NUCLEAR POWER CORPORATION OF INDIA LIMITED (A GOVT. OF INDIA ENTERPRISE)

Guided By: Prepared By:

Mr. Gaurav Sharma (Trg. Supt) KUSHAL VARSHNEY

Mr. Khagesh Chandra Rakesh (Trg. Officer) B.Tech (ECE, 4th Year)

Mr. H.C Gaur, SO/F Inderprastha Engineering College,

Mr. G.S.Rawat, SO/C Ghaziabad.

CCEERRTTIIFFIICCAATTEE

This is to certify that Mr.___________________________ has partially completed

/ not completed the Training in our Organization / Industry during the period 15-06-

2015 to 14-07-2015. His overall performance during the period was Excellent /

Very Good / Good / Average / Poor.

Signature & Seal of Training Manager

PREFACE

As we know that an engineer has to serve an industry, for that one must be aware of

industrial environment, their management, problems and the way of working out

their solutions at the industry.

After the completion of the course an engineer must have knowledge of

interrelation between the theory and the practical. For this, one must be familiar

with the practical knowledge with theory aspects.

To aware with practical knowledge the engineering courses provides a six weeks

industrial training where we get the opportunity to get theory applying for running

the various process and production in the industry.

I have been lucky enough to get a chance for undergoing this training at NARORA

ATOMIC POWER STATION. It is a constituent of board of NPCIL. This report

has been prepared on the basis of knowledge acquired by me during my training

period of 30 days at the plant.

ACKNOWLEDGEMENT

It was highly educative & interactive to take training at

NARORA ATOMIC POWER STATION. As technical

knowledge is incomplete without practical knowledge, I couldn’t

find any place better than this to update myself.

I am very much thankful to the Station director Shri. D. S.

Choudhary & Training superintendent Shri. G. Sharma for

allowing me for the industrial training at NAPS. Thanks to Shri.

Khagesh Chandra for their valuable guidance during my project.

I also take the opportunity to thanks Nuclear training Centre for

providing lecture on overview of the plant and providing me

Orange qualification.

S.No. DESCRIPTION

1.0 Introduction to NAPS

1.1 NAPS Plant layout

1.2 Some important data of NAPS

1.3 Nuclear Power stations in India

1.4 Principle of Nuclear Reactor

1.5 Nuclear Reaction

1.6 Heavy water and its usage

1.7 Moderator System

1.8 Primary heat transport system

1.9 Reactor fuel

1.10 Shut down system

1.11 Steam cycle

1.12 Main Control Room

2.0 Important measurement at NAPS

2.1 Pressure measurement

2.2 Temperature measurement

2.3 Level measurement

2.4 Flow measurement

3.0 Control Maintainance Section

4.0 Control Room Computer System

4.1 System descriptions

4.2 Communication system

4.3 VSAT

5.0 Public Address System

6.0 Reference

INTRODUCTION TO NAPS

One of the chief aims of the Department Of Atomic Energy is the development

of Nuclear Energy for economic generation as an alternative source of electric power when in due course the conventional sources will be exhausted in the

country. Petroleum prices are escalating. The amount of coal required for 400MWe power generations of the order of 5 x 106 KGs per day. Whereas a

Nuclear Power Station of the same capacity needs only 200 kg of Atomic Fuel per day. Transportation of coal of such magnitude over long distance is not

economical.

NARORA, a small ancient village, is situated on the bank of Holy River Ganga in the district Bulandshahr in Uttar Pradesh. The plant is about 60 km from Aligarh, which is the nearest population center. With the synchronization of the

Narora Atomic Power Station with northern grid through five lines of 220KV, it has occupied an important place on the power map of the India. With this, yet

another important milestone in the Indian nuclear program has been achieved, as NAPS is an effort towards standardization of PHWR Units & a stepping-

stone to the 500MWe units. A significant & unique feature of this project has been the evolution of the design suitable for seismic sites.

The NAPS is a twin unit module of 220MWe. Each of pressurized heavy water

reactors. The reactors use natural uranium available in India as fuel & heavy water produced in the country as moderator & coolant. A NAPP is the fourth

Nuclear Power Station in the country after Tarapur in Maharasthra, Rawatbhata in Rajasthan & Kalpakkam in TamilNadu. NAPS is the first indigenous Nuclear

Power Plant of India. The station has two pressurized heavy water reactors with installed capacity of 220MWe, each using natural uranium as fuel. The station is connected to high voltage network through five 220 KV lines, one to

Moradabad, one to Atrauli, one to Simboli, & two to khurja. It is designed for base load operation as a commercial station.

