Fast reactor cycle systems

The fast reactor development programme is a key part of the Japanese policy for greater energy independence. The feasibility studies on commercialised fast reactors cycle systems are in progress. The Japanese R D are being focused on the design of the candidate concepts and on fundamental tests of key technologies. 

With a purpose of probing a commercially feasible fast reactor system, a feasibility study on commercialized fast reactor cycle systems (FS) was initiated in 1999 (Aizawa, 2001). In the FS, survey studies were made to identify the most promising concept among various systems such as sodium-cooled fast reactors, gas-cooled fast reactors, heavy metal-cooled fast reactors (lead-cooled fast reactors and lead-bismuth cooled fast reactors), and water-cooled fast reactors with various fuels types such as oxide, nitride, and metal fuels. The FS concluded to select an advanced loop-type SFR with mixed oxide fuel named Japan sodium-cooled fast reactor (JSFR Kotake et al., 2005). 

Kotake, S., et al., 2005. Peasibihty study on commerciahzed fast reactor cycle systems current status of the PR system design. In Proceedings of GLOBAL 2005, Tsukuba, Japan, October 9-13, 2005. 

Takata, T., Koma, Y., Sato, K. et al. 2004. Conceptual design study on advanced aqueous reprocessing system for fast reactor fuel cycle. J. Nucl. Sci. Technol. 41 (3) 307-314. 

The whole set of possible thermochemical cycles has been considered and ranked based on a list of predefined criteria such as levels of temperatures required, rarity or toxicity of the reactants, number of electrochemical steps,. This led to the selection of a few cycles of interest (Mg-I, Ce-Cl and Cu-Cl). After further evaluation, Cu-Cl (shown in Figure 8) was retained. This cycle presents the advantage of dealing with only moderate temperature reactions (< 530°C), which offers the possibility of coupling it with other Gen-IV systems such as the Sodium Fast Reactor and the Supercritical Water Reactor. 

A new thermochemical and electrolytic hybrid hydrogen production system in lower temperature range has been developed by the Japan Nuclear Cycle Development Institute (JNC) to achieve the hydrogen production from water by using the heat from a sodium cooled fast reactor (SFR) [7]. 

Reactor physic studies for the transmutation of Am in separate subassemblies of a LMFR were made using a rather high Am-concentration (to restrict the number of the special assemblies), a typical fast reactor flux (3.61589 x 10 K/cm s) and depleted UOj as a. .matrix material. The calculations were done as fundamental mode bumup calculations with the KAPROS code system. The results show that for an irradiation cycle of 6 years the total amount of Am is halved, % of the original mass was fissioned and the remaining Vi transmuted mainly to Pu 238, Pu 242 and to Cm (242 and 244) and only a small percentage of the depleted UOj was fissioned. The power densities for varying Am and U contents could be adjusted between 500 W/cm (pure UOj) and about 1200 W/cm (pure Am... 

In parallel with the work done in collaboration with the European partners BNFL has conducted studies of the potential role of fast reactors in the UK and elsewhere. It is important to consider the fuel cycle as a whole and to make use of fast reactors in the optimum way to maximise safety and economic advantage while minimising environmental impact and proliferation risks. To this end accelerator-based systems as alternatives to critical reactors, and the thorium cycle as an alternative to the uranium-plutonium cycle, have been examined with particular reference to the implications for fuel fabrication, reprocessing and waste disposal. This work continues but the initial conclusion is that the critical Pu-fuelled fast reactor, properly integrated with reactors of other types, and with optimised arrangements for Pu recycling, has many attractive advantages. 

The main efforts in this century therefore must be concentrated to material conversion and management, which mean the realization of nuclear fuel cycle. Practically the following two steps are considered (1) an LWR fuel cycle that leads to advanced reactors such as the sodium fast reactor (SFR) and (2) an advanced nuclear energy system with related fuel cycle. The second step is more concerned with nuclear material and sensitive to nuclear arms. Therefore, the nuclear menace shall be fully concerned, and individuals as well as organizations in the nuclear community shall make up their minds to develop advanced nuclear energy system exclusively for peaceful use. Advanced nuclear energy system shall be developed for future prosperity of mankind and limited only to peaceful purposes. 

Scenario 2 - Using the reprocessed fuel of thermal reactors, a system of fast reactors develops, with all Pu, Np, Am, and Cm from INF of the former transferred into the fuel cycle of the latter. By the end of the twenty-first century, the energy output of the system of fast reactors is two times that of the thermal reactor mix. 

The solutions in physics and design of SFR and VHTR (HTGR) were discussed in the first part of the chapter. The second part of the chapter deals with the innovative approaches to development of naturally safe fast reactors with a closed fuel cycle, including LFR, which is treated as the main line in establishment of large-scale nuclear power. The other three reactor systems selected for the Generation IV Project are briefly discussed below. 

S. Ehrman and C. E. Boardman, System Considerations for Actinide Recycle in Fast Reactors, Proceedings ofGlobal 95 Fuel Cycle Conference, Versailles, France, September 1995. 

TUPPER, R., et al. Reactivity Control and Shutdown System for the U.S. ALAMR, Proc. Int. Conf. on Fast Reactors and Related Fuel Cycles, 28 October-1 November 1991, Kyoto, Japan. 

OKA, Y., et al.. Systems design of direct-cycle supercritical water cooled fast reactors. Nuclear Technology,. 109, pp. 1-10 (1995). 

XXn-10] MOISSEYTSEV, A., SIENICKI, J.J., WADE, DC., Cycle analysis of supercritical carbon dioxide gas turbine Brayton cycle power conversion system for liquid metal-cooled fast reactors, ICONE-11 (11 Int. Conf. on Nuclear Engineering, Tokyo, April 20-23, 2003), Paper ICONE 11-36023. 

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