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Radiatioactive Contamination in Storage Vaults

#1722


Determination of Radioactive Contamination and Conditions for Radioactive Wastes Storage in Interim Storage Ficilities (Vaults) of the Siberian Group of Chemical Enterprises (SGCE) for Substantiation of Measures for Safe Decommissioning of Plutonium-Produ

Tech Area / Field

  • ENV-RWT/Radioactive Waste Treatment/Environment

Status
8 Project completed

Registration date
16.12.1999

Completion date
23.09.2004

Senior Project Manager
Tocheny L V

Leading Institute
Siberian Chemical Combine, Russia, Tomsk reg., Seversk

Supporting institutes

  • Institute of Physical Chemistry, Russia, Moscow\nMIFI, Russia, Moscow

Collaborators

  • FRAMATOME, France, Paris La Défense\nAEA Technology, UK, Chesire, Risley Warrington\nForschungszentrum Jülich, Germany, Jülich\nCEA / DRN / DER / CEN Cadarache, France, Cadarache

Project summary

For time of plutonium-production, uranium-graphite reactors (PUGRs) operation, near to 30 years, spent changeable elements and defected structures (graphite sleeves, aluminum and zirconium tubes, parts of steel structures) have been withdrawn from reactors and disposed in repositories. Under reactors operation, these elements have been exposed to radioactive contamination in neutron activation and different accidents. As a result, after final shutdown of PUGRs, in the repositories whose operation time covers about 30-45 years now, there are disposed about ten thousand tons of SRAW with different compositions and contamination levels.

Different types of repositories were used for SRAW storing (trench-type, temporary near-to-reactor repositories, technological mines, etc). These types differ each other in disposition, design and size. Some repositories were partially filled up with water.

Available conditions of SRAW storing do not meet up-to-date requirements because existing repositories were not equipped with necessary system of protection barriers. It may be supposed that water leakages took place from some repositories, and there was a danger of radionuclide release out of repository boundaries. Also, mutual contamination of different SRAW types is possible inside repository. Therefore, it seems reasonable to include in research, together with samples of sleeve graphite, some quantity of the samples taken from the metal structures and water disposed in repositories as well as from repository walls, if possible.

In process of the project fulfillment, it will be carried out a selective study on radioactive contamination of the elements taken from different repositories including analysis of superficial and volumetric components of contamination with b-active radionuclides 14C and 3H, transuranium and fission product nuclides, activation and corrosion products. A set of spectrometric and radiochemical methods will be used in assays including original methods which have been developed and tested at previous step of investigations. Some ways of decontamination will be studied. It is planned to investigate three types of repositories, two repositories for each type. About 50-60 samples of graphite, metals, concrete and water taken from each repository will be assayed. Total number of the samples to be assayed will be 300-400. Major attention will be given to assays of the graphite samples contamination (180-240 samples).

The correlation between content of different radionuclides will be studied with aim to develop simple and fast instrumental method for contamination control. Such a method will enable us to make sorting of the repository content according to the contamination level and to make a decision on further destiny of different SRAW groups, on application of appropriate management technology. Some of such technologies will be tested, under the project, with the samples taken from repositories.

The comparison of assay results obtained for contaminated samples taken from repositories with those obtained for similar samples taken from the reactor rooms will give an information about influence of storing conditions on forming the contamination and about processes of radionuclide transport during storing.

The results obtained in the project fulfillment may be further used for solving similar problems under decommissioning of other plutonium-production reactors and RBMK-type reactors. Also, these results may be of interest for foreign specialists.

Previously, during fulfillment of the ISTC Project No. 561-96, its participants have developed a sampling technology, technology of the samples preparation for assay and their transportation from the SGCE to Moscow. The laboratories of the SGCE and MEPhI have been additionally equipped with measuring and computing techniques, methodological base has been expanded, experience of studies at decommissioned reactors has been gained and cooperation between specialists from different institutions have been arranged. Obtained results attracted attention of Russian and foreign specialists and were discussed at the International Workshops in Fall 1997 and Spring 1999 at MEPhI (Moscow), published in "Atomnaya Energiya" magazine, presented at the International Conference ICEM'99 (Nagoya, Japan) and at the IAEA Workshop on reactor graphite management.

All this gives a foundation to expect the team that has successfully fulfilled the project mentioned above will be able equally successfully and effectively to solve the problem of determining the radioactive contamination of SRAW disposed in near-to-reactor repositories for substantiation of measures for safe decommissioning of PUGRs.


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