Uranium utilizations

Fuel Recycle. Although the commercial CANDU reactors use the once-through natural uranium fuel cycle, it has been recognized for many years (22) that exceptional uranium utilization could be... 

When PWRs and CANDUs are compared on the basis of uranium utilization, the CANDU requires 19 percent less uranium from ore on a per kWhr basis (see Table 21.18). As there is now an abundance of low-cost uranium from ore and enrichment service, the electric utilities continue to favor the PWR and BWR types. Operating experience with graphite reactors in England, France, and Russia also has been generally satisfactory. However, the graphite moderator represents a large inventory of combustible material, which contributed significantly to the severity... 

Current known, recoverable world resources of uranium are approximately 3.1 million tons, estimated to be sufficient for about 50 years at current levels of consumption. A doubling of price from present levels is projected to create a 10-fold increase in these resources. Moving from current nuclear power technology to breeder reactors is estimated to increase uranium utilization another 60-fold (World Nuclear Association, 2002). Breeder reactors, however, would aggravate some of the issues now associated with the nuclear industry, including those surrounding safety and nuclear proliferation, while possibly reducing the waste disposal problem. 

Uranium (ca. 20% is used as the fuel, but mainly with 239pu in the form of a UO2/PUO2 mixture. The breeding blanket consists of depleted uranium from isotope separation plants or from reprocessing plants for spent nuclear fuels. Axially movable boron carbide absorbers are distributed in the fuel zone for shutting down purposes. The uranium utilized can be ca. 100 times better utilized than e.g. in light-water reactors. 

Since with this high uranium utilization less rich uranium deposits (down to the uranium concentration in seawater) also become economically viable, nuclear energy from breeder reactors is a practically inexhaustible energy source. 

Assume that a voltaic cell, proposed as a method for the purification of uranium, utilizes the redox reaction... 

Even with plutonium recycle, thus, this thermal reactor converts less than 1 percent of natural uranium to energy. This low uranium utilization results from the fact that the conversion ratio of to plutonium in a thermal reactor is less than unity. 

It is necessary to implement advanced uranium- gadolinium (U02-Gd203) fuel assemblies with Zr alloy guide tubes (GT) and Zr alloy spacer grids (SG) for continuous improvements of WWER-1000 fuel utilization. It is expected to improve fuel assembly dimensional stability and to save uranium consumption by increasing uranium utilization. 

The data in Table X indicate that a significant improvement in uranium utilization will be realized in changing from the natural or low-enrichment reactors to the HTGR-type advanced converter plant using the Th /U recycling. Another significant improvement will be possible when the GCFBR becomes available. 

In the business context, the international trends to more effective uranium utilization, closed fuel cycles with reprocessing and recycle of spent fuel, and more effective and efficient management of spent fuel and reduction of eventual wastes are becoming obvious. These trends require major exporters of nuclear reactors and uranium fuel with international commitments to develop an effective international presence and new technical processes to keep technology relevant and competitive (e.g., as evidenced by the Global Nuclear Energy Partnership efforts of the United States). 

Without any on-site fuel processing, MSRs can run as simple burners with excellent uranium utilization, even on a once-through cycle requiring only a fraction of the input uranium of conventional LWRs. Since even large increases in the price of uranium are acceptable in terms of fuel cycle costs for an MSR burner, the availability of world uranium resources would not become an issue for many centuries at least. 

Such a recycling of TRUs also has a positive impact upon lifetime uranium utilization. In ORNL studies, at the end of the 30-year cycle, there would be 736 kg of Pu of which 331 kg would be fissile 239 Pu and 241 Pu. Along with this would be 136 kg of 237 Np and small amounts of Am and Cm (quantities not reported). There would also be enough uranium left to start the next cycle with clean salt, leaving the TRUs as source of fissile top-up. This should save approximately 5%-10% on the lifetime uranium utilization. Thus, the DMSR without any recycling requires about 1525 tonnes uranium lifetime, with U only recycling requires 850 tonnes, and with U -i- TRU recycling requirements are down to perhaps 800 tonnes. 

The short, simple fuel assemblies for the HWR, called fuel bundles, are easily produced, and Korea, India, Argentina, Romania, and China all have independent fuel fabricafion facilities sufficient to meet their demand. Furthermore, HWR fuel-cycle costs are low because natural uranium is relatively inexpensive, the uranium utilization (amount of energy produced from the mined uranium) is good, and the fuel bundle design and manufacture is simple. 

