Cooling fastness

Uranium and mixed uranium—plutonium nitrides have a potential use as nuclear fuels for lead cooled fast reactors (136—139). Reactors of this type have been proposed for use ia deep-sea research vehicles (136). However, similar to the oxides, ia order for these materials to be useful as fuels, the nitrides must have an appropriate size and shape, ie, spheres. Microspheres of uranium nitrides have been fabricated by internal gelation and carbothermic reduction (140,141). Another use for uranium nitrides is as a catalyst for the cracking of NH at 550°C, which results ia high yields of H2 (142). 

Properties. Most of the alloys developed to date were intended for service as fuel cladding and other stmctural components in hquid-metal-cooled fast-breeder reactors. AHoy selection was based primarily on the following criteria corrosion resistance in Hquid metals, including lithium, sodium, and NaK, and a mixture of sodium and potassium strength ductihty, including fabricabihty and neutron considerations, including low absorption of fast neutrons as well as irradiation embrittlement and dimensional-variation effects. Alloys of greatest interest include V 80, Cr 15, Ti 5... 

The optimum precipitate is obtained by a more elaborate heal treatment the alloy is solution heat-treated (heated to dissolve the impurity), quenched (cooled fast to room temperature, usually by dropping it into oil or water) and finally tempered or aged for a controlled time and at a controlled temperature (to cause the precipitate to form). 

Many of the techniques available to purify alkali metals were initially developed to use with liquid sodium as a consequence of its large-scale application in liquid-metal-cooled fast-breeder reactors. These techniques can be summarized as filtration or cold trapping distillation or chemical (gettering). 

Sodium superheat experiments were performed in a forced-convection facility employing system parameters in the range of interest for application to loop- and pot-type liquid metal-cooled fast breeder reactors (LMFBRs). The test section was... 

Lee, D. H., 1970, Studies of Heat Transfer and Pressure Drop Relevant to Subcritical Once-through Evaporator, Paper IAEA-SM-130/56, Symp. on Progress in Sodium-Cooled Fast Reactor Engineering, Monte Carlo, Monaco. (4)... 

Liquid metal cooled fast breeder reactors (LMFBRs), 24 758 Liquid-metal fast-breeder reactor... 

I0.6.8.I Cladding failure in oxide fuel pins of nuclear reactors. The long-term operational performance of nuclear fuel pins is critically governed by the reactions that occur in the gap between the fuel and its cladding. Ball et al. (1989) examined this for the cases of (1) Zircaloy-clad pellets of U02+, in a pressurised water reactor (PWR) and (2) stainless-steel-clad pellets of (U, P)02+, in a liquid-metal-cooled fast-breeder reactor (LMFBR). In particular they were interested in the influence of O potential on Cs, I, Te and Mo and the effects of irradiation on the gaseous species within the fuel-clad gaps. 

This cycle uses solid reactants. Small dendritic copper particles are used to carry out the last reaction to make the transformation of all the solid copper to CuCl, thereby maximizing hydrogen yield. The reported efficiency of this cycle is 49% [66]. This low temperature cycle is believed to eliminate many of the engineering and materials issues associated with the other two previously discussed cycles, however this cycle is also in the initial stages of development [111]. The temperature ranges are such that lower temperature nuclear reactors, e.g. sodium-cooled fast reactors, could be used with this cycle [69]. A hybrid version of this cycle is under investigation in Argonne National Laboratory [66,112]. 

LDH LEU LIBD LAW LET LILW LIP LLNL LLW LMA LMFBR LOI LREE L/S LTA LWR Layered double hydroxide Low enriched uranium Laser-induced breakdown detection Low-activity waste Linear energy transfer Low- and intermediate-level nuclear waste Lead-iron phosphate Lawrence Livermore National Laboratory Low-level nuclear waste Law of mass action Liquid-metal-cooled fast-breeder reactor Loss on ignition Light rare earth elements (La-Sm) Liquid-to-solid ratio (leachates) Low-temperature ashing Light water reactor... 

Another application concerning the liquid-metal-cooled fast breeder reactors (LMFBR) was studied as development of advanced control rod materials for FBR (22). Fabrication tests and out-of-pile measurements were made of B4C/Cu cermet to obtain high-performance neutron absorber materials for LMFBR. A coating layer of Cu was formed on the surface of B4C/Cu powder, and then the coated B4C... 

