Final Survey of Decommissioning Site for Jinan MNSR

Radioactive levels of ¹³⁷Cs, ⁶⁰Co, ⁶⁵Zn and ⁹⁰Sr in decommissioning site of Jinan MNSR were surveyed finally by detecting β and γ spectra. ⁶⁵Zn in all samples was not detected. In reactor pool, the highest level of 49.3 Bq/kg of ⁶⁰Co exists at pool bottom just below the reactor core, and is produced by neutron activation. In other survey units, the highest levels of 5.7, 6.8 and 8.1 Bq/kg of ¹³⁷Cs, ⁶⁰Co and ⁹⁰Sr exist in transport passage, reactor hall and soil, respectively, and probably come from contamination of decommissioning practice. The survey results indicate that radioactive levels in all samples are lower than the clearance levels and the acceptable levels derived from the effective dose of 10 μSv/a, and that in most of samples are close to the background levels. The detection lower limits of ¹³⁷Cs, ⁶⁰Co and ⁶⁵Zn are 1.1, 1.0 and 1.3 Bq/kg, respectively. The uncertainty of survey results is less than 33.0%. The relative deviation between the measured value and the certified value of standard material GBW08304a is less than 3%.