Comparing the effectiveness of learning formats in radiation protection.

At the Belgian Nuclear Research Centre (SCK CEN) more than 850 employees advance the peaceful applications of ionising radiation through research, services and education and training. Several initiatives are taken to guarantee a safe working environment, one of them being a compulsory introductory safety training for all new employees, followed by refresher courses. With the objective to increase the flexibility for the participants and to optimise the teaching time of lecturers, the training format is adapted from face-to-face training to blended learning in which a significant amount of online learning is introduced. To appraise the perception and effectiveness of the original face-to-face training and the newly developed e-learning modules, and to compare both, information is gathered on two levels. Firstly, to monitor the perception of the participants regarding the face-to-face and e-learning formats an online questionnaire was launched. Secondly to evaluate the knowledge gain (difference between pre- and post-test results), the participants were requested to answer the same set of technical/scientific questions before and after the training. Results of the perception study show that the e-learning format was well received by the learners. For both learning formats an overall knowledge gain was noticed. The highest knowledge gain was noticed for the e-learning format. The results on perception and effectivity of the e-learning format confirm the further use of this format.

Neutron spectrometry around the VENUS reactor using Monte Carlo simulations and Bonner spheres measurements.

This paper presents the assessment of the neutron field near the VENUS reactor, particularly in areas near the reactor shielding where operators are frequently present during a reactor run. To obtain reference spectra in the area of interest, MCNPX simulations were performed. Reference spectrometry was also performed using a Bonner spheres system. The outcome of both calculations and measurements is compared.

The response of the BTI bubble detectors in mixed gamma-neutron workplace fields.

Bubble detectors have become a mature technology and are used as neutron dosemeters in a wide range of applications. At the SCK-CEN and Belgonucléaire they are used as official personal neutron dosemeter for the personnel. In the European Commission (EC) project of Evaluation of Individual Dosimetry in Mixed Neutron and Photon Radiation Fields (EVIDOS), a whole range of neutron dosemeters were irradiated in workplace fields in nuclear installations in Europe, including two types of bubble detectors. The responses of the bubble detectors are compared with the reference values determined using a directional spectrometer and a reference instrument to measure Hp(10).

Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part I: Scope and methods of the project.

Supported by the European Commission, the EVIDOS project started in November 2001 with the broad goal of evaluating state of the art dosimetry techniques in representative workplaces of the nuclear industry. Seven European institutes joined efforts with end users at nuclear power plants, at fuel processing and reprocessing plants, and at transport and storage facilities. A comprehensive programme was devised to evaluate capabilities and limitations of standard and innovative personal dosemeters in relation to the mixed neutron-photon fields of concern to the nuclear industry. This paper describes the criteria behind the selection of dosimetry techniques and workplaces that were analysed, as well as the organisation of the measurement campaigns. Particular emphasis was placed on the evaluation of a variety of electronic personal dosemeters, either commercially available or previously developed by the partners. The estimates provided by these personal dosemeters were compared to reference values of dose equivalent quantities derived from spectrometry and fluence-to-dose equivalent conversion coefficients. Spectrometry was performed both with conventional multisphere and with some original instrumentation providing energy and direction resolution, based on silicon detectors and superheated drop detectors mounted on or in spherical moderators. The results were collected in a large, searchable database and are intended to be used in the harmonisation of dosimetric procedures for mixed radiation fields and for the approval of dosimetry services in Europe.

Achievements in workplace neutron dosimetry in the last decade: lessons learned from the EVIDOS project.

The availability of active neutron personal dosemeters has made real time monitoring of neutron doses possible. This has obvious benefits, but is only of any real assistance if the dose assessments made are of sufficient accuracy and reliability. Preliminary assessments of the performance of active neutron dosemeters can be made in calibration facilities, but these can never replicate the conditions under which the dosemeter is used in the workplace. Consequently, it is necessary to assess their performance in the workplace, which requires the field in the workplace to be fully characterised in terms of the energy and direction dependence of the fluence. This paper presents an overview of developments in workplace neutron dosimetry but concentrates on the outcomes of the EVIDOS project, which has made significant advances in the characterisation of workplace fields and the analysis of dosemeter responses in those fields.

Characterisation of mixed neutron photon workplace fields at nuclear facilities by spectrometry (energy and direction) within the EVIDOS project.

Within the EC project EVIDOS, 17 different mixed neutron-photon workplace fields at nuclear facilities (boiling water reactor, pressurised water reactor, research reactor, fuel processing, storage of spent fuel) were characterised using conventional Bonner sphere spectrometry and newly developed direction spectrometers. The results of the analysis, using Bayesian parameter estimation methods and different unfolding codes, some of them especially adapted to simultaneously unfold energy and direction distributions of the neutron fluence, showed that neutron spectra differed strongly at the different places, both in energy and direction distribution. The implication of the results for the determination of reference values for radiation protection quantities (ambient dose equivalent, personal dose equivalent and effective dose) and the related uncertainties are discussed.

Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part II: Conclusions and recommendations.

The paper presents the main conclusions and recommendations derived from the EVIDOS project, which is supported by the European Commission within the 5th Framework Programme. EVIDOS aims at evaluating state of the art neutron dosimetry techniques in representative workplaces of the nuclear industry with complex mixed neutron-photon radiation fields. This analysis complements a series of individual papers which present detailed results and it summarises the main findings from a practical point of view. Conclusions and recommendations are given concerning characterisation of radiation fields, methods to derive radiation protection quantities and dosemeter results.

