Comparison of different PADC materials for neutron dosimetry

Investigations on track density and track size distributions of different PADC (poly allyl diglycol carbonate) materials have been performed. The PADC used for the tests has been produced by Thermo Electron (USA), Track Analysis System Limited (UK), Chiyoda Technol Corporation (Japan) and Intercast srl (Italy). For each PADC material 120 detectors were randomly selected out of 2 sheets: 60 detectors from one sheet have been irradiated with a personal dose equivalent of 3 mSv in the field of a 241Am-Be source at the calibration laboratory of PSI, whilst the other 60 detectors from the other sheet have been used as background samples. All detectors have been processed according to an identical etching procedure and have been analysed with TASLImage scanning system. For each set of detectors the value of the average background signal, the average neutron sensitivity and the detection limit with respect to a personal dose equivalent measured with a dosemeter based on PADC have been determined. The results of the investigations allowed a comparison of the neutron sensitivity and background signal behaviours of PADC materials from different manufacturers and the assessment of the variation of neutron sensitivity and background signal over a single shee

Performance of a PADC personal neutron dosemeter at simulated and real workplace fields of the nuclear industry

In the framework of the EVIDOS (Evaluation of Individual Dosimetry in Mixed Neutron and Photon Radiation Fields) project, funded by the EC, measurements with PADC personal neutron dosemeters were carried out at several workplace fields of the nuclear industry and at simulated workplace fields. The measured personal neutron dose equivalents of the PADC personal neutron dosemeter are compared with values that were assessed within the EVIDOS project by other partners. The detection limits for different spectra types are given. In cases were the neutron dose was too low to be measured by the PADC personal neutron dosemeter, the response is estimated by convoluting the responses to monoenergetic neutrons with the dose energy distribution measured within EVIDOS. The advantages and limitations of the PADC personal neutron dosemeter are discusse

Progress report of the CR-39 neutron personal monitoring service at PSI

At the Paul Scherrer Institute a personal neutron dosimetry system based on chemically etched CR-39 detectors and automatic track counting is in routine use since the beginning of 1998. The quality of the CR-39 detectors has always been a crucial aspect to maintain a trustable personal neutron dosimetry system. This paper summarises the 7 y experience in routine use. The effect of detector material defects which could lead to false positive neutron doses is described. The potentiality of improving the background statistics by extending the pre-etch time is investigated and involves as a drawback a quite lower sensitivity to thermal neutrons. Furthermore, the impact of small changes in the production process of the detectors on the response to fast and thermal neutrons is shown. For the personal dosimetry at CERN, a new dosimetry concept was launched by combining a CR-39 neutron dosemeter with a Direct-Ion Storage (DIS) dosemeter for photon and beta radiation. The usage period of the CR-39 dosemeters is prolonged now from 3 months up to 12 months. In this context, the long-term behaviour over 1 y of the background track density and the response to Am-Be are describe

Determination of the response function for two personal neutron dosemeter designs based on PADC

Since 1998 neutron dosimetry based on PADC (poly allyl diglycol carbonate) is done with a so-called original Paul Scherrer Institute (PSI) design at PSI. The original design (i.e. holder) was later changed. Both designs are optimised for use in workplaces around high-energy accelerators, where the neutron energy spectra are dominated by fast neutrons ranging up to some 100 MeV. In addition to the change of the dosemeter design a new evaluation method based on a microscope scanning technique has been introduced and the etching conditions have been optimised. In the present work, the responses obtained with the original and the new dosemeter designs are compared for fields of radionuclide sources and monoenergetic reference fields using the new evaluation method. The response curves in terms of the personal dose equivalent for normally incident neutrons were built as functions of the incident neutron energ

