Embrittlement recovery due to annealing of reactor pressure vessel steels

Technical Report · Fri Mar 01 04:00:00 EST 1996

DOI:https://doi.org/10.2172/269672· OSTI ID:269672

Eason, E. D.; Wright, J. E.; Nelson, E. E. ^[1]; Odette, G. R.; Mader, E. V. ^[2]

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1. Modeling and Computing Services, Boulder, CO (United States)
2. Univ. of California, Santa Barbara, CA (United States)

Embrittlement of reactor pressure vessels (RPVs) can be reduced by thermal annealing at temperatures higher than the normal operating conditions. Although such an annealing process has not been applied to any commercial plants in the United States, one US Army reactor, the BR3 plant in Belgium, and several plants in eastern Europe have been successfully annealed. All available Charpy annealing data were collected and analyzed in this project to develop quantitative models for estimating the recovery in 30 ft-lb (41 J) Charpy transition temperature and Charpy upper shelf energy over a range of potential annealing conditions. Pattern recognition, transformation analysis, residual studies, and the current understanding of the mechanisms involved in the annealing process were used to guide the selection of the most sensitive variables and correlating parameters and to determine the optimal functional forms for fitting the data. The resulting models were fitted by nonlinear least squares. The use of advanced tools, the larger data base now available, and insight from surrogate hardness data produced improved models for quantitative evaluation of the effects of annealing. The quality of models fitted in this project was evaluated by considering both the Charpy annealing data used for fitting and the surrogate hardness data base. The standard errors of the resulting recovery models relative to calibration data are comparable to the uncertainty in unirradiated Charpy data. This work also demonstrates that microhardness recovery is a good surrogate for transition temperature shift recovery and that there is a high level of consistency between the observed annealing trends and fundamental models of embrittlement and recovery processes.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (United States). Office of Nuclear Regulatory Research; Brookhaven National Lab., Upton, NY (United States)
• OSTI ID: 269672
• Report Number(s): NUREG/CP--0149-Vol.3; CONF-9510156--Vol.3; ON: TI96007986
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
22 GENERAL STUDIES OF NUCLEAR REACTORS
36 MATERIALS SCIENCE
ANNEALING
CHARPY TEST
DIAGRAMS
EMBRITTLEMENT
MATHEMATICAL MODELS
NUMERICAL DATA
PWR TYPE REACTORS
REACTOR VESSELS