SURVEILLANCE

PROGRAMMES FOR 60+

Milan BrumovskyUJV REZ, CZECH REPUBLIC

NUCLEAR CODES & STANDARDS WORKSHOP

July 7-8, 2014

RPV INTEGRITY AND LIFETIME

MAIN CONCERN OF RADIATION DAMAGE IN RPV IS EMBRITTLEMENT IN RPV BELTLINE THAT AFFECTS THE RPV INTEGRITY EVALUATION IN TWO ASPECTS:

IN NORMAL OPERATING CONDITIONS AND DURING PRESSURE TESTS – RADIATION EMBRITTLEMENT CREATES A SHIFT OF TEMPERATURE DEPENDENCE OF FRACTURE TOUGHNESS, I.E. PRESSURE-TEMPERATURE LIMITS TO THE HIGHER TEMPERATURES AND THUS THE GAP BETWEEN MINIMUM ALLOWED p-T LIMITS AND MAXIMUM ALLOWABLE ONES IS NARROWING AND THUS THE OPERATION IS BECOMING MORE COMPLICATEDDURING PRESSURIZED-THERMAL-SHOCK EVENTS p-T LIMITS ARE APPROACHING THE MAXIMUM ALLOWABLE ONES AND THUS SAFETY MARGING ARE STRONGLY DECREASING

RADIATION DAMAGE

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RADIATION EMBRITTLEMENT DEPENDS ON:

NEUTRON FLUENCE

IRRADIATION TEMPERATURE

TYPE OF STEEL – CARBON STEEL, LOW-ALLOY STEEL, MARAGING..

CONTENT OF IMPURITIES – P, Cu, ..Sb, Sn, As

ALLOYING ELEMENTS – Ni, Mn, …

RADIATION EMBRITTLEMENT

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RADIATION DAMAGE IS USUALLY EXPRESSED AS:

- RADIATION HARDENING- USUALLY NO PREDICTIVE FORMULAE IN CODES

- RADIATION EMBRITTLEMENT- PREDICTIVE FORMULAE IN CODES DIFFER FOR DIFFERENT MATERIALS/ COUNTRY OF PRODUCTION:

-US NRC REG.GUIDE 1.99/10 CFR 50.61A/ASTM E 900-2,

-RCC-M/RSE-M - FIM (BASE METAL), FIS (WELD METAL) – FRANCE

-KTA 3201, 3203 – GERMANY

-JEAC 4201-200 – JAPAN

- PNAE-G 7-002-86, IAEA TECDOC 1442 – WWER-440

-RD EO 1.1.2.09.0789-2009 – WWER-1000

- IAEA NULIFE VERLIFE (2012) – WWER RPVs

RADIATION EMBRITTLEMENT

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RADIATION EMBRITTLEMENT

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. OPERATING LIFETIME FLUENCE FOR WWERs, PWRs AND THE BWR

REACTOR TYPE FLUX, n.m-2

.sec-1

(E>1MeV)

LIFETIME* FLUENCE, n.m-2

(E>1MeV)

WWER-440 core weld 1.2 x 1015

1.1 x 1024

WWER-440 maximum 1.5 x 1015

1.6 x 1024

WWER-1000 3-4 x 1014

3.7 x 1023

PWR (W) 4 x 1014

4 x 1023

PWR (B&W) 1.2 x 1014

1.2 x 1023

BWR

4 x 10

13 4 x 10

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DESIGN FLUENCE FOR 40 YEARS OF OPERATION

RPV LIFETIME IS PRACTICALLY DETERMINED BY RPV BELTLINE MATERIALS RADIATION EMBRITTLEMENTRPV LIFETIME IS ASSESSED:

ON DESIGN STAGE: USING CODE PREDICTING FORMULAE FOR MATERIALS PLANNED FOR THE RPV MANUFACTURINGAND CALCULATED NEUTRON FLUENCE ON RPVDURING OPERATION: USING CODE PREDICTING FORMULAE FOR SPECIFIC BELTLINE MATERIALS USED IN THE GIVEN RPVAND CORRECTED WITH RESPECT TO REAL RADIATION EMBRITTLEMENT OF BELTLINE MATERIALS DETERMINED FROM TESTING SURVEILLANCE SPECIMENS (IRRADIATED INSIDE THE RPV AND PERIODICALLY WITHDRAWN)AND CALCULATED/EXPERIMENTALLY DETERMINED REAL NEUTRON FLUENCE ON RPVFOR LIFETIME EXTENSION: SURVEILLANCE DATA AND NEUTRON FLUENCE CALCULATION AND PREDICTION

RPV LIFETIME

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RPV LIFETIME IS USUALLY DETERMINED BY THE MAXIMUM ALLOWABLE SHIFT IN CHARACTERISTIC MATERIAL TRANSITION TEMPERATURE:

