Pumps 1. Inducer test to start 1979. 2. CRBRP test to start 1980. A REVIEW 3. Large pump test to start 1983. OF THE U.K. FAST REACTOR PROGRAMME: MARCH 1978 Reference Fuel Verification to be completed in 1982. R.D. SMITH Advanced Fuel United Kingdom Atomic Energy Authority, Selection in 1985. Risley, United Kingdom Facilities 1. Fuel storage at FFTF. 2. 70 MWt steam generator to be completed at LMEC 1978. 1. BACKGROUND TO THE 1978 REVIEW 3. FMEF design work started. The main events during 1977 concerning the nuclear power programme were the public inquiry into the proposal to buiid a new Thermal Oxide Reprocessing Plant (THORP) at VVindscale and the 4. HPFL design work started. government decision on the choice of nuclear reactors for the next stage of the thermal reactor pro- gramme. Both these events, though not directly concerned with fast reactor development have significant 5. TTF at LMEC in operation. implications for the UK fast reactor programme. Indeed, during the course of the Windscale inquiry it was made clear that there was to be an inquiry on fast reactors that would consider all the issues con- 6. Upgrading of TREAT to be completed in next several years. sequent upon the introduction of fast reactors as major contributors to the UK power supplies. Fast reactor matters were therefore not discussed extensively at Windscale - nevertheless some of the con- The efforts described would serve as a focal point for the expanded base clusions concerning the various facets of the use of plutonium for power generation were considered and program, but more importantly, it would assure a viable breeder option the conclusions are of importance to fast reactor development. which could meet the requirement stated by President Carter: "I believe that a strong research and development program for the breeder reactor The decision to build two further AGR power stations and in addition to develop the option of is essential to maintaining diversity of energy supply options for this adopting the Pressurised Water Reactor (PWR) System in the early 198O's impacts on the fast reactor country ...." programme mainly as a result of competition for resources. The Secretary of State for Energy has stated that the next decision to be made is that on the fast breeder reactor. In the meantime the development To summarize, from the U.S. domestic viewpoint, there appears to be time programme :s continuing at a rate of over £60M per year on the fast breeder development programme to develop a better product and to examine proliferation considerations including the operation of the Prototype Fast Reactor (PFR) at Dounreay. more deliberately. The Nuclear Power Company (NPC) responsible for the design and construction of nuclear reactors in the UK has continued work on the engineering design of the 1300 MW(E) fast reactor now called the Commerciai Demonstration Fast Reactor (CDFR). A restrained core design has now been developed to replace the free-standing design of the type used for the PFR and the engineering design of the plant is continually being revised and improved. The Central Electricity Generating Board (CEGB) continue to play an active part in the develop- ment programme. They have made their own studies of uranium demand and the system penetration characteristics of the fast reactor under varying assumptions for future system growth. These underline the need for achieving short plutonium tumround time in the fuel cycle, particularly where fast reactors are supported solely by plutonium produced in an adjoint thermal reactor programme, if ore demand is to be minimised. CEGB continue to support the operation of the PFR at Dounreay by secondment of suitably experienced staff. In addition scientific staff have been seconded to assist in reprocessing activity in the UK O ! and in sodium boiling experiments at KfK Karlsruhe. Secondment to the SNR-300 project continues. O ro CD The Nuclear Installations Inspectorate (Nil) have continued their independent assessment of fast caution a detailed survey of all the welds in the tube plate was carried out. The reactor was restarted in 57 reactor safety, devoting much effort to Whole Core Accidents (WCA). The work has included studies of May on Circuits 1 and 2, and Circuit 3 was recommissioned in July. Subsequently the reactor has the explosion yield of postulated accidents and the consequences for the population of extreme examples operated very reliably. of such accidents. Operation at reduced power levels has been required while thermal hydraulics were studied in the The behaviour in normal operation of a prestressed containment is being investigated and the primary circuit using special thermocouple probes loaded during die shutdown. Reduced power operation Inspectorate has participated in the APRICOT international comparative exercise on the analysis of struc- in the last quarter of the year was due to minor mechanical problems with some conventional