APC Galaxy 5000 120 kVA UPS system is recommended as the optimal systemproviding backup power given the proposed emergency electrical layout. The system isexpandable to meet the total loads required under an emergency situation. Total dischargetime is also an important metric to identify optimal UPS systems and will be explored in thenext section.


Determining the dischargewell as several other physical parameters of the battery itself. One of the major factors in

tracing shipping weight in kilograms of the UPS system versus the total cost. A previously identifiedpoint of interest is highlighted via a red circle



Performing the tradeoff analysis allows the investigation of numerous UPS systemssimultaneously through graphical interpretation. As a result of this analysis, one UPS systemwas able to be identified above the rest as providing optimal capacity, efficiency and weight,given its cost. The APC Galaxy 5000 120 kVA UPS system is recommended as the optimal systemproviding backup power given the proposed emergency electrical layout. The system is

eet the total loads required under an emergency situation. Total dischargetime is also an important metric to identify optimal UPS systems and will be explored in the


Determining the discharge time for a battery is a function of the load applied to the system aswell as several other physical parameters of the battery itself. One of the major factors in

Small Modular




Performing the tradeoff analysis allows the investigation of numerous UPS systemssimultaneously through graphical interpretation. As a result of this analysis, one UPS system

the rest as providing optimal capacity, efficiency and weight,given its cost. The APC Galaxy 5000 120 kVA UPS system is recommended as the optimal systemproviding backup power given the proposed emergency electrical layout. The system is



time for a battery is a function of the load applied to the system aswell as several other physical parameters of the battery itself. One of the major factors in


Page 31



plots is the raw quoted price from APC and does not include shipping costs. Shipping cost isdirectly proportional to the shipping weight and should be accounted for whentotal cost of ownership. The above plot illustrates that in general, the heavier the system, themore expensive the UPS system is. However, the previously identified nonMGE Galaxy 5000 120 kVA, also shows the lowest shipping weight of all analyzed systems






Reactors


The purpose of identifying shipping weight as an important metric is due to the implications ittotal UPS system cost. The system cost presented on the x-axis of the above tradeoff

plots is the raw quoted price from APC and does not include shipping costs. Shipping cost isdirectly proportional to the shipping weight and should be accounted for whentotal cost of ownership. The above plot illustrates that in general, the heavier the system, themore expensive the UPS system is. However, the previously identified non

pping weight of all analyzed systems





tracing shipping weight in kilograms of the UPS system versus the total cost. A previously identified

The purpose of identifying shipping weight as an important metric is due to the implications itaxis of the above tradeoff

plots is the raw quoted price from APC and does not include shipping costs. Shipping cost isdirectly proportional to the shipping weight and should be accounted for whentotal cost of ownership. The above plot illustrates that in general, the heavier the system, themore expensive the UPS system is. However, the previously identified non-inferior point, APC

pping weight of all analyzed systems







plots is the raw quoted price from APC and does not include shipping costs. Shipping cost isdirectly proportional to the shipping weight and should be accounted for when considering thetotal cost of ownership. The above plot illustrates that in general, the heavier the system, the

inferior point, APCpping weight of all analyzed systems –







plots is the raw quoted price from APC and does not include shipping costs. Shipping cost isconsidering the

total cost of ownership. The above plot illustrates that in general, the heavier the system, theinferior point, APC

– 540

simultaneously through graphical interpretation. As a result of this analysis, one UPS systemthe rest as providing optimal capacity, efficiency and weight,

given its cost. The APC Galaxy 5000 120 kVA UPS system is recommended as the optimal system


time for a battery is a function of the load applied to the system as


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choosing a battery is the Peukert number. The Peukert number relates the current load on abattery to the amount of time it takes to dissipate a certain capacity. For our tradeoff we usedthis equation:

t CRequired

I k

In the above equation, t is the time it takes to discharge the load, C is the capacity of electricalpower in ampere-hours of the batteries, I is the current load on the batteries, and k is thePeukert number. The factor we want to solve for is the discharge time, since we must be able toprovide a specified current load for at least 24 hours. The study is repeated for the 72 hourloads. As it turned out, a Peukert value of 1.13 would require more than one thousand batteriesto supply the 24 hour load, so this condition will constrain our design more than the 72 hourcase. The current load is held constant, since the demand of the plant is always the same,independent of the Peukert number, capacity of the batteries, and discharge time. Thecapacity, C, increases as the number of batteries is increased, assuming they are aligned inseries to provide the maximum power. The Peukert number is iterated from 1 to 1.15,simulating different battery properties. The Matlab code used for this scheme is displayedbelow:

The given values are all technical specifications of the APC SmartUPS VT 20kVA lead acidbattery. Converting the given 3 phase line-to-line voltage into the associated battery current


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requires the rated battery power and 0.8 power factor highlighted on the tech sheet. Theequation is as follows:

VLL

BPBI

*8.0*3

1000*

The design current (I) is calculated using the 24 hour battery load, described below:

