Radioactive Graphite Handling
Feasibility Study for the Development and Introduction of Radiation-Safe Technology for Handling Radioactive Graphite of Channel-Type Reactors
Tech Area / Field
- FIR-DEC/Decommissioning/Fission Reactors
- ENV-RWT/Radioactive Waste Treatment/Environment
3 Approved without Funding
Federal State Unitary Enterprise Research and Development Institute of Power Engineering named after N.A.Dollezhal, Russia, Moscow
- Siberian Chemical Combine, Russia, Tomsk reg., Seversk\nAll-Russian Research and Designing Institute of Complex Energetic Technology, Russia, St Petersburg\nMIFI, Russia, Moscow\nExperimental Designing Bureau of Machine Building (OKBM), Russia, N. Novgorod reg., N. Novgorod
- Nexia Solutions Ltd, UK, Preston\nForschungszentrum Jülich GmbH, Germany, Jülich
While power reactors using nuclear fuel are under decommissioning, an important task on environmental friendly localization of radioactive wastes (RW) should be solved in addition to technical, economic and social problems. In particular, among the problems related to the technology of RW handling, the engineering task on environmental friendly handling of exposed graphite (EG) being of special importance remains unsolved.
About 27 nuclear power units with gas- and water-graphite reactors have finally been put out of service worldwide so far. These are GCR in France, WAGR and magnox reactors in the Great Britain, HTR in Germany, GCR in Spain and Italy, HTR and LWGR (Hanford N) in USA, commercial uranium-graphite reactors (PVGR) in Russia, two VGR in Beloyarskaya NPP and RBMK-1000 in Ukraine. The graphite used in reactor cores, moderator and reflector during operation of these units was exposed to neutron irradiation.
Actuality and complexity of the problem related for environmental friendly handling of EG are conditioned by the following basic causes:
- large amount of EG have been amassed worldwide so far (over 230000t according to Framatome ANP – EDF data). In Russia this value amounts to about 60000t (see Table 1);
- substantial activity of radionuclides, of which half-life reaches several milleniums of years, is built up as a result of long-term neutron impact exerted in reactor graphite and impurities the graphite contains;
- a serious danger to environment is accumulation of carbon-14 (of which half-life makes 5730 years) in exposed graphite, which, if released into atmosphere, may cause global contamination of natural complexes on the Earth because they are members practically of any organic and inorganic compounds.
The analysis performed and multi-lateral consultations carried out by the Project Working Group have allowed for the following conclusions to be made:
- reprocessing of sleeve graphite, cardinal reduction in RW volume will allow to increase reliability of storage and reduce ecological risks to environment, to finally solve the problem of C-14;
- the work is reasonable to start with substantiation of an environmental friendly technology for reprocessing exposed graphite sleeves (having low radioactivity) from Russian commercial reactors;
- about 8000t of RW of which a substantial portion (about 5000 t) consists of graphite sleeves were accumulated at the Siberian Chemical Joint Workd (SHK, the city of Seversk), the conditions available at SHK are good to build a facility for reprocessing exposed sleeve graphite;
- the technology of incineration in a circulating boiling layer can be used as a basic one. The FRAMATOME ANP company, France has developed principle components of such a technology for the Le Creusot facility.
As a result of the Project fulfillment, there will be:
- developed a conceptual design of an pilot complex (PC) intended for extraction, incineration of exposed graphite sleeves and utilization of wastes;
- determined engineering, time-consuming, financial and institutional characteristics to realize the Project on creation of the PC;
- carried out investigations in propagation of engineering solutions developed under the Project for reprocessing RW of higher radioactivity and commercialization of these works;
- carried out experiments with the use of a laboratory facility to substantiate workability and ecological safety of the PC under development.