Radionuclides leak to the environment and cause harm to the public in design basis accident. Accurate evaluation of radioactivity and radiation dose in accident is crucial. In this paper, LOCA was selected as a typical design basis accident to carry out radiation dose evaluation for self-designed advanced PWR in China. The radioactivity and radiation dose evaluation models were established and used to analyze the radiation dose at the exclusion area boundary (EAB) and the outer boundary of low population zone (LPZ). Finally, the radiation dose of China’s advanced PWR was compared with that of the M310 reactor.After iodine releasing into the containment, the nuclides continued to decay, deposit, remove and leak, then released into the environment. For the longer half-life nuclides, such as 131I, 133I, 135I, they released to the environment continuously. For the shorter half-life nuclides, such as 132I and 134I, due to faster decay process, radioactivity from them no longer released into the environment after a few hours in the accident.For noble gases, the removal mechanism in the containment only relied on its own decay and leakage to the environment. Due to its extreme long half-life, 85Kr reduced slowly in the containment, and the accumulated amount releasing to the environment increased gradually. Because of shorter half-life of 83mKr, 85mKr, 87Kr and 88Kr, they would not release into the environment after about 10 hours in the accident. The trends of Xenon were similar to those of Krypton. The amount of 138Xe and 135mXe decreased quickly in containment and no longer released to the environment after about 2 hours in the accident. 133Xe may release the largest radioactivity to environment, more than 1015Bq.The total effective dose and thyroid dose increased with time, especially in the first day. Inhalation dose was the major contribution to the total effective dose, accounted for more than 80%. The total effective dose and thyroid dose of China’s advanced PWR at EAB and the outer boundary of LPZ were at least one order of magnitude smaller than that of M310, which fully met the requirements of Chinese GB6249. The difference of radiation dose between the two reactors was so significant, due to different site diffusion conditions and different radioactivity and dose calculation assumptions based on the reactor design and safety features. China’s advanced PWR made many improvements on the reactor design and further improved its safety, which may mitigate the consequences of accident.

Radiation Dose Evaluation of Typical Design Basis Accident for Advanced PWR in China

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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