Development of Iodine-129 Separation During Reprocessing of Spent Nuclear Fuel, Concentrating and Obtaining of the Forms, Suitable for a Long Term Storage of Burial
Tech Area / Field
- ENV-RWT/Radioactive Waste Treatment/Environment
- FIR-FUC/Fuel Cycle/Fission Reactors
3 Approved without Funding
Khlopin Radium Institute, Russia, St Petersburg
- SverdNIIChimMash, Russia, Sverdlovsk reg., Ekaterinburg\nNPO Mayak, Russia, Chelyabinsk reg., Oziorsk
- British Nuclear Fuels Ltd (BNFL) / Waste Disposal Research Group Sellafield R&D, UK, Cumbria, Seascale
Project summaryThis Project envisages the studies on management of iodine-129 in spent nuclear fuel (SNF) reprocessing with the aim of its confinement in a minimal volume and conversion into forms suitable for safe long-term storage or transmutation.
Iodine-129 is generated in NPP reactors as a result of uranium and plutonium fission. The total amount of I-129 generated in fuel depends on reactor type, fuel composition and fuel burn-up. This radionuclide evolves during SNF reprocessing, predominantly at the stage of fuel dissolution. In reprocessing there are formed considerable volumes of intermediate- and low-level wastes (ILW and LLW) which may be a source of I-129 entry into biosphere.
The necessity of retaining I-129 in SNF reprocessing is accepted all over the world. Special attention is paid to this radionuclide by the reason of adverse combination of its properties as follows:
· great period of half-life (17 millions years);
· variety of its chemical forms, their low chemical and thermal stability;
· high mobility of iodine in biosphere, that may be a hazard of global contamination to the environment;
· possible accumulation of I-129 in biosphere up to concentrations which can cause genetic disturbances in living organisms because of its biological activity (iodine content in human thyroid up to 10 mg), in addition to the increase of radiation loading.
Growing attention of the public to conservation of the pure biosphere calls for developing a reliable scheme for decontamination of process products (gases and liquids) from iodine-129 which is needed at existing and future commercial reprocessing plants.
At present there are several concepts on I-129 isolation from biosphere, and namely:
· disposal into stable geological formations;
· monitored special storage facilities;
· removal outside the Earth.
The ultimate blowing of I-129 from HNO3 solutions in the course of SNF dissolving process with its capture from gaseous stream and subsequent isolation from biosphere in the form of stable matrices is now considered as the most acceptable method for management of I-129.
For solving this problem, the following processes should be studied:
· removal of I-129 from HNO3 solutions on SNF dissolving;
· capture of I-129 from off-gases of SNF dissolution units;
· concentrating of I-129;
· conversion of I-129 into difficultly soluble chemical compounds;
· immobilization of I-129 in solid matrices suitable for safe long-term storage.
In the Project execution the multi-skilled scientists and specialists should be drawn; they were previously concerned with nuclear weapon production and have great experience of combined work on SNF and radwaste reprocessing and development of radiochemical technologies. At RPA "V.G. Khlopin Radium Institute" (KRI) the studies on I-129 management in SNF reprocessing have been conducted for many years. As a results, the method was developed for I-129 removal from HNO3 solutions on SNF dissolving which had successfully undergone tests at "Mayak" PA and was introduced into the process at the plant. Equipment for testing this method was elaborated by the specialists of Research Institute "SverdNII-chim-mash". The results of conducted studies are protected by a series of author certificates and patents. The experience of Radium Institute on I-129 management will be presented in the materials prepared by the institute's specialists for a Review of gas-cleaning methods at radiochemical plant that should be published by IAEA in 2001.
Main part of studies on I-129 blowing, its capture, concentrating and production of final composites for subsequent pressing will be carried out by the specialists of Radium Institute. The experimental data on I-129 capture and its concentrating are to be verified in standard SNF dissolving process at the plant by the specialists of "Mayak" PA and Radium Institute. Specialists from "SverdNIIchim-mash" will participate in modernization of facilities and elaboration of recommendations to development of test equipment.
The experiments will be conducted in existing equipment with the use of procedures for analytical determination of I-129 (including the unique ones – Yu. P. Zaspa, E.D. Protsenko, S.V. Kireev, V.K. Veselov, V.K. Yusupov. Laser-fluorescent control of 129J in SNF reprocessing. Radiochemistry, vol. 36, N 13, 1994 (in Russian)) developed by Radium Institute and "Mayak" PA.
The results obtained should allow to prepare the initial data on development of technologies for:
· recovery of I-129 from HNO3 solution in SNF dissolving process;
· capture of I-129 from off-gases of SNF dissolution unit;
· concentrating of I-129 in a minimal volume;
· conversion of I-129 into forms suitable for safe long-term storage.
The proposed Project conforms to the objectives stated in the ISTC charter (Article II, part A, section II) as supporting the fundamental and applied studies and technical developments in the field of the environmental protection, energy production and nuclear power safety.
In the framework of this Project, the activity of scientists and specialists will be aimed at realizing the civil needs of the environmental protection: preparation of the most long-lived radionuclide I-129 to safe long-term storage. Successful solution of the technical objectives stated in the Project can contribute to solving the International problem of radwaste reprocessing. The authors of the proposed Project believe that the solution of these scientific problems is of interest not only for the developed countries with nuclear power engineering, but also for the world community.