TOP VIEW OF NARORA ATOMIC POWER PLANT

NAPS LAYOUT

Reactor Building houses the Reactor Primary Heat Transport System, Moderator System, Reactivity System, Fuel Handling System & some of the

Auxiliaries. The Turbo-Generator & its associated conventional equipment, Emergency Diesel Sets, Control & Power MG Sets, Station Batteries, Electrical

Switch Gear Compressors, Chillers & Main Control Room are located in Turbine Building. Both the units share common facilities such as Service

Building, Spent Fuel Storage Bay (SFSB) & other auxiliary devices such as Heavy Water Upgrading & Waste Management Facility. NAPS have two

natural draught cooling & two induced draught cooling towers. NAPS have the following main parts: -

.

1. Administrative Building

5. Switchyard 9. Reactor Building

2. Domestic Water Head Tank

6. Stack 10. Purification Building

3. Canteen 7. Service Building 11. Turbine Building 4. NDCT 8. Supplementary 12. Pump House

SOME IMPORTANT DATA OF NAPS

DATA SPECIFICATION Transmission Lines Five

220 KV Narora – Moradabad Single Line

222200 KKVV NNaarroorraa ––HHaarrdduuaaggaannjj Single Line

220 KV Narora–Simbholi Single Line

220 KV Narora–Khurja Double Line

Stack Height 142 Meters

NDCT Height 128 Meters

NDCT Top Diameter 58 Meters

NDCT Base Diameter 107 Meters

Steam Pressure 40-48 Kg/cm2

PHT Pressure 87.0 Kg/cm2

Coolant Tubes 306

No.of Fuel Bundles in one channel 12

Fuel Bundle Weight 15Kgs

No. of Bundles in a core 3672

Condenser Vacuum 680 MM of Hg

RB Design Pressure 1.25 Kg/cm2 (g)

Station Load 18 - 20MWe

Generator Power 220MWe

Grid Voltage 220 KV

ISO-14001 certification 19th AUGUST 1999

NUCLEARPOWER STATIONS IN INDIA

Capacity Of The Running India’s Atomic Power Stations Given as

S.NO. Name of unit & Place CAPACITY Total

1. TAPS-1&2,Tarapur 2X160Mwe 320Mwe

2. TAPP-3&4,Tarapur 2X540Mwe 1080Mwe

3. RAPS-2,Rawatbhata 1X200Mwe 200Mwe

4. RAPS-3&4Rawatbhata 2X220Mwe 440Mwe

5. RAPS-5&6Rawatbhata 2X220Mwe 440Mwe

6. MAPS-1&2,Kalpakkam 2X220Mwe 440Mwe

7. NAPS-1&2,Narora 2X220Mwe 440Mwe

8. KAPS-1&2,Kakrapara 2X220Mwe 440Mwe

9. KGS-1&2,Kaiga 2X220Mwe 440Mwe

10. KGS-3&4,Kaiga 2X220Mwe 440Mwe

PRINCIPLE OF NUCLEAR REACTOR

A Nuclear Power reactor is only a source of heat, the heat being produced when the uranium atom splits (fission). The heat produces steam, which drives

the turbo-generator & produces electricity. Natural uranium, the fuel used in this reactor, consist of two types (isotopes) of uranium namely U-235 and U-

238 in the ratio of 1:139. It is the less abundant i.e. U-235 isotope that fissions and produces energy. When a U-235 atom is struck by a slow (or thermal)

neutron, it splits into two or more fragments. Splitting is accompanied by tremendous release of energy in the form of heat, radioactivity & two or three

fast neutrons. These fast neutrons, which fly out of the split atom at high speeds, are made to slow down with the help of moderator (heavy water). So

that they have high probability to hit other 92U235atoms which in turn releases more energy & further sets of neutrons and fission. Attainment of self-sustained fission of uranium atoms is called a ‘Chain Reaction’. At this stage

the reactor is said to have attained “criticality”.

