Small Power Reactors Research Articles

Study on High-Fidelity Thermal-Neutronic Coupling Method Based on the Unified Geometry Modeling and its Application in Experimental Reactor Core Calculation for SPERT

To solve the problem that the thermal-neutronic grid mapping relation is complicated and cannot be preset in a centralized manner due to the existence of irregular geometry in performing the thermal-neutronic coupled simulation calculation for various small power reactors and experimental reactors, this paper studies the thermal-neutronic coupling method based on the unified geometric modeling, using the high-fidelity numerical code for reactor neutronics calculation, NECP-X. This study establishes the mapping relation for the thermal-neutronic coupling on the basis of the neutronics model, and enables the direct transient calculation of the experimental reactor core for the special power excursion reactor test (SPERT) via combination with the transient calculation method in NECP-X. Then, this study calculates the steady-state case for the experimental reactors of SPERT, and compares the calculation results with the results gained from the Monte Carlo code. On this basis, this study conducts transient calculation and analysis for these experimental reactors and compares the corresponding results with the experimental results. The final results show that the eigenvalues from the neutronics calculation by the NECP-X and the rod power distribution calculation results are of high accuracy; that the grid mapping method based on the unified geometric modeling allows a easy and fast thermal-neutronic coupled calculation of the PWRs of complex geometry; and that compared with the experimental values, the curve of change in the total power and reactivity gained from transient calculation with time is more accurate and can provide refined distributions of power and temperature.

Thorium Fuel Utilization Analysis on Small Long Life Reactor for Different Coolant Types

A small power reactor and long operation which can be deployed for less population and remote area has been proposed by the IAEA as a small and medium reactor (SMR) program. Beside uranium utilization, it can be used also thorium fuel resources for SMR as a part of optimalization of nuclear fuel as a “partner” fuel with uranium fuel. A small long-life reactor based on thorium fuel cycle for several reactor coolant types and several power output has been evaluated in the present study for 10 years period of reactor operation. Several key parameters are used to evaluate its effect to the reactor performances such as reactor criticality, excess reactivity, reactor burnup achievement and power density profile. Water-cooled types give higher criticality than liquid metal coolants. Liquid metal coolant for fast reactor system gives less criticality especially at beginning of cycle (BOC), which shows liquid metal coolant system obtains almost stable criticality condition. Liquid metal coolants are relatively less excess reactivity to maintain longer reactor operation than water coolants. In addition, liquid metal coolant gives higher achievable burnup than water coolant types as well as higher power density for liquid metal coolants.

Preliminary Study of 20 MWth Experiment Power Reactor based on Pebble Bed Reactor

In this study, preliminary design calculations for experimental small power reactor (20 MWt) based on Pebble Bed Reactor (PBR) are performed. PBR technology chosen due to its advantages in neutronic and safety aspects. Several important parameters, such as fissile enrichment, number of fuel passes, burnup and effective multiplication factor are taken into account in the calculation to find neutronic characteristics of the present reactor design.

Preliminary Study of Safety Analysis of Pb-Bi Cooled Small Power Reactor with Natural Circulation

We report our study of the safety analysis in design of small power reactor which design based on the concept of a long-life core reactor cooled by lead-bismuth eutectic (LBE). The motivation of these studies is in order to design a next generation of reactors, we need to design a type of reactor that has inherent safety. We designed the small Pb-Bi cooled reactor with MOX-Nitrate as a fuel. In order to study the safety analysis of this reactor we conducted studies of chimney length effect to coolant flow rate in natural circulation and dependency of outlet temperature with coolant flow rate. From this work we obtained the optimum height of chimney at 15 m for the lead-bismuth eutectic flow rate 3500 kg/s and also we found the dependency of outlet temperature with lead-bismuth eutectic flow rate.

Neutronics and pumping power analyses on the Tokamak reactor for the fusion-biomass hybrid concept

The authors aim to develop a fusion-biomass combined plant concept with a small power fusion reactor. A concern for the small power reactor is the coolant pumping power which may significantly decreases the apparent energy outcome. Thus pressure loss and corresponding pumping power were studied for a designed Tokamak reactor: GNOME. First, 3-D Monte-Carlo Neutron transport analysis for the reactor model with dual-coolant blankets was taken in order to simulate the tritium breeding ability and the distribution of nuclear heat. Considering calculated concentration of nuclear heat on the in-board blankets, pressure loss of the liquid LiPb at coolant pipes due to MHD and friction forces was analyzed as a function of fusion power. It was found that as the fusion power increases, the pressure loss and corresponding pumping power exponentially increase. Consequently, the proportion of the pumping power to the fusion power increases as the fusion power increases. In case of ∼360MW fusion power operation, pumping power required for in-board cooling pipes was estimated as ∼1% of the fusion power.

A road map for the realization of global-scale thorium breeding fuel cycle by single molten-fluoride flow

For global survival, we need to launch a rapid regeneration of the nuclear power industry. The replacement of the present fossil fuel industry requires a doubling time for alternative energy sources of 5–7 years and only nuclear energy has the capability to achieve this. The liquid metal cooled fast breeder reactors (LMFBR) have the best breeding criteria but the doubling time exceeds 20 years. Further, the use of plutonium in these systems has the potential of nuclear proliferation. The Thorium Molten-Salt Nuclear Energy Synergetic System [THORIMS-NES], described here is a symbiotic system, based on the thorium–uranium-233 cycle. The production of trans-uranium elements is essentially absent in Th–U system, which simplifies the issue of nuclear waste management. The use of 233U contaminated with 232U as fissile material, instead of plutonium/ 235U makes this system nuclear proliferation resistant. The energy is produced in molten-salt reactors (FUJI) and fissile 233U is produced by spallation in Accelerator Molten-Salt Breeders (AMSB). This system uses the multi-functional “single-phase molten-fluoride” circulation system for all operations. There are no difficulties relating to “radiation-damage”, “heat-removal” and “chemical processing” owing to the simple “idealistic ionic liquid” character of the fuel. FUJI is size-flexible, and can use all kinds of fissile material achieving a nearly fuel self-sustaining condition without continuous chemical processing of fuel salt and without core-graphite replacement for the life of the reactor. The AMSB is based on a single-fluid molten-salt target/blanket concept. Several AMSBs can be accommodated in regional centers for the production of fissile 233U, with batch chemical processing including radio-waste management. FUJI reactor and the AMSB can also be used for the transmutation of long-lived radioactive elements in the wastes and has a high potential for producing hydrogen-fuel in molten-salt reactors. The development and launching of THORIMS-NES requires the following three programs during the next three decades: (A) pilot-plant: miniFUJI (7–10 MWe), (B) small power reactor: FUJI-Pu (100–300 MWe), (C) fissile producer: AMSB for globally deploying THORIMS-NES.

The prospect of mox fuel based Pb [sbnd]Bi cooled small nuclear power reactors

Safety performance of MOX fuel based Pb Bi cooled small fast power reactors has been analyzed and discussed. Though the thermal conductivity of MOX fuel is not large relative to that of nitride or metal fuel, but by proper combination of relatively small power density and relatively large natural circulation it can compensate fuel temperature decrease with coolant temperature increase smartly during unprotected loss of flow accident. Under such condition, accident analysis discussed in this paper show that under unprotected total loss of flow (ULOF) accident the reactor can survive inherently using combination of reactivity feedback. For unprotected rod run out transient over power (UTOP) accident the MOX reactor can overcome external reactivity by smaller power increase compared to that of nitride fueled reactors case. In this case doppler feedback plays much more important role compared to radial expansion component. So the MOX fueled small power reactors discussed here can survive both UTOP and ULOF accident with still enough temperature margin.

Advanced converters and reactors

As Western Europe and most countries of the Asia-Pacific region (except Australia) have only small natural uranium resources, they must import nuclear fuel from the major uranium supplier countries. The introduction of advanced converter and breeder reactor technology allows a fuel utilization of a factor of 4–100 higher than with present low converters (LWRs) and will make uranium-importing countries less vulnerable to price jumps and supply stops in the uranium market. In addition, breeder-reactor technology will open up a potential that can cover world energy requirements for several thousand years. The enormous development costs of advanced converter and breeder technologies can probably be raised only by highly industrialized countries, which have made nuclear power one of the mainstays of their energy programs. Those highly industrialized countries that have little or no uranium resources (Western Europe, Japan) will probably be the first to introduce this advanced reactor technology on a commercial scale. A number of small countries and islands will need only small power reactors with inherent safety capabilities, especially in the beginning of their nuclear energy programs. For economic reasons, the fuel cycle services should not be built up in such small countries or on islands, but rather should come from large reprocessing centers of countries having sufficiently large nuclear power programs or from international fuel cycle centers. Only in this way can the economic benefits of nuclear power be realized in small countries or islands of the Asia-Pacific region.

Supply of appropriate nuclear technology for the developing world: Small power reactors for electricity generation

A growing world population, expected to reach eleven thousand million people by the year 2050, implies a growing need for the expansion of energy conversion technology. Over 80% of the world's population growth is projected to be centred in the lesser developed countries (LDCs), that part of the world expected to experience the largest growth rates in energy consumption. Constraints on fossil fuels, such as oil, natural gas and coal, imply that other energy sources will be needed in large supply to fulfill LDC energy demands. This paper reviews the supply of small nuclear power plants (200 to 500 MWe electrical generating capacity) available on today's market, including the pre-fabricated designs of the United Kingdom's Rolls Royce Ltd and the French Alsthom-Atlantique Company. Also, the Russian VVER-440 conventionally built light-water reactor design is reviewed, including information on the Soviet Union's plans for expansion of its reactor-building capacity. A section of the paper also explores the characteristics of LDC electricity grids, reviewing methods available for incorporating larger plants into smaller grids as the Israelis are planning. Future trends in reactor supply and effects on proliferation rates are also discussed, reviewing the potential of the Indian 220 MWe pressurised heavy-water reactor, South Korean and Japanese potential for reactor exports in the Far East, and the Argentine-Brazilian nuclear programme in Latin America. This study suggests that small reactor designs for electrical power production and other applications, such as seawater desalination, can be made economical relative to diesel technology if traditional scaling laws can be altered by adopting and standardising a pre-fabricated nuclear power plant design. Also, economy can be gained if sufficient attention is concentrated on the design, construction and operating experience of suitably sized conventionally built reactor systems.

Application of Low Critical Mass Studies to Reactor Design

Recent theoretical and experimental work has established minimum critical masses for uranium and plutonium reactor fuels. Studies at Los Alamos show a minimum of 300 to 600 g in the critical mass of 235U for H2O or D2O moderator and D2O or Be reflectors. An H2O-moderated, Be-reflected core containing 0.070 g 235U/mliter has a very low critical mass, which is of interest in the design of small power reactors and has attractive features for a new high neutron flux reactor concept. This report relates nuclear parameter studies to specific design objectives and shows how special effects of geometry and materials are important to such studies.

Consultative Committee on Economic Development in South and Southeast Asia

The seventh meeting of the Consultative Committee on Economic Development in South and Southeast Asia (Colombo Plan) was held in Singapore from October 17 to 21, 1955, attended by the original members (Australia, Canada, Ceylon, India, New Zealand, Pakistan and the United Kingdom, together with Malaya and British Borneo), and by representatives of more recent member countries, Cambodia, Laos, Vietnam, the United States, Burma, Nepal, Indonesia, Japan, the Philippines, and Thailand. The United Kingdom announced at the meeting that it had decided to increase its commitment for technical assistance to Colombo Plan members to £7 million over the seven years beginning in April 1956, and the representative for the United States announced that his government had offered to establish in south or southeast Asia a center for nuclear research and training which would include a research reactor and a small power reactor. A communique issued at the conclusion of the meeting mentioned the increasing degree of self-help in the economic development of the region, and stressed the need to encourage private investment in the area. It was further announced that it had been decided at the meeting to extend the Colombo Plan, previously scheduled to end in 1957, until 1961.