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Decontamination of Beryllium Waste

#3381


Elaboration of Safe Methods for Radioactive Beryllium Waste Decontamination after Operation in a Nuclear Reactor

Tech Area / Field

  • ENV-RWT/Radioactive Waste Treatment/Environment
  • FIR-MAT/Materials/Fission Reactors

Status
8 Project completed

Registration date
17.10.2005

Completion date
31.01.2011

Senior Project Manager
Tyurin I A

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • NIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad

Collaborators

  • SCK-CEN, Belgium, Mol

Project summary

Name: Elaboration of safe methods for radioactive beryllium waste decontamination after operation in a nuclear reactor.

Field of Application: Decontamination, treatment and disposal of radioactive beryllium waste as irradiated material of the reactor neutron reflector and moderator.

Purpose: An analytical and experimental validation of decontamination, treatment and subsequent disposal of radioactive beryllium waste.

Main Task: An analytical and experimental study of the type and level of induced radioactivity of irradiated reflector and moderator beryllium blocks of research reactors, study of the possibility of its maximal reduction using different methods. Separation of the surface and volume radioactivity. Investigation of the influence of different decontamination methods for surface layers of irradiated beryllium blocks, including their etching, on the level of residual beryllium radioactivity. Study on the chemical composition of beryllium block material in the initial state and after its irradiation up to lifetime neutron doses of ~6-1022 cm-2, E>0,1MeV. Investigation of the behavior of metal and gaseous impurities in beryllium. Analytical and experimental investigation of a full radioisotopic composition of irradiated block material. Estimation of the contribution of each technological and irradiation induced impurity into the total radioactivity in the material volume. Analytical and experimental definition of time dependencies of the radioactivity reduction of irradiated beryllium products in the course of their long-term storage. Experimental definition of helium and tritium content in beryllium after its neutron irradiation at different parameters. Investigation of thermal stability and diffusion characteristics of these gases in the course of their short-term high-temperature annealing. Definition of composition of gas releasing from beryllium on high temperature annealing. Separation of active gases prior to tritium absorption by sorbent. Development of efficient methods for absorption of active gases (O2, N2 etc.) from a gaseous medium. Choice of getter material providing effective tritium absorption on irradiated material degassing and its retention during subsequent storage of sorbent. Study on the absorption rate of tritium, released on heating irradiated beryllium, by getter. Definition of the tritium content in the getter material and its residual concentration in beryllium. Definition of the getter surface phase composition (possible formation of corresponding oxide, nitride phases and beryllium condensate). Experimental definition of the activity of residual gases after tritium absorption by getter. Development of purification methods of helium from tritium traces after tritium absorption by getter from the gas medium. Establishment of the beryllium density after helium and tritium removal. Control of impurity phases in beryllium. Definition of experimental dependencies of the residual radioactivity level, physical-mechanical properties and characteristic beryllium microstructure features on annealing parameters. Investigation of the tritium behavior on annealing and elaboration of proposals on the monitoring of its release from the material and also during its further storage. Measurement of the metal impurities amount in beryllium, study of the possibility to reduce their content in the material after the completion of the beryllium block operation in the reactor. Try-out of the irradiated beryllium decontamination techniques from metal impurities using solid-phase chemical reactions, sublimation of beryllium acetate by extraction to chloroform and others. Generalization of the investigation results and preparation of recommendations for validation of the main procedure of safe reprocessing followed by disposal of radioactive beryllium waste including surface and volume decontamination and also chemical methods for removal of metal impurities.

New proposals and their advantages: Nowadays after completion of the operation in the reactor core irradiated reflector and moderator beryllium blocks are subject to immediate disposal in the storage facilities for highly radioactive solid waste just after irradiation. As a result, firstly, the useful storage capacities are not used in the best way since the products located there have large dimensions and complicated geometry. Secondly, due to high induced beryllium radioactivity, caused by the presence of high-activity and toxic impurities in them, its disposal is supposed in the storage facilities with highly radioactive nuclear fuel waste that is not advantageous either. The comprehensive study proposed will allow optimization of the radioactive beryllium waste disposal process by their preliminary maximum decontamination and conversion into a compact form.

Application effect: There are about twenty reactors operated in Europe where beryllium is used in the core construction elements. Therefore, there is a great quantity of beryllium radwaste and, therefore, issues of their safe reprocessing and disposal are of great importance both for European and world community. The use of the proposed methods for concentration of radioactive elements and for reduction of the beryllium activity will allow the reduction of the high-radioactivity waste volume. Along with pure applied research aspect related to the improvement of ecological situation and ecological protection, the proposed comprehensive study on the validation of safe reprocessing of irradiated beryllium and removal of tritium from it is also of fundamental character since it facilitates gaining of knowledge about the radiation damage nature of beryllium. The proposed work meets the national priorities of Russia and it is in full agreement with the ISTC goals. At present the European Community supports intensively the activities related to the safe disposal of nuclear engineering radwaste including beryllium as reflector and moderator material of research reactors. A reduction of highly radioactive beryllium waste is important primarily from the viewpoint of ecology. In this connection the implementation of the Project allows the Russian scientists to contribute into the solution of urgent ecological protection problems facing the European and world nuclear engineering.

Realization of this Project will allow the scientists and specialists, engaged in the sphere of nuclear weapon development and production (29 from RFNC-VNIIEF) or in the sphere of nuclear reactors development and operation (21 from SSC RF RIAR) to turn their efforts to solve the urgent problems of environmental protection, facing the atomic power engineering of the European and World community.


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