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L Lindborg

Publications and source records attributed to L Lindborg.

At least 19 recordsLinked to original sources
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↗
PubMed2004

Exposure of aircraft crew to cosmic radiation: on-board intercomparison of various dosemeters.

Owing to their professional activity, flight crews may receive a dose of some millisieverts within a year; airline passengers may also be concerned. The effective dose is to be estimated using various experimental and calculation tools. The European project DOSMAX (Dosimetry of Aircrew Exposure during Solar Maximum) was initiated in 2000 extending to 2004 to complete studies over the current solar cycle during the solar maximum phase. To compare various dosemeters in real conditions simultaneously in the same radiation field, an intercomparison was organised aboard a Paris-Tokyo round-trip flight. Both passive and active detectors were used. Good agreement was observed for instruments determining the different components of the radiation field; the mean ambient dose equivalent for the round trip was 129 +/- 10 microSv. The agreement of values obtained for the total dose obtained by measurements and by calculations is very satisfying.

Aircraft↗
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↗
PubMed2002

Recent studies on the exposure of aircrew to cosmic and solar radiation.

Investigations of the impact of cosmic and solar radiation on aircrew involve many challenges. The great variety of primary and secondary ionising and non-ionising radiation, the wide range of energies involved and the role played by the Earth's atmosphere and magnetic field and the Sun combine to produce a very complicated scenario. These factors are reflected in conditions on aviation routes where exposure to radiation varies with altitude, latitude and stage of solar cycle. The great increase in air travel and consequent rise in numbers of aircrew whose occupation requires them to work in this environment has prompted new concern about exposure risks at aviation altitudes. The situation has also been highlighted by the tendency for aircraft to fly at higher altitudes in recent years and by the 1990 recommendations of the ICRP that exposure of civil aircrew be considered as being occupational. These have recently been translated into a legal requirement in the European Union. Several studies have been completed using a very wide range of detectors on subsonic and supersonic routes and new investigations are underway. With the completion of the DOSMAX project in another three years or so. world data for a whole solar cycle will be more complete than ever before. Results indicate that for most routes investigated during solar minimum, aircrew are unlikely to receive doses in excess of 6 mSv.y(-1).

Aerospace Medicine↗
PubMed2001

Cosmic radiation measurements on-board aircraft with the variance method.

The microdosimetric variance-covariance method has been used for cosmic radiation measurements on-board aircraft. Two independent methods of data analysis are presented; the first based on a high energy neutron calibration and the second on identification of single high LET events in the measured multiple event spectrum. Reduced dose levels at high geomagnetic latitudes are observed on one flight in a period of enhanced solar activity as indicated by a reduced ground-level neutron fluence rate. It is shown that with a reduced 137Cs-calibration factor, a Geiger-Mueller tube can be used as a low LET monitor, and that the wall thickness of a tissue-equivalent proportional counter is not crucial for flight measurements. No covariance is observed on any flight indicating it is sufficient to base dose determinations on variance measurements with only one detector. The uncertainties involved are also discussed in some detail.

Aircraft↗
PubMed2001

The response of the sievert instrument in neutron beams up to 180 MeV.

Measurements with a tissue-equivalent proportional counter (TEPC) using the variance-covariance method have been performed in neutron beams between 71 keV and 180 MeV and in the cosmic radiation reference field (CERF) at CERN. The results show that with appropriate linear QD(yD) relations, the ambient dose equivalent can be determined within about 55% in these beams. Build-up measurements show that wall thickness is not crucial for H* determinations at 60 and 180 MeV.

Brachytherapy↗
PubMed2001

Harmonisation and dosimetric quality assurance in individual monitoring for external radiation.

The current situation amongst Member States is that there are widely differing national requirements for dosimetric services and for dosemeter performance. It is clear that with the free movement of workers within the European Union (EU) and the requirements for individual dosimetry given in Council Directive 96/29 EURATOM, a degree of harmonisation of requirements and procedures of EU Member States would be desirable. A EURADOS action group, made up of members from each of the EU Member States plus Switzerland, was set up with the overall objectives of consolidating within the EU the quality of individual monitoring using personal dosemeters and assisting movement towards harmonised procedures. An outline of the work of the action group is given and the term 'harmonisation' is discussed.

Europe↗
PubMed2001

Present status of approval procedures in the EU member states and Switzerland.

