PubMed Health⌕ Search

Biomedical subjects

M Luszik-Bhadra

Publications and source records attributed to M Luszik-Bhadra.

At least 19 recordsLinked to original sources
PubMed2007

Compliance of electronic personal neutron dosemeters with the new International Standard IEC 61526.

The recommendations and test requests for the dose equivalent response of personal neutron dosemeters formulated by the new International Standard IEC 61526 are summarised. In particular, IEC 61526 allows the use of broad fields if dosemeters do not fulfil the hard requirements using monoenergetic neutrons. Some broad fields which can work as a replacement field using ISO sources (252Cf, 252Cf (D2O mod.), 241Am-Be) and simulated workplace fields (CANEL and SIGMA) are described. This work shows the results of recent measurements of the personal dose equivalent response for the dosemeters Thermo Electron EPD-N2, Aloka PDM-313 and the prototype dosemeter PTB DOS-2002, and discusses their compliance with respect to the new IEC 61526 standard.

Electronics↗
PubMed2006

Determination of the full response function of personal neutron dosemeters.

The response of neutron dosemeters may be determined directly from measurements, provided a sufficiently large number of measurements in monoenergetic neutron fields covering the entire energy range of interest is available. In practice this is not feasible due to the lack of monoenergetic neutron fields in the thermal and intermediate energy region (i.e. energies<24 keV). To deal with this difficulty, we have developed a method which can take into account additional information about the response of the dosemeter. Our analysis makes use of two types of data, measurements made using monoenergetic neutron beams and measurements made in neutron fields with broad energy distributions. The dosemeter responses are described using a parametrised model, based on a minimum of assumptions: that they should fit the data within experimental uncertainties, and that they should remain close to a simple interpolation of the monoenergetic and thermal neutron field data.

Algorithms↗
PubMed2006

Overview of active personal dosemeters for individual monitoring in the European Union.

In 2001, the European Radiation Dosimetry Group, EURADOS, started a working group on 'Harmonisation of Individual Monitoring in Europe and the Dissemination of Information on New Techniques in this Field'. Within this group, one of the projects consisted of analysing the status of active personal dosemeters (APDs) in Europe. This paper reviews the regulatory requirements for APDs in 15 EU member states and summarises the main characteristics of commercial and new developments in this field. In particular, it focuses on the comparison of APD performance and standard passive dosimetry systems. Based on this information, an evaluation is initiated to establish why several countries are reluctant to accept APDs for dose records.

Environmental Exposure↗
PubMed2006

Performance of the electronic personal dosemeter for neutron 'Saphydose-N' at different workplaces of nuclear facilities.

This paper mainly aims at presenting the measurements and the results obtained with the electronic personal neutron dosemeter Saphydose-N at different facilities. Three campaigns were led in the frame of the European contract EVIDOS ('Evaluation of Individual Dosimetry in Mixed Neutron and Photon Radiation Fields'). The first one consisted in the measurements at the IRSN French research laboratory in reference neutron fields generated by a thermal facility (SIGMA), radionuclide ISO sources ((241)AmBe; (252)Cf; (252)Cf(D(2)O)\Cd) and a realistic spectrum (CANEL/T400). The second one was performed at the Krümmel Nuclear Power Plant (Germany) close to the boiling water reactor and to a spent fuel transport cask. The third one was realised at Mol (Belgium), at the VENUS Research Reactor and at Belgonucléaire, a fuel processing factory.

Dose-Response Relationship, Radiation↗
PubMed2006

Evaluation of individual monitoring in mixed neutron/photon fields: mid-term results from the EVIDOS project.

EVIDOS is an EC sponsored project that aims at an evaluation and improvement of radiation protection dosimetry in mixed neutron/photon fields. This is performed through spectrometric and dosimetric investigations during different measurement campaigns in representative workplaces of the nuclear industry. The performance of routine and, in particular, novel personal dosemeters and survey instruments is tested in selected workplace fields. Reference values for the dose equivalent quantities, H(*)(10) and H(p)(10) and the effective dose E, are determined using different spectrometers that provide the energy distribution of the neutron fluence and using newly developed devices that determine the energy and directional distribution of the neutron fluence. The EVIDOS project has passed the mid-term, and three measurement campaigns have been performed. This paper will give an overview and some new results from the third campaign that was held in Mol (Belgium), around the research reactor VENUS and in the MOX producing plant of Belgonucléaire.

Equipment Design↗
PubMed2006

Electronic neutron personal dosemeters: their performance in mixed radiation fields in nuclear power plants.

