Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: The performance of type EP-450 ferritic-martensitic steel under neutron irradiation at low temperatures

Abstract

Up-to-date structural materials for fast breeder reactor core applications must have a high irradiation performance at large displacement doses (up to 100 dpa and more) achieved at high burn-up (12-15%) in the fuel. Type 13Cr2MoNbVB (EP-450) ferritic-martensitic steel used as the material of hexagonal wrappers in the BN-600 and BN-350 fast reactors exhibits a high resistance to swelling. It is known, however, that the steel is prone to an embrittlement at low irradiation temperatures. Eight hexagonal wrappers irradiated in the BN-600 and BN-350 reactors up to 85-90 dpa have been investigated, and data on tensile and impact properties have been obtained. Central parts of the wrappers irradiated up to higher damage doses than others exhibited satisfactory tensile properties, i.e. at high neutron dose, at temperatures in the range from 450 to 500 deg. C, there is no severe degradation of tensile and impact properties. For these irradiation temperatures, mechanical properties of ferritic-martensitic steels depend only slightly on damage dose as compared to a low temperature neutron irradiation (<350 deg. C). The highest levels of strengthening and embrittlement in the steel were observed after irradiation at 320 deg. C. At high doses the performance of the ferritic-martensitic steel EP-450 in a fast reactor will be limited at low temperatures. TEM-study data on the microstructure of irradiated wrapper material are presented.

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Reference:

Influence of high dose irradiation on core structural and fuel materials in advanced reactors. Technical committee meeting, Obninsk (Russian Federation), 16-19 Jun 1997

International Atomic Energy Agency, Vienna (Austria)

IAEA-TECDOC--1039, pp:139-144