Japanese Journal of Health Physics

A method was developed to estimate ⁹⁰Sr contamination density on a concrete surface or on the surface of soil or water within 1 g/cm² using 70-μm dose equivalent rates. The 70-μm dose equivalent rates from contaminated areas of various sizes were calculated at heights of 3.0, 5.0, 10.0, and 50.0 cm using egs5 Monte Carlo code. The ratio between the measured 70-μm dose equivalent rate ratio at 50 cm and that at 3.0, 5.0, or 10 cm can be used to estimate the effective radius of the contaminated area by using the calculation results. The contaminated density is obtained from the measured 70-μm dose equivalent rate with the calculated radially dependent conversion factor.

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The Expert Committee on Radiation Protection of the Lens of the Eye was established under the Japan Health Physics Society in April, 2013 (completed, March, 2015). The Committee looked at new/revised documents and standards related to the eye lens published by international organizations such as the International Commission on Radiological Protection (ICRP) and the International Commission on Radiation Units and Measurements (ICRU). The Committee also examined recent and previous studies related to eye-lens radiation exposure and dosimetry in Japan. These findings were published in this journal as the Interim Report of the Committee. Since then, the Committee expanded its activity to give an overview the current progress of eye-lens dosimetry R&D at the National Institute of Advanced Industrial Science and Technology, along with research related to radiation management and estimated eye-lens exposure of Japanese nuclear-power-plant workers (including those at Fukushima Daiichi Nuclear Power Plant) for publishing an addendum Committee report. These additional findings are reported here.

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In a mixed field of photon and beta radiations, the same dose assigned to skin is normally assigned to the dose to the lens of the eye as a conservative estimate of H_p(3). In exceptional cases where a very high beta dose might be imparted of the same order with the dose limit, however, the conservatively biased dose must be too limiting, and thereby an accurate estimate of beta H_p(3) is desirable. This addendum report of the Japan Health Physics Society Expert Committee on Radiation Protection of the Lens of the Eye presents a practical proposal of when and how the dosimetry of beta H_p(3) should be made.

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Following the Statement on Tissue Reaction issued by the International Commission on Radiological Protection (ICRP), revisions and discussions are underway in various international organizations about the standards, guidelines and methods for the eye dosimetry. We have previously discussed these issues in six interim reports, followed by two addendum reports on lens dosimety. This addendum report reviews ongoing overseas discussion and work in relation to research on radiogenic cataracts and implementation of the new eye lens dose limit, such as those in the European Commission, Low Dose Research towards Multidisciplinary Integration (DoReMi), Open Project for European Radiation Research Area (OPERRA), and the Unite Sates National Council on Radiation Protection and Measurements (NCRP). This report serves as the last part of a series of reports by the Japan Health Physics Society Expert Committee on Radiation Protection of the Lens of the Eye.

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