Reactor, breeder start

After a peak at 2010, the amount of Pu stored is supposed to start decreasing due to the expected increase in MOX fuel fabrication and its usage in Light Water Reactors (LWRs). Obviously, the utilization of MOX fuel by LWRs would gradually reach a balance in which the fissile Pu in the LWR fuel is ca. 5% of the total fuels. Consequently, the utilization of U resources would not be drastically improved. The ultimate utilization will be attained in the Fast Breeder Reactor (FBR) fuel cycle, in which a conversion of fertile 238U to 239Pu overwhelms the consumption of the 239Pu. 

It should be noted that breeders would not reduce the demand for uranium ore for many decades because several LWR and/or HWR converters (which produce fissionable material, but less than consumption) are required during the run-in of a breeder cycle to equilibrium. The doubling time of a breeder (the time required for the breeder to produce sufficient fissionable material to start up a second breeder reactor) might be a significant part of its operating life. Furthermore, natural uranium will be required for the thorium cycle, if it is used, and for startup of the fusion cycle. The tritium for the fusion cycle will be made in nuclear reactors, as it now is for nuclear weapons. The nuclear industry will always be dependent on a continuing supply of uranium from ore. 

The nuclear future may well lie with the fast breeder reactor which uses uranium some 60 times more efficiently than current fission reactors. Prototype breeder reactors are in operation in Russia and Japan and were so until recently in the UK and France. They will be required post-2030 or so if a major new nuclear programme is embarked on, as uranium resources are predicted to start running into short supply at about that time. 

The further processing of the uranyl nitrate solution, which in some plants is postpurified with silica gel, is directed towards further enrichment of the uranium. If this is not worthwhile due to a too low - U-content, the product is converted into uranium(Vl) oxide, a storable compound. This can serve as a starting material for possible later utilization in fast breeder reactors. The uranium(VI) oxide is either produced indirectly by way of ammonium diuranate or by direct calcination. If further enrichment is foreseen, uranium(Vl) fluoride or uranium(lV) fiuoride is produced, the latter being fluorinated in the enrichment plant to uranium(VI) fluoride. 

If the operational conditions and design of a reactor are adjusted to maximize the amount of Pu produced it is possible to operate the reactor to produce more fertile isotopes than were originally used to start the reactor. This operational mode is called the breeder reactor. The breeder reactor can greatly extend the amount of potential energy available from uranium because it is possible to use the 99.3% U present in natural uranium, as fuel. It is also possible to use thorium (Th" ) in a breeder reactor to produce fertile U. The use of the breeder reactor will extend the lifetime of the nuclear fission energy source to several hundred years. 

In a typical breeder reactor, nuclear fuel containing uranium-235 or plutonium-239 is mixed with uranium-238 so that breeding takes place within the core. For every uranium-235 (or plutonium-239) nucleus undergoing fission, more than one neutron is captured by uranium-238 to generate plutonium-239. Thus, the stockpile of fissionable material can be steadily increased as the starting nuclear fuels are consumed. It takes... 

Monju is Japan s prototype fast breeder reactor 280 MWe(714MWt), fueled with mixed oxides of plutonium and uranium, cooled tty liquid sodium. Construction was started in 1985 nd initial criticality was attained in April 1994... 

This report describes the development and activities on fast reactor in Japan for the period of April 1996 - March 1997. During this period, the 30th duty cycle operation has been started in the Experimental Fast Reactor "Joyo". The cause investigation on the sodium leak incident has completed and the safety examination are being performed in the Prototype Fast Breeder Reactor "Monju". The three years design study since FY1994 on the plant optimization of the Demonstration FBR has been completed by the Japan Atomic Power Company (JAPC). 

As for the demonstration fast breeder reactor (DFBR) of Japan, the Japan Atonaic Power Company (JAPC) conducted conceptual design studies for the past several years, and confirmed the feasibility of top entry loop type reactor concept. Based on results of the design studies, the Federation of Electric Power Companies (FEPC) decided in January 1994 to start construction of the DFBR plant at the beginning of the 2000 s. FEPC also decided the basic specifications of the DFBR plant. 

Widespread use of the fast breeder reactor could increase the utilization of uranium by approximately 50-fold. This type of reactor can be started up on plutonium derived from conventional reactors and operated in closed circuit with its reprocessing plant. Such a reactor, supplied with natural or depleted uranium for its fertile blanket, can be operated so that each toime of ore yields 60 times more energy than in a conventional reactor. 

So nature s own reactor was perhaps active some 2000 million years ago. Water is thought to have been the moderator. Fission of started the process. In the actual period the content of (counted on total uranium) is estimated to have been 3%. This is one reason why the reactor started. With the content 0.72% of today a spontaneous reactor of Oklotype is not possible. The abundant access to made the formation of possible. Thus this natural reactor was a true breeder reactor. 

The construction of Monju, the prototype fast breeder reactor (FBR) which PNC has built as part of the Japanese FBR development programme, was completed in April 1991, and system start-up tests are presently underway. Monju is a loop-type sodium-cooled fast breeder reactor with U-Pu mixed oxide fuel. It supplies 280 MWe to the grid and is situated on the Tsuruga Peninsula facing the Sea of Japan, about 400 km west of Tokyo. 

The research and development work on high temperature gas cooled reactors in China started in 1970s [XVII-1-3]. Initially, the work was focused on gas cooled breeders using thorium fuel cycle. The R D and design work was carried out for a helium cooled thorium breeder of 100-MW output, using spherical fuel elements. The activities included ... 

The] promising perspective is expansion of nuclear energy using fast breeder reactors starting with enriched uranium fuel and step-by-step replacement with plutonium Juel. 

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