USE OF ENRICHED LEAD-206 FOR REDUCING CHARGES FOR SPENT LEAD COOLANT UTILIZATION IN FAST REACTORS

Authors & Affiliations

Khorasanov G.L.1, Ivanov A.P.1, Blokhin A.I.1, Prusakov V.N.2, Cheltsov A.N.2, Sosnin L.Y.2
1State Scientific Centre - A.I. Leipunsky Institute for Physics and Power Engineering, Obninsk, Russia
2The Russian Research Centre "Kurchatov Institute", Moscow, Russia

Abstract

Now at designing advanced fast reactors (FRs) it is recommended to envisage such decisions which reduce expenses for removal radwaste after FR decommission. Charges for disposing spent coolants and structural materials are of $20/kg. Thus, for a FR such as the BN-600 expenses for utilization of the sodium coolant (800 tons) and containment materials (3800 tons) will cost $90 mln. For the FR of the same capacity but exploiting lead as a coolant, charges for spent lead storage will demand $200 mln as lead is 11.7 times heavier than sodium. Estimations performed specify the impossibility of clearing a lead coolant from radiation control after its exploiting in FRs during 30 years. It is due to an accumulation of long-lived bismuth radioisotopes, Bi-207, Bi-208, Bi-210m, and alpha-active polonium, Po-210. Po-210 and long-lived Bi radioisotopes can be practically excluded from the lead coolant in enriching lead natural with stable isotope Pb-206. In the FR neutron spectrum such nuclear reactions as (n,γ), (n,2n) and (n,3n) are mostly responsible for transmutation of nuclei. For Pb-206 as a target reaction (n,g) results in formation of stable lead isotopes, Pb-207 and Pb-208. Reactions (n,2n) and (n,3n) with Pb-206 nuclei form another stable lead isotope, Pb-204, and lead radioisotope, Pb-205, which is beta-emitter with energy of particles less than 5 keV and consequently is exempted from radiation control. Thus, the using of Pb-206 allows to take off the problems concerning the coolant residual activity. In this case, cost of lead enriching must be comparable with charges for spent lead utilization. In the RNC "Kurchatov Institute" several grams of Pb-206 enriched up to 95 percent were produced using a laboratory centrifuge cascade and tetrametyl of lead as a process gas. Estimations of charges for proceedings the large amounts of Pb-206 at manufactories with high separation capacity are carried out. This investigation is performed at financial support of the Russian Foundation for Basic Research and Administration of Kaluga region.

Keywords
FR,fast reactors, radwaste, lead coolant, Pb-204, long-lived radioisotopes, Bi–207, Bi–208, Bi–210m, alpha-active polonium, Po–210

Article Text (PDF, in Russian)

References

UDC 621.039.526

Problems of Atomic Science and Technology. Series: Nuclear Constants", issue 2, 2001