The monitoring of environmental radioactivity is important for public health protection. In France, environmental radioactivity is specifically monitored by a network of certified laboratories. Indeed the Nuclear Safety Authority (ASN) delivers three to five year governmental agreements to each laboratory provided that it succeeds in proficiency tests (PTs) organized by the Institute for Radiological Protection and Nuclear Safety (IRSN). To ensure a direct traceability chain in radioactivity measurements, the Laboratoire National Henri Becquerel (LNE-LNHB), as the French national laboratory for radionuclide metrology, has been organizing national PTs for more than 40 years. LNE-LNHB also regularly realizes specific PTs to train the laboratories to the regulatory tests of IRSN. Most tests are based on aqueous solutions but there is a growing demand for tests on solid matrices to be measured by γ-spectrometry. Measurement of radionuclides from environmental samples includes a wide variety of matrix compositions and densities. Since 2009, LNE-LNHB is working on the production of suitable calibration reference materials to improve the traceability of environmental radioactivity measurements in France. To address this issue, LNELNHB intends to produce mixed γ-ray reference materials with a known mass activity and a composition as representative as possible of real environmental samples. The use of such materials will also improve the calibration of γ-spectrometry measurement systems due to a more accurate determination of the self-attenuation correction by measuring a known sample whose composition is close to the real one. This paper describes the development of the preparation protocol and the characterization of traceable matrices, spiked with various γ-ray emitters. A PT exercise has been organized with a low density matrix produced. The results of the participants are mentioned in this article.

For radioprotection, the reference quantity is air kerma. For an cobalt-60 beam, the reference dosimeter is a cavity ionization chamber whose volume is measured. The new LNE-LNHB reference is based on six different chambers instead of one as was done previously. Although every new ionization chamber was treated as much as possible in the same way (manufacturing, measurements of volumes, wall effect calculations, current corrections), a maximum discrepancy of 0.2% was observed between the final measurement results from each chamber. The final value of the air kerma rate in reference conditions was determined as the mean value of the measurement results from all six chambers. Among the different factors whose determination is necessary to calculate the air kerma rate, some are considered independent of or common to all the graphite-walled ionization chambers (for example, mean energy expended by an electron to produce an ion pair in dry air), while others vary for each chamber (for example, air cavity ionic collection volume). Considering that the uncertainties of the individual ionizationchamber measurement results seem slightly underestimated, the uncertainty on the mean of the six chamber-dependent factors products was taken equal to the standard deviation of the sample composed of the six chamber-dependent factors products (0.08%). Compared to the previous standard, the air kerma rate of the ⁶⁰Co photon beam would then increase by 0.09% and the air kerma rate uncertainty would drop from 0.38% to 0.31%. This article describes the procedure used to establish the primary standard in terms of absorbed dose to tissue of LNE-LNHB.

For the last four years, the LNE-LNHB/LMD has been developing methods and material to measure the X-ray spectra of its X-ray tubes used to perform primary standards and transfers in medical or industrial fields. Two different measuring devices have been built. They include the possibility to use three different semiconductor detectors (Si-PIN, GeHP, CdTe) equipped with tungsten collimators with small apertures. Two rotation and translation stages were included to these benches for an automatic and precise alignment of the couple detector/collimator on the beam axis. Correction methods were developed for each detector, to take into account all the detection artefacts taking place into the semi-conductor crystal. They were included in specific spectrum correction programs. Characterization of 28 LNE-LNHB/LMD reference beams was carried out. It allows testing and validating all the different algorithms of spectrum correction developed at the laboratory. These results were compared to the calculated spectra obtained with the XCOMP5r and SpekCalc V1.0 software.

Molecular radiotherapy consists in the injection of a therapeutic agent with known activity in order to deliver a high-dose radiation directly to the tumors while sparing healthy tissues. The Euramet/EMRP project MetroMRT "Metrology for Molecular Radiotherapy" was intended to bring together national metrology laboratories and nuclear medicine services in order to give them metrological support in the field of molecular radiotherapy. In particular, LNE-LNHB was involved in the project for the standardization of ⁹⁰Y-labelled resin microspheres (SIR-Spheres). This therapeutic agent produced by Sirtex (Sydney, Australia) for selective internal radiotherapy is dedicated to the treatment of unresectable hepatic tumors by radioembolization. The primary activity measurement of ⁹⁰Y microspheres was carried out after their complete dissolution in the Sirtex vial. Two types of measurements using the TDCR method were used, one based on liquid scintillation and the other on the Cherenkov effect. An original method for the dissolution was developed at LNE-LNHB to optimize the homogeneity of the radioactive solution dedicated to primary measurements. A comprehensive description of the dissolution protocol implemented is reported in this article. The calibration of the ionization chambers at LNE-LNHB for the reference transfer of ⁹⁰Y-microspheres to end-users is also addressed. The influence of the inhomogeneity of the vial geometry on the uncertainty associated with calibration factors in the case of pure β ^- emitters such as ⁹⁰Y is presented. The standardization of SIR-Spheres was also aimed at lowering the 10% relative uncertainty given by Sirtex on the ⁹⁰Y-microspheres activity (3 GBq).

In this work we present the results of the first part of a research project aimed at offering a complete response to dosimeter manufacturers and users of the nuclear industry demand for high energy (6 MeV–9MeV) photon radiation beams for radiation protection purposes. Classical facilities allowing for the production of high energy photonic radiation (proton accelerators, nuclear reactors) are very rare and need large investment for development and use. We thus propose a novel solution, consisting in the use of a medical linear accelerator, allowing for a significant decrease of all costs. Using Monte-Carlo simulations (MCNP5 and PENELOPE codes), we have built a specifically designed electron-photon conversion target allowing for obtaining a high energy photon beam (with an average energy weighted by fluence of 6.17 MeV) for radiation protection purposes. Due to the specific design of the target, this “realistic” radiation protection high energy photon beam presents a uniform distribution of air kerma at a distance of 1 m, over a (30 × 30) cm² area. Two graphite cavity ionization chambers for ionometric measurements have been built. For one of these chambers we have measured the charge collection volume allowing for its use as a primary standard. The second ionization chamber is a transfer standard, as such it has been calibrated in a 60Co source, and in the high energy photon beam for radiation protection. The measurements with these ionization chambers allowed for an evaluation of the air kerma rate in the high energy photon beam for radiation protection: the values cover a range between 80 mGy·h^-1 and 210 mGy·h^-1, compatible with radiation protection purposes. Finally, we have calculated using Monte-Carlo simulations conversion coefficients from air kerma to dose equivalents in the range between 10 keV and 22.4 MeV, in specific geometrical set-ups, and for the spectral distribution of the fluence in the beam produced by the linear accelerator of LNE-LNHB.