J-P. Degros

Bio: J-P. Degros is an academic researcher from French Alternative Energies and Atomic Energy Commission. The author has contributed to research in topics: Certified reference materials & Liquid scintillation counting. The author has an hindex of 1, co-authored 1 publications receiving 16 citations.

Measurement of 36 Cl in nuclear wastes and effluents: Validation of a radiochemical protocol with an in-house reference sample

Abstract: 36Cl is a beta-emitter with a very low specific activity. It is produced during the irradiation of nuclear fuel, in the reactor core of power plants, from neutron capture by stable 35Cl that may be present at trace level in any part of the irradiated material. Due to its long half-life (T1/2 = 3.01 . 105 y), 36Cl may be significant in impact assessment studies of disposal sites of nuclear wastes. Considering these different elements, the National Radioactive Waste Management Agency (Andra-France) requests information on the 36Cl content of the waste packages destined to be stored at Andra sites. As for other halogens, the measurement of 36Cl is a difficult analytical task in view of its potential losses during the different chemical steps and also because of the lack of international certified reference material needed to validate the chemical and measurement procedures. This paper describes the methodology processed to constitute an in-house solid reference sample with a known content of stable and radioactive chlorine. The original radiochemistry developed to extract 36Cl from solid samples and purify it before a liquid scintillation counting is explained. The comparison of the results given by this radiochemical protocol and other methods allow its validation. The replication of the measurements on the constituted reference materials gives a repeatability around 8% at a confidence level of 95% that is very close to the calculated combined uncertainty value.

Liquid scintillation counting for determination of radionuclides in environmental and nuclear application

Abstract: Liquid scintillation counting (LSC) is a major technique not only for measurement of pure beta emitting radionuclides, but also radionuclides decay by electron capture and alpha emission. Although it is a conventional radiometric technique, but still a competitive techniques for the measurement of many radionuclides. This paper summaries the major development of this measurement technique in instrumentation, methodology and applications in the past decades. The progresses in the instrumentation and methodology mainly focus on the commercialization of triple-to-double coincidence ratio based LSC techniques and its application in the determination of different radionuclides. An overall review and discussion on the LSC based analytical methods for the determination of major radionuclides in environmental researches, decommissioning of nuclear faculties and nuclear application are presented, in both measurement techniques and sample preparation using radiochemical separation. Meanwhile the problems and challenges in the development and application of the LSC are also discussed.

Determination of 36Cl in nuclear waste from reactor decommissioning.

Abstract: An analytical method for the determination of 36Cl in nuclear waste such as graphite, heavy concrete, steel, aluminum, and lead was developed. Several methods were investigated for decomposing the samples. AgCl precipitation was used to separate 36Cl from the matrix elements, followed by ion-exchange chromatography to remove interfering radionuclides. The purified 36Cl was then measured by liquid scintillation counting. The chemical yield of chlorine, as measured by ICPMS, is above 70% and the decontamination factors for all interfering radionuclides are greater than 106. The detection limit of this analytical method for 36Cl is 14 mBq. The method has been used to determine 36Cl in heavy concrete, aluminum, and graphite from the Danish DR-2 research reactor.

Organic matter chlorination rates in different boreal soils: the role of soil organic matter content.

Abstract: Transformation of chloride (Cl(-)) to organic chlorine (Cl(org)) occurs naturally in soil but it is poorly understood how and why transformation rates vary among environments There are still few measurements of chlorination rates in soils, even though formation of Cl(org) has been known for two decades In the present study, we compare organic matter (OM) chlorination rates, measured by (36)Cl tracer experiments, in soils from eleven different locations (coniferous forest soils, pasture soils and agricultural soils) and discuss how various environmental factors effect chlorination Chlorination rates were highest in the forest soils and strong correlations were seen with environmental variables such as soil OM content and Cl(-) concentration Data presented support the hypothesis that OM levels give the framework for the soil chlorine cycling and that chlorination in more organic soils over time leads to a larger Cl(org) pool and in turn to a high internal supply of Cl(-) upon dechlorination This provides unexpected indications that pore water Cl(-) levels may be controlled by supply from dechlorination processes and can explain why soil Cl(-) locally can be more closely related to soil OM content and the amount organically bound chlorine than to Cl(-) deposition

Transformation of Chloride to Organic Chlorine in Terrestrial Environments: Variability, Extent, and Implications

Abstract: Chloride (Cl-in) is a key component in a number of biogeochemical risk assessment models and, as a rule, these models assume that Cl-in behaves conservatively in soil. However, this assumption is c ...