Direction distributions of neutrons and reference values of the personal dose equivalent in workplace fields.

Within the EC project EVIDOS, double-differential (energy and direction) fluence spectra were determined by means of novel direction spectrometers. By folding the spectra with fluence-to-dose equivalent conversion coefficients, contributions to H*(10) for 14 directions, and values of the personal dose equivalent Hp(10) and the effective dose E for 6 directions of a person's orientation in the field were determined. The results of the measurements and calculations obtained within the EVIDOS project in workplace fields in nuclear installations in Europe, i.e., at Krümmel (boiling water reactor and transport cask), at Mol (Venus research reactor and fuel facility Belgonucléaire) and at Ringhals (pressurised reactor and transport cask) are presented.

Neutron area survey instrument measurements in the EVIDOS project.

Neutron survey instruments have been exposed at all the measurement locations used in the EVIDOS project. These results have an important impact in the interpretation of the results from the project, since operationally the survey instrument will be used for an initial assessment of and routine monitoring of the ambient dose equivalent dose rate. Additionally, since the response of these instruments is in some cases very well characterised, their systematic deviations from the reference quantities provide an important verification of the determination of those quantities.

Application of workplace correction factors to dosemeter results for the assessment of personal doses at nuclear facilities.

Ratios of H(p)(10) and H*(10) were determined with reference instruments in a number of workplace fields within the nuclear industry and used to derive workplace-specific correction factors. When commercial survey meter results together with these factors were applied to the results of the locally used personal dosemeters their results improved and became within 0.7 and 1.7 of the reference values or better depending on the response of the survey meter. A similar result was obtained when a correction was determined with a prototype reference instrument for H(p)(10) after adjustment of its response. Commercially available survey instruments both for photon and neutron H*(10) measurements agreed with the reference instruments in most cases to within 0.5-1.5. Those conclusions are derived from results reported within the EC supported EVIDOS contract.

Summary of personal neutron dosemeter results obtained within the EVIDOS project.

Within the EC project EVIDOS ('Evaluation of Individual Dosimetry in Mixed Neutron and Photon Radiation Fields'), different types of active neutron personal dosemeters (and some passive ones) were tested in workplace fields at nuclear installations in Europe. The results of the measurements which have been performed up to now are summarised and compared to our currently best estimates of the personal dose equivalent Hp(10). Under- and over-readings by more than a factor of two for the same dosemeter in different workplace fields indicate that in most cases the use of field-specific correction factors is required.

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.

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.

Basic radiation protection training for nurses and paramedical personnel: Belgian experience and future perspectives.

When using ionising radiation for medical diagnosis or treatment of patients, understanding of relevant radiation protection principles and issues is indispensable. In Belgium, nurses and paramedical staff are required to acquire knowledge for protecting the patient against the detrimental effects of ionising radiation by means of a vocational training course. The experience with and challenges for this training course are presented here from a lecturer's point of view, together with a proposal for a future approach that harmonises the training content, its level and quality, according to European recommended standards.

Comparison between thermoluminescence and electronic dosimetry results at the Belgian Nuclear Research Centre.

At the Belgian Nuclear Research Centre, SCK.CEN, the official dose of record is measured by thermoluminescence dosemeters (TLDs), read out on a monthly basis. The workers who frequently enter controlled areas also wear an electronic dosemeter (ED), in addition, as an ALARA tool. In this paper the dose values registered by both dosimetry systems during 1 year are compared. Special attention was given to the determination of the background radiation. The general agreement was good, although the TLD gave slightly higher values. An exercise like this yielded useful information on the storage and use of dosemeters by personnel and on the lowest limit of detection obtained with both systems.

Thermoluminescent characteristics of LiKYF5:Pr3+ and KYF4:Tm3 crystals for applications in neutron and gamma dosimetry.

Thermoluminescent (TL) properties of two concentration series lithium potassium yttrium fluoride doped with praseodymium (LiKYF5:Pr3+) and potassium yttrium fluoride doped with thulium (KYF4:Tm3+) have been investigated after gamma and neutron irradiation. The main purpose of this research is to see whether these materials are suitable for gamma and/or neutron dosimetry purposes. It has been found that the compounds of both series are sensitive to 60Co gamma radiation. A maximal TL sensitivity is found for LiKY0.99Pr0.01F5 and KY0.99Tm0.01F4. However, for this doping level the intensity of the TL glow peak is about 7 times less than that for LiF:Mg,Ti (TLD-700). The TL sensitivity to thermal neutrons is relatively higher than that to 60Co photons. No TL sensitivity to fast neutrons was observed.

Procedures for neutron scattering corrections in a calibration facility with a non-symmetric set-up.

When calibrating neutron monitors, it is important to correct for scattering effects. In general, the correction factors depend on the type of source and monitor used, and on the configuration of the calibration room. These correction factors have been determined for the specific non-symmetric configuration of the calibration room used at SCK.CEN by means of the different analytical techniques recommended by the ISO. These results are compared with each other and also with the outcome of numerical calculations performed using the Tripoli-3 and MCNP 4B code.

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.