Table 1: 24-hour battery loads by safety-related functions

24 Hour Loads1 Value (kW)

Nuclear Instrumentation 50

Reactor Precision System 90

Engineered Safeguard System 90

Distributive Control System 80

Control Room Load 150

Network Hardware 20

Emergency Lighting 100

Solenoid Valves 20

Motor Operated Valves 200

Total Load 800

Load per Division 200

Each of the named loads was taken from the Babcock & Wilcox Generation mPower SmallModular Nuclear Reactor designed load list for the 125VDC battery divisions. With a total offour 24 hour battery divisions (labeled A thru D), the values were then estimated by scalingdown similar loads from an advanced boiling water reactor.2 The load per division was thenused as an input for the design current calculation and a relationship between discharge timeand cost was then generated.

Typical deep-cycle (lead acid) batteries have Peukert numbers from 1.05-1.15. It is possible touse start up batteries, with Peukert numbers less than 1.05, but they do not provide enoughpower to make them cost effective. Start-up batteries are used for smaller applications, whichcycle many times and do not require large, long lasting loads. For this application the designrequires large loads to be supplied for long periods of time, but do not require many cycles asthe system is designed for emergency use only. The relationship highlighting the feasibilityrange for the 24 hour divisions is shown below:

1 mPower Class 1E_DC UPS Load List for PRA.PDF2 GE Nuclear Energy ABWR Design Control Document


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The three points completing the triangle each have unique design decisions associated withthem. Cost is maintained moving vertically upward along the graph, demonstrating its directdependence on number of batteries. The input Peukert number decreases from one curve tothe next (moving upward) as a result of the inverse relationship between discharge time andPeukert number. The boxed point on the bottom left of the Feasibility Triangle is the lowestcost, lowest discharge time resultant of an input Peukert number of 1.05. In order to increasethe discharge time one must increase the number of batteries (while maintaining the samePeukert number), this is shown in the top right boxed point of the triangle. Interestingly, thelower right boxed point of the triangle is described by the same (highest) cost but a lowerdischarge time, indicative of the fact that minimizing the design value of the Peukert number isimperative to battery performance.

Similar analysis of the 72 hour loads was conducted after generating load values from the sameBabcock & Wilcox and GE Nuclear Energy sources.

0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

x 107

0

10

20

30

40

50

60

70

Cost ($)

Dis

char

ge

Tim

e(h

ours

)

DecreasingPeukertNumber

24 HourRequirementLine

Lowest Cost,Lowest Discharge Time

Highest Cost and Discharge Time,Lowest Feasible Peukert Number

Highest Cost, Lowest DischargeTime, Highest Peukert Number

Figure 23: 24-hour load discharge time versus cost analysis


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Table 2: 72-hour battery loads by safety-related functions

72 Hour Loads Value (kW)

Post Accident Monitoring System 15

Control Room Load 100

Emergency Lighting 45

Remote Shutdown Station 40

Total Load 200

Load per Division 100

After updating the MATLAB code with the decreased load per division, the following figure wasgenerated:

An equivalent Feasibility Triangle is formed between the three boxed points, which are allabove the 72 hour requirement line. This line forms the bottom cutoff where there are notenough batteries to support either the design load or required discharge time of the system.Moving along the 72 hour requirement line between the two boxed points (indicative ofPeukert numbers between 1.05 and 1.15) yields the following data:

0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

x 107

0

20

40

60

80

100

120

140

160

Cost ($)

Dis

char

geT

ime

(Ho

urs

)

Lowest Cost, LowestDischarge Time

Highest Cost and Discharge Time,Lowest Feasible Peukert Number

72 Hour Requirement Line

Highest Cost, Lowest DischargeTime, Highest Peukert Number

DecreasingPeukertNumber

Figure 24: 72-hour load discharge time versus cost analysis


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Table 3: Number of batteries required to meet the 72-hour load

Number of Batteries Peukert Number Cost ($) Cost ($M)

921 1.05 14000000.00 14

970 1.06 14750000.00 14.75

1030 1.07 15670000.00 15.67

1110 1.08 16880000.00 16.88

1190 1.09 18100000.00 18.1

1270 1.1 19320000.00 19.32

1360 1.11 20690000.00 20.69

1460 1.12 22210000.00 22.21

The number of batteries was not calculated for Peukert numbers below 1.05 because these arenot physically possible for lead acid batteries of the type analyzed in this report. As shown inthe figure, for the prescribed battery quantity range (500 to 1500), a Peukert number greaterthan 1.12 could not achieve the 72 hour requirement.

Seen in Figure 1, a lower Peukert number correlates to a lower number of batteries requiredand thus a lower cost.

Figure 25: Correlation between number of batteries, cost, and peukert number

The trend above assumed the same batteries were used for the entire load, so it is based onone design option. Ideally this type of relation would be analyzed for many different types ofbatteries, but due to the particular application deep-cycle batteries must supply the majority ofthe load.

