Temporal Attenuation of Gamma Dose Rate in Air Due to Radiocesium Downward Mobility in Soil

• Published in: Health physics (1958) Vol. 120; no. 2; pp. 163 - 170
• Main Author: Velasco, Hugo
• Format: Journal Article
• Language: English
• Published: United States Lippincott Williams & Wilkins 01-02-2021; by the Health Physics Society; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Accidents; Air Pollutants, Radioactive - analysis; Attenuation; Cesium; Cesium 134; Cesium 137; Cesium isotopes; Cesium radioisotopes; Cesium Radioisotopes - analysis; Diffusion coefficient; Diffusion rate; Dosage; Fukushima Nuclear Accident; Gamma Rays; Mobility; Nuclear accidents; Nuclear accidents & safety; Nuclear power plants; Radiation Dosage; Radiation Monitoring - methods; Radioisotopes; Soil - chemistry; Soil investigations; Soil Pollutants, Radioactive - analysis; Soils; Time Factors
• ISSN: 0017-9078; 1538-5159; 1538-5159
• DOI: 10.1097/HP.0000000000001294

ABSTRACTThe Chernobyl and Fukushima Dai-ichi Nuclear Power Plant accidents have demonstrated that radiocesium deposited on the ground was one of most important pathway contributions to the air dose rate. Cesium-134 contributes more significantly in the first period of 2–3 y. However, Cs external exposure may remain relevant for decades. The contribution to the air dose rate attributable to these radionuclides is maximum at the deposition time and then usually decreases over time. The dose rate temporal reduction is a consequence of both the radionuclide physical decay and the radionuclide downward mobility in soil. In this investigation, this decreasing behavior of the air dose rate is approached using an empirical attenuation function, and its coefficients are computed in terms of the effective diffusion coefficient and downward migration rates of radiocesium in soil. The methodology is tested for different hypothetical scenarios and in real situations, including areas affected by the two major accidents at nuclear power plants.