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Research Papers: Nuclear Power

# Weld Material Investigations of a WWER-440 Reactor Pressure Vessel: Results From the First Trepan Taken From the Former Greifswald NPP

[+] Author and Article Information
Udo Rindelhardt

Forschungszentrum Dresden-Rossendorf (FZD), PF 510119, D-01324 Dresden, Germanyu.rindelhardt@fzd.de

Hans-Werner Viehrig

Forschungszentrum Dresden-Rossendorf (FZD), PF 510119, D-01324 Dresden, Germanyh.w.viehrig@fzd.de

Joerg Konheiser

Forschungszentrum Dresden-Rossendorf (FZD), PF 510119, D-01324 Dresden, Germanyj.konheiser@fzd.de

Jan Schuhknecht

Forschungszentrum Dresden-Rossendorf (FZD), PF 510119, D-01324 Dresden, Germanyj.schuhknecht@fzd.de

J. Eng. Gas Turbines Power 131(2), 022904 (Jan 05, 2009) (7 pages) doi:10.1115/1.3032461 History: Received July 29, 2008; Revised August 06, 2008; Published January 05, 2009

## Abstract

Between 1973 and 1990 four units of the Russian nuclear power plants type WWER-440/230 were operated in Greifswald (former East Germany). Material probes from the pressure vessels were gained in the frame of the ongoing decommissioning procedure. The investigations of this material started with material from the circumferential core weld of unit 1. First, this paper presents results of the reactor pressure vessel (RPV) fluence calculations depending on different loading schemes and on the axial weld position based on the Monte Carlo code TRAMO . The results show that the use of the dummy assemblies reduces the flux by a factor of 2–5 depending on the azimuthal position. The circumferential core weld (SN0.1.4) received a fluence of $2.4×1019 neutrons/cm2$ at the inner surface; it decreases to $0.8×1019 neutrons/cm2$ at the outer surface. The material investigations were done using a trepan from the circumferential core weld. The reference temperature $T0$ was calculated with the measured fracture toughness values, $KJc$, at brittle failure of the specimen. The $KJc$ values show a remarkable scatter. The highest $T0$ was about $50°C$ at a distance of 22 mm from the inner surface of the weld. The Charpy transition temperature $TT41J$ estimated with results of subsized specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens. The VERLIFE procedure prepared for the integrity assessment of WWER RPV was applied on the measured results. The VERLIFE lower bound curve indexed with the Structural Integrity Assessment Procedures for European Industry (SINTAP) reference temperature, $RTT0SINTAP$, envelops the $KJc$ values. Therefore for a conservative integrity assessment the fracture toughness curve indexed with a RT representing the brittle fraction of a data set of measured $KJc$ values has to be applied.

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## Figures

Figure 1

WWER-440 reactor with trepan positions

Figure 2

Horizontal sectional drawing of the WWER-440 core with positions of dummy assemblies

Figure 3

Flux distribution E>0.5 MeV and 1.0 MeV outside of the RPV (110 cm above the core bottom)

Figure 4

Development of the fluences E>1.0 MeV and E>0.5 MeV at the inside of RPV in the flux maximum

Figure 5

The fluences E>1.0 MeV and the fluences E>0.5 MeV in an axial position 70 cm over the core bottom

Figure 6

The fluences E>0.5 MeV and E>1.0 MeV at the welds SN0.1.3, SN0.1.4, and SN0.1.5

Figure 7

Trepan 1-1 with the location of the welding seam

Figure 8

Cutting scheme of disk 1-1.1, as an example

Figure 9

Course of the reference temperatures T0 and T0SINTAP through the welding seam SN0.1.4

Figure 10

KJc values measured on Charpy size SE(B) specimens, adjusted to 1T (25.4 mm) specimen size, versus the test temperature normalized to T0 of the individual disks, and master curves

Figure 11

KJc values measured on Charpy size SE(B) specimens, adjusted to 1T (25.4 mm) specimen size versus the test temperature normalized to RTT0 of the different disks and VERLIFE lower bound curve

Figure 12

KJc values measured on Charpy size SE(B) specimens, adjusted to 1T (25.4 mm) specimen size versus the test temperature normalized to RTT0SINTAP of the different disks and VERLIFE lower bound curve

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