The development of radiation embrittlement models for US power reactor pressure vessel steels J.A. Wang * , N.S.V. Rao, S. Konduri Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States Received 6 January 2005; accepted 7 November 2006 Abstract A new approach of utilizing information fusion technique is developed to predict the radiation embrittlement of reactor pressure vessel steels. The Charpy transition temperature shift data contained in the Power Reactor Embrittlement Data- base is used in this study. Six parameters-Cu, Ni, P, neutron fluence, irradiation time, and irradiation temperature – are used in the embrittlement prediction models. The results indicate that this new embrittlement predictor achieved reductions of about 49.5% and 52% in the uncertainties for plate and weld data, respectively, for pressurized water reactor and boiling water reactor data, compared with the Nuclear Regulatory Commission Regulatory Guide 1.99, Rev. 2. The implications of dose-rate effect and irradiation temperature effects for the development of radiation embrittlement models are also discussed. Ó 2006 Elsevier B.V. All rights reserved. 1. Introduction The application of the information fusion tech- nique to RPV radiation embrittlement was first developed by the authors [1]. In this earlier work, general electric boiling water reactor (BWR) RPV surveillance data consisting of 112 RPV surveillance data points from RPV base and weld materials were used to develop embrittlement models. For this data, the information fusion approach achieved about 56% and 62% reductions in uncertainties for base and weld materials, respectively, compared to the prediction of the Nuclear Regulatory Commis- sion’s (NRC’s) Regulatory Guide 1.99, Rev. 2. Currently, based on the ASTM E10.02 database and the Oak Ridge National Laboratory (ORNL) Power Reactor Embrittlement Database (PR- EDB) [2,3], about 900 RPV surveillance transition temperature shift data points are available for base and weld materials from the US Power Reactor Surveillance Program. Despite the demonstrated effectiveness of the information fusion technique in predicting RPV embrittlement in BWR data [1], its scope is somewhat limited, since these BWR data constitute only a relatively small portion of the overall RPV surveillance data. Thus, further verifi- cation of the general applicability of the informa- tion fusion technique to determining the radiation 0022-3115/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2006.12.013 * Corresponding author. Fax: +1 865 574 2274. E-mail address: wangja@ornl.gov (J.A. Wang). Journal of Nuclear Materials 362 (2007) 116–127 www.elsevier.com/locate/jnucmat