JiNan MNSR (Miniature Neutron Source Reactor) with thermal power 30kW is an undermoderated reactor of pool-tank type, and UAL4 alloy with 235U enrichment of 90% as fuel, light water as coolant and moderator, and metallic beryllium as reflector. The fission heat produced by the reactor is removed by the natural convection. JiNan MNSR went critical in May 1989, and shutdown in March 2008. The reactor operated 19 years safely with the accumulated power of 8.82×104 kWh. The main use was NAA (Neutron Activation Analysis) work.
The spent fuel was removed from the JiNan MNSR site in Nov. 2009 already. The Jinan MNSR decommissioning documents were approved by Chinese competent authorities in Dec. 2010. The work on site was started in Jan. 2011, and completed in March 2011, the wastes were removed from the Jinan MNSR site. The decommissioning scope of JiNan MNSR includes decommissioning of its related systems, equipment and structures. The weight of intermediate level radioactive is 204.1kg, and the weight of low level radioactive waste is 2297 kg. They were all transported to West-north Waste disposal plant.
The final measuring results are that α and β surface contamination in the reactor building are less than 0.06Bq/cm2 and 0.5Bq/cm2 respectively; the specified activities of the nuclides of 137Cs, 60Co and 90Sr in the soil are less than 1.4 Bq/kg,1.7 Bq/kg and 8.14 Bq/kg respectively; the specified activities of the nuclides of 137Cs, 60Co and 65Zn in the solid sample in the reactor building are less than 5.7 Bq/kg,7.8 Bq/kg and 1.7 Bq/kg respectively.
The specified values for α and β surface contaminations in the reactor building are 0.08Bq/cm2 and 0.8Bq/cm2 respectively; they are 12 Bq/kg, 3 Bq/kg and 10 Bq/kg respectively for the limited values of the specified activities of the nuclides of 137Cs,60Co and 90Sr in the soil; the limited values of specified activities of the nuclides of 137Cs,60Co and 65Zn are 100Bq/kg respectively in the solid samples in the reactor building. The measuring results show that JiNan MNSR site meets the requirements of the unrestricted use.
