Positron Annihilation Study of RPV Steels Radiation Loaded by Hydrogen Ion Implantation

Specimens of 15Kh2MFAA steel used for reactor pressure vessels V-213 (VVER-440 reactor) were studied by positron annihilation techniques in terms of their radiation resistance and structural recovery after thermal treatment. The radiation load was simulated by experimental implantation of 500 keV H+ ions. The maximum radiation damage of 1 DPA was obtained across a region of 3 µm. Radiation-induced defects were investigated by coincidence Doppler broadening spectroscopy and positron lifetime spectroscopy using a conventional positron source as well as a slow positron beam. All techniques registered an accumulation of small open-volume defects (mostly mono- and di-vacancies) due to the irradiation, with an increase of the defect volume ΔVD ≈ 2.88 × 10−8 cm−3. Finally, the irradiated specimens were gradually annealed at temperatures from 200 to 550 °C and analyzed in detail. The best defect recovery was found at a temperature between 450 and 475 °C, but the final defect concentration of about ΔCD = 0.34 ppm was still higher than in the as-received specimens

Non-destructive Examination of Helium Implanted HTRs Construction Materials

High chromium steels belong to the most prospective materials for reactor pressure vessel of High Temperature Reactors as well as for more components used in GEN IV facilities. Radiation resistance of GEN IV materials is a significant attribute. Therefore the process of microstructure deterioration due to irradiation followed by degradation of mechanical properties must be consistently investigated. This paper is focused on microstructure study of 9% chromium steels (T91, P91) and observation of residual stress as well as open volume defect accumulation after helium ion implantation performed at room temperature. Helium ion implantation should simulate changes of structure due to knocking-out of atoms during neutron irradiation. Investigated materials were studied by non-destructive experimental techniques based on the positron annihilation in the matter (Positron Annihilation Spectroscopy, Doppler Broadening Spectroscopy) and magnetic properties of iron alloys (Magnetic Barkhausen Noise Measurement). Results indicate higher resistance of T91 to defect formation during implantation than P91, although T91 shows higher residual stress in microstructure prior to implantation.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Radioactive waste management: Review on clearance levels and acceptance criteria legislation, requirements and standards

In 2011 the joint research project Metrology for Radioactive Waste Management (MetroRWM) of the European Metrology Research and Development Program (EMRP) started with a total duration of three years. Within this project, new metrological resources for the assessment of radioactive waste, including their calibration with new reference materials traceable to national standards will be developed. This paper gives a review on national, European and international strategies as basis for science-based metrological requirements in clearance and acceptance of radioactive waste.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard