FAST REACTOR EXPERIENCE

France, Japan and the Russian Federation presented the status on sodium cooled fast reactor experience preservation made in these coimtries. The reports underlined these countries large experience with design, construction and operation of sodium cooled fast reactors. The discussions underlined the importance of the IAEA support for knowledge preservation of fast reactor experience. 

It is found that from induced activity and dose rate considerations, stellite can be replaced by either Colmonoy-6 or Tribaloy-700. Based on fast reactor experience with colmonoy, colmonoy has been chosen. An approximate estimate of the shield requirement assuming a permissible dose rate of 100 mR/h have been worked out. In the following discussions, as the basic SS component itself becomes radioactive and requires shielding, reduction in shield thickness is with respect to the minimum shielding required for the SS component [5]. 

The feedback from the operating fast reactors is achieved through a systematic review of the design of each system and component in the light of the European reactor experience and to die extent possible all fast reactor experience worldwide. 

P. Greebler, G. L. Gyorey, B. A. Hutchins, and B. M. Segal, Implications of Recent Fast Critical Experiments on the Basic Fast Reactor Design Data and Calculational Methods. Proc. Intern. Conf. Fast Reactor Experiments and Their Analysis, Oct. 10-13,1966, p. 66. 

Fast Reactor Experience and Fast Flux Technology... 

Temporal analysis of products (TAP) reactor systems enable fast transient experiments in the millisecond time regime and include mass spectrometer sampling ability. In a typical TAP experiment, sharp pulses shorter than 2 milliseconds, e.g. a Dirac Pulse, are used to study reactions of a catalyst in its working state and elucidate information on surface reactions. The TAP set-up uses quadrupole mass spectrometers without a separation capillary to provide fast quantitative analysis of the effluent. TAP experiments are considered the link between high vacuum molecular beam investigations and atmospheric pressure packed bed kinetic studies. The TAP reactor was developed by John T. Gleaves and co-workers at Monsanto in the mid 1980 s. The first version had the entire system under vacuum conditions and a schematic is shown in Fig. 3. The first review of TAP reactors systems was published in 1988. 

On the other hand, liquid metal-cooled fast reactors (LM-FRs), or breeders, have been under development for many years. With breeding capability, fast reactors can extract up to 60 times as much energy from uranium as can thermal reactors. The successful design, construction, and operation of such plants in several countries, notably France and the Russian Federation, has provided more than 200 reactor-years of experience on which to base further improvements. In the future, fast reactors may also be used to burn plutonium and other long-lived transuranic radioisotopes, allowing isolation time for high-level radioactive waste to be reduced. 

Miquel, P., and Boudry, J. C., "First Experiments on the Reprocessing of Fast Reactor Fuels in France," Paper presented at 82nd AIChE Mtg., Atlantic City, N.J., 1976. 

Relevant to water radiolysis in nuclear reactor, G-values of the water decomposition by fast neutrons have been determined by using a fast reactor at elevated temperatures [59]. Since fast neutron radiolysis is equivalent to proton radiolysis because of the recoil proton formation through the elastic collision of fast neutrons with H2O molecules [60], an alternative approach as a model experiment is the ion beam radiolysis with different LET particles from accelerators at elevated temperatures [61]. 

The Technical Committee Meeting (TCM) on Unusual Occurrences During LMFR Operation Review of Experience and Consequences for Reactor Systems was held on the recommendation of the International Working Group on Fast Reactors (IWGFR) at the IAEA Headquarters in Vienna from 9 to 13 November 1998. Participants from nine countries (China, France, India, Japan, Kazakhstan, the Republic of Korea, the Russian Federation, the United Kingdom and the United States of America) were in attendance. 

The design of the sterns and components was also reexamined considering the experience and knowledge accumulated at other fast reactors, research and development results and new findings. As a result of the review, some additional aspects were appeared. Some existing systems and components related to sodium leakage were found to require modification, and it was recommend that new systems and components should be introduced. Typical systems and components are ... 

The experience of Superphenix thus furthered the technical quality of the next fast reactor generation. 

OPERATING EXPERIENCE WITH BELOYARSK FAST REACTOR BN600 NPP... 

The experience from BN600 power generation shows BN600 to be reliable in control, safe and highly valuable for further commercial deployment of large fast reactor power plants at the current stage of nuclear power development. 

Review of various anomalous events and abnormal operation experience gained in the process of Russian fast reactors operation is given in the paper. The main information refers to the BN-600 demonstration reactor operation. 

Considerable experience has been gained by the Russian specialists on tests and operation of sodium cooled fast reactors (over 100 reactor-years). Based on this experience, modifications were made of systems and components of the reactors in operation, as well as of the BN-800 reactor design. 

In this respect, the experience gained in the process of operation of the BN-600 which is the largest in Russia fast reactor, is of the highest value. Therefore, in this paper, events occurred on the BN-600 reactor are mainly described. 

In Fig. 1 the lay-out of electric heaters and thermal insulation on sodium piping is shown. The heaters have 100% reserve. Earthing of the main and stand-by heaters is continuously monitored. Leaking sodium creates an electric contact between the heater and the pipe wall. Simultaneous failure of both the operating and stand-by heaters is indicative of a sodium leak. Such systems have been installed at all our fast reactors. Their operation experience has shown high reliability and sensitivity of such systems. 

We hope that fast reactor operating experience gained in Russia will undoubtedly be of use for the specialists in other countries, where this direction is under consideration. 

Fast Breeder Test Reactor (FBTR) is a 40 MWt/ 13.2 MWe sodium cooled, mixed carbide fuelled, loop type reactor. It has two primary and secondary sodium loops and a common steam water circuit, which supplies high pressure, high temperature superheated steam to turbine generator (TG). Heat is rejected in cooling tower (Fig 1). A 100% capacity dump condenser is provided for reactor operation even when the TG is not in service. The mmn aim of the reactor is to generate experience in the design, construction and operation of sodium cooled fast reactors and to serve as an irradiation facility for the development of fuels and structural material for fast reactors. It achieved first criticality in Oct 85 with Mark I core... 

C. Picker, A.S. Fraser, "Experience of cracking in austenitic stainless components of the UK prototype fast reactor", Int. J. Pres. Vessel Piping, 65,1996, 283-293. 

L. Martin et al., "Leak before Break operating experience from European fast reactors". Proceedings of International conference on Fast reactor and related fuel cycles, FR-91,, Kyoto, Japan, Oct 28-Novl,1991. 

Design of liquid metal cooled fast reactors (LMFRs) is still in evolution, and only a small number of LMFRs are in operation aroirnd the world. Specialists operating these LMFRs have gained valuable experience from incidents, failures, and other events that took plaee in the reactors. These unusual occurrences, lessons learned and measures to prevent recurrences are often either not reported in literature, or reported only briefly and without sufficient detail. Hence there is a need for specialists designing and operating LMFRs to share their knowledge on unusual occurrences. 

Large experience has been already gained with sodium cooled fast reactor operation. The use of sodium as a coolant poses fire danger in case of its leakage and interaction with air or water. Operating experience testifies the possibility of coping with the mentioned problem, but the quest for excellence calls for future improvement in LMFRs technology. 

Considerable experience has been gained in the Russian Federation with lead-bismuth (PbBi) eutectic alloy application as reactor coolant. Since Bi is sufficiently rare and expensive metal, and also it is a source of volatile a-active Vo, the proposal to use lead as a coolant in power fast reactors is now under consideration in several countries. Lead based alloys are currently being considered for hybrid systems (accelerator driven fast reactors) in which the coolant could double as the spallation source for driving the core. 

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