The Calculation Study Of The Concentration And The Radiation Dsoe Of Airborne Radionuclides From Nuclear Facility

In China, most of nuclear facilities having made great contribution to thenational defense and scientific research for the country are located in the westinland. As the development of nuclear plants from coastal areas to inland,there will be more and more inland nuclear facilities. For the specialgeographical environment and meteorological condition of inland areas,especially the meteorological condition of high frequency of small wind, it isvery hard for airborne radionuclides to transport and diffuse under suchcondition, so it is easy for serious radioactive pollution accidents to takeplace. Therefore, the study of radionuclides dispersion and radiation impactunder site with high frequency of small wind makes big sense to the guidanceof nuclear facilities construction and accident emergency as well as to protectpeople from suffering radiation hazard.Basing on Gaussian plume model and Gaussian puff model, a newmodel is established in this paper, which is used to calculate dispersion ofairborne radionuclides at low wind spread under normal condition. Thencompile the model into a program, and use it to calculate the concentration ofthe airborne radionuclides around an inland military nuclear facility in thewest within 80 kilometers under normal condition. In addition, combiningstatistical information of the agriculture, planting and livestock industryaround nuclear facility within 80 kilometers, a reasonable dose model is usedto calculate the maximum individual annual effective dose equivalent of thepublic. The results show that, the nuclide concentration is reduced as the increase of the distance from the source. The descend gradient is big, whenthe distance is within 10 km, otherwise, the descend gradient greatly reduced.Under normal condition of nuclear facility, the maximum individual annualeffective dose equivalent of the public is 6.37×10-8 Sv/a. This value is only0.025% of the natinoal limit and 0.003% of average individual naturalbackground radiation dose. Individual effective dose equivalent is mainlycontributed by the nuclide contribution of I-131, and it exposes human bodymainly via the ingestion path. Of eating food category, vegetables contributemost of dose, for its large intake and short storage time.In this paper, a CALPUFF simulation model is choosed to simulate theatmospheric dispersion of airborne radionuclides under accident condition.The conclusions are as follows: the high frequency of calm along with theunstable atmospheric stratification at the nuclear facility site limitstransportation of radionuclides in horizontal direction, but significantlyincreases dispersion of radionuclides in vertical direction, forming peakconcentration and peak radiation dose near source. Under selected accidentcondition and weather condition, the maximum individual effective doseequivalent around nuclear facilities within 80 kilometers is 1.80×10-7 Sv (notcontaining radiation dose via ingestion). Compared with the ingestion dosepercentage of I-131 under normal conditon, the individual maximumeffective dose equivalent is calculated to be 8.08×10-4Sv, which is only 0.8%of the national major accident dose limit.