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Title: The Information Fusion Embrittlement Models for U.S. Power Reactor Pressure Vessel Steels

Abstract

The complex nonlinear dependencies observed in typical reactor pressure vessel (RPV) material embrittlement data, as well as the inherent large uncertainties and scatter in the radiation embrittlement data, make prediction of radiation embrittlement a difficult task. Conventional statistical and deterministic approaches have only resulted in rather large uncertainties, in part because they do not fully exploit domain-specific mechanisms. The domain models built by researchers in the field, on the other hand, do not fully exploit the statistical and information content of the data. As evidenced in previous studies, it is unlikely that a single method, whether statistical, nonlinear, or domain model, will outperform all others. More generally, considering the complexity of the embrittlement prediction problem, it is highly unlikely that a single best method exists and is tractable, even in theory. In this paper, we propose to combine a number of complementary methods including domain models, neural networks, and nearest neighbor regressions (NNRs). Such a combination of methods has become possible because of recent developments in measurement-based optimal fusers in the area of information fusion. The information fusion technique is used to develop radiation embrittlement prediction models for reactor RPV steels from U.S. power reactors, including boiling water reactors andmore » pressurized water reactors. The Charpy transition temperature-shift data is used as the primary index of RPV radiation embrittlement in this study. Six Cu, Ni, P, neutron fluence, irradiation time, and irradiation-parameters are used in the embrittlement prediction models. The results-temperature 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.« less

Authors:
 [1];  [1];  [2]
  1. ORNL
  2. AOL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Center for Computational Sciences
Sponsoring Org.:
Work for Others (WFO)
OSTI Identifier:
931640
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: ASTM 23rd Symposium on Effects of Radiation on Materials, San Jose, CA, USA, 20060612, 20060615
Country of Publication:
United States
Language:
English
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; 36 MATERIALS SCIENCE; EMBRITTLEMENT; IRRADIATION; NEURAL NETWORKS; NEUTRON FLUENCE; POWER REACTORS; PRESSURE VESSELS; PWR TYPE REACTORS; RADIATIONS; REGULATORY GUIDES; STEELS; TEMPERATURE DEPENDENCE; WATER

Citation Formats

Wang, Jy-An John, Rao, Nageswara S, and Konduri, Savanthi. The Information Fusion Embrittlement Models for U.S. Power Reactor Pressure Vessel Steels. United States: N. p., 2007. Web.
Wang, Jy-An John, Rao, Nageswara S, & Konduri, Savanthi. The Information Fusion Embrittlement Models for U.S. Power Reactor Pressure Vessel Steels. United States.
Wang, Jy-An John, Rao, Nageswara S, and Konduri, Savanthi. Mon . "The Information Fusion Embrittlement Models for U.S. Power Reactor Pressure Vessel Steels". United States. doi:.
@article{osti_931640,
title = {The Information Fusion Embrittlement Models for U.S. Power Reactor Pressure Vessel Steels},
author = {Wang, Jy-An John and Rao, Nageswara S and Konduri, Savanthi},
abstractNote = {The complex nonlinear dependencies observed in typical reactor pressure vessel (RPV) material embrittlement data, as well as the inherent large uncertainties and scatter in the radiation embrittlement data, make prediction of radiation embrittlement a difficult task. Conventional statistical and deterministic approaches have only resulted in rather large uncertainties, in part because they do not fully exploit domain-specific mechanisms. The domain models built by researchers in the field, on the other hand, do not fully exploit the statistical and information content of the data. As evidenced in previous studies, it is unlikely that a single method, whether statistical, nonlinear, or domain model, will outperform all others. More generally, considering the complexity of the embrittlement prediction problem, it is highly unlikely that a single best method exists and is tractable, even in theory. In this paper, we propose to combine a number of complementary methods including domain models, neural networks, and nearest neighbor regressions (NNRs). Such a combination of methods has become possible because of recent developments in measurement-based optimal fusers in the area of information fusion. The information fusion technique is used to develop radiation embrittlement prediction models for reactor RPV steels from U.S. power reactors, including boiling water reactors and pressurized water reactors. The Charpy transition temperature-shift data is used as the primary index of RPV radiation embrittlement in this study. Six Cu, Ni, P, neutron fluence, irradiation time, and irradiation-parameters are used in the embrittlement prediction models. The results-temperature 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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • The information fusion technique is used to develop radiation embrittlement prediction models for reactor pressure vessel (RPV) steels from U.S. power reactors, including boiling water reactors and pressurized water reactors. The Charpy transition temperature-shift data is used as the primary index of RPV radiation embrittlement 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,more » 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.« less
  • 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 Database 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.more » 2. The implications of dose-rate effect and irradiation temperature effects for the development of radiation embrittlement models are also discussed.« less
  • This three-volume report contains papers presented at the Twenty-Fourth Water Reactor Safety Information Meeting held at the Bethesda Marriott Hotel, Bethesda, Maryland, October 21--23, 1996. The papers are printed in the order of their presentation in each session and describe progress and results of programs in nuclear safety research conducted in this country and abroad. Foreign participation in the meeting included papers presented by researchers from Czech Republic, Finland, France, Japan, Norway, Russia and United Kingdom. This volume is divided into the following sections: reactor pressure vessel embrittlement and thermal annealing; reactor vessel lower head integrity; and evaluation and projectionmore » of steam generator tube condition and integrity. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.« less
  • Annealing studies of irradiated and unirradiated pressure vessel steel have led to the conclusion that an active defect complex (ADC) is responsible for the enhanced embrittlement associated with steels containing significant levels of copper (>0.1%). These complexes, which already exist in the unirradiated steel, accumulate vacancies, produced either thermally or by neutron bombardment, and grow to such a size that the dislocation mobility is impaired and the yield stress increased. The number density of the sites appears to be a function of the copper level in the steel. Thus in low-copper steels the site spacing is too great to affectmore » the yield stress. The stable size of the complex seems to be an inverse function of temperature. Thus after preservice stress relief heat treatment the sites are too small to influence the mechanical properties of the vessel steel. At lower temperatures, however, exposure to a vacancy flux causes the sites to grow to their equilibrium size at a rate determined by both the availability of vacancies and the number density of the sites. Post-irradiation annealing will cause the ADCs to shrink to a size that is stable at the annealing temperature. The ADCs also act as traps to positions and cause the line shape of the 511-keV annihilation peak to narrow. This effect appears to be related to the site size. Herein lies a prospect for remote interrogation of a reactor pressure vessel to assess the state of embrittlement resulting from this mechanism, both through life and after annealing.« less