Yoshimura K, Watanabe T, Kurikami H. Vertical and horizontal distributions of
137Cs on paved surfaces affected by the Fukushima Dai-ichi Nuclear Power Plant accident.
J Environ Radioact 2020;
217:106213. [PMID:
32217245 DOI:
10.1016/j.jenvrad.2020.106213]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 02/14/2020] [Accepted: 02/16/2020] [Indexed: 06/10/2023]
Abstract
Vertical and horizontal distributions are fundamental for sampling and in-situ gamma spectrum measurement strategies. The distributions of 137Cs were investigated for paved surfaces affected by the Fukusima Dai-ichi Nuclear Power Plant accident. Additionally, the effects of the distributions on the measurement uncertainties of in-situ spectrometry were evaluated. Relaxation mass depth, representing the depth profile of 137Cs, was estimated to be less than 0.23 g cm-2. Variation in the relaxation mass depth, of 0.1-0.23 g cm-2, led to a minor error (less than 5%) in the spectral analysis of the137Cs inventory (activity per unit area, kBq m-2). The 137Cs inventory, within a 20 × 20 m square of 400 cells each measuring 1 m2, showed an uneven distribution with large variation; coefficient of variation ranged from 54 to 136% of geometric average inventory of 424 kBq m-2. Increasing the grid size decreased 137Cs inventory variation among cells, revealing the relationship between instrument field of view and the spatial uncertainty of the results of in-situ gamma spectrometry.
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