0

5

10

15

20

25

0

200

400

600

800

1000

1200

1400

1600

1.04 1.05 1.06 1.07 1.08 1.09 1.1 1.11 1.12 1.13

Co

st($

M)

Nu

mb

er

of

Bat

teri

es

Peukert Number

Number of Batteries

Peukert Number vs Cost

Expon. (Number ofBatteries)


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Conclusion

Returning to our problem statement:

When a Small Modular Reactor suffers a Total Station Blackout, a redundant DC power supplyof adequate capacity must be available to supply power to the reactor safety systems andpermit the orderly shutdown of the reactor.

After extensive modeling of the power requirements for a Small Modular Reactor, trade studieswere conducted to determine the optimum redundant DC power supply system (batteries) interms of cost and performance. Two types of emergencies were studied: an emergency whereall critical reactor systems (including reactor coolant pumps/infrastructure and monitoringsystems) required the redundant DC power supply for 24 hours to prevent a major disaster, anda milder emergency where only a subset of these systems required the redundant DC powersupply for 72 hours in order to allow for a controlled shutdown of the reactor.

The Peukert number for each battery type considered was the most important factor in theanalysis. Batteries with too low a Peukert number would not meet the power requirementsand batteries with too high a Peukert number would be unnecessarily expensive. Batteries withPeukert numbers in the range of 1.05 to 1.12 are ideal for this application. Redundant DCpower supplies using batteries in this Peukert range would cost an estimated $14M-$22M perreactor. Given that the typical cost of a complete nuclear power plant is on the scale of billionsof dollars, this amount is very reasonable.

Future areas of analysis could include:

1. Studies of methods to prevent environmental damage to the redundant power supplies(flooding, fire, seismic activity, extreme heat/cold)

2. Trade studies to explore other types of redundant power supplies (instead of electricitybeing stored as chemical energy, could it be stored as kinetic, thermal, or other forms ofpotential energy?)

3. Trade studies to explore ways to reduce the power demands of the critical reactorsafety systems (more efficient pumps for example)

Nuclear power can be a safe and affordable means of meeting the growing US energy demand.The Fukushima Daiichi event reminds us that there are still design problems that must beresolved before a large scale rollout of Small Modular Reactors is feasible. The redundant DCpower supply system is a critical design feature and must be capable of preventing Total StationBlackout/Loss of Coolant Accident events. Our trade studies show that this design element canbe successfully accommodated at a very reasonable cost.


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References

ABWR Design Control Document. Rep. GE Nuclear, 1997. Print.Back-Up Power Supply Single Line for MPower Reactor Plant. Rep. Frederick: Bechtel, 2011.

Print.Carelli, M. D., B. Petrovic, and C.W. Mycoff. "Economic Comparison of Different Size Nuclear

Reactors." 2007 LAS/ANS Symposium (2007). Print.Electrical Power Systems: DC Sources - Operating. Tech. no. B 3.8-73. Frederick: Bechtel, 2012.

Print.Lee, Doug. Introduction to B&W MPower Program. 7 July 2011. IAEA Interregional Workshop.

<http://www.iaea.org/NuclearPower/Downloads/Technology/meetings/2011-Jul-4-8-ANRT-WS/3_USA_mPOWER_BABCOCK_DELee.pdf>.

"Nuclear Energy: Just the Facts." Nuclear Energy Insititute. Washington, D.C. 10 Oct. 2010.Lecture.

“Nuclear Regulatory Commission." NRC: Home Page. Web. 05 Apr. 2012.<http://www.nrc.gov/>.

Preliminary Class 1E DC Load List for MPower Reactor Plant. Tech. Frederick: Bechtel, 2012.Print.

Ragheb, Magdi. Nuclear, Plasma, and Radiation Science: Inventing the Future. University ofIllinois, Urbanna-Champaign. 2012. Web. 19 Feb 2012.<https://netfiles.uiuc.edu/mragheb/www/NPRE%20402%20ME%20405%20Nuclear%20Power%20Engineering/>.

Rosner, Robert, and Stephen Goldberg. "Small Modular Reactors – Key to Future Nuclear PowerGeneration in the U.S.." Energy Policy Institute at Chicago. N.p., 11/2011. Web. 5 Apr2012.<https://epic.sites.uchicago.edu/sites/epic.uchicago.edu/files/uploads/EPICSMRWhitePaperFinalcopy.pdf>.

Safety Analysis Evaluation Methodology Requirements for the B&W mPower Reactor.Babcock&Wilcox. November 2011. Web. 19 Feb 2012.

“The Virtual Nuclear Tourist.” The Virtual Nuclear Tourist. Web. 05 Apr 2012.<http://www.nucleartourise.com/>.

Tucker, William. “America’s Last Nuclear Hope: Small Reactors May Save Us Yet.” The AmericanSpectator. The American Spectator Foundation. March 2011. Web. 19 Feb 2012.


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Appendix: Mid-Semester and Final PowerPoint Presentations

(attached)

small modular reactors final reportpdf

Documents