Characteristics of the New Embrittlement Correlation Method for the Japanese Reactor Pressure Vessel Steels

2009 ◽  
Author(s):  
Naoki Soneda ◽  
Akiyoshi Nomoto
Keyword(s):  
Pressure Vessel ◽  
Correlation Method ◽  
Reactor Pressure Vessel ◽  
Surveillance Data ◽  
New Method ◽  
Rate Equations ◽  
Mathematical Form ◽  
Microstructural Changes ◽  
Pressure Vessel Steels ◽  
Reactor Pressure

Neutron irradiation embrittlement of reactor pressure vessel steels is an important ageing issue for the long term operation of light water reactors. A new embrittlement correlation method was developed by CRIEPI and the Japanese electric utilities in 2007. This method is primarily based on the fundamental understandings on the embrittlement mechanisms: i.e. microstructural changes were modeled by the mathematical form of rate equations, and the predicted microstructural changes were further correlated with the mechanical property changes in transition temperature region. The coefficients of the rate equations were optimized using the Japanese surveillance data of RPV embrittlement. This method was adopted as the revision of the Japanese code, JEAC 4201–2007, in 2007. In this paper, after a brief explanation on the new correlation method, the predictions of the new method will be investigated through comparisons with the previous correlation, JEAC4201–2004, and the US surveillance data in order to identify the characteristics of the new method.

Characteristics of the New Embrittlement Correlation Method for the Japanese Reactor Pressure Vessel Steels

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Naoki Soneda ◽  
Akiyoshi Nomoto
Keyword(s):  
Pressure Vessel ◽  
Correlation Method ◽  
Reactor Pressure Vessel ◽  
Surveillance Data ◽  
New Method ◽  
Rate Equations ◽  
Mathematical Form ◽  
Microstructural Changes ◽  
Pressure Vessel Steels ◽  
Reactor Pressure

Neutron irradiation embrittlement of reactor pressure vessel steels is an important aging issue for the long-term operation of light water reactors. A new embrittlement correlation method was developed by Central Research Institute of Electric Power Industry and the Japanese electric utilities in 2007. This method is primarily based on the fundamental understandings on the embrittlement mechanisms, i.e., microstructural changes were modeled by the mathematical form of rate equations, and the predicted microstructural changes were further correlated with the mechanical property changes in transition temperature region. The coefficients of the rate equations were optimized using the Japanese surveillance data of RPV embrittlement. This method was adopted as the revision of the Japanese code, JEAC4201-2007, in 2007. In this paper, after a brief explanation on the new correlation method, the predictions of the new method will be investigated through comparisons with the previous correlation, JEAC4201-2004, and the U.S. surveillance data in order to identify the characteristics of the new method.

Industry Practice for the Neutron Irradiation Embrittlement of Reactor Pressure Vessel Steels in Japan

2009 ◽  
Author(s):  
Norimichi Yamashita ◽  
Masanobu Iwasaki ◽  
Koji Dozaki ◽  
Naoki Soneda
Keyword(s):  
Neutron Irradiation ◽  
Pressure Vessel ◽  
Correlation Method ◽  
Surveillance Data ◽  
Surveillance Program ◽  
Irradiation Embrittlement ◽  
Term Operation ◽  
Pressure Vessel Steels ◽  
Reactor Pressure

Neutron irradiation embrittlement of reactor pressure vessel steels (RPVs) is one of the important material ageing issues. In Japan, almost 40 years have past since the first plant started its commercial operation, and several plants are expected to become beyond 40 years old in the near future. Thus, the safe operation based on the appropriate recognition of the neutron irradiation embrittlement is inevitable to ensure the structural integrity of RPVs. The amount of the neutron irradiation embrittlement of RPV steels has been monitored and predicted by the complementally use of surveillance program and embrittlement correlation method. Recent surveillance data suggest some discrepancies between the measurements and predictions of the embrittlement in some old BWR RPV steels with high impurity content. Some discrepancies of PWR RPV surveillance data from the predictions have also been recognized in the embrittlement trend. Although such discrepancies are basically within a scatter band, the increasing necessity of the improvement of the predictive capability of the embrittlement correlation method has been emphasized to be prepared for the future long term operation. Regarding the surveillance program, on the other hand, only one original surveillance capsule, except for the reloaded capsules containing Charpy broken halves, is available in some BWR plants. This situation strongly pushed establishing a new code for a new surveillance program, where the use of the reloading and reconstitution of the tested specimens is specified. The Japan Electric Association Code, JEAC 4201–2007 “Method of Surveillance Tests for Structural Materials of Nuclear Reactors,” was revised in December, 2007, in order to address these issues. A new mechanism-guided embrittlement correlation method was adopted. The surveillance program was modified for the long term operation of nuclear plants by introducing the “long-term surveillance program”, which is to be applied for the operation beyond 40 years. The use of the reloading, re-irradiation and reconstitution of the tested Charpy/fracture toughness specimens is also specified in the new revision. This paper reports the application and practice of the JEAC4201–2007 in terms of the prediction of embrittlement and the use of tested surveillance specimens in Japan.

Thermodynamic models of low-temperature Mn–Ni–Si precipitation in reactor pressure vessel steels

2014 ◽  
Vol 4 (3) ◽  
pp. 101-105 ◽  
Author(s):  
Wei Xiong ◽  
Huibin Ke ◽  
Ramanathan Krishnamurthy ◽  
Peter Wells ◽  
Leland Barnard ◽  
...  
Keyword(s):  
Low Temperature ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Thermodynamic Models ◽  
Pressure Vessel Steels ◽  
Image Position ◽  
Reactor Pressure

Abstract

scholarly journals 3-D Atom Probe Observation of Solute Atom Clusters in Reactor Pressure Vessel Steels

Materia Japan ◽  
2008 ◽  
Vol 47 (12) ◽  
pp. 619-619
Author(s):  
Kenji Nishida ◽  
Kenji Dohi ◽  
Akiyoshi Nomoto ◽  
Naoki Soneda
Keyword(s):  
Pressure Vessel ◽  
Solute Atom ◽  
Atom Probe ◽  
Reactor Pressure Vessel ◽  
Atom Clusters ◽  
Pressure Vessel Steels ◽  
Reactor Pressure
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