april 30 –may 18, 2018 albuquerque, new mexico, usaalbuquerque, new mexico, usa ... ultimately,...
Post on 05-Jul-2020
1 Views
Preview:
TRANSCRIPT
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 1
30. Nuc lear Reac tors and Sa fe ty
April 30 – May 18, 2018Albuquerque, New Mexico, USA
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC,a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration undercontract DE-NA0003525.
SAND2018-4015 PE
Reactors and Safety
Learn ing Object ives
After completing this module, you should be able to:• Describe key characteristics of pressurized water reactors
(PWR) and research reactors• List five generic types of reactor safety systems• Recognize importance of protecting safety equipment
2
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 2
Reactors and Safety
Reactor Steam Cyc le
• Fission heat transferred to water• Water heated to steam
Direct (1-Loop) – Within reactor Indirect (2-Loop) – Outside reactor in
heat exchanger / steam generator
3Courtesy of Nuclear Engineering International
Water also is necessary to slow down (moderate)
neutrons for the chain reaction to occur
Boiling Water Reactor (BWR)
Pressurized Water Reactor (PWR)
Reactors and Safety
Reactor Steam Cyc le (cont ’d)
• Fission heat transferred to liquid water• Water heated to steam• Steam turns turbine-generator
to produce electricity• Condenser water removes heat
to increase efficiency Once-through – natural or artificial body
of water Cooling towers
• Wet• Dry
4
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 3
Reactors and Safety
Mul t ip le Barr ier Conta inment
• Four major elements of reactor multiple-barrier containment for fission products1. Pellet
2. Cladding
3. Primary System
4. Reactor Containment Building
5
Reactors and Safety
BWR/PWR Fuel
• Pellets: UO2• Fissile: 235U 2-4 wt%• Cladding: Zircaloy
6
Research Reactors• Fuel Material – UO2• 20-90+wt% 235U• Clad rods or plates –
aluminum, zirconium, steel, ...
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 4
Reactors and Safety
PWR Fuel Bundles
7
Research Reactors• Single elements, small rod
or plate bundles
Reactors and Safety
PWR Safety and Contro l Rods / C lusters
8
Research Reactors• 12+ Safety / Control Rods• 1 Safety Rod / 2 Control Rods
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 5
Reactors and Safety
PWR Pr imary System
9
Research Reactors• Pressurized vessel /
forced circulation• Open pool / natural
circulation
Reactors and Safety
Reactor Safety
• Prevent accidents• Take protective actions
Identification and correction • Mitigate
Long-term response to and control of consequences• Conduct safety analyses
10
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 6
Reactors and Safety
Reactor Energy Sources
• 98% retention of radioactive products in fuel pellets Provide cooling Prevent fuel melting
• Stored energy in fuel, coolant, and structures• Nuclear transients
Increased power level Large power pulse
• Decay heat from fission products• Chemical reactions among fuel, cladding, and coolant• External events (natural, such as floods; human caused)
11
Reactors and Safety
Des ign-Bas is Acc idents
• The basis for assessing the overall safety acceptability of a particular reactor design
• Classifications include: Overcooling and undercooling Loss-of-flow (LOFA) and Loss-of-coolant (LOCA) Reactivity increase / neutron multiplication Failure to shut down (“SCRAM”) Spent-fuel system-radioactivity release External events (natural or human-caused events)
• Beyond-design-basis accidents
12
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 7
Reactors and Safety
Gener ic Safety Systems
• Provide mitigation by Prevent overheating, fuel melting, and other damage Prevent large-scale dispersal of fission products Reliability is enhanced through redundancy in subsystem
function and location• Five generic safety systems
1. Reactor trip2. Emergency core cooling3. Post-accident heat removal4. Post-accident radioactivity removal5. Containment integrity
13
Reactors and Safety
Gener ic Reactor Safety Systems
14
4. PARR – Removal of Radionuclides from Containment Atmosphere
1. RT – Rapid Shutdown of Reactor to Limit Core
Heat Production
2. ECC – Core Cooling to PreventRelease of Radionuclides from Fuel
3. PAHR – Removal of Heat from Containment to Prevent
Overpressurization
5. CI – Prevention of Dispersal of Radionuclides to Environment
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 8
Reactors and Safety
Reactor Tr ip / Emergency Core Cool ing
1. Reactor trip (RT) (“SCRAM”) Neutron poison control rods (also used for
routine control) Injection of soluble boric-acid poison
2. Emergency core cooling (ECC) Injection of borated water (cooling and
reactivity reduction) • Multiple trains • High, intermediate, or low pressure• Coincides with needs versus event history
Recirculation of coolant • From reactor building sump• Long-term coolant supply
15
• Control rod insertion
• Moderator dump
• Coolant injection
• Pool natural circulation
Reactors and Safety
Post-Acc ident Heat / Radioact iv i ty Removal3. Post-accident heat removal (PAHR)
