Comparison of calculated beta- and gamma-ray doses after the Fukushima accident with data from single-grain luminescence retrospective dosimetry of quartz inclusions in a brick sample via Journal of Radiation Research

ABSTRACT

To estimate the beta- and gamma-ray doses in a brick sample taken from Odaka, Minami-Soma City, Fukushima Prefecture, Japan, a Monte Carlo calculation was performed with Particle and Heavy Ion Transport code System (PHITS) code. The calculated results were compared with data obtained by single-grain retrospective luminescence dosimetry of quartz inclusions in the brick sample. The calculated result agreed well with the measured data. The dose increase measured at the brick surface was explained by the beta-ray contribution, and the slight slope in the dose profile deeper in the brick was due to the gamma-ray contribution. The skin dose was estimated from the calculated result as 164 mGy over 3 years at the sampling site.

 The main fission products from the Fukushima Daiichi nuclear power plant (FDNPP) accident are ^129mTe-¹²⁹Te, ¹³¹I, ¹³²Te-¹³²I, ¹³⁴Cs, ¹³⁶Cs and ¹³⁷Cs [1–4]. These radionuclides emit gamma rays and beta rays through β⁻ decay. However, there are few studies about dose estimation from beta-ray irradiation following the FDNPP accident [5–7]. The beta-ray dose contributes to the whole-body dose among small biota, such as insects, plant leaves, and human skin. Therefore, beta-ray dose estimations are important for the risk assessment of the impact of the FDNPP accident (including on small biota) to clarify the effects of this large-scale radiological accident.

Retrospective dosimetry with brick samples has been used to evaluate the gamma-ray dose of the Hiroshima atomic bomb [8–10], the Chernobyl nuclear power plant accident [11–14], and the Semipalatinsk nuclear weapon testing [15, 16]. Recently, Stepanenko et al. [17] used retrospective dose evaluation of brick samples to estimate gamma-ray doses and perform beta-ray dose reconstruction for the FDNPP accident with a similar method to that used for a Hiroshima tile sample [18]. 

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