[en] summary of discussions from the Workshop: I. Lessons Learned from Testing and Evaluation of Surveillance Capsules: France has extracted approximately 200 capsules from 58 reactors so that they have a very large surveillance capsule database. Their analysis methods were standardized in the 1990's, and libraries in use at that time are still in use in analyses today. The C/A ratios are good; however, there are biases. The importance of a good covariance matrix was stressed. One of the issues is the fission spectrum; it was noted that ENDFB-VII has revised the Pu-239 fission spectrum by about 4%. Fission dosimeters and the importance of knowing the exact composition, density, and impurities in the dosimeters were discussed. If a powder form of the dosimetry material is used, France uses x-rays to determine accurate densities. Niobium dosimetry in place of uranium and neptunium dosimetry (which is no longer being manufactured) and what will happen to the niobium during a 60-year lifetime was discussed. It is desired to have no oxidation of the niobium, which requires either a vacuum environment, which is difficult in such a small geometry, or inerting the dosimetry. The Workshop participants discussed whether they should recommend that uranium and neptunium spheres continue to be manufactured. II. Re-evaluation of Data for VVER: The importance of re-evaluating data for VVER reactors was discussed since the database is used to predict behavior of material responses. Spain uses U.S. Regulatory Guide 1.190, which allows for 20% uncertainty in neutron fluence, to assess material behavior. France uses an upper value of +2 sigma of the mean value. III. Uncertainties of Ex-Vessel Dosimetry: The use of ex-vessel dosimetry is probably not going to be used in VVERs for adjustments together with the results from in-vessel dosimetry because of the bad location of the in-vessel surveillance capsules above the core. Westinghouse noted that some reactor pressure vessels are thicker than the as-built designs because tight tolerances were specified on only the inside diameter (and not on the thickness); if in-service inspection data is available, then this thickness should be used in ex-vessel calculations for more accurate calculations. IV. Benchmarking of Neutron Calculations: Discussions on this topic focused on the need to expand benchmarks beyond fluence to include temperatures and stress-strain. There is a good understanding of the magnitude and uncertainty in neutron fluence parameters. Currently there is only 1 benchmark (VENUS) with heat generation rates, so there is a need for three-dimensional heat generation rate benchmarks. An EPRI study noted that gamma heating can drive some reactor internals temperatures above the threshold limits. Westinghouse has evaluations that bound all plants and are developing inspection guides based on the bounding case. However, newer plants did not see the higher temperatures because of the use of low-leakage fuel on the core perimeter. Some plants are replacing baffle bolts. The defective bolts can be used to verify the neutron fluence calculations using retrospective dosimetry. V. Developing and Using Reference Dosimetry: Reference dosimetry would need to be well-calibrated; a large amount of data would be needed under very controlled conditions. VI. 60 to 80 Year Extensions In Spain, the approach is to use ex-vessel dosimetry to monitor the reactor pressure vessel fluence; the irradiation of new surveillance capsules is not planned in the PWRs. The Bulgarian recommendation is exchanging ex-vessel dosimetry every cycle for VVER-440 reactors. In VVER-1000 reactors, the dosimetry can be exchange every 2 or 3 cycles. Currently, the U.S. is 'considering' life extensions to 80 years

[en] This publication summarizes the long term operation (LTO) conditions in European NPPs and provides recommendations on reactor pressure vessel (RPV) irradiation surveillance based on the work performed 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 Commission. Specific scientific and technical issues addressed in this publication are the following: - Surveillance standards and procedures. - Reuse of tested irradiated surveillance specimens. - Transferability of test reactor results to LWR conditions. - Extension of RPV irradiation surveillance programmes. - Withdrawal scheme for LTO surveillance programmes. The objective of the surveillance guidelines is to support the potential end-user (utilities, nuclear power plants, research institutes, etc.) in selecting the appropriate strategy and technical approaches for RPV irradiation surveillance for LTO. In this way contributing to a reliable monitoring of long-term irradiation effects in RPV, and supporting the European efforts towards harmonisation of procedures for RPV surveillance and safety assessment in the light of LTO.

[en] Highlights: • Radiation effects in reactor pressure vessel steels under long term operation. • Indications of late blooming effects were found in some cases. • Significant flux effect on the size of defect clusters in high-Cu weld materials. • Guideline for monitoring radiation embrittlement during life extension. - Abstract: LONGLIFE (“Treatment of long term irradiation embrittlement effects in RPV safety assessment”) was a collaborative project of the 7th Framework Programme of EURATOM under the umbrella of NULIFE/NUGENIA, aiming at an improved understanding of irradiation effects in reactor pressure vessel steels under conditions representative of long term operation. The LONGLIFE project was completed by the end of January 2014. The paper gives an overview of the main project results and their implications for future research, as discussed at the final project workshop. The microstructural database for neutron-irradiated RPV steels was extended considerably and existing gaps on mechanical property data were closed. Indications of late blooming effects (LBE) were found in some cases, but clear criteria for the occurrence/exclusion in terms of irradiation conditions and chemical composition have still to be developed. The commonly accepted trend, that low flux and low irradiation temperature promotes LBE, is supported. A significant flux effect on the size of defect clusters was observed in two high Cu weld materials, while the changes of mechanical properties are not affected by the neutron flux. The database requires completion in particular for low-Cu RPV steels. The shift of reference temperature T₀ over the thickness location of a VVER-440 welding seam does not follow the prediction Russian code, because of the strong variation of the intrinsic weld bead structure. Therefore, the effect of the initial microstructure and of the heterogeneity on the radiation behaviour has to be addressed in future works. Existing embrittlement trend curves models were applied to the LONGLIFE data base. None of the trend curves could predict the behaviour of the entirety of the LONGLIFE materials sufficiently. A guideline for monitoring radiation embrittlement during life extension periods was developed

[en] Highlights: • The important role of Operating Experience Feedback is emphasised. • Events relating to cracks and leaks in the reactor coolant pressure boundary are analysed. • A methodology for event investigation is described. • Some illustrative results of the analysis of events for specific components are presented. - Abstract: The presence of cracks and leaks in the reactor coolant pressure boundary may jeopardise the safe operation of nuclear power plants. Analysis of cracks and leaks related events is an important task for the prevention of their recurrence, which should be performed in the context of activities on Operating Experience Feedback. In response to this concern, the EU Clearinghouse operated by the JRC-IET supports and develops technical and scientific work to disseminate the lessons learned from past operating experience. In particular, concerning cracks and leaks, the studies carried out in collaboration with IRSN and GRS have allowed to identify the most sensitive areas to degradation in the plant primary system and to elaborate recommendations for upgrading the maintenance, ageing management and inspection programmes. An overview of the methodology used in the analysis of cracks and leaks related events is presented in this paper, together with the relevant results obtained in the study