Present status of the personal neutron dosemeter based on direct ion storage

In this paper the present status of the Direct Ion Storage Neutron (DIS-N) prototype dosemeter (RADOS) is described. The separation of neutron from photon dose equivalent has been improved by adding tin shieldings. The neutron energy response has been changed by additional plastic covers containing 40% B4C in order to reduce the over-response to thermal neutrons. The responses of the dosemeters were determined for standard photon and neutron fields (monoenergetic neutrons, neutron sources and simulated workplace fields). Irradiations in real workplaces were also performed. The dependence of the neutron response on the angle of incidence was measured for different neutron source

Performance of a personal neutron dosemeter based on direct ion storage at workplace fields in the nuclear industry

In the framework of the EVIDOS project, funded by the EC, measurements were carried out using dosemeters, based on ionisation chambers with direct ion storage (DIS-N), at several workplace fields, namely, at a fuel processing plant, a boiling and a pressurised water reactor, and near transport and storage casks. The measurements and results obtained with the DIS-N in these workplaces, which are representative for the nuclear industry, are described in this study. Different dosemeter configurations of converter and shielding materials were considered. The results are compared with values for personal dose equivalent which were assessed within the EVIDOS project by other partners. The advantages and limitations of the DIS-N dosemeter are discusse

Influence of variation of etching conditions on the sensitivity of PADC detectors with a new evaluation method

At the Paul Scherrer Institut, a personal neutron dosimetry system based on chemically etched poly allyl diglycol carbonate (PADC) detectors and an automatic track counting (Autoscan 60) for neutron dose evaluations has been in routine use since 1998. Today, the hardware and the software of the Autoscan 60 are out of date, no spare components are available anymore and more sophisticated image-analysis systems are already developed. Therefore, a new evaluation system, the ‘TASLIMAGE', was tested thoroughly in 2009 for linearity, reproducibility, influence of etching conditions and so forth, with the intention of replacing the Autoscan 60 in routine evaluations. The TASLIMAGE system is based on a microscope (high-quality Nikon optics) and an ultra-fast three-axis motorised control for scanning the detectors. In this paper, the TASLIMAGE system and its possibilities for neutron dose calculation are explained in more detail and the study of the influence of the variation of etching conditions on the sensitivity and background of the PADC detectors is described. The etching temperature and etching duration were varied, which showed that the etching conditions do not have a significant influence on the results of non-irradiated detectors. However, the sensitivity of irradiated detectors decreases by 5 % per 1°C when increasing the etching temperature. For the variation of the etching duration, the influence on the sensitivity of irradiated detectors is less pronounce

Characterisation of the PSI whole body counter by radiographic imaging

A joint project between the Paul Scherrer Institut (PSI) and the Institute of Radiation Physics was initiated to characterise the PSI whole body counter in detail through measurements and Monte Carlo simulation. Accurate knowledge of the detector geometry is essential for reliable simulations of human body phantoms filled with known activity concentrations. Unfortunately, the technical drawings provided by the manufacturer are often not detailed enough and sometimes the specifications do not agree with the actual set-up. Therefore, the exact detector geometry and the position of the detector crystal inside the housing were determined through radiographic images. X-rays were used to analyse the structure of the detector, and 60Co radiography was employed to measure the core of the germanium crystal. Moreover, the precise axial alignment of the detector within its housing was determined through a series of radiographic images with different incident angles. The hence obtained information enables us to optimise the Monte Carlo geometry model and to perform much more accurate and reliable simulation

Genome-wide association study for 13 udder traits from linear type classification in cattle

Udder conformation traits are known to correlate with the incidence of clinical mastitis and the length of productive life. The results of a genome-wide association study based on imputed high-density genotypes of 1,637 -Brown Swiss sires and de-regressed breeding values for 13 udder traits are presented here. For seven traits significant signals could be observed in five regions on BTA3, BTA5, BTA6, BTA17, and BTA25. For fore udder length and teats diameter significant SNPs were found in a known region around 90 Mb on BTA6. For the trait rear udder height significant SNPs are positioned in the coding region of the SNX29gene. Several significant SNPs around 62 Mb on BTA17 are associated with the traits rear udder width, frontteat placement and rear teat placement. The function of potential candidate genes and the influence of substructure will be addressed as next steps