Coolant temperature reduction • Heat exchangers for ECC water recirculation
Containment-building pressure control• Containment-atmosphere coolers• Steam-condensing water sprays
4. Post-accident radioactivity removal (PARR) Filter chemically active iodine and aerosol / particulate
constituents Noble-gas constituents can only be contained – or released in a
controlled manner Containment sprays to remove radioactivity
• Water sprays remove chemically reactive radioactive material
• Additives can increase removal, e.g., of elemental iodine16
• Heat exchanger
• Filtration
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 9
Reactors and Safety
Conta inment Integr i ty
5. Containment integrity (CI) Last line of defense against fission-product release Building: Leak-tight steel liner (pressure vessel); thick
reinforced concrete Isolate penetrations, e.g., with remotely operated valves Other safety features control overall pressure
17
Research Reactors• Containment • Confinement (negative pressure
and filter)• Open pool / water volume
Reactors and Safety
PWR
18
Research Reactors – Decreasing complexity
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 10
Reactors and Safety
Case Study: Three Mi le Is land Nuc lear S ta t ion
19
Reactors and Safety
TMI-2: Acc ident Sequence
• Before 4 a.m. on March 28, 1979 Running at 97% power Seemingly minor problems
• Small loss of coolant through pressurizer valve to drain tank• Emergency feedwater valves closed
– Post-maintenance– Unintentional, unknown to operators
• Blockage in the demineralizer for steam-generator water
20
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 11
Reactors and Safety
4:00:36 a.m. March 28, 1979
• INITIATOR: Unable to clear demineralizer blockage• No main feedwater• Main feedwater pump tripped off-line • Turbine tripped off-line• Emergency feedwater pump auto-started• Pressurizer pilot-operated relief valve (PORV) opened to
reduce pressure• Reactor tripped on overpressure signal
- - - Normal system response (first 8 sec) - - - Chain-reaction shutdown Decay-heat source remains
21
Reactors and Safety
22
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 12
Reactors and Safety
TMI-2: Acc ident Sequence
• Emergency feedwater blockage Prevented steam-generator function Distraction until valves re-opened Overall effect on accident progression uncertain
• PORV indicated “closed” (solenoid was de-energized) PORV actually was stuck open Unrecognized small-break loss of coolant accident (SBLOCA) in
progress• High-pressure injection (HPI) auto-start• HPI throttled
Open PORV Spurious indication of too much water
23
Rumored to be sabotage!
Reactors and Safety
TMI-2: Acc ident Sequence• Control room situation
Included 1300 annunciator lights; single klaxon 800 alarm initiations within 14 minutes
• Decay heat 200 MWt at shutdown
• → 40 MWt at 1 hr Electric arc furnace
• 130 MW-hr ↔ 300 ton Steel Fuel melting
24
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 13
Reactors and Safety
Consequences• Environmental
Brought under control rapidly Minimal damage “Public apprehension”
• Functional / Financial Loss of TMI-2 reactor Clean-up costs 6.5-yr to restart TMI-1
• Nuclear industry Backfit and license-related costs Reactor orders cancelled
25
Reactors and Safety
Research Reactor Sabotage Scenar io Types
• Direct Attack: Adversary brings energy to disperse radioactive material Explosive or incendiary attack on inventories of radioactive
material Prevented by denial of access to radioactive material inventories
• Indirect Attack: Adversary uses energy in facility process/ equipment to disperse radioactive material Reactivity Insertion Accident (RIA) Disable SCRAM system and heat removal Disable decay heat removal Disable other safety equipment required to prevent radioactive
material release Prevented by denial of access to safety equipment
26
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 14
Reactors and Safety
Acc ident vs. Sabotage
TMI Accident Sabotage Equivalent
Condenser blocked Condenser disabled
Valves closed Close / damage valves
Pressurizer open Any major coolant loss
Injection throttled Injection disabled
Pumps turned off Pumps disabled
Hydrogen ignition Ignite hydrogen
27
Research Reactors• Disable cooling• Uncover fuel
Uncover Fuel
Reactors and Safety
Protect Safety Equipment
• Protecting safety equipment Engineering Safety Aspects of the Protection
of Nuclear Power Against Sabotage (NSS-4) Anything that can happen by accident can be
made to happen• Consider threat capabilities• Consider events with radioactive release or
where one more failure (sabotage) would cause radioactive material release
• Identifying Vital Areas Identification of Vital Areas at Nuclear Facilities
(NSS-16) Detailed guidance for identification of vital areas
28
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 15
Reactors and Safety
Case Study: React iv i ty Inser t ion Acc ident a t SL-1 Reactor
29
Reactors and Safety
S tat ionery Low Power No. 1 (SL-1) Reactor
• 3-MWT prototype for proposed arctic military application• Complex design for research reactor
Direct, boiling water cycle 200 kW electric, 400 kW heat (disposed of directly to the