WESTERN PWR AND BWR - RTNDT BASED ON DROP WEIGHT TESTS AND CHARPY NOTCH IMPACT TESTS AND/OR STATIC FRACTURE TOUGHNESS TESTS (MASTER CURVE APPROACH)

WWER – BASED ON CHARPY IMPACT TESTS AND/OR STATIC FRACTURE TOUGHNESS TESTS (MASTER CURVE APPROACH)

TWO APPROACHES ARE APPLIED IN THIS ASSESSMENT:PWR BASED ON ASME DESIGN RULES (USA ORIGINAL DESIGN) –PROBABILISTIC APPROACHEUROPEAN PWR (INCLUDING WWER) –DETERMINISTIC APPROACH

BOTH APPPROACHES ARE NOT EQUIVALENT

RPV LIFETIME

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RADIATION DAMAGE IS EVALUATED BY TWO PRINCIPAL METHODS:

CALCULATING USING NORMATIVE TREND CURVES

CHECKING BY RESULTS OF SURVEILLANCE SPECIMEN TESTS

RADIATION DAMAGE EVALUATION

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NORMATIVE TREND CURVES

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PROBLEMS WITH USING NORMATIVE TREND CURVES –ETC:

RELATIVE LARGE SCATTER OF PREDICTIONS BASED ON CHEMICAL COMPOSITION OF RPV MATERIALS

up to ± 50 °Ce.g.

AFTER

M.KIRK

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NORMATIVE TREND CURVES

PROBLEMS WITH USING RESULTS OF SURVEILLANCE SPECIMEN TESTING:

UNDERPREDICTED SHIFTS FOR HIGH NEUTRON FLUENCE

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AFTER

W.SERVER

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NORMATIVE TREND CURVES

PROBLEMS WITH USING RESULTS OF SURVEILLANCE SPECIMEN TESTING:

ONLY FEW DATA FOR LARGE FLUENCESS NECESSARY FOR RPV LIFETIME EXTENSION TO 60+ YEARS

6.8.201

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40 Y

Surveillance Guidelines for Life extension were developed in the project

The guidelines briefly describe several promising tools and techniques that can be used for embrittlement monitoring during life extension periods:

Reconstitution of broken specimens,

Use of miniature specimens,

Advanced fracture toughness approaches (Master Curve, Unified Curve),

Enhanced surveillance strategy

EU PROJECT - LONGLIFE

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Testing a different capsule (with a higher lead factor) than originally planned.

•Irradiate the standby capsules, if available, in positions with a higher lead factor.

•Retain surveillance capsules in vessel for longer period of time, then increasing the neutron fluence accumulated by the capsule.

•Move the surveillance capsule to a higher lead factor position in the vessel. For example, to empty position of previous removed and tested surveillance capsule.

•Reinsert previously removed capsule for additional irradiation (using specimen reconstitution if needed).

•Manufacture new capsule if archive materials are available. E.G. SUPPLEMENTARY AND EXTENDED SURVEILLANCE PROGRAMMES FOR WWER-440 IN NPP DUKOVANY (CZECH), PAKS (HUNGARY), BOHUNICE AND MOCHOVCE (SLOVAKIA)

Extension of the standard surveillance programmes

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Suitable alternatives to the lack of archivematerials are:

•The reconstitution of specimens from tested capsules.

•The use of an integrated surveillance programme. •The use of “tailored” or “surrogate” material. This strategy was used by Loviisa NPP Unit 1,Bohunice 1 and 2 and Rovno 1 in developing the new surveillance programme for operation after annealing

Availability of surveillance material

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Withdrawal schedule of Surveillance Capsules

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A Coordinated Reactor Vessel Surveillance Programme(CRVSP) can be used to obtain vessel embrittlement data with high fluence and long irradiation times.

The Guidelines give recommendations for developing a CRVSP.

EXAMPLES:INTEGRAL SURVEILLANCE PROGRAMME FOR WWER-1000 RPVs IN NPP TEMELIN FOR CZECH AND UKRAINIAN NPPs

Coordinated Surveillance Programmes

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GREAT EFFORT IS NOW CONCENTRATED ON IMPROVEMENT OF ETC – EXPERIMENTAL TREND CURVES – IN MANY PWR/BWR/WWER OPERATING COUNTRIES TO GET MORE PRECISE TRENDS, WITH LESS UNDERCONSERVATISM AND APPLICABLE FOR NEUTRON FLUENCES TO BE OBTAINED FOR 60+ YEARS OF OPERATION

THE BEST SOURCE OF RADIATION DAMAGE/EMBRITTLEMENT INFORMATION IS AND WILL BE ONLY SURVEILLANCE SPECIMEN PROGRAMMES, EITHER STANDARD OR EXTENDED/INTEGRATED etc.

CONCLUSIONS

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THANKS FOR YOUR KIND

ATTENTION

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