ENVIRONMENTAL QUALIFICATION (EQ) OF SAFETY EQUIPMENTS …sresa.org.in/L11-2PKumar.pdf · environmental qualification (eq) of safety equipments for indian nuclear power plants (npps)

ENVIRONMENTAL QUALIFICATION (EQ)

OF SAFETY EQUIPMENTSFOR INDIAN NUCLEAR

POWER PLANTS (NPPs)

By P. Kumar AD(OES), NPCIL

ENVIRONMENTAL QUALIFICATION (EQ)

OF SAFETY EQUIPMENTSFOR INDIAN NUCLEAR

POWER PLANTS (NPPs)

By P. Kumar AD(OES), NPCIL

General Plant Layout – PHWR(TAPP 3&4)

Workshop on 'Reliability and Life Assessment of Electronic Systems - Methods & Techniques'

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Link to DBA

Reactor Building


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Fabrication of Equipment for NPPs• Stringent Specification /requirements• Conservative design • Stringent derating guidelines for components• Use of JSS approved/MIL grade/Screened

components• PCBs made as NPCIL guidelines from approved

vendors• Vendor selection after thorough evaluation/

assessment• In Process Quality Control/stage inspection at

various stages of manufacturing• Well documented reports (History Docket)

Acceptance Tests • Visual/Mechanical inspection• IR/Voltage proof test• Pre-functional Tests• Functional Tests(varied power supply)• Burn-in-Test• EMC Test • Climatic Tests

– Dry Heat Test– Damp Heat Test

• Seismic Test


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Why Environmental Qualification (EQ) for NPPs?

• Environmental requirements of Equipment/ components of a conventional plant and a Nuclear Power Plant are different.

• In NPP even after the Nuclear Reactor is shutdown, decay heat is to be continuously removed to maintain the fuel integrity. Hence many safety/ safety related equipment have to operate satisfactorily even after shut down of the reactor.

• Components/equipment are exposed to nuclear radiation

….Contd

Environmental Qualification for NPP• Design Basis Accidents in NPPs

– Loss of Coolant Accident(LOCA)– Main Steam Line Break(MSLB)– In case of an accident, environmental conditions – pressure

temperature, humidity and radiation increases rapidly. There may be some chemical spray also. These results into harsh environment within the containment.

– Typical values for LOCA : Temperature 119 0 C and pressure 0.87 kg/cm2(g) for a short duration. Radiation exposure canbe as high as 1 M Rad

– Typical values for MSLB : Temperature 1630 C and pressure 1.34 kg/cm2(g) for a short duration. No radiation

– The environmental conditions return to near normal , with high humidity , in about two hours.

– There is a probability of a seismic event occurring after the above event which also needs to be addressed.

Link LOCA CurveLink to MSLB Curve


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Why Environmental Qualification?

• All safety related instruments/equipment need to perform satisfactorily during normal as well as accident period which also includes a seismic event

• In order to meet the above intended function, equipment have to be specifically designed, evaluated/tested and qualified.

• Environmental qualification shall demonstrate that equipment will perform its required function during and following a design basis accident, taking into consideration stressors associated with all service conditions

• The above forms the basis of Environmental Qualification (EQ)

Primary Safety FunctionIn case of an accident following funtions are to be carried out–Safe shut down of Reactor –Core heat removal –RB containment box-up & Cooling


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APPLICABLE STANDARDS AND GUIDES• IEEE-323 Standard for Qualifying Class-1E Equipment for Nuclear Power

Generating Stations• CSA –N 290.13-05 Environmental Qualification of Equipment for CANDU

Nuclear Power Plants• IEEE-317 Electrical Penetration Assemblies in Containment Structures for

Nuclear Power Generating Stations• IEEE-383 Type Testing of Class 1E Electric Cables, Field splices and

Connections for Nuclear Power Generating Stations• IEEE-344 Recommended Practice for Seismic Qualification of Class 1E

Equipment for Nuclear Power Generating Stations• IEEE-334 Qualification of Continuous Duty 1E Motors for Nuclear Power

Generating Stations• IEEE-382 Qualification of Safety-Related Actuators for Nuclear Power

Generating Stations• AERB Code SG/D-1 Safety Classification and Seismic Categorisation for

Structures , Systems and Components of Pressurized Heavy Water Reactors • IAEA Safety Reports Series No. 3 - Equipment Qualification In Operational

