Comparison of the accident process, radioactivity release and ground contamination between Chernobyl and Fukushima-1

TLDR

Chernobyl was a power‑surge reactor‑core destruction, whereas Fukushima‑1 was a loss‑of‑coolant core‑meltdown, producing distinct radionuclide releases and ground‑contamination patterns, with Chernobyl involving a broader range of radionuclides and Fukushima dominated by volatile species. Fukushima released more noble gases but contaminated a ten‑fold smaller area with 137 Cs, whereas Chernobyl’s 137 Cs deposition yielded higher immediate (770 µGy h⁻¹) and cumulative (970 mGy) exposure, with radiocesium contributing 49 % of Chernobyl’s and 98 % of Fukushima’s dose.

Abstract

In this report, we have reviewed the basic features of the accident processes and radioactivity releases that occurred in the Chernobyl accident (1986) and in the Fukushima-1 accident (2011). The Chernobyl accident was a power-surge accident that was caused by a failure of control of a fission chain reaction, which instantaneously destroyed the reactor and building, whereas the Fukushima-1 accident was a loss-of-coolant accident in which the reactor cores of three units were melted by decay heat after losing the electricity supply. Although the quantity of radioactive noble gases released from Fukushima-1 exceeded the amount released from Chernobyl, the size of land area severely contaminated by 137 Cesium ( 137 Cs) was 10 times smaller around Fukushima-1 compared with around Chernobyl. The differences in the accident process are reflected in the composition of the discharged radioactivity as well as in the composition of the ground contamination. Volatile radionuclides (such as 132 Te- 132 I, 131 I, 134 Cs and 137 Cs) contributed to the gamma-ray exposure from the ground contamination around Fukishima-1, whereas a greater variety of radionuclides contributed significantly around Chernobyl. When radioactivity deposition occurred, the radiation exposure rate near Chernobyl is estimated to have been 770 μGy h −1 per initial 137 Cs deposition of 1000 kBq m −2 , whereas it was 100 μGy h −1 around Fukushima-1. Estimates of the cumulative exposure for 30 years are 970 and 570 mGy per initial deposition of 1000 kBq m −2 for Chernobyl and Fukusima-1, respectively. Of these exposures, 49 and 98% were contributed by radiocesiums ( 134 Cs + 137 Cs) around Chernobyl and Fukushima-1, respectively.