Repository heating

The M effects of repository excavation and swelling of back filling material proved to be small. Our results focus on TM effects at 100 years of repository heating in the lower formation, as described in section 3.6. The changes in fracture transmissivity as a function of radial distance from the repository centre, r, are shown in Figure 4. 

TRU are those containing isotopes, like 241Am and 243Am, that follow uranium in the periodic table and whose half-lives are >20 years. If their level of activity was more than 100 nanocuries of alpha-emitters per gram of waste material (up from 10 nanocuries/g in 1982), the waste could be disposed of by shallow burial. Otherwise, the waste had to be placed in retrievable storage for eventual transfer to a permanent repository. TRUs generally have low levels of radioactivity, generate very little heat, and can be handled by ordinary means without remote control (Eisenbud 1987 Murray 1994). 

In the past, the extraction of Sr and Cs was investigated for some practical applications (heat and gamma ray sources) but the main interest today is for decreasing the thermal power and the potential hazard of nuclear waste in underground repositories. Results of extractions with some... 

The Medical Repository for 1802 stated that at Dennis, in the county of Barnstable [Massachusetts], common salt is crystallized from ocean water, without culinary heat or boiling, in considerable quantity. The amount is stated at 20,000 bushels a year of domestic sea salt. This is estimated at one-fifth of the quantity consumed in the Cape Cod fishery annually (39). 

Gross bouyant motion of the repository due to heating of large areas and volumes of salt... 

The large-scale bouyancy effects of an idealized heated repository have also been calculated (6). Expansion of the heated salt will result in a density differential with respect to the surrounding salt. This plus the reduced viscosity of the hot salt tends to form slow convective cells in the salt. Calculations of a repository in homogeneous salt loaded with 10-year old HLW at 100 kilowatts per acre show a peak upward velocity (approximately 1.5 cm/year) of the repository horizon would occur between 200 and 300 years and then slowly decrease. Displacement would be about 6.5 meters at 400 years. Incorporating a more viscous layer above the repository level to more closely simulate the actual WIPP site geology leads to maximum velocities about one-third those obtained in homogeneous salt. After 400 years the upward displacement for this latter case would be about 2.1 meters. More... 

The first barrier is the form of the waste, which will immobilize the radioactive materials. The waste form should not be damaged by heat or radiation nor be attacked by groundwater. The waste is placed in a steel canister, which is resistant to leaching. The canister is surrounded by packing materials that prevent radioactivity from escaping, and the entire repository is backfilled with a material that absorbs or resists chemical intrusion. The final barrier is the host medium that separates the repository from the surrounding area. 

Typical heat production in the moderator-fuel blanket is 750- 1500 MW. The excess heat is used to generate electricity that helps to pay for the operation of the facility. The transmuted material will have 20% of the original plutonium and minor actinides of the input material and will contain significant fission product activities. This transmuted material can be put into geologic storage, reducing the long-term hazard of the repository material. The overall feasibility of this accelerator transmutation of waste (ATW) has not been established yet. 

Minimize the cost of the disposal of HLW in a deep geological repository by reducing not only the volume of the wastes, but also the heat load of the... 

Repository capacity Increase five-fold Decrease mass and heat-load of waste for disposal ... 

For polysaccharide dispersions, SV is exceedingly small relative to Vi. Equations (3.11) and (3.12) are mathematical propositions that the exchangeable energy stored in a dispersed polysaccharide solute is equal to the energy absorbed from an external source and any increase in surface area of the solute is consequently a repository of +A . Conversely, aggregation and desorption correspond to a loss of energy, felt as heat in the latter occurrence ( —A ) when a dry polyaccharide powder is wetted (positive adsorption). 

Within the bulb is a large repository of the expansion liquid. However, be aware that you cannot obtain an accurate temperature reading by placing just the thermometer bulb in the test material. When only the thermometer s bulb is under the heat s influence, the amount of expansion (or contraction) of the liquid beyond the bulb region is unknown. Any liquid not immersed in the sample being measured is not under the same influence as the liquid that is immersed. For example, if the bulb were placed in a boiling solution while the stem was in an arctic frost, the liquid in the stem would be contracted more than it would be if the stem was in a warm room. 

It appears that the repository capacity for high-level wastes will be heat-limited to one kilowatt/acre. This is equivalent to one ton of fuel after storage for ten years. The spent fuel discharged by the year 2000 will require about 2700 subterranean acres. This would be reduced to 1000 acres if the uranium and the plutonium were removed, and considerably less than that if the strontium and the cesium also were removed. Although reprocessing would reduce the transuranic content by a factor of 10 to 50, this amount would be an insignificant fraction of the transuranic hazard in the waste. 

The classical Purex process was designed to produce nearly pure uranium and plutonium. The Chemical Engineering Division of Argonne National Laboratory has demonstrated UREX+, an advanced aqueous process with five extraction trains that split commercial reactor spent fuel into five streams 1) a nearly pure uranium stream (95.5% of the heavy metal in the spent fuel) 2) technetium sent to transmutation (0.08 /o) 3) Pu/Np converted to MOX fuel for LWR fuel and Am/Cm for transmutation or fast-flux reactor fuel (0.962 /o) 4) Cs/Sb decay heat producers sent to interim decay storage (0.017 /o) and 5) a mixed fission product stream (3.44 /o) composed of gases and solids incorporated into a waste form for geological repository disposal.f The percentages shown are computed from Table 1. 

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