JOYO experimental reactor

The experimental reactor Joyo, located in the O-arai Engineering Center(OEC) of PNC, has provided abundant experimental data and excellent operational records attaining 51,078 hours operation in total by the end of March 1995, since the first criticality in 1977. 

To accomplish this plan, the sodium cooled experimental reactor JOYO is now under operation in the Japan Atomic Energy Agency (JAEA), a new organization combining the former Japan Nuclear Cycle Development Institute (JNC) and Japan Atomic Energy Research Institute (JAERI). The JOYO reactor is being operated to develop and validate sodium, fuel, and material technologies, etc. 

Design features Compared with the experimental reactor Joyo, the prototype reactor Monju has about seven times the thermal capacity - (Joyo 100 MWt Monju 714 MWt - and a provision for power generation. 

Approval of the Test Matrix and Associated Changes for the JOYO-1 Irradiation Test of Structural Materials in the JOYO Experimental Fast Reactor to Support Space Reactor Development", dated April 16, 2005... 

The CREDO data base contains data from The Fast Flux Test Facility in Richland, Washington, The Experimental Breeder Reactor - II in Idaho Falls, Idaho, The test loops of the Energy Technology Engineering Center (ETEC) in Canoga Park, California, The JOYO Liquid Metal Fast Breeder Reactor at the 0-Arai Engineering Center (OEC) in Japan, and the test loops of OEC. 

Mixed oxide (MOX) fuel, 21.0-wt% Pu in 18.0-wt% enriched uranium, was irradiated from the 16 to 35 cycle at the 3" row in the experimental fast reactor JOYO. Tire effective full power days were 1019.33, and the peak bumup was 143.8 GWd/t. Atotal of 1560 days have passed from the reactor shut down to analysis. 

In Japan, fast reactor development program symbolises national nuclear fuel recycling program, as it is stated in the national long-term plan [2.3]. The experimental fast reactor Joyo has shown excellent performance for more than 20 years. The prototype reactor Monju (280 MW(e)) was stopped temporarily due to the leak in the non-radioactive secondary circuit in 1995. The design of demonstration fast reactor (DFBR-600 MW(e)) is in progress [2.4, 2.5]. 

OPERATIONAL EXPERIENCE AND UPGRADING PROGRAM OF THE EXPERIMENTAL FAST REACTOR JOYO... 

Twenty years of sueeessful operations at the experimental fast reactor JOYO provide a wealth of experience eovering eore management, chemical analysis of sodium and cover gas for impurity control, natural convection tests, upgrade of fuel failure detection system, corrosion product measurement, development of operation and maintenance support system, and replacement of major components in the cooUng systems. Some of the data obtained is stored in a database to preserve the related knowledge. This experience and accumulated data will be useful for the design of future fast reactors. 

The experimental fast reactor JOYO at the Japan Nuclear Cycle Development Institute s Oarai Engineering Center attained initial criticality in April 1977 and was the first liquid metal cooled fast reactor in Japan. From 1983 to 2000, JOYO operated with the MK-II core as an irradiation test bed to develop the fuels and materials for future Japanese fast reactors. Thirty-five duty cycle operations and thirteen special tests with the MK-II core were completed by June 2000 without any fuel pin failures or serious plant trouble. The reactor is currently being upgraded to the MK-III core. This paper provides a review of the operational experiences obtained through the JOYO s operation. 

SAWADA, M., et al.. Experiment and Analysis on Natural Convection Characteristics in the Experimental Fast Reactor JOYO, Nuclear Engineering and Design, 120 (1990) pp. 341-347. 

AOYAMA, T., et al., The Operational Experience of the Experimental Fast Reactor JOYO, Proc. 3" Asian Symposium on Research Reactor, Ibaraki, Japan, 11-14 November 1991, JAERI (1991) pp. 75-82. 

MAEDA, Y, et al.. Current Status and Upgrading Program of the Experimental Fast Reactor JOYO, Proc. World Nuclear Congress and Expo (ENC 98) Trans., Nice, France, 25-28 October 1998, Vol. IV, Workshops, (1998) pp. 21-30. 

YOSHIDA, A., et al.. Upgrading Program of the Experimental Fast Reactor Joyo, Book of Abstracts Int. Conf on Nuclear Engineering (ICONE-9), Nice, France, 8-12 April 2001, Vol. 2, ASME (2001) p. 492. 

Japan. During the period from April 1996 to March 1997, the 30th duty cycle operation has been started on the experimental fast reactor Joyo. The cause investigation on sodium leak incident has been completed and safety examination is being performed on the prototype fast reactor Monju. 

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). 

Figure 2.1 Operating History of Experimental Fast Reactor JOYO...

In Japan, the self-actuated shutdown system (SASS) has been developed as a passive safety feature (Takamatsu et al. 2007 Nakanishi et al. 2008) using the phenomena that electromagnetic force of the control rod latch will be lost when alloy temperature exceeds the Curie point. Several kinds of in-sodium transient testing have been carried out together with in-pile experiments in the experimental fast reactor Joyo. This mechanism is effective to the robust restraint core, which is designed for seisnuc requirements. 

In Japan, the experimental fast reactor "Joyo started operation in 1975 following the criticality test equipment called fast critical assembly (FCA). Joyo has run irradiation tests for domestic fuel material and increased the core thermal output as well. At the beginning of operation, the thermal output of the core was 100 MW. Currently, it employs a third-generation core, called the MK-in, with 140 MW thermal output. 

The experimental FBR "Joyo" and the prototype FBR "Monju" were developed by the Power Reactor and Nuclear Fuel Development Corporation (PNC). 

Sawada, M., Arikawa, H., Mizoo, N., 1990. Experiment and analysis on natural convection characteristics in the experimental fast reactor Joyo. Nuclear Engineering and Design 120, 341-347. 

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