Irradiated for 4 cycles inside the reactor, the irradiation surveillance capsule (ISC) was withdrawn and transported to Nuclear Power Institute of China (NPIC) for dismantling in the hot cell. This paper presented tensile tests and Charpy-V impact tests on non-irradiated and irradiated specimens. Tensile tests were performed at room temperature and 300 °C respectively, and Charpy-V impact tests were performed at series temperatures. Instrumented impact curves and tensile curves were obtained and analyzed. Impact absorbed energy, lateral expansion and crystallinity transition curves were plotted by a hyperbolic tangent function. The irradiation-induced shift of transition temperature, upper shelf energy, tensile strength and yield strength were determined. And irradiation-embrittlement effect on RPV was evaluated by prediction and measurement of irradiation-induced transition temperature shift. Results showed that the parameters including neutron fluence and transition temperature were in normal range, and the next capsule could be withdrawn according to original irradiation monitoring program.Copyright © 2010 by ASME

Irradiation-Embrittlement of Reactor Pressure Vessel Steel

\n Fast neutron irradiation causes embrittlement of the reactor pressure vessel (RPV) material; therefore, it may end operation life before design lifetime. Well-known method to recuperate crystal lattice dislocations is annealing. In the current version of thorium fueled supercritical water-cooled reactor (SCWR) design proposed by the Institute of Nuclear Technology at Budapest University of Technology and Economics (BME NTI), the supercritical fluid flows upward between the core barrel and the inner surface of the RPV thereby, the coolant would keep the RPV's temperature at ∼500 °C. This reverse coolant flow direction would decrease the embrittlement of RPV by constant annealing. To minimize the fast neutron flux increase, a relatively thin shielding connected to the inner surface of the barrel could be used. This presents fast neutron irradiation analysis, performed for different settings of the shielding to reduce fast neutron flux reaching the inner surface of RPV.

Fast Neutron Irradiation Optimization of Thorium-Fueled SCWR Reactor Pressure Vessel

Actions/issues prior to annealing: Materials considerations

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.

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

Annealing of a reactor pressure vessel embrittled by neutron irradiation constitutes the only known technique to restore the initial material properties, to an extent that depends on the annealing conditions and on the materials. This technique is used in WWER-440 type reactor pressure vessels. A very important related issue is the one of re-embrittlement behaviour of the material after the annealing. In this respect, there is an obvious link with radiation embrittlement understanding. This report compiles the vast amount of information on annealing and re-embrittlement, which is available in the European countries where such annealing operations have been performed. In addition this topic was also investigated in various TACIS-PHARE projects, and the conclusions are included here as well. To complete the state-of-the-art, the results from a number of annealing experiments carried out in US on “Western” type RPV steels have also been considered. How to obtain EU publications Our priced publications are available from EU Bookshop (http://bookshop.europa.eu), where you can place an order with the sales agent of your choice. The Publications Office has a worldwide network of sales agents. You can obtain their contact details by sending a fax to (352) 29 29-42758. The mission of the JRC is to provide customer-driven scientific and technical support for the conception, development, implementation and monitoring of EU policies. As a service of the European Commission, the JRC functions as a reference centre of science and technology for the Union. Close to the policy-making process, it serves the common interest of the Member States, while being independent of special interests, whether private or national.

Kohopaa Jyrki

Papers

Annealing and Re-embrittlement of Reactor Pressure Vessel Materials - State of the Art Report