Radiochemical determination of ¹²⁹I and ³⁶Cl in MEGAPIE, a proton irradiated lead-bismuth eutectic spallation target

Abstract

Abstract:The concentrations of the long-lived nuclear reaction products 129 I and 36 Cl have been measured in samples from the MEGAPIE liquid metal spallation target. Samples from the bulk target material (lead-bismuth eutectic, LBE), from the interface of the metal free surface with the cover gas, from LBE/steel interfaces and from noble metal absorber foils installed in the cover gas system were analysed using Accelerator Mass Spectrometry at the Laboratory of Ion beam Physics at ETH Zürich. The major part of 129 I and 36 Cl was found accumulated on the interfaces, particularly at the interface of LBE and the steel walls of the target container, while bulk LBE samples contain only a minor fraction of these nuclides. Both nuclides were also detected on the absorber foils to a certain extent (≪ 1% of the total amount). The latter number is negligible concerning the radio-hazard of the irradiated target material; however it indicates a certain affinity of the absorber foils for halogens, thus proving the principle of using noble metal foils for catching these volatile radionuclides. The total amounts of 129 I and 36 Cl in the target were estimated from the analytical data by averaging within the different groups of samples and summing up these averages over the total target. This estimation could account for about half of the amount of 129 I and 36 Cl predicted to be produced using nuclear physics modelling codes for both nuclides. The significance of the results and the associated uncertainties are discussed.

Adsorption of volatile polonium species on metals in various gas atmospheres: Part II – Adsorption of volatile polonium on platinum, silver and palladium

“…This agrees reasonably well with predictions of the adsorption enthalpy of single polonium atoms on palladium surfaces obtained by DFT calculations and also with the value predicted by the MIEDEMA model. This trend is also confirmed by experimental results from the analysis of metal absorbers foils used in the MEGAPIE facility at PSI [23], revealing about two orders of magnitude higher polonium surface concentration on palladium compared to silver.…”

Thermochromatographic behavior of iodine in fused silica columns when evaporated from lead–bismuth eutectic

“…For example, the distribution of nuclides between steel surfaces of components and the LBE itself were studied, and polonium production rates predicted using particle transport codes have been confirmed by radiochemical analysis [8][9][10]. While the MEGAPIE experiment provided valuable qualitative and semi-quantitative information regarding radionuclide transport and retention in an LBE system, further experiments are required to assess the fundamental thermodynamic properties governing retention of radionuclides in the coolant and by surface adsorption effects.…”

Radionuclide Chemistry in Nuclear Facilities Based on Heavy Liquid Metal Coolants: Past, Present and Future

“…Furthermore, also their spatial distribution within the target was determined. [23] The most important findings can be summarized as follows:…”

“…Therefore, they are depleted in the bulk LBE. [23,[25][26][27][28] Surface enrichment was also found for electronegative elements such as chlorine and iodine. [23,29] These findings may be important for the safety assessment of nuclear installations, especially concerning dose rate estimations and the evaluation of structure material damage.…”