Accelerator transmutation of waste

One of the potential ways to improve repository performance dramatically is through transmutation of long-lived isotopes. We have embarked on a roadmapping process for Accelerator Transmutation of Waste, together with colleagues from Japan, Russia, France, and other countries. 

Typical heat production in the moderator-fuel blanket is 750- 1500 MW. The excess heat is used to generate electricity that helps to pay for the operation of the facility. The transmuted material will have 20% of the original plutonium and minor actinides of the input material and will contain significant fission product activities. This transmuted material can be put into geologic storage, reducing the long-term hazard of the repository material. The overall feasibility of this accelerator transmutation of waste (ATW) has not been established yet. 

A variation of the PUREX process is being proposed by the US Department of Energy as a possible alternative partitioning scheme for the transmutation of wastes. This aqueous process called UREX, only removes uranium from spent commercial LWR fuel and leaves plutonium in the HLW stream with the other minor actinides and fission products. Nonaqueous pyroprocessing, a variation of the ANL electrorefining process, is then proposed to be used to separate both the plutonium and minor actinides so that they can be transmuted in an ADS. For further information related to potential modifications of this process for other accelerator transmutation of waste applications, see ANL-99/15 (1999). 

For an in-depth comparison of fast reactors and accelerator-driven systems for transmutation of actinides and long-lived fission products, see (OECD/NEA 2002). For more information on accelerator transmutation of waste (ATW) program in the USA, see refs. Jarvinen et al. (1992), LANE (1999), and DOE (2001). 

LANL (1999) Roadmap for the development of accelerator transmutation of waste target and blanket system... 

The economics of a closed fuel cycle within the already mentioned system with 20 LWRs and 3 PEACER parks with 12 PEACER reactors (PEACER system) was evaluated in comparison with the present-day fuel cycle of an advanced LWR (ALWR). A preliminary economic analysis has been conducted using cost figures suggested in the accelerator-driven transmutation of waste (ATW) roadmap the cost of pyro-processing within the PEACER system was conservatively assumed to be twice the value suggested in this roadmap. The overall fuel cycle cost of the PEACER system was preliminarily evaluated to be about 24% lower than that of the ALWR fuel cycle, as presented in Table XXIV-7. 

Such fission potentials might also have practical relevance. The possibility of transmutation of nuclear waste and the production of energy by accelerator-driven systems is under consideration. Accurate fission potentials are needed, particularly in the actinide region, to predict the fission cross sections for these applications. 

It is possible to use the SVBR reactor as a sub-critical blanket of a proton accelerator driven system for transmutation of long-lived radioactive waste [XIX-10]. 

Fig. 7.4. The proton beam strikes the lead target generating neutrons which are moderated in the surrounding heavy water blanket. Molten salt carrying fissile material for heat generation and electric power production circulates in the heavy water blanket through double-walled pipes. Some of this power drives the accelerator. Nuclear waste including that produced in the molten salt is also circulated through the blanket in a separate loop and transmuted to stable and short-lived nuclides which are extracted and...

So, it is expedient to separate them from the HLW that may be vitrified and incorporate these actinides into crystalline matrices (nuclear waste forms) or fabricate them into solid targets for transmutation in nuclear reactors or accelerators. There are a variety of processes for processing and partitioning the actinides - TRUEX (USA, Japan, Russia), DIAMEX (USA, Japan, EEC), TRPO (PRC), SANEX (USA, EEC, PRC), are under development [6]. The basic process in these technologies is extraction (or precipitation) of actinides from HLW solutions using special reagents. These methods provide for the separation of a high-actinide fraction or joint extraction of actinides, rare earths, and zirconium. The proportion of elemental concentrations in typical fractions is (in wt.%) actinides - 10-15, rare earths - 60-65, zirconium - 20-25 [7]. 

For the AFC to be most effective and reduce the inventory of minor actinides at a reasonable rate, dedicated devices that produce a hard or fast neutron spectrum will be required. Such devices include the advanced liquid metal reactors (ALMRs), a fast reactor configured to operate as an actinide incinerator rather than breeder and accelerator-driven systems (ADSs). Fast reactor technology discussed earlier in this chapter is relatively mature whereas the development of ADS is in its infancy. Accelerator-based waste transmutation programs are ongoing in France, Japan, USA, and CERN. 

Ignatiev, V.V. 2003. Molten Salt Fuels for Nuclear Waste Transmutation in Accelerator Driven Systems. Review of National Accelerator Driven System Programmes for Partitioning and Transmutation. In Proceedings of an Advisory Group Meeting, Taejon, Republic of Korea. 

P T involves three steps (i) partitioning of long-lived radionuclides (minor actinides (Np, Am, Cm) and fission products (I, Tc, Cs)) from high level waste (ii) development of fuel and targets containing these long-lived elements in view of their (iii) transmutation in different burners (fission reactors and accelerator driven transmutation devices). The progress achieved in these three areas can be summarized as follows. 

It is possible to destroy some radionuclides with long half-lives by transforming them into either stable nuclides or into nuclides with shorter half-lives. Transmutation, a nuclear process, transforms one nuclide into another by bombardment with subatomic particles in nuclear reactors or in particle accelerators designed for this purpose. Treatment of nuclear fuel waste by transmutation would first require reprocessing the used fuel and partitioning the waste stream to separate the resulting species according to the various nuclear methods to be used to transmute the (Afferent radionuclides. 

XXX-17] FURUKAWA, K., LECOCQ, A., KATO, Y, MITACHI, K., Radioactive waste management in global application of Th molten-salt nuclear energy synergetics with accelerator driven breeders. Specialist meeting Accelerator-Driven Transmutation Technologies for Radwaste and Other Applications (24-28 June, 1991, Saltsjobaden, Stockholm, Sweden), LA-12205-C Conf SKN Rep.No.54 UC-940, p. 686-697 (1991). 

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