Fuel recycle requirements

Fuel Recycle Requirements. We asstime that the final product returned for fuel fabrication and recycle is a mixed uranium-plutonium dioxide material, partially decontaminated from fission products. The questions of fissile material enrichment, radiation levels, and required handling facilities are not addressed. 

Now that the first generation of nuclear power plants is well established, more attention is being focussed on the R D required to ensure that nuclear power can continue to contribute to the energy supply for the foreseeable future. Two areas which are interdisciplinary but involve a large chemical input are waste disposal and fuel recycle. 

AECL has evaluated some of the basic information and development requirements in some detail (24, 25) and has outlined the type of fuel recycle development program which would be required. It would involve research and development of thorium fuels and fuel fabrication methods, reprocessing, demonstration of fuel management techniques and physics characteristics in existing CANDU reactors and demonstration of technology in health, safety, environmental, security and economics aspects of fuel recycle. 

It would require 20 to 25 years to complete the research, development and demonstration program. This is compatible with the present Canadian uranium resources situation. Chemistry and chemical engineering would play a major role in most areas of such a fuel recycle program. 

All the components of the nuclear-fission power system are fully operational except for ultimate waste disposal. However, spent fuel is not reprocessed in the United States because there is currently an adequate supply of natural uranium and enrichment services availab 1 e domestically and from other countries at a 1 ower cost than that of the recovered fissionable material from spent fuel. Also, the United States unilaterally declared a moratorium on reprocessing in the early 1980s in an attempt to reduce the spread of nuclear weapons. Current economics do not favor a return to reprocessing and fuel recycling in the United States at this time in as much as it does dramatically increase the amount of interim and final waste storage capacity that is required. 

More realistically, this material (Pu(>2 plus fission products) would require either some further decontamination from deleterious fission products or further treatment to obtain a product having the necessary characteristics for fuel recycle (particle size, chemical form of fission products, other ). This further treatment has not been investigated to date and probably will not be until we have a better knowledge of the fission-product distribution and chemical form. 

Extensive development and demonstration work, beyond that required for a small LWR-based concept, may be required. These reactors also require foel that is enriched to nearly 20% and therefore fuel recycling may be necessary to achieve economic performance. Because of the developmental uncertainties and the possible need to include fuel recycling in the stem, the cost of implementing a system design based on liquid metal coolant is uncertain. 

The plasticity and heat content of fresh TSP (or SSP) make it much easier to granulate than cured TSP less recycle, water, and steam are required. Presumably, less fuel is required for drying. Total electric power consumption is somewhat lower, and labor requirements are only 36% of that required for the conventional" two-step process. The product is said to be superior in hardness, shape, uniformity, and smoothness. 

PNC has a plan to construct the FBR Fuel Recycling Pilot Plant to verify the whole plant system and it will be the first step for achieving the cost requirement. 

In fuel recycle, criticality safety is controlled by a set of criticality cmitrol requirements (CCR). Current programs, in general, are set up with the goal that at least two independent concurrent violations of CCR are required before criticality can occur. However, one must always guard against the possibility of a criticality occurring with one, or no, violation of CCR. The partially develed left-hand branch of the tree illustrates a way... 

Notes Ntunbers in parentheses are percentage change from reference PWR. System uranium requirements and fuel disposal requirements for recycling options refer to an equilibrium system, in which the fresh fuel requirements of the "receiving" reactor (CANDU or PWR) are exactly met by the spent fuel discharge rate of the "supplying" PWRs. 

Initially, SSTAR core loadings can be based on uranium nitride fuel or U/ transuranic/ nitride fuel using transuranics recovered from LWR spent fuel. In the longer term, for recycle of SSTAR spent fuel returns (after 20 years), development and demonstration of electrometallurgical reprocessing for transuranic nitride fuel will be required. A key requirement is to recover the enriched N [XXII-15]. Some theoretical work on fuel recycle and small-scale experiments have been conducted in Japan mainly at the Japan Atomic Energy Research Institute (JAERI). 

The enrichment of the U-Pu-Zr ternary fuel in equilibrium cycle (with all TRUs recycled) is recommended to be less than 30 weight % to fall within the currently established metallic fuel database. The design of a fuel assembly should support the metal fuel reliability requirements, including the limits for peak fuel burn-up and fast neutron fluence. 

To analyze the reactor characteristics in both cases requires selection of an operational pattern and connections of all structural elements of the nuclear power system. In this case, the technologies of fuel recycling with superficial purification of fission products can be used. Nuclide flows supplied to the reactor depend on the amount, purpose and characteristics of all structural elements. Analyses show that the effectiveness of fuel utilization depends on the organization of nuclide flows in the nuclear power system to a greater extent than on the breeding ratio level of a fast reactor. 

Some applications may require the use of an additional barrier layer, for example, fuel tanks require a fuel impermeable barrier, and food containers such as tomato ketchup may require a barrier to prevent odours penetrating through the outer layers. The simplest barrier configuration incorporating recyclate is a 4-layer structure as illustrated in Figure 6.14. The adhesive layer is needed to bond the layers together as often the required material combinations do not stick to one another. The adhesive layer, sometimes termed the tie layer, ensures a good bond is formed. 

Nuclear Fuel-Cycle Requirements. There are two t)q)es of nuclear fuel cycles once through (open) and recycle (closed). The AHTR, VHTR, and MSR can be operated in eiftiermode while the LFR and GFR require a closed fuel cycle. With a once-through fuel cycle, the fuel is made with enriched uranium and the spent nuclear fuel (SNF) is a waste. With a recycle fuel cycle, the SNF is chemically processed to recover fissile materials that are used to produce new fuel. 

Scale of deployment. Reactors with once-through fuel cycles (AHTR and VHTR) can be rapidly deployed on a large scale. Creation of the fuel cycle requires only constmction of a relatively low-cost fuel fabrication plant (at most a few tens of milhons of dollars). Reactors that require SNF recycle [5] will require many decades to deploy on a large scale and involve very large expenditures of resources because (1) economics demands constmction of large-scale facilities to recover fissile material from SNF and (2) the current inventories of fissile material in SNF are limited. The limited fissile inventories imply that many decades will be required to obtain the neeessary materials for deployment of sufficient reactors on a scale that makes a major impact on the world s H2 production. Such fuel cycles require very-large-scale commitments over very long time periods but, require very little uranium or thorium to operate. 

Partial oxidation of heavy Hquid hydrocarbons requires somewhat simpler environmental controls. The principal source of particulates is carbon, or soot, formed by the high temperature of the oxidation step. The soot is scmbbed from the raw synthesis gas and either recycled back to the gasifier, or recovered as soHd peUetized fuel. Sulfur and condensate treatment is similar in principle to that required for coal gasification, although the amounts of potential poUutants generated are usually less. 

The plant is designed to satisfy NSPS requirements. NO emission control is obtained by fuel-rich combustion in the MHD burner and final oxidation of the gas by secondary combustion in the bottoming heat recovery plant. Sulfur removal from MHD combustion gases is combined with seed recovery and necessary processing of recovered seed before recycling. 

Supply Projections. Additional supphes are expected to be necessary to meet the projected production shortfall. A significant contribution is likely to come from uranium production centers such as Eastern Europe and Asia, which are not included in the capabihty projections (27). The remaining shortfall between fresh production and reactor requirements is expected to be filled by several alternative sources, including excess inventory drawdown. These shortfalls could also be met by the utili2ation of low cost resources that could become available as a result of technical developments or pohcy changes, production from either low or higher cost resources not identified in production capabihty projections, recycled material such as spent fuel, and low enriched uranium converted from the high enriched uranium (HEU) found in warheads (28). 

As the recycled fuel composition approaches steady state after approximately four cycles (1), the heat and radiation associated with and Pu require more elaborate conversion and fuel fabrication facihties than are needed for virgin fuel. The storage, solidification, packaging, shipping, and disposal considerations associated with wastes that result from this approach are primarily concerned with the relatively short-Hved fission products. The transuranic... 

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