Neutron dose estimation by 24Na measurements in the triage of exposed individuals after criticality accidents: a case study of the Tokaimura criticality accident.

We investigated the neutron dose estimation for the triage of personnel involved in criticality accidents by conducting 24Na measurements via the whole-body measurement method. For a case study, we examined the September 1999 Japan Nuclear Fuel Conversion Co. criticality accident (internationally known as "the Tokaimura accident").

Attempt to re-estimate organ doses of victims in non-homogeneous exposure accident by means of the state-of-the-art Mesh-type Reference Computational Phantom-a case study of an IR-192 source accident.

An attempt was made to estimate organ doses of a victim in a high-dose non-homogeneous exposure accident caused by a sealed 192Ir gamma-ray source. The Gilan accident was selected as a case study. Organ doses including testis, red bone marrow and so on were properly estimated by applying the Monte Carlo calculation with the state-of-the-art adult male Mesh type Reference Computational Phantom.

Establishment of a 241Am gamma calibration field based on international standards and its conversion coefficients.

A 241Am gamma (γ)-ray calibration field that meets the requirements for a γ-ray reference field as specified in the ISO 4037 standard series was established in the Facility of Radiation Standards of the Japan Atomic Energy Agency. The reference air kerma rates were measured using a reference ionization chamber calibrated by the N-80 quality X-ray calibration field of the national metrology standard in Japan and with a correction to account for differences in photon energy due to the calibration field. Conversion coefficients for the 241Am γ-ray calibration field, including those not listed in the ISO 4037 standard series, were calculated based on the measured γ-ray fluence rate spectra.

Occupational radiation dose on the hand of assisting medical staff in diagnostic CT scans.

Chronic radiation exposure increases the risk of skin damage of medical personnel engaged in radiology. However, hand dose measurements in computed tomography (CT) for diagnostic purposes have not been evaluated. The occupational radiation dose to the hands of CT assistants was herein investigated to evaluate its compliance with the equivalent dose limit for the hand (500 mSv/year).

Effectiveness of simplified dose estimation equations for triage after criticality accident-a case study of dose assessment in the JCO criticality accident.

The dosimetry for the triage of personnel encountering a criticality accident was investigated. The JCO criticality accident of 1999 was selected as a case study, and attention was paid to the identification and the segregation of severely exposed personnel. A series of Monte Carlo calculations revealed that simplified equations proposed by ANSI to estimate dose with respect to distance work well to determine the region of interest for triage.

Characterization of small radiophotoluminescence dosemeter in terms of HP(0.07) for extremity dose monitoring of medical personnel.

An additional extremity monitoring using a ring badge must be appropriately conducted for inhomogeneous exposure around radiation workers' extremity. Commercially available glass dosemeters are characterized in terms of Hp(0.07) for the application of additional extremity monitoring.

Development of a new integrated IN-VIVO counting system at the QST.

A new in-vivo counting system that functions as both a whole-body counter (WBC) and a lung counter (LC) was developed at the QST to enhance its dose assessment capability. This paper presents an overview of this system and the results of its performance tests. For use of the system as a WBC, three high purity germanium (HPGe) detectors installed in a 20-cm-thick iron shielding chamber are linearly arrayed over a subject lying on the bed, whereas two of the three HPGe detectors are placed over the subject's chest from side to side when using the system as an LC.

Estimation of inhomogeneous occupational exposure to the lens of the eyes and the extremities of radiation workers in a research accelerator facility.

We performed an experimental investigation on occupational exposure of the eye lens and the extremity of radiation workers engaged in handling of highly activated materials in a small research accelerator facility. Using a simplified physical phantom to simulate the relevant inhomogeneous radiation exposure situations, the personal dose equivalents obtained at the eye lens and the extremities of radiation workers handling heavily radioactive converters were measured together with the dose measured by personal dosemeters worn on their trunk. Results of mockup experiments and the Monte Carlo calculations suggest that the quantitative estimation of the eye lens doses can be estimated from the trunk dose, while the extremity doses vary considerably from the dose readings from the trunk, depending on the use of simple point-source or volume source geometry.

DOSE MEASUREMENT PRECISION OF AN RPLD-BASED EYE LENS DOSEMETER APPLICABLE TO THE MEDICAL SECTOR.

We demonstrate a practical calibration method and its applicability for a commercially available radiophotoluminescence dosemeter (RPLD), i.e. the GD-352M (AGC Techno Glass, Shizuoka, Japan) to eye lens dose monitoring, by performing the calibration according to the ISO recommendations.

PROBABILISTIC ANALYSES OF 131I THYROID ACTIVITY IN PERSONS WITH SURFACE CONTAMINATION IN DIRECT MEASUREMENT WITH A STANDING-TYPE WHOLE-BODY COUNTER AS AN EMERGENCY RESPONSE IN A RADIOLOGICAL INCIDENT.

The authors' previous study suggested that a simple standing-type whole-body counter called FASTSCAN (Canberra, Meriden, CT, USA), widely installed throughout Japan after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in March 2011, could be used for thyroid measurements in internal dose assessment after a future radiological incident accompanied by the release of 131I into the environment. The present study performed Monte-Carlo simulations using a computational human phantom with several patterns of body surface contamination and used the results to formulate a method for probabilistic analyses of 131I thyroid activity in persons with surface contamination. The major advantage of this method is that the upper limit of the thyroid activity can be determined from the relative frequency distribution without identifying where body surface contamination remains.