REACTOR CYCLE:

Heavy Water is used in the Reactors as moderator & reflector for the neutrons

and as coolant for the Reactor fuel. The two functions are separate, each having its own closed circulating system. The fuel coolant system is called the Primary Heat Transport System, and is a high pressure, high temperature circuit. The

moderator and reflector circuit is called the moderator system, and is a low pressure, low temperature circuit. The Pressure tubes &Calandria Tubes are

insulated from each other in the Reactor core by Carbon di-oxide Gas in the annular space between the calandria tubes and the coolant tubes. Figure shown

below is a simplified schematic diagram of the Reactor Cycle. Heavy water at 293 0C enters the Steam Generator tubes to raise steam from Demineralized

Water in shell side, for the turbine and returns back to the Reactor at 249 0C. The working pressure, which is the mean of the pressure, in the Reactor inlet &

outlet headers is 87.0 Kg/cm2.

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Moderator (D2O) system circulating pump take suction from bottom of

calandria& discharge back to calandria through moderator heat exchangers for maintaining moderator temperature. Moderator inlet to calandria is at its middle

point from two opposite sides. Working pressure and temperature of moderator system are 8 Kg/cm2 and 650C respectively with a cover gas pressure of 0.25

Kg/Cm2.

In order to avoid escape & loss of Heavy Water from PHT / Moderator System, a high standard of integrity is maintained by using multiple seals & leakage

collection system in the liquid phase. D2O Vapour recovery Dryer Systems is

used for the vapour phase collection.

TURBINE AND STEAM CYCLE: At rated power, 1.33 x 106 Kg/hour of saturated steam at 39.7 Kgf/cm2 pressure

is provided by Four Steam Generator to supply to the Turbine. The Turbine rated at 220 Mew, is a tandem compound machine with one high-pressure

cylinder and one low-pressure cylinder with double flow. From the outlet of the HP cylinder, the steam at a pressure of 5.6 Kg/Cm2 passes to a pair of moisture separator and then to a pair of reheater, where steam is heated up to 233oC for

admission to the low-pressure cylinder. Steam exhausted from the L.P. turbine is condensed in a single pass condenser capable of maintaining a vacuum of 680

mm of Hg with a NDCT cooled water temperature of 320C. The feed water is

heated in six stagesup to 1710C and sent to the Steam Generators. The Steam

Re-heater drain is returned separately to Steam Generators.

NUCLEAR REACTION:

The basic atomic energy we get from the process called nuclear fission of the 92U235 atom with the thermal neutron. The typical fission reaction is as follows: -

92U235 + 0n1 38 Sr94 + 54Xe140 + 2 0n1 + y (Heat Energy) +

γ(Natural Uranium Oxide)

92U235 + 0n1 56Ba141+ 36Kr92 + 3 0n1 +y (Heat Energy) +Y

The fission process releases energy. The transformation of this energy is as shown below: -

Nuclear Fission Energy

Heat energy

(Formation of steam)

Mechanical energy

(Operating Turbine & Generator)

Electrical energy

(With the help of generator)

HEAVY WATER AND ITS USAGE Heavy water is used as both the moderator and coolant. Heat energy is transported by coolant from reactor to the vertical, integral U-tubes in shell type

of heat exchangers, which functions as a boiler to produce steam and drives Turbo Generator. The heavy water (D2O) is identical to the ordinary water (H2O) as far as the chemical properties are concerned. However, in physical

properties there are minor variations (boiling point 101.4oC and freezing point 3.82oC). The deuterium (D2) in heavy water is an isotope of hydrogen (H2)

having one neutron and one proton in its nucleus. The absorption cross-section of heavy water for neutron is far less than the ordinary water, which helps in

neutron economy

MODERATOR SYSTEM The moderator system is a heavy water and helium system. Calandria is always

full of moderator up to 96% and remaining volume is covered by helium gas, which acts as cover gas. Moderator is used to slow down the speed of fast

neutron. Moderator (D2O) system circulating pump take suction from bottom of calandria and discharge back to calandria through moderator heat exchanger for

maintaining moderator temperature. Working pressure and temperature of moderator system are 8Kg/cm2 and 63oC respectively.

PRIMARY HEAT TRANSPORT SYSTEM The fuel coolant system is called the primary heat transport system and is a high pressure and high tempckt. The coolant transports this heat to the four steam

generators. Four pumps maintain the circulation through pressure tubes around the fuel bundles, each having a capacity of 3560m3/hr. The coolant temperature

at inlet & outlet of a reactor are 249oC & 293.4oC respectively at a pressure of 101 kg/cm2& 87 Kg/cm2 respectively. A pressuring pump maintains the system

pressure using automatic feed & bleed principle instrument relief valves & suitableregulating & protective system action limit the system pressure to 93.91

Kg/cm2. PHT is constantly pressurized at 87Kg/cm2 to keep it in liquid form at 295oC. High pressure, high temperature heavy water areas have been separated from high pressure, high temperature light water areas for recovery of high

isotopic purity heavy water.

