| 1. |
- Ballesteros, Antonio, et al.
(författare)
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Reactor Pressure vessel surveillance
- 2014
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Ingår i: Nuclear Engineering International. - : GLobal trade media. - 0029-5507. ; 59:12, s. 19-20
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Tidskriftsartikel (refereegranskat)abstract
- This publication summarizes techniques suitable for surveillance program for the objective of long term operation (LTO) on European NPPs and provides recommendations on reactor pressure vessel (RPV) irradiation surveillance based on the work preformed in the work package 7 "Surveillance guidelines" of the LONGLIFE international project. The LONGLIFE project "treatment of long term irradiation embrittlement effects in RPV safety assessment" was 50% funded by the Euratom 7th framework programme of the European commision. The project coordinated by the Helmholtz-centrum Dresden Rossendorf successfully finalized in 2014.
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| 2. |
- Blomström, Johan, et al.
(författare)
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Experience with Embrittlement Trend Curves in Swedish PWRs
- 2023
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Ingår i: Radiation Embrittlement Trend Curves and Equations and Their Use for RPV Integrity Evaluations. - : ASTM International. ; , s. 382-397
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Konferensbidrag (refereegranskat)abstract
- There are currently two operating pressurized water reactors in Sweden, currently planning for 60 years of operation until 2041 and 2043. The acceptance of operation time is continuously evaluated at least every 10 years in a comprehensive mandatory periodic safety review that requires the utilities to continuously update and implement the developments in science and technology. The RPV welds have been shown by the applied surveillance program to be the limiting material for operation. The welds are manufactured according to the same specifications with a chemical composition with high nickel and manganese content. The welds show a large increase in transition temperature shift with an almost linear relationship to neutron fluence that is underestimated by most of the established embrittlement trend curves (ETCs). The current regulations from the Swedish Radiation Safety Authority are in general not detailed and prescriptive and hence permit plant-specific ETCs if they are sufficiently justified and based on proper material and plant conditions. This paper describes the bases for the ETCs and an ongoing work to revise the ETCs to enable the use of a material-specific master curve for crack initiation, KIC, with compliance with the reactor vessel integrity analyses.
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| 3. |
- Efsing, Pål, 1965-, et al.
(författare)
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Long term irradiation effects on the mechanical properties of reactor pressure vessel steels from two commercial PWR plants
- 2013
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Ingår i: ASTM Special Technical Publication. - : ASTM International. ; , s. 52-68
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Konferensbidrag (refereegranskat)abstract
- The Swedish nuclear power plants all have plant specific surveillance programs which includes samples from all relevant materials that are subjected to a fluence-level that exceeds 1*1017 n/cm2 over the estimated period of operation for the specific power plants. The Swedish pressurized water reactor (PWR)-plants are currently planning for a service period beyond 50 years of operation. As a portion of that, two of the three PWR units at the Ringhals site are conducting a major effort to verify the fitness to service of the reactor pressure vessel (RPV). In this case it is the weld in the belt-line region of the RPV, which is the apparent limiting factor. The weld metal contains high Nickel and high Manganese levels, not commonly used in other PWR-reactors. The effort includes a densified testing of the available surveillance capsule material in order to better understand the degradation phenomena and also an extended testing scope. A spin off effect of this program is that high fluence data for the base material also is made available from the testing. The chemical composition of the base metal is valid for many of the currently operating PWR-vessels. This study is an analysis of both the weld and the base material data extracted from the surveillance program. The results are evaluated against currently available data and correlation curves. In general, the results point out that the current Regulatory Guide 1.99 revision 2-correlation regarding the prediction of as-irradiated transition temperature is under-conservative for the tested material. The transition temperature shift, here evaluated as the temperature shift at 41J, is under-predicted by the correlation by as much as 70°C in some cases and increases with increasing fluences. However, prediction made by the French average irradiation embrittlement prediction formula, FIM-formula, is consistently better but still slightly under conservative.
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| 4. |
- Efsing, Pål, 1965-, et al.
(författare)
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Ringhals Units 3 and 4 - Fluence determination in a historic and future perspective
- 2012
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Ingår i: Journal of ASTM International. - : ASTM International. - 1546-962X. ; 9:4, s. 104012-9
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Tidskriftsartikel (refereegranskat)abstract
- The Ringhals site is situated on the Swedish southwest coastline. At the site, there are four operating nuclear power plants. Historically, the Swedish policy has been that the nuclear power plants were to be closed in 2010. The present position is to operate the units until their technical and economic lifetime has run out. The units shall be maintained and invested in to ensure a lifetime of at least 50 years, but the actions taken shall not limit the time to this date. When the initial surveillance capsules were evaluated, it was noted that the material properties of the weld material of unit 3 and 4 showed some deviations from the expected behaviour. Currently there is an extensive project running for re-evaluating the embrittlement situation from a long-term operating perspective. One part of the project is aimed at more accurately determining the fluence levels of the reactor pressure vessels (RPVs). The basis for the early evaluations of the dosimeters in the surveillance capsules and the corresponding fluence evaluation had an operating lifetime of 25 years as a target value. Therefore, the accuracy and refinement of the measurement and calculation were taken to be good enough to suit this life span. Looking back at the results from the dosimetry measurements there are a few discrepancies. Some of the dosimeters were disintegrated and some measurements had comparatively large uncertainties. When starting this project there were some re-evaluations done with the old fluence prediction model. For every new run and refinement there appeared new difficulties, and the decision was to start the evaluation from scratch.Then there are two questions remaining regarding the fluence: What is the current fluence level? What will the resulting fluence be after 60 years of operation, when we have up-rated output power of both reactors? This paper aims to describe the view of the fluence evaluation in the surveillance program of the RPV, both in a historical and prospective view.
