On the estimation of WWER-1000 RPV materials embrittlement by a standard surveillance program

V. Vasilchenko, V. KovyrshinState Scientific and Technical Centre NRS, Kiev, Ukraine

E. Grynik, V. Revka, Institute for Nuclear Research NASU, Kiev, Ukraine

Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia 2

Background WWER-1000 RPV material radiation embrittlement estimation is based on valid

Charpy impact test data (according to PNAE G-7-002-86 a fluence scatter for specimens should not exceed 15 %)

There are some shortcomings in surveillance assembly design related to a high scatter ( 35 %) in fluence values for irradiated Charpy V-notch specimens

The high scatter in fluence values raises doubts regarding the estimation of a critical brittleness temperature shift

Some surveillance sets include the modernized assemblies with flat containers that allows irradiating the Charpy V-notch specimens according to PNAE G-7-002-86 requirements

Specimen reconstitution technique is also used to get valid surveillance test data

What is the difference in RPV material radiation embrittlement rate estimated by standard and modernized surveillance program, and the reconstitution technique

Objective

Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia 3

Materials and specimens

WWER-1000 RPV weld metal with high nickel (1,55  1,88 % wt) and

manganese (0,67  0,97 % wt) content

Surveillance Charpy V-notch specimens (10 mm x 10 mm x 55 mm)

Standard surveillance program

• Khmelnitsk NPP-1 (Kiev Institute for Nuclear Research)

• Rovno NPP-3, South-Ukrainian NPP-2, Zaporozhye NPP-3 (RSC Kurchatov

Institute)

Modernized surveillance program

• South-Ukrainian NPP-2 (Kiev Institute for Nuclear Research)

Reconstitution technique

• Rovno NPP-3, South-Ukrainian NPP-2, Zaporozhye NPP-3 (RSC Kurchatov

Institute)

Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia 4

Radiation shift for Rovno NPP-3 weld metal

Reconstitution technique provides with ∆TF shift data for higher neutron fluence

Reconstitution technique results in a high scatter of ∆TF shift data relative to a regression line

Standard surveillance program gives a chemistry factor AF that is in a good agreement with embrittlement rate estimated using a reconstitution technique

Charpy impact test data from the standard surveillance program may be considered as valid for Rovno NPP-3 unit

Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia 5

Radiation shift for Khmelnitsk NPP-1 weld metal

4 irradiated surveillance sets allow specimens to be grouped by fluence to meet PNAE G-7-002-86 requirements without a reconstruction

∆TF shift data based on the different

approaches describe a tendency of material radiation embrittlement in the same way

Chemistry factor AF based on the

standard surveillance test data can be used to estimate the KHNPP-1 weld metal embrittlement rate

Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia 6

A comparison of radiation embrittlement rate

Notes: *) specimen grouped by neutron fluence

**) modernized surveillance assembly

Unit

AF, 0C

(standard surveillance program)

AF, 0C

(reconstitution technique)

RONPP-3 12,6 11,8

KHNPP-1 22,1 22,6 *)

SUNPP-2 22,9 24,0

SUNPP-2 22,0 **) 24,0

ZANPP-3 16,2 13,0

Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia 7

Radiation embrittlement rate according to the different approaches

There is a good correlation between the AF values for KHNPP-1, SUNPP-2

and RONPP-3 units

Chemistry factor AF for ZANPP-3

based on the reconstitution technique is noticeably less in comparison to standard surveillance test data

Application of the reconstitution technique does not always confirm the embrittlement rate obtained from a standard surveillance program

Open symbol is data for SUNPP-2 modernized assembly

Safety Assurance of NPP with WWER MNTK-2007 , May 29 – June 1 2007, FSUE EDO “GIDROPRESS”, Podolsk, Russia 8

Conclusions

Standard surveillance program gives a chemistry factor AF that is in a

good agreement with embrittlement rate estimated using a reconstitution technique for KHNPP-1, SUNPP-2 and RONPP-3 RPV weld metal

Chemistry factor AF for ZANPP-3 RPV weld metal based on the

reconstitution technique is noticeably less in comparison to standard surveillance test data

Charpy impact test data from the standard surveillance program can be used to get a reliable estimation of weld metal radiation embrittlement rate for KHNPP-1, SUNPP-2, RONPP-3 and ZANPP-3 units