Rapid analysis of Np and Pu isotopes in small volume urine by SF-ICP-MS and ICP-MS/MS.

Internal contamination with alpha-particle emitting actinides, such as Np, Pu, Pu, is likely to bring a large amount of dose to the tissues of persons even if the intake amount is small. To provide timely information for prompt decision-making in radiation emergency therapy, we developed a simple and rapid method for urinary bioassay to determine ultra-trace Np and Pu isotopes using SF-ICP-MS and ICP-MS/MS. To avoid polyatomic interferences and tailing effects from U, Np and Pu isotopes were collected after removing U effectively using a simple single chromatographic column packed with 2 mL AG MP-1M anion exchange resin, exhibiting a high decontamination factor of 10 for U.

APPLICABILITY OF A COMMERCIALLY AVAILABLE ACTIVE EXTREMITY DOSE-RATE METER TO EYE LENS DOSE MONITORING.

A commercially available active extremity dosemeter is a promising candidate for medical staff aid individual monitoring of the eye lens. We investigated the applicability of the newly developed active extremity dosemeter, which uses a low-energy photon probe, to eye lens dose monitoring by performing a complete characterization of the dosemeters. Performance tests revealed that the active extremity dosemeter would overestimate personal dose equivalent, Hp(3), when the probe is worn close to the lens of the eye of a medial worker without any improvement in the response.

EXPERIMENTAL DETERMINATION OF ANISOTROPIC EMISSION OF NEUTRONS FROM 252CF NEUTRON SOURCE WITH THE SPHERICAL PROTECTION CASE.

The anisotropic emission of neutrons from a cylindrical X1 252Cf source with the spherical external casing was experimentally determined. The influence of metal materials and shapes of the external casing to the anisotropy factor, FI(θ), was assessed by the Monte Carlo calculation, before performing the measurement. The results of the calculation implied that light- and spherical-shaped external casing decreases the anisotropic emission of neutrons from a cylindrical source and the nature of the material does not affect the anisotropic emission to a large extent.

EXPOSURE INHOMOGENEITY FROM 241AM AND 90SR/90Y SOURCES IN TERMS OF THE EYE LENS MONITORING IN THE NUCLEAR FACILITIES.

This article highlights the issues of exposure inhomogeneity that are relative to eye lens monitoring for low-energy photons from 241Am and beta-rays from 90Sr/90Y including a personal protective equipment because eye lens exposure has been concerned more than before due to the proposed reduction of relevant dose limit. These nuclides are common and concerned sources in the nuclear industry. Our previous study presented a quantitative estimation of exposure inhomogeneity, which was applied to simple but typical exposure situations.

ESTABLISHMENT OF A LOW DOSE RATE GAMMA RAY CALIBRATION FIELD FOR ENVIRONMENTAL RADIATION MONITORING DEVICES.

For routine calibration of dosemeters used for environmental radiation monitoring, a low dose rate 137Cs gamma ray calibration field that fully satisfies the requirement of the ISO 4037 series was established in the Facility of Radiation Standards in Japan Atomic Energy Agency. Two different methods were employed to determine the reference air kerma rate, namely a conventional ionisation chamber and a G(E) function method used a newly developed scintillation spectrometer. To fulfil the requirement of the ISO 4037 and suppress scattering of Cs gamma ray within the room as far as possible, a suitable lead collimator was introduced to limit the irradiation area at test points and placed at the middle height in an irradiation room with a grating floor.

QUANTITATIVE ESTIMATION OF EXPOSURE INHOMOGENEITY IN TERMS OF EYE LENS AND EXTREMITY MONITORING FOR RADIATION WORKERS IN THE NUCLEAR INDUSTRY.

To manage the equivalent doses for radiation workers, exposure inhomogeneity is an important factor in the decision-making process related to protection measures and additional monitoring. Our previous study proposed the methodology to evaluate the inhomogeneity of exposure quantitatively. In this study, we applied proposed method to five different types of actual exposure situations encountered in the nuclear industry.

CHARACTERIZATION OF AN IN-HOUSE DEVELOPED MULTI-CYLINDRICAL MODERATOR NEUTRON SPECTROMETER.

This article describes the characterization of an in-house developed multi-cylindrical moderator neutron spectrometer, which consists of a cylindrical 3He proportional counter and cylindrical moderator shells of different sizes. The response matrix of the spectrometer was calculated by Monte Carlo simulations for neutron energies from 1 × 10-8 to 10 MeV and verified with measurements in 0.144 MeV, 1.

CORRECTION FACTORS FOR ATTENUATION AND SCATTERING OF THE WALL OF A CYLINDRICAL IONIZATION CHAMBER IN THE 6-7 MeV HIGH-ENERGY PHOTON REFERENCE FIELD.

In high-energy photon reference fields the value of the air kerma rate is determined by using ionization chambers (ICs). From the charge collected inside the IC the dose can be calculated using a set of calibration and correction factors according to ISO 4037-2. A crucial parameter is the correction for the attenuation and scattering of the primary radiation due to the chamber wall.