Preliminary source term and consequence assessment of primary cover gas leakage accident for CLEAR-I

• The source term and consequences of a simulated leakage accident in the primary gas cover for the China LEAd-based Research Reactor are assessed.
• The LBE coolant bound a fraction of the volatile fission products.
• Radioactive materials released of the accident were mainly noble gas elements, especially xenon.
• The individual effective dose and lifetime thyroid dose decreased exponentially with increasing distance from the reactor and both were less than the control limits.

China LEAd-based Research Reactor (CLEAR-I) is a 10 MWt research reactor cooled with lead–bismuth. The cover gas system on top of the reactor cavity prevents the coolant from being exposed directly to the air and is important for reactors cooled with liquid metal. We carried out a preliminary analysis of a leakage simulation for the primary cover gas as a design basis accident of CLEAR-I. The radioactive sources and the consequences of release of radioactive material for the population around the reactor were determined. The results show that Xe-133 was the nuclide released in the largest amounts. Release of airborne radioactivity under the simulation conditions resulted in a maximum individual effective whole-body dose of only 6.06 × 10−6 mSv and a thyroid dose of only 3.54 × 10−6 mSv for adult, which are six and five orders of magnitude, respectively, lower than the upper limits set in Chinese regulation GB6249-2011. The results indicate that the consequences would be very small for such an accident for CLEAR-I, and no emergency actions would be required.