Nuclear Power Plants: Upgrading, Preserving And Reviewing

11

EQ PROCESS • Master list preparation

Major Inputs requireda. Component and its details b. Tag No. c.Normal environmental conditions d. Accidental environmental conditions e. Radiation dosef. Qualification level g. Function and Mission timeh. Categorization for qualification


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Categorization for Qualification

• Category 1- To be tested • Category 2- To be modified & tested

• Category 3- Justification Note• Category 4- To be replaced• Category 5- Already qualified

Mission time

One of the most important parameters that needs to be specified in the EQ Masterlist is the ‘Mission time’ for an equipment .This is the period of time over which a system or an equipment (or its component) is required to perform the function successfully to meet its design requirements, after the initiation of a design basis accident . It may be noted that mission times may be different for various equipment (or its component) within the same system .


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QUALIFICATION METHODS

• Type testing • Operational experience/feedback• Justification • Combination of any of the above

A TYPICAL EQ TESTING SEQUENCE & ACCEPTANCE CRITERIA

Testing Sequence• Radiation Ageing* • Thermal Ageing* • LOCA/MSLB Chamber test • Seismic Test

* Order of testing can be interchanged


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Acceptance Criteria • Individual Test procedures are being

prepared and issued for all the instruments • Performance tests are carried out and

baseline data is generated.• Equipment is evaluated after each of the

EQ tests and is compared with baseline data.

• Wherever possible, performance is evaluated while the equipment is undergoing EQ test

• Acceptance is subject to the deviations within the specified limits arrived based on the performance requirements.

RADIATION AGEING

• Total Dose = Cumulative dose over the service life + 1.1 x Accident dose

• Maximum Dose Rate = 1 MRad/hr


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Temperature and Radiation resistance properties of Elastomers

Parameters Natural Rubber

Neoprene Nitrile Rubber( BUNA-

N)

EPDM Viton Butyl Rubber

Teflon Nylon 6

Max. Temperature

700C 900C 1100C 1200C 2040C 1000C 200 0C 1100C

Max. Radiation Dose in MRad

10 6 10 65 0.8 6 6 50

THERMAL AGEING

• Normal Ageing cannot be resorted to find out the life of the components as it takes very long time .

• Accelerated thermal ageing process is adopted to reduce the time of testing -Time of testing is computed by Arrhenius Equation.

• The test is carried out in thermal chamber at an elevated temperature – limited to about 100 C above the maximum operating temperature.

• Thermal ageing should last for a minimum of 100 hours


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ARRHENIUS METHODOLOGY

• Arrhenius methodology is generally used approach for describing the relationship between material life and temperature. The Arrhenius model is valid when a dominant chemical reaction controls the thermal ageing process. Other reactions can occur, however, if they are not controlling, the use of the Arrhenius equation is still valid.

R=Ae(-Ea/KBT)

R= Reaction rate Ea = Activation energy of the reaction KB=Boltzmann’s constant (1.38 x 10-23 J/K)T= Absolute Temperature As a thumb rule , reaction rate doubles for every 10 Deg C

rise

LOCA/MSLB CHAMBER TEST

•LOCA chamber simulates the harsh environment resulting due to LOCA/MSLB.•This tests the ability of the equipment to perform its requiredsafety function while being subjected to the pressure, temperature, and humidity effects associated with the environment of a designbasis accident. •The test conditions shall encompass the pressure -temperature conditions arrived based on analysis, including the margins :Pressure -10% of peak transient gauge pressure to a maximum of

70 kPa Temperature - 8oC over and above the peak transient temperatureTesting period : Maximum 48 hours

Link to MSLB Profile Link to LOCA Profile


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SEISMIC TEST

• Shake table is used for seismic testing.

• Equipment is tested for range up to 3.5 g in all the 3 orthogonal axes for a Frequency range varying from 1 to 50 Hertz.

EQUIPMENTS NORMALLY QUALIFIED BY EQ TESTING

• PRV• Limit Switch• Solenoid Valve• E/A Converter • Transmitter • Junction Box• Pressure Switch• RTDs• Motors• Cable


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EQUIPMENTS QUALIFIED BY JUSTIFICATION

• Valves & Valve Actuators • Heat Exchangers • Pumps

Experience with EQ testing• All equipment have passed Radiation Ageing Test

except Electronic Transmitters.• Following have been qualified successfully.