REACTOR FUEL

Fuel from the reactor is in the form of bundles 49.53 cm long & 8.17cm dia&

each bundle consists of 19 hermetically seal zircaloy tubes containing compact & sintered pallets of natural uranium. Twelve such bundles are located in each

fuel channel.

SHUTDOWN SYSTEMS

NAPS are provided with two diverse & independent shut down system, one fast

acting & other slow acting. The primary shutdown system has shutoff mechanism at 14 locations in the reactor. Each of the 14 mechanisms has

cadmium sandwiched steel as neutron absorbing element. Normally these rods are parked outside core during power operation & fully in on a trip signal. The

rods are held out of reactor core by rope & drum arrangement. These rods drop in the core under gravity whenever a trip signal is received, & make the reactor

sub-critical in less than 2.3 sec.

The secondary shutdown system is a fast acting back up system to the primary shutdown system. This system provides sufficient reactivity worth by promptly filling twelve vertical tubes in the reactor core with a neutron absorbing liquid

(Lithium Pentaboratedeca –hydrate). The principle is such that four when liquid filled tanks are pressurized than the liquid rises up in liquid tubes located inside

reactor. It makes the reactor sub-critical in 1.4 sec.

Both the shut down systems are backed by Automatic Liquid Poison addition system injecting controlled quantities of boron into the moderator after

receiving the appropriate signal to ensure guaranteed sub-criticality of the reactor for prolonged periods. Whenever there is total blackout of the station &

automatic liquid poison system is not available, addition of poison, under gravity, to moderator is incorporated.

STEAM CYCLE The turbine is an impulse reaction type, designed for saturated steam duty,

revolving at 3000 rpm with steam condition of 39.71 kg/cm2 pressure & 0.26% wet & 250.3oC at inlet to stop valves. The turbine each rated at 235 Mew is a tandem compound machine with one high-pressure cylinder and one low-

pressure cylinder with double flow. From the outlet of the high pressure cylinder the steam passes to a pair of moisture separator and then to a pair of

reheater where steam is heated up to 233oC and 5.6/cm2 for admission to the low-pressure cylinder. Steam exhausted from the L.P turbine is condensed in a

single pass condenser. Steam is extracted from suitable stages of the turbine to provide for 6 stage regenerative feed heating, with a final feed water

temperature of 171oC.

Deareator L.P Turbine

L.P Heaters

1,2,3

Condenser

Boiler Feed Pump

Pump

Moisture Sep.

& Reareater

Pump

Air ejector

H.P Heater

5&6 H.P Turbine

Boiler

MAIN CONTROL ROOM:

Control Room as the name suggests, what it is? It is a place from where every instrument device etccan be controlled in either field or Reactor Building.

Control Room is the most important place in any nuclear power plant. It is a place, which has full control over the reactor and all its peripheral. It has

separate system wise, panels for both units. On any error in any device or system an audiovisual indication is produced in the control room. It also has

fuel-handling panel from where staff members can see the calandria channel by CCTV cameras and refueling is done from this panel only.

To present the operator with the desired information in a compact, overall fashion and reduce the large number of recorders, meters and annunciating

windows used in the earlier plants, a computer based operator information system is introduced in NAPS called as control room computer system (CRCS).

This system is designed as purely informative system, with no control features being included in the system. The information is presented in any desired

format and alarm annunciations are provided by color CRT displays. The standardization input signal is used in CRCS. The input signal is represented as

0.5-4.5V. At zero signal reading is 0.5Vand at full signal reading is 4.5V.The representation of row signal from sensors is represented into the standard form

by Signal Conditioning Modules (SCM). There are separate SCM for different type of signal. These SCM are separate for both units and are located in the

Control Room Computer system itself. Moreover all the paperless recorders installed at NAPS are connected to a common computer through LAN, where

all the data is stored and constantly monitored.

CHANNEL TEMPERATURE

MONITORING SYSTEM (CTM):

Channel Temperature Monitoring System measures 1. The temperatures of the coolant (PHT) at the outlet of all the 306

channels and 2. The differential temperatures of sixteen selected channels.

This system mainly

Detects low coolant flow and apply corrective action for reactor safe condition.

