On an Optimal Minor-Actinide Transmutation Regime in a Molten-Salt Reactor
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ON AN OPTIMAL MINOR-ACTINIDE TRANSMUTATION REGIME IN A MOLTEN-SALT REACTOR M. N. Belonogov, I. A. Volkov, D. G. Modestov, G. N. Rykovanov, V. A. Simonenko, and D. V. Khmel’nitskii
UDC 621.039.542.44
The basic regularities in the transmutation Np, Am, and Cm in a molten-salt burner reactor are examined on the basis of the results of neutronic calculations of an idealized infinite homogeneous medium consisting of metal halogenides with low atomic mass. It is shown that an optimal equilibrium regime for the transmutation of Np, Am, and Cm in a molten-salt burner reactor could exist. In this regime, makeup fuel consists of the actinides of the spent nuclear fuel of power reactors; only fission products are extracted. The optimal regime obtains at a definite concentration of actinide fluorides in the fuel composition. The concentration is determined by the size of the reactor and depends relatively weakly on the composition of the spent nuclear fuel, type of salt solvent, and frequency of fuel reprocessing during a run.
One of the priorities in nuclear energy is volume reduction of accumulated radioactive wastes by recycling the neptunium, americium, and curium nuclei present in spent nuclear fuel and, if possible, the long-lived fission products. To specify the indicated composition of Np, Am, and Cm, we shall use the notation MASNF – minor actinides in spent nuclear fuel. One of the solutions proposed for this problem in our country is their transmutation in a molten-salt burner reactor MSR-B [1–3]. Transmutation is understood to mean conversion into fission products the nuclei of MASNF and actinides formed on their interaction with neutrons and as a result of decay. Advantages of the MSR-B are absence of any need for fabricating fuel tablets and fuel pins, possibility of organizing continuous or portional reprocessing of fuel, making it possible to minimize the reactivity margin compensating burning, and possibility of attaining high production rate for the transmutation of MASNF thanks to their high content in the fuel [1]. Different designs of molten-salt reactors in the form of critical reactor facilities as well as some critical systems with an external source of neutrons [4] have been studied for a quite long time: Russian designs include the MOSART reactor [5] and a reactor with a fast neutron spectrum based on the energetics of LiF–NaF–KF with molar composition (%) 46.5LiF– 11.5NaF–42KF [6]; French design of the AMSTER graphite reactor for burning transuranium elements [7]; American design of the TIER subcritical system [8]; and Czechoslovakian design of the reactor SPHINX with a fast neutron spectrum [9]. The characteristics of the operating regimes of a specialized reactor must resolve as much as possible the problems with which it was tasked. For MSR-B it is necessary to secure the required production rate of transmutation of MASNF while minimizing the production of other radioactive wastes, aside from fission products, and minimizing the consumption of uranium and plutonium as the basic components of nu
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