This work describes spectral distributions of neutrons obtained as function of energy and direction at four workplace fields at the Krümmel reactor in Germany. Values of personal dose equivalent H(p)(10) and effective dose E are determined for different directions of a person's orientation in these fields and readings of personal neutron dosemeters--especially electronic dosemeters--are discussed with respect to H(p)(10) and E.

Dose-Response Relationship, Radiation↗
PubMed2006

Aspects of harmonisation of individual monitoring for external radiation in Europe: conclusions of a EURADOS action.

Following the publication of the EU Council Directive 96/29, EURADOS coordinated two working groups (WGs) for promoting the process of harmonisation on individual monitoring of occupationally exposed persons in Europe. An overview of the major findings of the second WG is presented. Information on the technical and quality standards and on the accreditation and approval procedures has been compiled. The catalogue of dosimetric services has been updated and extended. An overview of national regulations and standards for protection from radon and other natural sources in workplaces has been made, attempting to combine the results from individual monitoring for external, internal and workplace monitoring. A first status description of the active personal dosemeters, including legislative and technical information, and their implementation has been made. The importance of practical factors on the uncertainty in the dose measurement has been estimated. Even if a big progress has been made towards harmonisation, there is still work to be done.

Europe↗
PubMed2005

Space radiation measurements on-board ISS--the DOSMAP experiment.

The experiment 'Dosimetric Mapping' conducted as part of the science program of NASA's Human Research Facility (HRF) between March and August 2001 was designed to measure integrated total absorbed doses (ionising radiation and neutrons), heavy ion fluxes and its energy, mass and linear energy transfer (LET) spectra, time-dependent count rates of charged particles and their corresponding dose rates at different locations inside the US Lab at the International Space Station. Owing to the variety of particles and energies, a dosimetry package consisting of thermoluminescence dosemeter (TLD) chips and nuclear track detectors with and without converters (NTDPs), a silicon dosimetry telescope (DOSTEL), four mobile silicon detector units (MDUs) and a TLD reader unit (PILLE) with 12 TLD bulbs as dosemeters was used. Dose rates of the ionising part of the radiation field measured with TLD bulbs applying the PILLE readout system at different locations varied between 153 and 231 microGy d(-1). The dose rate received by the active devices fits excellent to the TLD measurements and is significantly lower compared with measurements for the Shuttle (STS) to MIR missions. The comparison of the absorbed doses from passive and active devices showed an agreement within +/- 10%. The DOSTEL measurements in the HRF location yielded a mean dose equivalent rate of 535 microSv d(-1). DOSTEL measurements were also obtained during the Solar Particle Event on 15 April 2001.

Aerospace Medicine↗
PubMed2004

Measurement of energy and direction distribution of neutron and photon fluences in workplace fields.

Within the EU Project EVIDOS, a spectrometer with 24 silicon detectors mounted on the surface of a polyethylene sphere is used for the determination of the energy and direction distribution of neutrons and photons. It has been characterized with respect to neutron radiation with energies from thermal up to 15 MeV and to photon radiation with energies from 65 keV to 6 MeV. The first measurements described here were performed in the simulated workplace field, CANEL, at Cadarache, with the purpose of checking the instrument and the unfolding procedures.

Environmental Exposure↗
PubMed2004

The electronic neutron/photon dosemeter PTB DOS-2002.

During the last few years, PTB has developed the electronic dosemeter DOS-2002. It is of an especially simple design (1 silicon detector) and detects the photon and neutron personal dose equivalent with a low detection threshold of 0.016 and 10 microSv, respectively. Its dosimetric characteristics have been determined in neutron fields with energies ranging from thermal energies up to 15 MeV and in photon fields with mean energies from 65 keV to 7 MeV. It can be used in a wide temperature region from -20 degrees C to +50 degrees C, shows almost no interference in electromagetic fields but is still shock sensitive.

Body Burden↗
PubMed2004

Electronic personal dosemeters: the solution to problems of individual monitoring in mixed neutron/photon fields?

An overview is given showing the main principles of the present-day electronic neutron dosemeters. The radiological performance of the devices is described in a comparative way. This includes chiefly the personal dose equivalent Hp(10) response for monoenergetic neutrons and in practical fields with broad energy distributions and estimations of the low dose limit for neutrons.

Artifacts↗
PubMed2004

Individual neutron monitoring in workplaces with mixed neutron/photon radiation.