In considering the operational safety and accident analyses of sodium-cooled fast reactors, similar information on the release of fission products from sodium is needed. Although the extent of vaporization can often be calculated from thermodynamic considerations (3, 4), appropriate transport models are required to describe the rate phenomena. In this chapter the results of an analytical and experimental investigation of cesium transport from sodium into flowing inert gases are presented. The limiting case of maximum release is also considered. 

In a typical fast breeder nuclear reactor, most of the fuel is 238U (90 to 93%). The remainder of the fuel is in the form of fissile isotopes, which sustain the fission process. The majority of these fissile isotopes are in the form of 239Pu and 241Pu, although a small portion of 235U can also be present. Because the fast breeder converts die fertile isotope 238 U into the fissile isotope 239Pu, no enrichment plant is necessary. The fast breeder serves as its own enrichment plant. The need for electricity for supplemental uses in the fuel cycle process is thus reduced. Several of the early hquid-metal-cooled fast reactors used plutonium fuels. The reactor Clementine, first operated in the Unired States in 1949. utilized plutonium metal, as did the BR-1 and BR.-2 reactors in the former Soviet Union in 1955 and 1956, respectively. The BR-5 in the former Soviet Union, put into operation in 1959. utilized plutonium oxide and carbide. The reactor Rapsodie first operated in France in 1967 utilized uranium and plutonium oxides. 

Memmott, M.J., et al. (2007), Hydrogen Production by Steam Electrolysis Using a Supercritical C02-cooled Fast Reactor, NIT-NES-TR-007, MIT Center for Advanced Nuclear Energy Systems, February. 

The Cu-CI thermochemical cycle has been under development for several years. The goal is to achieve a commercially viable method for producing hydrogen at a moderate temperature ( 550°C). This chemical process, if successfully developed, could be coupled with several types of heat sources, e.g. the supercritical water reactor, the Na-cooled fast reactor or a solar heat source such as the solar power tower with molten salt heat storage. The use of lower temperature processes is expected to place less demand on materials of constmction compared to higher ( 850°C) temperature processes. 

The amount of 1 can be increased by carrying out the reaction at a lower temperature on cooling to -78 °C compounds 1,4 and 5 are obtained in the ratio 2 2 1, whereas 6 is no longer observed. With cooling, fast stirring, and slow addition of the reagent the yields of 1 are even higher. 

Actinide nitrides are known for Th through Cm. All of the nitrides are high melting compounds with melting points of 2630 °C, 2560 °C, and 2580 °C for Th, Np, and Pu, respectively. The actinide nitrides can decompose to give N2. Thorium, uranimn, and plutonium nitrides are well known and can be used as nuclear fiiels. Fuels of this type, especially uranium and mixed uranium plutonium nitrides, can be used in lead-cooled fast reactors, which have been proposed as a possible next-generation nuclear reactor and for use in deep-sea research vehicles. 

Among the reactor types studied over the past 4-5 decades, but not reaching the stage of market introduction on a commercial basis, are high-temperature gas-cooled reactors and sodium-cooled fast breeders. Current proposals are aware of the issues raised above, but still far from deal with all of them. The reactor industry has recently concluded that a new generation of safer reactors will require substantial breakthroughs (particularly in materials science) that may push commercialisation at least 25 years into the future (USDoE, 2002b). The proposed concepts are summarised in Table 5.3. 

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. 

The determination of the coefficient of heat transfer through the reaction vessel wall was very important. Special calculations and determinations proved that with the rate of circulation of glycerol used the vessel waU was cooled fast enough to assume that the outer wall was kept at a constant temperature. The coefficient of heat transfer through the wall is equal to waii/t/waii, where /I wall is the thermal conductivity and dmw the thickness of the wall. 

The projections are based on a recent forecast (Case B) by the Energy Research and Development Administration (ERDA) of nuclear power growth in the United States (2) and on fuel mass-flow data developed for light water reactors fueled with uranium (LWR-U) or mixed uranium and plutonium oxide (LWR-Pu), a high temperature gas-cooled reactor (HTGR), and two liquid-metal-cooled fast breeder reactors (LMFBRs). Nuclear characteristics of the fuels and wastes were calculated using the computer code ORIGEN (3). 

---