Experience and trends at the Belgonucleaire plant

The BN Dessel plant started operation in 1973. During the initial period (up to 1984), the plant was equipped to fabricate FBR as well as LWR fuel (5 tHM/year) within the framework of LWR demonstration and FBR programmes. The first ten years of operation have laid down the basis for all modifications or improvements in the fields of fuel fabrication and control processes, waste management, safety and safeguards, which were implemented in the 1984-1985 refurbishment. On this occasion, the MIMAS fabrication process has been introduced to make MOX fuel reprocessable in the operating conditions of the modern reprocessing plants (COGEMA in La Hague and BNFL in Sellafield) and the capacity of the plant has been upgraded to the current nominal capacity of 35 tHM per year (with a maximum licensed of 40 tHM per year). The nominal fabrication capacity was achieved in 1989, maintained consistently since then at least at that level, approaching even the license limit. The process has proved its high flexibility, in particular in terms of the large variety of MOX manufactured for both PWRs (14 x 14, 15 x 15, 16 x 16, 17 x 17, types) and BWRs (8 x 8, 9 x 9, 10 x 10 types), of the size of the campaign (from less than 4 tHM to 28 tHM), of the origin of the PuO2 (from COGEMA and BNFL reprocessing plants, Pu from second generation), of the Pu content (up to 8.6 w/o in HM). From 1986 up to the end of March 1999, more than 21 t Pu as PuO2 have been processed into more than 388 tHM of MIMAS fuel, delivered or to be delivered for use in 796 PWR assemblies and 184 BWR assemblies for 21 large power reactors (17 PWRs and 4 BWRs) in 5 countries (France, Germany, Switzerland, Japan, Belgium). The MOX fuel produced has been demonstrated to reach at least the same performance as the UO2 fuel used simultaneously in the same reactors. An increasing number of the MOX assemblies are discharged at a burnup of at least 45 GWd/tHM assembly average. One assembly reached 51 GWd/tHM assembly average after 6 irradiation cycles. No failures due to the MOX were noticed. Since the mid 1990's, the plant is being backfitted without interruption of the fabrication, to incorporate improvements resulting from accumulated experience to improve still further the flexibility of the plant while meeting the more challenging future requirements in particular in terms of radioprotection regulation (degraded plutonium isotopic composition, higher burnup design fuel assemblies, ICRP 60) as well as in terms of economics (recycling of the scrap, reduction of the fabrication generated waste). (author)