EVIDOS ('evaluation of individual dosimetry in mixed neutron and photon radiation fields') is an European Commission (EC)-sponsored project that aims at a significant improvement of radiation protection dosimetry in mixed neutron/photon fields via spectrometric and dosimetric investigations in representative workplaces of the nuclear industry. In particular, new spectrometry methods are developed that provide the energy and direction distribution of the neutron fluence from which the reference dosimetric quantities are derived and compared to the readings of dosemeters. The final results of the project will be a comprehensive set of spectrometric and dosimetric data for the workplaces and an analysis of the performance of dosemeters, including novel electronic dosemeters. This paper gives an overview of the project and focuses on the results from measurements performed in calibration fields with broad energy distributions (simulated workplace fields) and on the first results from workplaces in the nuclear industry, inside a boiling water reactor and around a spent fuel transport cask.

Artifacts↗
PubMed2004

An unfolding method for directional spectrometers.

The development of new spectrometers that are sensitive to the directional distribution of neutrons requires new unfolding methods that can determine the distribution of the neutron fluence as a function of energy and angle. Such information is needed to compute non-isotropic dosimetric quantities (e.g. personal dose equivalent and effective dose). We describe an unfolding method that applies the maximum entropy principle to this problem. It maximises the relative entropy, defined as the information-theory entropy of the distribution of the neutron fluence relative to a distribution that encodes prior knowledge, subject to constraints imposed by the measurements. We provide examples of the applicability of the method using data from two directional spectrometers of different design that have been developed in the context of EVIDOS, a project concerning mixed neutron-photon field analysis in the nuclear industry.

Anisotropy↗
PubMed2004

Active personal dosemeters for individual monitoring and other new developments.

In this paper, we will present a first (but not complete) status description of active personal dosemeters (APDs) and their implementation in European countries. In modern radiation protection practices, APDs are becoming absolutely necessary operational tools for satisfying the ALARA principle. Despite their success, they are relatively new for individual monitoring of workers. Regulation, legal requirements and calibration procedures are different in European member states. A catalogue of commercially available and prototype devices is presented. Improvement on devices and in implementation of calibration method are expected in the forthcoming years. End-user feedback experience and requirements are reported.

Body Burden↗
PubMed2002

Individual monitoring in mixed neutron/photon fields using a single silicon detector.

A device based on a single silicon detector of special converter/detector design optimised for the determination of the neutron dose equivalent is also used for the determination of the photon dose equivalent. While the neutron dose is determined on the basis of signals corresponding to energy depositions above 1.5 MeV, depositions between 80 keV and 150 keV are used for the photon dose equivalent. In this way, a photon response is achieved which varies by less than 30% in the energy region from 80 keV to 7 MeV for irradiation at normal incidence and at 60 degrees to the normal. The lower limit of detection is of the order of 1 microSv. Neutrons contribute to the photon reading by less than 2% in mixed fields with a comparable dose equivalent from neutrons and photons.

Equipment Design↗
PubMed2002

Experience in long-term neutron dose equivalent measurements using etched track detectors with (n,alpha) converters in moderators.

Etched track Makrofol detectors combined with Kodak BN-1 boron (n,alpha) converters were used inside a 30 cm diameter polyethylene (PE) sphere for the measurement of the neutron ambient dose equivalent. We found unexpectedly high values for the neutron dose equivalent of about 250 microSv instead of 25 microSv for 3 months' exposure in the natural environment. Results from such detectors etched in the authors' labortories revealed that the tracks could only be induced by spontaneous particle emission from the converter. This was confirmed by track diameter analysis and additional special etching of deeper detector layers. Eight surface barrier detectors were used simultaneosly for several days to measure the alpha spectra of the converters. The overall count rate in the energy range 2.5-7.5 MeV was 10 alpha particles d(-1) x cm(-2) for most of the converters and about 10 times less than this for some of them. To identify the nuclides responsible for alpha emission within the converters, gamma spectra of converters were measured for 8 days using a highly sensitive low-background gamma spectrometry system The spectra clearly indicated a small contamination (10 +/- 3 mBq) of the converter foils with 225Ra (T(1/2) = 5.7 y) typically originating from 232Th.

Alpha Particles↗
PubMed2001

Development of personal neutron dosemeters at the PTB and first measurements in the space station MIR.

A passive neutron dosemeter with thermoluminescence and etched-track detectors was used in the space station MIR in 1995 and 1997 and during some shuttle flights to MIR. High neutron doses of about 200 microSv d-1 were measured with track detectors, while the contribution of protons to the track density was estimated to be small. An active personal dosemeter based on silicon diodes providing a direct readout, improved sensitivity and spectrometric properties is proposed for additional monitoring. Firstly, measurements with a prototype were performed in the stray radiation fields of the CERN-EU Reference Radiation Facility. When mounted on a phantom at different positions, both the passive and the active dosemeter provide the directional distribution of neutrons via an unfolding procedure. This can be helpful for a better understanding of the complex radiation field in space and for comparisons with calculations.

Calibration↗