Provides a signal for flux tilt control Helps in efficient fuel management by monitoring channel

outlet temperature and other related temperature.

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ccrroossss sseeccttiioonnaall aarreeaa ::

r . L R = --------- A

Where R = Resistance (ohms), r = Resistivity (ohms), L = Length , A = Cross sectional area

RTD Materials: The criterion for selecting a material to make an RTD is:

the material must be malleable so that it can be formed into small wires.

it must have a repeatable and stable slope or curve.

the material should also be resistant to corrosion.

the material should be low cost

it is preferred that the material have a linear resistance verses temperature slope

One of the common RTD materials is Platinum with a temperature coefficient of 0.00385 - 0.003923 Ω/Ω/°C and practical temperature range of -452 to +1100°F (-269 to +593°C). The platinum RTD has the best accuracy and stability among the common RTD materials. The resistance versus temperature curve is fairly linearand the temperature range is the widest of the common RTD materials. Platinum has a very high resistivity, which means that only a small quantity of platinum is required to fabricate a sensor and making platinum cost competitive with other RTD materials. Platinum is the only RTD commonly available with a thin film element style. Platinum is the primary choice for most industrial, commercial,

laboratory and other critical RTD temperature measurements. Copper, nickel and nickel iron are also commonly used RTD materials which are usually used in low-cost non-critical applications. Reference grade platinum is made from 99.999% pure platinum. It will produce a maximum temperature coefficient of 0.003926Ω/Ω/°C. The maximum temperature coefficient can only be achieved in Standard Platinum Resistance Thermometers (SPRT) for laboratory use. Types of RTD:

Wire wound type Coiled element type

Thin film element 2-wire RTD

Similarly, there are 3 and 4-wire RTD as well. The RTD used in

nuclear applications is the wire wound strap-on type.

CTM Basic Circuit:-

Current flow at 300 deg. Celsius~17 mA

Current flow at 30 deg. Celsius~19 mA The TA card consists of a comparator and a relay. The RTD strapped on

channel outlet measures the temperature of channel which results as voltage across it. This voltage can be determined by applying voltage divider rule across

the potentiometer (VRTD). This voltage is applied to +ve terminal of the comparator. On the –ve terminal, RTD voltage corresponding to 299 degree

Celsius is applied. When VRTD is less than V299, the comparator o/p is –ve and hence the relay is energized. If temp. exceeds 299 degree Celsius, the

comparator o/p becomes +ve and the relay de-energizes. Hence, the increase in temp. can be monitored.

A modified circuit involves use of 15V instead of 36V reference voltage.

Modified:- As the reference voltage decreases, the voltage across RTD for the same

temp.also decreases. This in turn decreases the self-heating error. Accuracy increases but sensitivity, i.e., per degree voltage change decreases.

Zone Temperature Monitoring

The entire CTM matrix of 306 coolant channels are grouped into 8 Zones and they are named as A1, B1, C1, D1, A2, B2, C2 and D2.Zones A1, B1, C1 and

D1 each consists of 31 channels. Zones A2 and C2 each consists of 48 channels whereas, zones B2 and D2 each consists of 43 channels. Signals from the wiper of 10-ohm potentiometer are connected to comparator cards as input signals. A

voltage signal corresponding to 299 deg C is fed as the reference signal alarm. The two installations “TA” alarm contacts are wired with 2/2 coincidence

circuit for reactor setback. The comparator circuit also provides the voltage signal to light LED during alarm condition. The LEDs for all channels are

arranged in matrix form in each panel. On the comparator PCB, 40K ohm resistance is mounted whose one end is connected to input signal and the other

end is brought out on the PCB connector. These resistors of the zones are averaged to get the summing signal for ZMT. The reference signal

corresponding to 299 deg C (required for channel outlet temperature very high comparison) and 250 deg C (required for zone mean temperature indication

above 250 deg C) are derived from 36V power supply itself. The reference signal corresponding to 299 deg C and 250 deg C are fed to buffer amplifiers

and the output of buffer amplifiers are connected to comparator cards and ZMT indicating alarm meters respectively. Zone mean temperature is defined as the arithmetic mean of the temperature of

all the channels of a particular zone. Signals from wiper of 10 ohms potentiometer are also fed to CTM computer through 220K ohms resistors,

which provide display/print out of a single or all channel temperature data and alarm annunciation.