– All the Control and Power cables (PVC, FRLS, etc.)– Cable EPs– Scale Down models of safety system motors.– Pressure Switch– RTDs, Solenoid Valves, Limit Switches of some

manufacturers


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Equipment which could not pass through at different stages of EQ

• Indigenous make Limit Switch failed due to moisture ingress during LOCA –Efforts are being made to resolve this problem

• PRV failed during Thermal Ageing due to use of plastic parts – use metallic/superior elastomers. With the above changes PRV successfully qualified

• JBs failed due to moisture ingress during LOCA• Electronic Transmitters

Work done on Electronic Transmitters• Transmitters(imported/local make)failed both

during Radiation Ageing & LOCA test without Radiation Ageing.

Efforts taken:• Improved shielded enclosure provided• Studied closely the behavior of various stages

the circuit at high temperature by using improvised arrangement ie by using a domestic for pressure cooker and accordingly made necessary changes.

• Successfully tested upto 1070 C for about 50 minutes


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Improvised set up for LOCA test Development of Transmitter

Improvised set up for LOCA test Development of Transmitter


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Test Facilities available in India

• RSD BARC– Radiation Ageing, Thermal Ageing, LOCA test

• R&D Centre, TAPS 3&4• Thermal Ageing and LOCA test

• ERDA, Vadodara • Thermal Ageing and LOCA test

Shake Table test facilities in India• ERDA, Baroda : 150 Kg Uniaxial shaketable (0.6m x 0.6m)

• ECIL, Hyderabad : 100 Kg Uniaxial shaketable(0.7m x 0.7m), 35 cm stroke length

• SERC, Chennai : 30 T Triaxial shaketable (4m x 4m), 4 vertical & 4 hori. Actuators

• CPRI, Bangalore : 10 T Triaxial table(3m x 3m), 4 ver & 4 hor actuators

• IGCAR, : 10 T Triaxial tableKalpakkam (4m x 4m), 4 ver & 4 hor actuators

• IIT Roorkee : 20 T Biaxial shaketable(3.5m x 3.5m), 2 ver & 1 hor actuator 32


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PRESERVING ENVIRONMENTAL QUALIFICATION

• After establishing qualification , the same has to be preserved through out the operating life of the plant

• Preservation Manuals are to made and are to be strictly followed– Color coding /separate tagging for qualified equipment– Strict controls shall be exercised during procurement,

storage and replacement.– Replacement plan for the identified parts shall be strictly

monitored– Condition monitoring to be implemented wherever

required.– Record of baseline data of all the EQ equipment shall be

maintained.– History docket shall be maintained

Acknowledgement

• Bulk of EQ testing was conducted at RSD, BARC. About 150 equipment have been tested and about 70 have been completed upto LOCA test. As on date, all the three tests (Radiation, Thermal and LOCA Chamber) can be carried out only at RSD, BARC.

• RSD, BARC also extended support in establishing LOCA and Thermal test Facilities at R&D Centre, TAPS 3&4

We take this opportunity to thank RSD, BARC for their unstinted support.

•


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Thank you………

Transient LOCA profile encompassed by LOCA chamber test profile

Link to Chamber testWhy EQ


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Transient MSLB profile encompassed by MSLB chamber test profile

Link to Chamber testLink to Why EQ

LOCA & Thermal Chamber Test Facility at ERDA

Link to Test Facilities


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Thermal Chamber Facility at R&D Centre TAPS 3&4

Link to Test Facilities

LOCA Chamber at R&D Centre TAPS 3 &4

Link to Test FacilitiesLink to LOCA Test US Autoclave


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Transient LOCA profile encompassed by LOCA chamber test profile

Link to Chamber test

Transient MSLB profile encompassed by MSLB chamber test profile

Link to Chamber testLink to Why EQ


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Limit Switch Failed in LOCA test

Leak Path

Link to Failed Eqpt

Steam Autoclave Test Chamber in US

Link to LOCA Test


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Documents

ENVIRONMENTAL QUALIFICATION (EQ) OF SAFETY EQUIPMENTS …sresa.org.in/L11-2PKumar.pdf · environmental qualification (eq) of safety equipments for indian nuclear power plants (npps)