The expert committee on development and utilization of phantoms had activities from April, 2004 to March, 2006 sponsored by the Japan Health Physics Society. The purpose of the committee was to accumulate and share the latest information concerning phantoms and related technical issues, and to discuss how and for what phantoms should be utilized in future. The committee had twelve meetings and one symposium. Many people took part in the activity including the committee members, observers and other participants; we had a certain number of lectures covering versatile topics and chances to discuss essential problems including sophistication and standardization of phantoms. Some parts of the information we obtained in this activity will be presented in the articles in series.

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A dose assessment program, called RADAPAS (Rapid Dose Assessment Program from Activated Sodium in Criticality Accidents), was developed to evaluate absorbed dose to an exposed person from induced activity of sodium-24, ²⁴Na, in human body. A generally used personnel computer is available to run the developed program. RADAPAS prepares databases of energy spectra and dose conversion coefficients, which had been derived beforehand from Monte Carlo calculations with the MCNP-code. Information necessary for dose calculation is given by a dialogue method with interface displays. The dose to human body can be estimated from measured specific activity of ²⁴Na using the incorporated data and the interactively specified condition in RADAPAS. In order to validate its availability, RADAPAS was implemented to assess radiation dose in an experiment carried out at the Transient Experiment Critical Facility (TRACY) and for heavily exposed persons in the first criticality accident in Japan. The results show that RADAPAS is applicable to estimation of the magnitude of absorbed dose to a victim to determine initial medical treatment soon after a criticality accident.

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We are at a critical time in the history of radiation protection dosimetry. The paradigm shift away from the more-than-30-years-old stylized human models is imminent with the development of 30 voxel-based tomographic models in recent years that are based on medical images. Recently, researchers gathered at an international conference to share the latest work and to establish collaborations. This invited review paper introduces various types of modelling and summarizes the latest developments including a Consortium on Computational Human Phantoms (CCHP) that is aimed at facilitating intercomparison and sharing of data for radiation protection purposes.

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