In-pile testing of sub-modules for the HCPB demo blanket concept at the HFR petten

This paper describes the test objectives developed by the Helium Cooled Pebble-Bed Blanket (HCPB) team and presents the conceptual design of the in-pile test of HCPB sub-modules at the HFR Petten. The content can be summarized in 4 points: i) the in-pile testing of blanket sub-modules for the HCPB concept is to concentrate on the effect of neutron irradiation on the thermal-mechanical behaviour of the breeder pebble-bed at representative levels of temperature and defined thermal-mechanical loads; ii) a conceptual design for the in-pile test elements and irradiation facility has been elaborated. The experiment comprises the simultaneous irradiation of four independent test elements. The test matrix contains reference and alternative breeder material, two characteristic test temperatures, and different levels of constraint for the breeder pebble beds; iii) nuclear analysis shows typical power densities for the test elements in the range of 25-40 W/cm3. Lithium burn-ups of 3-4 % can be reached in one year of irradiation in a peripheral core position of the HFR, with a 3 dpa damage level for the RAFM structural material. Thermal and mechanical analyses confirm the feasibility of the test element design to meet the test requirements and allow safe operation of the test; iiii) the design will be further detailed taking into account recent findings on the out-of-pile thermal-mechanical behaviour of pebble-beds and modelling. Manufacturing and assembly is foreseen for 1999 to allow to start the irradiation in the HFR by the end of 1999. Dismantling, inspections and P.I.E. will be performed in the period 2001 to mid 2002. (authors)