Activation analysis of concrete and graphite in the experimental reactor RUS

Abstract

The decommissioning and dismantling of nuclear installations after their service life involves the necessary disassembling, handling and disposing of a large amount of radioactive equipment and structures. In particular, the concrete that has been used as a biological reactor shield and graphite that has been used as a moderator-reflector represent the majority of waste, requiring geological disposal. To reduce this undesirable volume to the minimum and to successfully plan the dismantling and disposal of radioactive materials to storage facilities, the activations of the structures should be accurately evaluated. In the framework of the decommissioning and the dismantling of the experimental reactor of the University of Strasbourg, detailed activation estimates have been conducted to characterise the graphite and the structural materials present in the reactor environment. For this purpose, the chemical compositions of fresh graphite samples and different types of concrete have been determined by activation analysis in the research reactors OSIRIS and ORPHEE of CEA Saclay (France). Then, the activations of graphite, concrete and other materials have been calculated in the whole reactor, as a function of the three main nuclear data libraries, i.e. ENDF, JEF and JENDL. In parallel, the activations of representative graphite and concrete samples have been measured experimentally. The comparison of theoretical predictions with experimental values validates the approach and the methodology used in the present study and tests the consistency and the reliability of the nuclear data used for activation analysis. We believe that a similar approach could also be used for the decommissioning of industrial nuclear reactors.

The Assessment of the Radioactive Inventory for the Solid Wastes from VVR-S Nuclear Research Reactor Decommissioning

“…For hard-to-detect radionuclides: 55 Fe, 63 Ni, 59 Ni the specific and the total activity was calculated with the scaling factors method using 60 Co as the reference radionuclide [2]. To estimate the scaling factors, theoretical calculations, gamma spectrometric measurements and data from the literature [3,4,5] were used. At the decommissioning phase, the reactor block inventory is estimated based on gamma ray measurements of the waste containers and on scaling factors methods of the hard-to-detect radionuclides activities [2].…”

Strange bedfellows: The curious case of STAR and Moata

“…For an Argonaut class reactor, the first three reactions are important for the production of 14 C in graphite and concrete, with reaction (1) expected to dominate due to the large neutron cross section and the abundance of 14 N. Activation estimates were undertaken for the reactor of the University of Strasbourg (RUS), a 100 kW Argonaut reactor [7]. The methodology involved activation of graphite and concrete samples to determine their chemical composition, calculation of expected activation and an experimental program to measure the activation in selected samples.…”

Boron‐polymer composites engineered for compression molding, foaming, and additive manufacturing

“…Over the past few years, there has been an influx of new research that focuses on developing alternative materials for radiation shielding. The push for updated shielding materials, needed to protect humans and matter from ionizing radiation, increases as new paths are revealed in space travel, [1][2][3][4][5] nuclear reactor technology, 6,7 and medical research. 8,9 In particular, boron is routinely used to shield thermal neutrons due to its large (n, α) crosssection (3840 barns for 10 B, natural isotopic abundance is 19.6% and 80.4% for 11 B).…”