Spent fuel composition

HI. Hamilton, C. J., N. D. Holder, V. H. Pierce, and M. W. Robertson HTGR Spent Fuel Composition and Fuel Element Block Flow, Report GA-A13886, vol. 1, July 1976. 

Table 2.1 lists specific radionuclides that may be present in nuclear fuel rods or industrial sources used to construct a dirty bomb. It also lists the radiological half-lives of each radionuclide, whether they are present in fresh or spent fuel rods, and their potential industrial applications. Note that the actual suites of isotopes for given fuel rods will vary depending on the origin and composition of the original fuel mixture. The uranium and plutonium isotopes found in fuel rods may also be found... 

A PAFC, operating on reformed natural gas (900 Ib/hr) and air, has a fuel and oxidant utilization of 86% and 70% respectively. With the fuel and oxidant composition and molecular weights listed below, (a) How much hydrogen will be consumed in lb mol/hr (b) How much oxygen is consumed in lb mol/hr (c) What is the required air flow rate in lb mol/hr and Ib/hr (d) How much water is generated (e) What is the composition of the effluent (spent) fuel and air streams in mol % ... 

The spent oxidant composition is calculated in a similar manner. We note that in both the PAFC and PEFC the water is generated on the cathode (air) side. This can be seen from the cathode reaction listed below and the following table listing the fuel cell reaction quantities. 

For the above example, determine the composition of the effluent (spent) fuel stream in mol % including the effect of the water gas shift equilibrium. Assume an effluent temperature of 1200°F. 

An SOFC is operating on 100 % methane (CH4) and a fuel utilization of 85%. (a) What is the composition of the effluent (spent) fuel in mol % Assume that the methane is completely reformed within the fuel cell, and the moisture required for reforming is supplied by internal recirculation. 

The relatively long-lived isotopes of Pu suitable for chemistry and metallurgy are those of masses 238, 239, 240, 241, 242, and 244. Plutonium formed in nuclear reactors occurs as a mixture of isotopes. A typical isotopic composition of Pu in spent fuel containing 10.4 kg of Pu/ton of fuel is given in Table VIII. 

Table 1. Chemical compositions (ivr%) of low-pressured water reactor (LWR) spent fuel and uraninite from Oldo reactors 10. 16 and Cigar Luke...

The spent fuel matrix is a ceramic material with a fascinating chemical composition and a large degree of phase heterogeneity. The physical state and chemical composition of spent fuel largely depends on the bum-up of the fuel once it is taken out of the reactor. In Fig. 6 we indicate the dependence of the chemical composition on the bum-up for a series of PWR fuels. However, the fact that remains constant is that U02 constitutes the major component of spent fuel, ranging within a total of 95-98% in weight (see Fig. 7). 

Depending on the water composition other radical species are formed, such as carbonate and chloride radicals. This imposes net oxidizing conditions at the water—fuel interface because the generated oxidants, molecular oxygen and hydrogen peroxide, predominate under a radiation, and other radical species like OH- or CQf- are more active than the generated reductants, mainly molecular hydrogen. This is why we propose that the spent fuel-water interface is a dynamic redox system, independently of the conditions imposed on the near field (Merino et al. 2001). 

Elemental Compositions of various Spent Fuels and Liquid Concentrations in a Dissolved Solution... 

On the premise of the transmutation of Ans (particularly Am and Cm) by fast neutrons, the Ans recovered must be adequately decontaminated from Lns. The required decontamination factor (DF) should be considered from the viewpoints of neutron absorption cross sections of Lns and interactions of Lns (in target) with the cladding material see Table 1.1 (condition described in ASTM C833-01 <20 mg Lns/g TRU). Taking the compositions of spent fuel to be reprocessed into account (see Table 1.2), the DF required is ca. 1000 for PWR-U02 (60 GWD/t) and 140 for PWR-MOX (60 GWD/t). Thus, a DF of about 2000 will be a tentative goal. 

Furnace temperature is measured with thermocouples. It is controlled to 1300 K by adjusting fuel combustion rate and air preheat temperature. Feed forward control based on scheduled changes in spent acid composition and feed rate is employed to optimize the process (Rohm and Haas, 2003). 

Tracer techniques, for example, are used to obtain very small but representative and measurable samples of highly radioactive spent fuel solutions. One millilitre of the solution is then spiked with a known amount of uranium and plutonium tracer isotopes. A few microlitres of the spiked solution are dried and shipped to SAL. One to fifty nanograms of uranium or plutonium extracted from this tiny sample are sufficient for a complete analysis representing the composition of half a tonne of irradiated fuel with an accuracy of 0.3 to 0.5%. 

Aqueous Process. In 1967-68, a hot reprocessing test had been conducted using the spent fuel (ca. 600 MWD/T) from JRR-3 (Japan Research Reactor-3) (6). About 200 g of purified plutonium was recovered by a modified PUREX process from aluminum-claded uranium fuels of natural isotopic composition. 

TABLE 13.6 The composition of typical spent fuel from a commercial nuclear reactor... 

These changes in composition bring about changes in reactivity of the fuel, which eventually decreases to such an extent that the reactor will no longer be critical unless the spent fuel is replaced with fresh fuel. 

In this paper, we provided the rationale and definition of a benchmark test called BMTl to look at the implications of THM couplings on safety parameters in the near field of a hypothetical repository. This hypothetical repository possesses composite features since it is based on a Japanese design, with a Japanese bentonite used as buffer material and the heat output characteristics of Japanese spent fuel. However, the permeability and strength characteristics of the rock mass are based on typical properties of granites of the Canadian Shield. 

As the exact composition of spent fuel varies considerably and depend on many factors, the reader will find slightly varying figures in this text. 

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