Top

Home page > Dosimetry

Dosimetry


The laboratory provides a service which evaluates external radiation exposure and is used by other research laboratories of CNRS and Universities all over France. The laboratory is approved by French authorities to offer dosimetry solutions for various exposure conditions in mixed fields of photon-, beta or neutron radiation. The dosimetry systems consist of radio photo luminescent detectors (RPL), solid state nuclear track detectors (SSNTD) and thermo-luminescent detectors (TLD). An overview of the dosimetry infrastructure is presented. The total volume of dosimeters processed is roughly stable year-on-year, however figures show a progressive increase in extremities dosimetry. Finally, the laboratory invests in the necessary projects for the sustainability of the dosimetry activities.

Activities and results

Key figures

Annually the service monitors the doses of over 2 300 workers and 700 controlled areas. This monitoring was carried out using about 18400 passive dosimeters. Although the total volume of analyzes is stable over the period 2009/2013 (±2%), the breakdown by categories (whole body, extremities) shows an increase in extremity dosimetry in the last few years. It has increased by 14% in 2011 and a rise of 20% is expected in 2013.

Monitoring of the workforce for education and research groups in 2012 shows a total collective effective dose (photons, neutrons) of 12.25 man.mSv and a maximum individual dose accumulated over 12 months of 0.54 mSv. Our workforce monitoring in the education/research sector represents 15% of the total monitored in France and contributes to 3 % of the National collective dose for this group of the population.

The 260 agents who were monitored at extremities (photons, beta) in 2012 constitute 25% of the total group followed in France in the field of Education and research. The maximum individual dose accumulated over 12 consecutive months is 4.25 mSv and remains much lower than the prescribed dose limits for the public.

Review of the dosimetry infrastructure

Whole body /Neutron dosimetry

A first characterization of the neutron dosimetry system was carried out between 2010 and 2012 in order to provide a complete and accurate view of the overall dosimetric performance (threshold, linearity, response to radon, angular and energy response). The difficulties faced in conducting these studies were the limited availability of facilities providing mono-energetic beams of qualified reference dosimetric radiation, and the high cost of these irradiations. The completion of this work has shown that the performance of this system is not completely satisfactory, particularly in the energy range below 2MeV. A joint project involving the Dosimetry Service and Instrumentation Division is currently under discussion and is aimed at optimization of the response of neutron dosimeters as a function of energy.

Whole body /Photon and Beta dosimetry

The review of the RPL dosimetry system, installed in July 2009, reveals a good performance since its deployment and has the following advantages :

Measuring performance : reduction of the threshold ; improved dosimetric performance : linearity, energy response, angular response ; reduction of measurement uncertainties.

Features management system (more reliable identification system ; implementation of traceability in realtime providing and operating steps ; new features for the automatic management of natural background radiation ; gradual reduction of the delay for the edition of results)

Cost reduction of the calibration measurement systems.

The superior performance of this system has been demonstrated several times from 2010 to 2013 in the context of National and European inter-comparisons organized respectively by IRSN (Institute for Radiological Protection and Nuclear Safety) and Eurados (European Radiation Dosimetry Group).

Responsibilities in dosimetry management.

ASN Approval and Cofrac Accreditation

The Nuclear Safety Authority (ASN) approves the dosimetry laboratories for the assessment of doses received by workers. Our laboratory received this approval by ASN on April 2, 2010 for a period of 3 years and on March 31, 2013 for a period of 5 years. The scope of the approval includes the measurement of personal dose equivalents for the whole body to photon-, beta- or neutron radiation fields. During this mandate, the Cofrac accreditation of the laboratory was the subject of a pluri-annual audit program and the laboratory obtained a re-accreditation for a period of 5 years starting in June 2012. An extension to the accreditation scope for extremity dosimetry is planned for late 2015.

Responsibilities in field dosimetry

There is a request by the Ministry of Labor to establish a National exposure register for individual workers. This would allow use of accumulated data to reconstruct the cumulative effective dose over several years, or even over the worker’s whole life. Significant efforts will be undertaken to define specifications with our partners (doctors, experts in radiation protection, employers) and authorities (Ministry of Labour, ASN, IRSN).

The laboratory also offers its expertise in other projects. One example is the collaboration with the IRSN to explore the secondary neutron doses received by pediatric patients during intracranial proton therapy treatments at the Curie Institute in Orsay. The results from these studies have been published in Journal of Radiation Protection Dosimetry. A poster was presented during the seminar of the French Society for Radiation Protection (SFRP) in 2013.

The knowledge of the laboratory, acquired during the implementation of the quality system, has been the subject of an article in the book ’The quality approach in public research and higher Education’ by Editions Quae in 2009. A talk was presented at the 4th meeting of CNRS quality network in research (QeR).

A member of our laboratory is involved as an expert in standardization committees of BNEN (Bureau of Standards for Nuclear Facilities). He recently participated in the revision of the 62387 standard that applies to all kinds of passive dosimetry systems and in a review of the order of 30 December 2004 on individual information dosimetry of workers exposed to ionizing radiation.

To meet the legitimate societal matters about the impact of radioactivity, the service dosimetry is now a member of Becquerel IN2P3 network.

Finally, the lab also offers training skills in radiation dosimetry. Courses and seminars are organized several times each year inside or outside the Institute (universities, INSTN). Our laboratory participates in training through research master levels, we have offered internship subjects for M1 or M2 each year since 2008.


 

IPN

Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
UMR 8608 - CNRS/IN2P3

Ce site est optimisé pour les navigateurs suivants Firefox, Chrome, Internet explore 9