Long Term Operation and Surveillance Specimen Program of WWER RPVs

2010 ◽  
Author(s):  
Milan Brumovsky ◽  
Milos Kytka
Keyword(s):  
Czech Republic ◽  
Pressure Vessel ◽  
Laboratory Tests ◽  
Thermal Ageing ◽  
Reliable Information ◽  
Life Extension ◽  
Irradiation Embrittlement ◽  
Term Operation ◽  
Reactor Pressure

Long Term Operation (LTO) to 60 or 80 years of operation also requires a reliable information about the potential irradiation embrittlement (and also thermal ageing) of reactor pressure vessel materials. Such information is usually obtained from testing specimens within the surveillance specimen program that is designed for the design RPV life, regularly for 40 years only. Life extension requires modification of such program (if there is still time to perform it) or a design of a new – extended one. Such program should have to contain RPV archive materials that are not in every case available. Thus, combination of archive materials and possible surrogate materials must be taken into account for this program. Some complication can be expected with thermal ageing data as some laboratory tests at higher temperatures must be realized. The paper describes such program for NPP Dukovany, Czech Republic with WWER-440 type reactors that are now more than 20 years of operation.

Surveillance Specimen Program for Lifetime Extension of RPV

2010 ◽  
Author(s):  
Milan Brumovsky ◽  
Milos Kytka
Keyword(s):  
Pressure Vessel ◽  
Nuclear Power ◽  
Thermal Ageing ◽  
Reactor Pressure Vessel ◽  
Life Extension ◽  
Irradiation Embrittlement ◽  
Term Operation ◽  
Reactor Pressure ◽  
Lifetime Extension

Plant life extension (as well as Long Term Operation) to 60 or 80 years of operation also requires a reliable information about the potential irradiation embrittlement (and also thermal ageing) of reactor pressure vessel materials. Such information is usually obtained from testing specimens within the surveillance specimen program that is designed for the design reactor pressure vessel (RPV) life, regularly for 40 years only. Life extension requires modification of such program (if there is still time to perform it) or a design of a new – extended one. Such program should have to contain RPV archive materials that are not in every case available. Thus, combination of archive materials and possible surrogate materials must be taken into account for this program. Some complication can be expected with thermal ageing data as some laboratory tests at higher temperatures must be realized. The paper describes such program for Nuclear Power Plant (NPP) Dukovany, Czech Republic with WWER-440 type reactors.

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.

Time-Limited Ageing Analyses for Justification of Long-Term Operation of Paks NPP

2010 ◽  
Author(s):  
Tama´s Ja´nos Katona ◽  
Sa´ndor Ra´tkai ◽  
A´gnes Ja´nosine´ Bi´ro´ ◽  
Pe´ter Go˝si
Keyword(s):  
Pressure Vessel ◽  
Fatigue Analysis ◽  
Thermal Ageing ◽  
Reactor Pressure Vessel ◽  
Usual Practice ◽  
Term Operation ◽  
Internal Structures ◽  
Class 1 ◽  
Reactor Pressure

In this paper a comprehensive set of the time-limited ageing analyses for justification of long-term operation of WWER-440/213 type units will be presented. The scope covers mainly fatigue analyses of Safety Class 1 and 2 structures and components, reactor pressure vessel pressurized thermal shock analyses, etc. like in usual practice in case of PWRs. However some specific analyses are required for comprehensive justification of long-term operation, e.g. high cycle fatigue analysis of flow-induced vibration of internal structures of the reactor pressure vessel and internal structures of the steam generators, thermal ageing analysis of Safety Class 1 and 2 components, analysis for material property change of heavy concrete structures of reactor shielding, crack propagation analysis of detected defects, thermal stratification analysis, fatigue analysis of the containment for increased pressure level during integral leak-tightness test. The necessity of the specific analyses is discussed. Arguments are based on the WWER operation experience and engineering considerations. Specific requirements and methodology for routine and specific time-limited ageing analyses and the most important results with explanation of possible consequences will also be presented.