IMPORTANT MEASUREMENT

AT NAPS

INTRODUCTION: It encompasses monitoring and control of various plant parameters principle of

redundancy, diversity testability and maintainability are given prime consideration. A high degree of automation is aimed at to promote reliability.

The system is design to confirm to fail safe criteria. All visual indication to control, which may require intervention during operation, is located in a single

central control room. The safety systems are generally triplicates, the safety function being achieved by 2 out of 3 logic’s. Each channel is totally

independent of other channels with separate sensor, signal handing equipment, cable routes and power supplies. In channel temperature monitoring system, only two channels are used with coincident logic of 2 out of

2 to reduce the power. The instrumentation for the control and protection system is kept separate and independent of each other. A computer based

operator information system is used for data information display for operators. If any default occurs in the system it will inform the operator by audio-visual

window annunciates system, which is provided on control room panels to cover certain essential parameters.

PRESSURE MEASUREMENT: Pressure is one of the important variable encountered in the nuclear power plant, because uncontrolled it can lead to severe damages and loss of efficiency.

Following are the some important examples of pressure measurement.

Primary heat transport is pressurized to prevent vapor flashing and thus power fluctuations.

Moderator pump suction pressure is controlled to ensure that the helium-circulating tank will not flood under certain conditions.

Steam pressure is controlled to ensure economic efficiency and power control.

Pressure is actually the measurement of force acting on area of surface. The

units of measurement are either in pounds per square inch (PSI) in British units or Pascal (Pa) in metric. One PSI is approximately equal to 7000 Pa.

Common pressure detectors are Diaphragm, strain gauge, and bourdon tubes,

differential pressure transmitters.

Scale of pressure measurement is 1) Gauge pressure

2) Absolute pressure 3) Vacuum scale, usually stated in inches of mercury below

atmospheric Pressure.

P Gauges=P absolute – P atm P vacuum=P atm – P absolute

TEMPERATURE MESUREMENT:

The primary sensor used in the temperature measurement is

thermocouple (T/C), bimetallic strip and resistance temperature

detector (RTD).

Thermocouple : - A T/C consists of two pieces of dissimilar metals

with their ends joined together. When heat is applied to the junction, a

voltage, in the range of mille-volts (mV), is generated. A

thermocouple is said to be self-powered.

Resistance Temperature Detector: - The resistance of device

various as the temperature increases. RTD is one of the most accurate

temperature sensors. Not only does it provides good accuracy it also

provide excellent stability and repeatability.

LEVEL MEASUREMENT: The measurement of level in nuclear power plant assume sample significance specially in heavy water system as can be seen from the below given example:

Moderator level is measured and control for reactivity adjustment. Dump tank sump level is a measure to ensure a low level will not lead to

dump cavitations. Storage tank level is a direct indication of heavy water contents; a drop in level

could be only because of leakage. Boiler drum level is measured and controlled to provide adequate heat sink for

the reactor and to match the requirement of steam to turbine.

Ultrasonic method of level measurement: -The ultrasonic operates on the principle of sonar. Sound waves are sent out to the free surface of liquid under

test and are reflected back to the receiving unit, level changes are accurately measured by detecting the time intervals taken for the waves to travel to the

surface and back to the receiver. The longer the time interval, the farther away is the liquid surface, which in turn is an indication of level measurement.

The ultrasonic gauge needs physical contact with the material. It is non-disturbance technique. It can be use for solid and liquid material level measurement.

FLOW MEASUREMENT: The flow measurement is very important in process industries because it

establishes definite ratios and quantities of process materials for production quantity control. In nuclear plants, flow measurement is critical for cooling

loops such as calandria spray flows; adjuster rod coolant flow is measured in selected channels only. In case of other cooling loop such as bleed cooler,

moderator heat exchanger, a low process water flow would result in high outlet temperature. In moderator circulation system, a low flow could point towards

cavitations of pumps. In turbine generator steam, flow directly depends on the load. Flow can be measured by venturi tube

Venturi Tube: -The flow of liquid through the venturi tube establishes the

pressure differential, which can than be measured and related to the flow rate. In this tube, a large pressure recovery can be made, and flows can travel through it with much higher velocity without the turbulence, which destroys the accuracy

of orifice plates.