environment)• 14 kg HEU (93%) in 40 aluminum fuel-plate assemblies• 9 T-shaped control rod assemblies• Steel vessel 1.4-m diameter × 4.4-m high
(4.5-ft diameter × 14.5-ft high)• Turbine, condenser, piping, pumps• Multiple shielding types
30
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 16
Reactors and Safety
SL-1 Schemat ic
31
Reactors and Safety
Conf inement and Support Bui ld ings
32
C o n d e n s e r & Ve n t i l a t i o n
O p e r a t i n g F l o o r L e v e l
Ve s s e l & S h i e l d i n g
Support BuildingConfinement Building
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 17
Reactors and Safety
Acc ident Informat ion
• January 3, 1961 – Three shifts Maintenance of auxiliary systems Reactor core measurement preparation (required vessel head
and control rod removal) Control rod drive reinstall – 3 operators
• Site central alarm with cause unknown Fire crew responded: Support Building radiation level 25 r/hr Health Physics responded: Reactor Building (Confinement
Building) radiation level 200 r/hr• Operator withdrew central (highest worth) control rod
“as rapidly as he was able”• Caused Reactivity Insertion Accident (RIA) (“excursion”)
33
Reactors and Safety
Acc ident V ideo
<https://www.youtube.com/watch?v=yjljS0aQbCc>
34
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 18
Reactors and Safety
Acc ident vs. Contro l led-Excurs ion Example• SL-1 accident scenario
System supercritical Power increased in a 4-ms period Coolant steam voids and fuel element expansion – and
ultimately, destruction – terminated the excursion• Controlled-excursion example
Sandia’s Annular Core Research Reactor (ACRR)• Special control rode fired (N2 pressure) out of the core• System begins a “prompt supercritical” excursion
https://www.youtube.com/watch?v=pa0Fmcv83nw• Temperature feedback first slows chain
reaction, then causes a self-shutdown before any fuel damage occurs . . .
35
Reactors and Safety
Consequences and Lessons Learned• Consequences
Steam explosion scattered the core Water hammer lifted vessel ~3 meters Total energy release equivalent to ~28 kg of TNT Two operators killed immediately, and the third died soon after
from head injury Reactor room highly contaminated with fission products
• Dose rate 0.5 to 1 Sv/h (50 to 100 rem/h) • Only slight radiological release outside building
Three lessons for similar (prototype) reactors More than a single control rod for critical Minimize manual control rod operation Pressure-tight containment required
36
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 19
Reactors and Safety
Damage
37
Steel Plate and Cooling Lines
Core, Vessel, Control Rods
Reactors and Safety
Protect Safety Equipment
• Protect Control Rod Safety Identify decay heat removal requirements from safety analysis If a Probabilistic Safety Analysis (PSA) has been prepared, it
likely documents the consequences of loss of decay heat removal• Protect against Disabled Decay Heat Removal
Locate required safety equipment and identify disablement approaches
• Insider tampering• Local sabotage• Sabotage controls / power• Attack on primary coolant boundary for water-cooled reactors • Vehicle bombs / standoff attacks (if within the DBT) may disable
both decay heat removal and confinement
38
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 20
Reactors and Safety
Protect Other Safety Equipment
• Operating Experience (IAEA-TECDOC-1762)
• Anything that can happen by accident can be made to happen Consider threat capabilities Consider events with radioactive
release or where one more failure (sabotage) would cause radioactive material release
39
Reactors and Safety
IAEA TDL-004
• Nuclear Security Management for Research Reactors and Related Facilities
• Single source guidance for all aspects of nuclear security Nuclear materials and radioactive materials Sabotage and theft protection
• Identifies synergies between theft and sabotage protection
• Provides detailed guidance for establishing security systems, measures, and programs meeting NSS-13 recommendations
40
30 – Nuclear Reactor and Safety
The Twenty-Seventh International Training CoursePage 21
Reactors and Safety
Des ign for Unique Secur i ty Chal lenges
• Design for easy experiment / core reconfiguration More difficult to control access to equipment that:
• Reconfigures core configuration• Controls reactivity
• Broad visual access for teaching More difficult to secure information about potential equipment
sabotage targets• Need for multi-national experimenter access to critical
areas More difficult to verify trustworthiness of individuals with access
to critical areas
41
Reactors and Safety
Summary• Safety systems provide mitigation by
Preventing overheating, fuel melting, and other damage Preventing large-scale dispersal of fission products Reliability is enhanced through redundancy in subsystem
function and location• Five generic safety systems
1. Reactor trip2. Emergency core cooling3. Post-accident heat removal4. Post-accident radioactivity removal5. Containment integrity
• Protect safety equipment … anything that can happen by accident can be made to happen
42
top related