The European Union Council Directive 96/29/EURATOM requires that 'individual monitoring shall be ... based on individual measurements which are established by an approved dosimetric service' and that 'Each Member State shall make arrangements to recognise, as appropriate, the capacity of ... approved dosimetric services'. At present, approval of dosimetric services does not have the same meaning within EU Member States and Switzerland. In some countries, service and dosemeter approval is clearly separated, in some others only one of the two is supposed to be tested, and in others no approval is required. Dosimetric requirements and criteria are based on different international documents (e.g. IEC, ISO, ANSI, CEC report) or national specific rules. Approval frequency can be once, every 2 or more years. Approval can be based on either evaluation of technical and management reports, irradiation tests, inspection on-site or the three steps together. In most cases, approval involves photon dosimetry while beta and neutron dosimetry test procedures are not as well established. However, comparisons may lead to some convergent evolution of procedures and to a greater degree of harmonisation and quality consolidation.

European Union↗
PubMed2001

Performance testing of personal dosemeters from eleven dosimetry services in Sweden.

The Swedish regulation, SSI FS 98:5, requires that radiological workers of category A use dosemeters from an approved personal dosimetry service. The 11 services operating in Sweden at the moment use five different types of dosemeter. All have been tested for their ability to determine Hp(10) and some of them to determine Hp(0.07) according to the European Commission report Radiation Protection 73, EUR 14852, of 1994. The five unique systems have been tested regarding the angular and energy dependence of the response of the dosemeters. The test points for the determination of Hp(10) are all, except one, within the trumpet curve and for the unique systems it is shown that the uncertainty related to angular response at three different energies is within the required +/- 40% except for the lowest X ray quality 40 kV. The energy dependence dominates over the directional dependence and the choice of radiation quality for calibration is of great importance for the system performance.

European Union↗
PubMed1999

The use of TEPC for reference dosimetry.

The radiation fields on board aircraft are quite complex and cover an energy range that is unusual in ordinary radiation protection work. Usually dosemeters measure only one radiation quality and the mixture found on board makes measurements complicated. There is also some doubt when it comes to the best choice of quantity for this application and no radiation standards exist for this kind of radiation field. For those reasons there is a need to find a standard measurement procedure that could serve as a reference for other, maybe simpler, measurements or for calculations of route doses. The only direct reading dosemeter that both measures the absorbed dose to tissue and the radiation quality (in terms of lineal energy) is the tissue-equivalent proportional counter (TEPC). The instrument was originally developed for scientific purposes and is still used as such. The detector consists of a gas filled cavity surrounded by a few mm thick wall. Both wall and gas consists of tissue-like material. The measurement principles are explained. Results observed with TEPC instruments are demonstrated. A preliminary collection of data reported by different groups from measurements on board aircraft will be shown. The results agree within +/- 20%. The conclusion is that TEPC instruments have the capacity of serving as reference instruments.

Aerospace Medicine↗
PubMed1997

Dosimetry for occupational exposure to cosmic radiation.

In the course of their work, aircraft crew and frequent flyers are exposed to elevated levels of cosmic radiation of galactic and solar origin and secondary radiation produced in the atmosphere, aircraft structure, etc. This has been recognised for some time and estimates of the exposure of aircraft crew have been made previously and included in, for example, UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) publications. The recent increased interest has been brought about by several factors--the consideration that the relative biological effectiveness of the neutron component as being underestimated; the trend towards higher cruising altitudes for subsonic commercial aircraft and business jet aircraft; and, most importantly, the recommendations of the International Commission on Radiological Protection (ICRP) in Publication 60, and the revision of the Euratom Basic Safety Standards Directive (BSS). In 1992, the European Dosimetry Group (EURADOS) established a Working Group to consider the exposure to cosmic radiation of aircraft crew, and the scientific and technical problems associated with radiation protection dosimetry for this occupational group. The Working Group was composed of fifteen scientists (plus a corresponding member) involved in this field of study and with knowledge of radiation measurement at aviation altitudes. This paper is based on the findings of this Working Group. Where arrangements are made to take account of the exposure of aircraft crew to cosmic radiation, dose estimation procedures will not be necessary for persons for whom total annual doses are not liable to exceed 1 mSv, and therefore, in general, for crew on aircraft not routinely flying above 8 km. Where estimates of effective dose and, in the case of female staff who are pregnant, equivalent dose to the embryo or fetus, are required (for regulatory or other purposes), it was concluded that the preferred procedure was to determine route doses and fold these with data on staff rostering.

Aircraft↗
PubMed1992

On the calibration of plane-parallel ionization chambers for electron beam dosimetry.