INTRODUCTION TO

CONTROL MAINTENANCE SECTION (CMS): Control Maintenance Section (CMS) is an Instruments maintenance Section that carries out all the control system jobs related to electronics and process

instrumentation. Calibration Lab (ISO-17025 certified) also known, as NAPS Instruments Testing Laboratory is an important part of CMS. This lab consists

of instruments and master instruments, which are calibrated periodically and can be further used in the field. Role of calibration lab in control maintenance

section: i) To maintain standardization of all master instruments from standardization

Organizations i.e. ERTL (N), NPL

ii) To maintain healthiness of all master instruments.

iii) To calibrate all test equipments with master equipments.

CMS maintains healthiness of all electronics and process instruments of the plant with the help of routine checks, preventive maintenance and attends

breakdown maintenance jobs as earliest without affecting power generation. Actually, in NAPS, CMU lab is divided into three sections:

a) Electro-technical lab (temperature. = 25+ 2.5 deg C and Relative Humidity

=35 to 65%). b) Temperature lab (Temperature. = 25+ 2.5 deg C and Relative humidity =35 to 65%).

c) Pressure lab (temp. = 23+ 1.0 deg C and reactive humidity 45 to 55%).

CONTROL ROOM COMPUTER

SYSTEM (CRCS): CRCS system is a comprehensive information storage/retrieval

system with varieties of features, which are exclusively designed according to the needs of the nuclear power plant operator. It is meant for acquiring data

from host, processing and presenting to the operator with the information required to check the healthiness of the plant and analyze its behavior during its

operation. CRCS is a configured as a client server configuration built around an Ethernet

LAN. The servers are dual redundant working in Active as well as Hot Standby mode. This LAN is called the Work Station LAN(WSLAN). The CRCS

provides most of the information, which was usually displayed on panel meters in earlier plant. It is used for dynamic value, bar graph display. Graphical

display of plant parameters, Alarm reporting, trending, mimic display, disturbance recording etc. This system is used for data co-ordination and

management purpose. This system has the following points:

1200 Analog points for field parameters monitoring

1280 Digital input points for field contacts monitoring.

256 Event sequence record digital input points.

128 Digital output points for DNM processing, Tritium in air

monitoring.

SYSTEM DESCRIPTIONS: i) Buffer Terminal Cabinet (BTC):-

All the field signals are terminated at the BTC panels. From BTC

another cable is connected to different (I/O) panels of CRCS.

ii) I/O panels:-

There are four I/O panels in CRCS. One I/O panels is having 300 analog points, 320 digital input points, and 32 digital input points and 32 digital output points. Analog field input is terminated at Signal Conditioning

Modules (SCM) through BTC.

iii) Signal Conditioning Module (SCM):-

All the analog signals are terminated at SCM. SCM provides isolation and conditioning of the signal. The output of SCM is uniform i.e. 0.5Vdc

to 4.5Vdc signal.

The SCM converts the field signal in the range of 0.5V to 4.5Vdc. This signal is connected to analog input (AI) card. 30 such inputs are

connected to one AI card and 10 such AI cards are there in one I/O. These AI cards are used to mutiplexing and converting the signal from analog to

digital. 32 Ch. ADC & multiplexer are used in AI cards. Ch no. 16 and Ch no. 32 are used as a reference low and reference high channels.

iv) Digital input card:-

The field input contacts are terminated at digital I/P cards through BTC. 32

such field inputs are connected to each digital card. 10 such digital input

cards are available in each I/O. Each I/O handles 320 nos. potential free field contacts suitable for 24Vdc operation and voltage level inputs.

v) I/O Bus interface card:-

I/O bus interface card is used as a buffer card and transferring the data to the I/O bus.

vi) I/O Bus to ISA Bus interface card:-

Once the data is transferred to the I/O bus it is required to be fed to the industrial PC for computing the data. To communicate between I/O bus and ISA

bus interface card is used. Once the data is transferred to ISA bus now it is available to industrial PC for processing.

vii) Industrial PC:- It is Dual redundant industrial Pentium -II 233 MHz PC. Dual PCs are

available in single housing. The digital data is processed here and converted into raw value. This raw value is transferred to server, through Local Area

Network (LAN) Soft ware of each PC checks the healthiness of the other redundant PC.

viii) Server:-

There are two servers in which one is active server & other is standby server. These servers work in hot stand mode. Each server has the plant database. It

updates the data by communicating with every I/O node in the system, sends output to the printers connected on request and sending data request query to the

I/O nodes and data to the display station periodically. It is a Pentium - III 500 MHz computer.

ix) Display Station:- This is a client of the server to display the data in different formats like bar

charts, trends curves, dynamic value of parameters etc. Display stations are installed at panels of C/R. These are abbreviated as UCRT & ACRT. Total

numbers of UCRT’s and ACRT’s are as follows in each unit.