plant items. tural response to WCA pressure loads. A further leak in Evaporator No. 3 was detected, located and plugged in less than two weeks. The USA government policies with regard to the development of the fast reactor have had some Equipment to provide a larger steam dump capacity has been installed. This will increase opera- impact on the UK fast reactor programme. In particular the UK is participating in the International tional flexibility and should prevent tripping of the reactor as a consequence of turbine trips during start- Nuclear Fuel Cycle Evaluation (INFCE) programme, including possible alternative fuel cycles for fast up or shutdown sequences. Operation on all three circuits was resumed during December; then in reactors, and is devoting some effort to this work, even though it is thought unlikely that any practicable January 1978 there was a severe storm which disconnected Dounreay completely from the grid of the major changes in the fast reactor fuel cycle are likely to result. North of Scotland Hydro-electric Board (NSHEB). This is the first time since the stair of construction that this has occurred. The loss of grid connection tripped both reactor and turbine. The diese! alterna- tors and guaranteed power supply systems all operated correctly and the decay heat was rejected through 2. THE DOUNREAY FAST REACTOR (DFR) the thermal syphon loops. The station was restarted early in February 1978 and operated at high power until the planned refuelling and maintenance shutdown in March. The length of this shutdown will DFR was closed down as scheduled on 23 March I 977 after seventeen yeais of successful operation depend on the time taken to re-blade the end rows of the LP turbine. Erosion shields had been removed as a development and test facility. in 1973 and wear has been exacerbated by the prolonged operation under non-standard steam conditions. During the last run before closure a series of coolant boiling experiments was carried out in which During this year steam generator performance has been much improved, the only leaks occurring on specially contained experimental rigs containing fast reactor type ruel pins at various levels of burn-up Evaporator No. 3 which haH been severely contaminated with sodium during early operations. Measure- were operated with gradually reduced coolant flow with repeated periods of local coolant boiling. One ments of the temperatures in the hot sodium pool and above-core structures, with development work and rig was in tact subjected to 12 runs and a total of nearly 24 hours above boiling temperatures. Detailed rig tests, confirm that sustained full power operation will be possible with the core-loading arranged analysis of the results of the experiments is still being made but in general it appears that the following during the present shutdown. broad conclusions can be drawn: Good proeress has been made with commissioning of the irradiated-fuel caves, including the com- (1) Fast reactor fuel is extremely durable. plete sodium filling of the equipment tanks and the filter testing. Many of the moves of irradiated fuel and (2) Boiling behind a blockage develops axially rather than radially and therefore has little effect on components between the in-reactor store and caves have been completed for the next reioad. the bulk flow through the sub-assembly. (3) In cases where pin failure occurs it is innocuous and would be easily detected well within the 4. COMMERCIAL DEMONSTRATION FAST REACTOR (CDFR) time scale required by safety considerations. (4) In general, theoretical predictions of the outset of boiling are substantiated. 4.1 Core design and parameters Since the closure of DFR, work has continued on the decontamination of certain items of plant, the A review of the different designs of heterogeneous cores is being prepared. It is not certain that recovery of certain components for examination and the disposal of some NaK. a worthwhile improvement in safety will be achieved by the adoption of such a core but the UK designers are considering in some detail the engineering effects of the various alternatives. The main factors to be The reactor will be partially decommissioned, and the outer containment sphere retained, possibly as an industrial exhibition hall. influenced are the overall size of the core and the disposition of absorber rods and nucleonic inst-uments. As work continues on the restrained core, a definitive design has been produced and analysed. The 3. PROTOTYPE FAST REACTOR (PFR) conclusion is that this design of restrained core is satisfactory. Design of the diagrid and carriers has resulted in an alternative scheme featuring hydraulic hold-down for the carriers distinct from the earlier The last review was made just after the reactor had reached its full thermal power of 600 MW with mechanical hold-down system. Fabrication problems of both diagrid and carriers will be examined to an electrical output of 200 MW.