The procedure recommended by different dosimetry protocols for the determination of the absorbed dose to air chamber factor, ND,pp, of plane-parallel chambers, comparing absorbed dose determinations in a high-energy electron beam with a reference cylindrical chamber having a known ND,cyl factor, has been investigated. Attention has been focused on the case that the chamber serving as reference has a solid aluminium central electrode. It has been found that using a wide spread Farmer-type chamber (NE 2571), together with recommendations which specifically take into account central electrode corrections for electron beam dosimetry, kcelpcel = pcel-global(IAEA) = 1.008, yields inconsistent results compared with those obtained from a fully homogeneous ionization chamber; for the NE 2571 chamber, a value kcelpcel = pcel-global(IAEA) congruent to 1.0 has been obtained. Analytical calculations of kmkatt for Farmer-type cylindrical chambers and experimental determinations of the product kmkattkcelpcel in electron beams agree within experimental uncertainties, with no evidence of statistical significance for the commonly used assumption pcel = 1, which yields a 0.8% correction (due to kcel only) for the effect of the NE 2571 aluminium electrode in electron beam dosimetry. The use of a 'NACP-chamber' specific factor (kpp or kmkatt) to obtain ND,pp from NK,pp in NACP plane-parallel chambers has been found unsatisfactory, and direct experimental determinations of ND,pp are recommended instead. It is suggested that Standard Dosimetry Laboratories provide ND,pp calibration factors in 60Co beams.

Calibration↗
PubMed1990

Influence of microdosimetric quantities on observed dose-response relationships in radiation therapy.

The steepness of dose-response curves in radiation therapy depends to a large extent on the statistics of cell killing. This is so if the last few clonogenic tumor cells have to be hit or eradicated by other means to cure the patient. The steepness is dependent on the number of clonogenic cells in the tumor and the possible variation in their sensitivity. However, the uniformity of the dose distribution is also important and a decreased slope may result when the delivery of the dose is nonuniform or statistically uncertain. The variance in the energy imparted at the microdosimetric level to individual cell nuclei constitutes the ultimate limit of the variance in delivered dose at a given mean tumor dose. Considering all dosimetric variances it is shown that for low-LET beams the conventional microdosimetric variance will dominate, while in neutron and high-LET beams in general the microdosimetric variance may contribute significantly to the observed dose-response relationship. As a result the normalized slope of the dose-response curve for tumor control and normal tissue complications with neutrons and other high-LET beams will be reduced compared to that with photons. This conclusion is found to be in quantitative agreement with available data from clinical trials with neutron therapy. Finally, it is pointed out that for beams with a very high RBE and LET it may be favorable to deliver a fraction of the total dose in the form of conventional low-LET radiation. This addition of low-LET radiation may be desirable to ensure a dose to all clonogenic tumor cell nuclei that is sufficiently high and uniform to achieve a high probability of tumor control.

Dose-Response Relationship, Radiation↗
PubMed1989

Microdosimetric measurements and the variance-covariance method. Some experimental experience.

Systematic and statistical uncertainties in the variance-covariance method have been investigated. Two spherical wall-less detectors have been used to determine the dose mean lineal energy (yD) in a neutron beam of 5.7 MeV produced by a Van de Graaff accelerator. It is shown that certain systematic uncertainties influenced the mean yD of the two detectors much less than yD from only one of them. A statistical uncertainty of 6% (95% confidence level) was achieved if yD was calculated from 2000 measurements. In this particular experiment insufficient shieldings of the preamplifiers positioned in the beam turned out to limit the possibility to measure below 20 nm.

Analysis of Variance↗
PubMed1986

Microdosimetry of pulsed radiation fields employing the variance method.

The relationship between dose mean lineal energy and relative variance has been exploited previously to derive yD from the calculated variance in current measurements in steady and uniform radiation fields. Recently Kellerer and Rossi made the observation that utilization of two detectors can make the variance technique practicable in time-varying fields. We report here the first measurements of yD for 10 MeV X rays and 9 and 18 MeV electrons from a pulsed linear accelerator using the variance method. Two independent analog-to-digital converters were used to obtain data from two spherical proportional counters in synchrony with the beam pulse. The method is described in detail and results are reported for site diameters of 1/2, 1, and 2 microns. Data for an accurate determination of yD can be obtained with this technique in less than 1 min, making possible an essentially "on line" determination of yD or zD in a clinical situation.

Electrons↗
PubMed1983

Intercomparison of Nordic exposure secondary standards for soft roentgen rays.

An intercomparison of exposure secondary standards for soft roentgen rays in use in the Nordic countries is reported. One of the standards was used as a reference standard against which all the other standards were calibrated. The statistical uncertainty in the calibrations was estimated to be 0.8 per cent (at the 95% confidence level) and the maximum systematic uncertainty in the intercomparison was estimated to be 0.8 per cent. The observed differences, at most about one per cent, were not considered significant. It was concluded that for this type of chambers a period of about five years is acceptable between recalibrations against a primary standard unless stability checks indicate otherwise.

Calibration↗