These features ensure low fueling costs, good uranium utilization, high capacity factors, and good fuel performance. 

A consequence of the high neutron economy of the HWR is high uranium utilization. Although natural uranium HWR fuel achieves an apparently low average burnup of only about 20% to 25% of that of enriched PWR fuel, HWRs extract about 38% more energy per Mg of U3O8 compared with PWRs (OECD/NEA 1994). The HWR, therefore, makes efficient use of natural uranium resources. The use of NUE fuel also avoids the production of... 

Uranium Consumption, Uranium Utilization, Equivalent NU Burnup, and Spent Fuel Arisings for Various HWR and PWR Fuel Cycles and FlWR/PWR Systems... 

Fuel-Cycle Option Natural U Consumption MgU/GW(e)a Uranium Utilization MW(e)d/Mg UasU,0, Equivalent Natural U Bumup MW(th)-d/kg NU Spent Fuel Arisings MgHE/GW(e)a... 

The already high uranium utilization (in terms of electrical energy derived from the mined uranium) is increased by 32% and 36% compared with natural uranium fuel, for 0.9% and 1.2% SEU, respectively (Table 15.2). As lower enrichment plant tails become economical through advances in enrichment technology, the improvements in uranium utilization with SEU will become even larger 43% for 0.9% SEU, and 56% for 1.2% SEU with 0.1% enrichment plant tails, relative to natural uranium. Lower enrichment-plant tails pushes the optimal enrichment level higher. 

The inverse of uranium utilization is uranium consumption. Relative to a PWR, natural uranium requirements in an HWR are 30% lower with natural uranium fuel. Enrichments to 0.9% SEU and 1.2% SEU would increase the fuel bumup by a factor of 2 and 3, respectively, relative to natural uranium fuel. This amounts to 45% lower uranium consumption with 0.9% SEU. The reduction in mined uranium requirements also has environmental benefits at the front end of the cycle, which will become even more important in the coming decades as cheaper, higher-grade uranium ore resources are depleted, requiring the mining of greater volumes of lower-grade ores. 

In the Indian HWR, with the whole core loaded with 1.2% SEU fuel, is foimd to be 1.254. The easy way of suppressing this excess reactivity is to use boron as the moderator. Apart from the fact that this negates the benefit of the improved uranium utilization of the SEU in the initial core, this approach will give rise to severe power peaking, and an increase in void reactivity during a loss of coolant accident (LOCA). The power peaking would be worse than in the case of the natural uranium core because the channel flow distribution of the Indian HWR has been designed to match the power distribution in the equilibrium core. As fuel burnup proceeds, the bundle powers become acceptable, but the coolant outlet temperatures in the peripheral channels increase beyond their rated values. 

A significant improvement in uranium utilization and reduced quantities of spent fuel per unit of electrical energy produced... 

In the next phase of the 4S, when recovered plutonium and minor actinides (MA) would become politically and commercially available because of the shortage of natural fissile materials, fresh fuel consisting of the reprocessed fissile materials and depleted or natural uranium could be installed in the 4S. A fast neutron spectrum of the 4S avoids the degradation of fissile materials through burn-up therefore, the recovery process for the spent fuel of the 4S could be repeated many more times than for LWRs, resulting in a higher degree of natural uranium utilization. 

A conventional nuclear reactor has a very low efficiency regarding uranium utilization. Unlike the lighter isotope, the heavy isotope (which is the major component) will never be utiHzed. A breeder reactor produces more fuel than it consumes. With molten sodium as a coolant, the main isotope in natural uranium, absorbs neutrons and reacts according to the formulas given in Figure 52.9 (section 52.16.3). 

A fuel bum-up / fuel cycle concept for thermal and fast reactors provides for a high degree of natural uranium utilization without the recyele and reprocessing of spent nuclear fuel. The deployment projection for CANDLE - HTGR is 2015 the deployment projection for CANDLE - fast reactors is 2040-2045. The degree of natural uranium utilization in CANDLE - fast reactors may reach 40% (absolute). 

Ryu, K., Sekimoto, H., 2000. A possibility of highly efficient uranium utilization with a pebble bed fast reactor. Annals of Nuclear Energy 27, 1139—1145. Elsevier. 

Plant-scale liquid metal reactors are in operation in France and Russia to establish the engineering technology and to evaluate their role in increasing the efficiency of uranium utilization. France, without a significant primary energy supply, wants to minimize imports of uranium. Although the United... 

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