THE THORIUM MOLTEN SALT REACTOR: LAUNCHING THE THORIUM CYCLE WHILE CLOSING THE CURRENT FUEL CYCLE

French researchers of the Reactor Physics Group of the Laboratoire de Physique Subatomique et de Cosmologie Roepot very Promising results from their TMSR research. They are building a strong case for large non-Moderated Thorium Molten Salt Breeders. Such reactors would be very useful for Baseload power generators. The main draw back for a no moderator reactor would be the much larger starting charge required if TMSR/LFTR type reactors were expected to generate most electrical energy or to provide most energy for the national economy. A World Wide deployment by 2050 would creat a very large shortage of fissionable materials for start up charges even with graphite core reactors.

THE THORIUM MOLTEN SALT REACTOR: LAUNCHING

THE THORIUM CYCLE WHILE CLOSING THE CURRENT

FUEL CYCLE

E. MERLE-LUCOTTE, D. HEUER, M. ALLIBERT, V. GHETTA,

C. LE BRUN, R. BRISSOT, E. LIATARD, L. MATHIEU

LPSC, Université Joseph Fourier, IN2P3-CNRS, INPG

LPSC, 53, avenue des Martyrs, F-38026 Grenoble Cedex - France

ABSTRACT

Molten salt reactors, in the configuration presented here and called Thorium Molten Salt Reactor

(TMSR), are particularly well suited to fulfil the criteria defined by the Generation IV forum, and

may be operated in simplified and safe conditions in the Th/233U fuel cycle with fluoride salts. The

characteristics of TMSRs based on a fast neutron spectrum are detailed in this paper, focusing on

their excellent level of deterministic safety. We aimed at designing a critical TMSR able to burn

the Plutonium and the Minor Actinides produced in the currently operating reactors, and

consequently to convert this Plutonium into 233U. This leads to closing the current fuel cycle

thanks to TMSRs started with transuranic elements on a Thorium base, i.e. started in the Th/Pu

fuel cycle. We study the transition between the reactors of second and third generations to the

Thorium cycle in a European frame. -

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Conclusion

The Thorium Molten Salt reactor (TMSR) presented here with no moderator in the core appears as a

very promising, simple and suitable concept of molten salt reactor. The non-moderated TMSR

configurations considered in this paper, based on a fast neutron spectrum, present particularly

interesting characteristics. Their deterministic safety level is excellent. They can be started with a fuel

made from the TRU wastes produced in current LWRs. Their rather large initial fissile inventory does

not prevent fast deployment thanks to their good 233U breeding. The technology which in principle

does not involve the transportation of radioactive materials outside the reactor site as well as the

presence of 232U within the fuel can be considered as restricting proliferation risks.

The concept itself has some appealing aspects compared to earlier versions of MSRs. The reactor core

is extremely simple. Simulation calculations do not point to major reprocessing constraints. In

particular the fluxes considered should allow the batch mode reprocessing to be installed in the

vicinity of the reactor. Initial studies of the scientific feasibility of the on-line control of the salt

composition and of its chemical and physical properties have not unearthed a showstopper.

When it comes to Generation-4, it appears that the major nuclear energy powers have given a higher

priority to the SFR concept. This mostly reflects a justified confidence in a technology which,

although it has not yet reached all the performances expected for a GEN-4 reactor, has already been

successfully tested in numerous projects. But all the properties detailed in this paper, especially its

deterministic safety performances and its ability to reduce the radio-toxicity of wastes currently

produced, put the TMSR in a very favourable position to fulfil the conditions defined by the GEN IV

International Forum. Moreover this TMSR concept may be very appealing to countries which hold

important thorium resources and have some remaining adjustment margins in the definition of their

nuclear energy policy. The TMSR is thus an excellent candidate to produce the large amounts of

nuclear energy that the world will need in the near future.