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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

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 2.4×1019neutrons/cm2 at the inner surface; it decreases to 0.8×1019neutrons/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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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

WWER-440 reactor with trepan positions

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Figure 2

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

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Figure 3

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

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Figure 4

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

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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

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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

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Figure 7

Trepan 1-1 with the location of the welding seam

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Figure 8

Cutting scheme of disk 1-1.1, as an example

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Figure 9

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

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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

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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

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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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