UCRT - Utility Cathode Rays Tube -10 Nos. ACRT - Alarm Cathode Rays Tube -02 Nos.

UCRT - To display the bar chart trending, dynamic value and taking the

print out of the query generated by the user.

ACRT - To display the current alarms and printing on alarm printer with audio sound.

x) POWER SUPPLY:-

There are following type of power supply used for one I/O system.

i) 24VDC - For SCM power supply & digital contact inputs.

ii) ±15VDC - For operational amplifiers

iii) +5VDC - For logic ckt

COMMUNICATION SYSTEM AT

NAPS:

VERY SMALL APERTURE TERMINAL (VSAT) SATELLITE

COMMUNICATION SYSTEMS

A very small aperture terminal (VSAT) is a two way satellite ground station

with a dish antenna that is smaller than 3meters, VSAT data rates typically range from narrowband up to 4M bits/s. VSAT access satellite in

geosynchronous orbit to relay data from small earth station (terminals) to other terminals (in mesh configuration) or master earth station ”hubs” (in star

configuration). A VSAT end user needs a box that interface between the user’s computer and

an outside antenna with a transceiver. The transceiver receives or sends a signal to a satellite transponder in the sky. The satellite sends and receives signal from

an earth station computer that act as a hub for the system. Each end user is interconnected with the hub station via the satellite in a star topology. For one

end users to communicate with another, each transmission has to first go to the hub station, which retransmits it via the satellite to the other end users VSAT.

VSAT handles data, voice and video signals.

VSAT offers a number of advantages over terrestrial alternative for private application companies can have total control of their own communication

system without dependence on their companies Business and home users get higher speed reception than if using ordinary telephone services.

POWER LINE CARRIER COMMUNICATION Apart from other modes of communication like telephone system, wireless etc., communication can also be established through the transmission line, which is

known as Power Line Carrier Communication (PLCC). This system provides direct and independent communication between main plant and other

substations and load dispatch center of U.P. State Electricity Board (UPSEB) grid. This will be exclusively used for communication in relation to Power

System Operation and control. The carrier communication system is coupled to the 220KV power lines through coupling Capacitor Voltage Transformers (C.V.T’S).

Public address System A public address system (PA system) is an electronic amplification system

with a mixer, amplifier and loudspeakers, used to reinforce a sound source, e.g.,

a person giving a speech, a DJ playing pre-recorded music, and distributing the

sound throughout a venue or building.

Small systems

The simplest PA systems consist of a microphone, a modestly powered mixer

amplifier and one or more loudspeakers. Simple PA systems of this type, often

providing 50 to 200 watts of power, are often used in small venues such as

school auditoriums, churches, and small bars. A sound source such as a CD

player or radio may be connected to a PA system so that music can be played

through the system.

Public address systems typically consist of input sources, preamplifiers and/or

signal routers, amplifiers, control and monitoring equipment, and loudspeakers.

Input sources refer to the microphones and CD Players that provide a sound

input for the system. These input sources are fed into the preamplifiers and

signal routers that determine the zones to which the audio signal is fed. The

preamplified signals are then passed into the amplifiers. Depending on a

country's regulations these amplifiers will amplify the audio signals to 50V,

70V or 100V speaker line level. Control equipment monitors the amplifiers and

speaker lines for faults before it reaches the loudspeakers. This control

equipment is also used for separating zones in a PA system. The loudspeaker is

used to transduce electrical signals into analog sound signals.

Large systems

Some PA systems have speakers that cover an entire campus of a college or

industrial site, or an entire outdoor complex (e.g., an athletic stadium). More

than often this PA system will be used as voice alarm system that make

announcement during emergency to evacuate the occupants in a building.

Telephone paging systems

Some analog or IP private branch exchange (PBX) telephone systems use a

paging facility that acts as a liaison between the telephone and a PA amplifier.

In other systems, paging equipment is not built into the telephone system.

Instead the system includes a separate paging controller connected to a trunk

port of the telephone system. The paging controller is accessed as either a

designated directory number or central office line. In many modern systems, the

paging function is integrated into the telephone system, and allows

announcements to be played over the phone speakers.

REFERENCES:

i) Wikipedia

ii) NPCIL

iii) Nuclear Physics

iv) NAPS STC guide