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| 5. |
- May, Johannes, et al.
(författare)
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Extended mechanical testing of RPV surveillance materials using reconstitution technique for small sized specimen to assist Long Term Operation Extended mechanical testing of RPV surveillance materials using reconstitution technique for small sized specimen to assist Long Term Operation
- 2014
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Ingår i: Journal of ASTM International. - : ASTM International. - 1546-962X .- 1546-962X. ; STP:1576
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Tidskriftsartikel (refereegranskat)abstract
- For the Ringhals 3 and 4 PWR RPV, results from the irradiation surveillance program are available also for neutron fluences which cover long-term operation (LTO). These standard surveillance results are based on the RTNDT concept. The belt-line welds of both RPVs have an elevated nickel-content of 1.6 wt.-% and, as a consequence, irradiation response is higher than predicted by model equations. Therefore, the mechanical testing program has been expanded, exceeding the requirements of the standard testing program and covering both base and weld materials. To improve the understanding of the material behavior, extended Master Curve testing was performed on PCCV and subsize SE(B) specimens from irradiation surveillance capsules with the help of specimen reconstitution technique. Special care has been taken on the limited amount of weld material within the available broken Charpy halves before specimen reconstitution.Results have been compared to existing data on similar base and weld materials from the German research programs CARISMA and CARINA. Late-blooming effects or sudden saturation effects are not observed for base or weld materials under LTO conditions. The data for the four different weld materials of similar chemical composition indicate that not only the chemical composition, but also other influencing factors like e.g. the welding heat treatment may be important for the reference temperature of the unirradiated state as well as for the irradiation behavior. To investigate this effect more in detail, a future investigation program will be discussed including manufacturing of a surrogate weld material with the same chemical composition as in Ringhals 3 and 4 RPV. The influence of heat treatment condition can be investigated by applying different heat treatments and subsequently performing test reactor irradiation and mechanical testing. Specimen reconstitution will be required due to limited space inside the test reactor irradiation capsules.
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| 6. |
- Roudén, Jenny, et al.
(författare)
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Thermal Aging of LAS Weld Metal from Decommissioned Nuclear Components in Swedish PWRs
- 2023
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Ingår i: Radiation Embrittlement Trend Curves and Equations and Their Use for RPV Integrity Evaluations. - : ASTM International. ; , s. 204-216
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Konferensbidrag (refereegranskat)abstract
- Thermal aging has been considered a secondary aging and degradation mechanism for the low-alloy steels used in nuclear power plants. Given the relative interest in lifetime extensions, this has to be revised considering the extent of time at temperature during a 60-year operation time or even beyond. Traditionally, the effect has been coupled to the nonhardening effects caused by phosphorus and sulphur diffusion to available phase or grain boundaries, or both, resulting in a marked embrittlement of these low-alloy steels. This phosphorus segregation is proposed to be the main embrittlement mechanism for the weld metals investigated in this study. In the high-manganese/nickel/silicon-bearing weld metal used in both pressurizers (PRZs) and reactor pressure vessels (RPVs), some of the material extractions from the Ringhals power plant show a larger than expected effect from thermal aging, possibly by the formation of agglomerates in the matrix due to higher nickel content. Further, some of the tested materials showed a hardening effect after in-service exposure at temperature. The results presented here show that even though there are elements to be included in the fitness-for-service analysis of the power plants, with traditional prerequisites for the RPV it will be limited regarding the operating window. An empirically based embrittlement trend curve, related to thermal aging, for the PRZ will be developed after further testing of these materials.
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| 7. |
- Roudén, Jenny, et al.
(författare)
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Towards Safe Long-Term Operation of Reactor Pressure Vessels
- 2015
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Ingår i: ATW. Internationale Zeitschrift für Kernenergie. - : Nucmag.com. - 1431-5254. ; 60:5, s. 287-293
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Tidskriftsartikel (refereegranskat)abstract
- This publication summarizes the long term operation (LTO) conditions on European NPPs and provides recommendations on reactor pressure vessel (RPV) irradiation surveillance based on the work preformed in the work package 7 "Surveillance guidelines" of the LONGLIFE international project. The LONGLIFE project "treatment of long term irradiation embrittlement effects in RPV safety assessment" was 50% funded by the Euratom 7th framework programme of the European commision. The project coordinated by the Helmholtz-centrum Dresden Rossendorf successfully finalized in 2014.
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| 8. |
- Sandberg, Urban, et al.
(författare)
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Shielding fuel assemblies used to protect the beltline weld of the reactor pressure vessel from fast neutron radiation in Ringhals unit 3 and 4
- 2010
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Ingår i: International Conference on the Physics of Reactors 2010, PHYSOR 2010. - LaGrange Park : American Nuclear Society. - 9781617820014 ; , s. 1534-1540
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Konferensbidrag (refereegranskat)abstract
- The beltline weld on the reactor pressure vessel of Ringhals units 3 and 4 has a lifetime estimate of 40 years under the current operating conditions. In the event of power up rates and lifetime extension the irradiation embrittlement of the beltline weld may be a limiting condition. One way to solve this problem is to limit the fast neutron radiation on the reactor pressure vessel. This paper will focus on a solution with specially designed assemblies for the positions that have the highest influence on the fast neutron dose for the beltline weld.
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