Assessment of RPV Surveillance Materials Program Data of a BWR

2016 ◽  
Author(s):  
Rogelio Hernández Callejas ◽  
A. Liliana Medina-Almazán ◽  
Fco. Javier Merino Caballero ◽  
Salvador Vázquez Belmont
Keyword(s):  
Energy Use ◽  
Nuclear Reactor ◽  
Safety Margin ◽  
Life Extension ◽  
Irradiation Embrittlement ◽  
Limiting Condition ◽  
Safety Operation ◽  
Program Data ◽  
Reactor Pressure

Irradiation embrittlement is a limiting condition for the long-term safety operation of a nuclear Reactor Pressure Vessel (RPV). When a Boiling Water Reactor (BWR) is approaching its initial licensing, in order to operate the reactor for another 20 years and more, it should be demonstrated that the irradiation embrittlement of the reactor vessel materials will be adequately managed by ensuring that the fracture toughness properties are above a certain level of the required safety margin. In this work the Charpy specimens recovered from two surveillance capsules of two BWRs (fluence 3.58×1017 – 9.03×1017 n/cm2) were impact tested at temperatures selected to establish the toughness transition and upper shelf of the irradiated RPV materials. The measured transition temperature shifts (ΔRTNDT) and the Upper Shelf Energy (USE) for the plate and weld materials were compared to the predictions calculated according to Regulatory Guide 1.99 Rev.2. The credibility of surveillance data were analyzed according with the five criteria established in the Regulatory Guide 1.99, Revision 2. The Master Curve (MC) approach and the instrumented impact tests using pre-cracked Charpy specimens were implemented in order to fully validate this techniques that can be used for embrittlement monitoring during life extension periods.

International Database on Reactor Pressure Vessel Materials for Long-Term Operation of NPPs

2012 ◽  
Vol 180 (3) ◽  
pp. 443-449 ◽  
Author(s):  
A. Kryukov ◽  
A. Ballesteros ◽  
C. Bruynooghe ◽  
U. Von Estorff
Keyword(s):  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
International Database ◽  
Term Operation ◽  
Reactor Pressure

scholarly journals Long-term operation of a boiling pressure vessel and its internals

2019 ◽  
Vol 52 (4) ◽  
pp. 200-221
Author(s):  
Otso Cronvall
Keyword(s):  
Power Plant ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Pilot Project ◽  
Computational Time ◽  
Degradation Mechanisms ◽  
Term Operation ◽  
Reactor Pressure

This study concerns the long-term operation (LTO) of a boiling water reactor (BWR) reactor pressure vessel (RPV) and its internals. The main parts of this study are: survey on the susceptibility to degradation mechanisms, and computational time limited ageing analyses (TLAAs). The ageing of nuclear power plants (NPPs) emphasizes the need to anticipate the possible degradation mechanisms. The BWR survey on the susceptibility to these mechanisms uses the RPVs and significant internals of the Olkiluoto power plant units OL1 and OL2 as a pilot project. For the components that screened in, the potential to brittle, ductile or other degradation is determined. This was carried out by applying structural mechanics and fracture mechanics procedures. Only some most significant cases and results are presented here.

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

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Norimichi Yamashita ◽  
Masanobu Iwasaki ◽  
Koji Dozaki ◽  
Naoki Soneda
Keyword(s):  
Neutron Irradiation ◽  
Correlation Method ◽  
Pressure Vessels ◽  
Surveillance Data ◽  
Surveillance Program ◽  
Irradiation Embrittlement ◽  
Water Reactor ◽  
Term Operation ◽  
Reactor Pressure

Neutron irradiation embrittlement of reactor pressure vessel steels (RPVs) is one of the important material aging 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 complemental use of the surveillance program and embrittlement correlation method. Recent surveillance data suggest some discrepancies between the measurements and predictions of the embrittlement in some old boiling water reactor (BWR) RPV steels with high impurity content. Some discrepancies of pressurized water reactor (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, reirradiation, 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.

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