Enriched uranium levels

HELP HEU HFO HFR HLW HREE HRL HT HTGR HWR Hydrological evaluation of landfill performance Highly enriched uranium Hydrous ferrous oxide or ferric hydroxide Hot fractured-rock High-level nuclear waste Heavy rare earth elements (Gd-Lu) Hard rock laboratory High temperature High-temperature gas-cooled reactor Heavy water reactor... 

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... 

As discussed before, quadrupole based ICP-MS allows multi-element determination at the trace and ultratrace level and/or isotope ratios in aqueous solutions in a few minutes as a routine method with detection limits of elements in the sub pgml-1 range and a precision for determined trace element concentration in the low % range (RSD - relative standard deviation). The precision for isotope ratio measurements varies between 0.1% and 0.5% RSD. This isotope ratio precision is sufficient for a multitude of applications, e.g., for evidence of contamination of sample with depleted or enriched uranium in urine (this technique is used in the author s laboratory in a routine mode14) or the isotope dilution technique for the quantitative determination of trace element and species concentration after doping the sample with enriched isotope spikes. 

According to the open-source empirical record, there have been clear examples of demand for Russia s NBC weapons knowledge. For example, in the nuclear sector, the agreement that Iran has with Minatom to build the light-water reactor at Bushehr is an example of the demand for Russian nuclear expertise, but not specifically weapons expertise. Given that Iran has vast natural reserves of oil and has attempted to enrich uranium to weapons-useable levels, Bushehr could well be a means for Iran to get plutonium for nuclear weapons. 

Table 2-8 shows the mass equivalents for natural and depleted uranium for radiation levels that caused potential radiological effects in rats exposed once for 100 minutes to airborne 92.8% enriched uranium with an estimated specific activity of 51.6 pCi/g (Morris et al. 1989). These mass equivalent values for natural and depleted uranium for the minimal concentration of radioactivity that is expected to induce potential radiological effects are well above levels that would be expected to be inhaled or ingested. In addition, the mass equivalents for natural and depleted uranium for potential radiological effects are 3,600 and 76,500 times higher, respectively, than the occupational exposure limits (short-term exposure) recommended by the National Institute for Occupational Safety and Health (NIOSH 1997). Therefore, MRLs for uranium based on studies that used enriched uranium are inappropriate. 

In animal studies, mice injected with doses ranging from 0.05 to 1.0 jg U/testis as enriched uranium fluoride showed a general tendency for an increase in chromosome breaks with an increasing dose of enriched uranyl fluoride. At high-dose levels, the statistically significant difference of break frequencies between treated and control mice disappeared 60 days after treatment (Hu and Zhu 1990). 

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. 

A modification of the Redox process, the U-hexone process, was used at the Idaho Chemical Processing Plant of the U.S. AEC, to recover highly enriched uranium from U-A1 alloy fuel elements irradiated in the Materials Testing Reactor. The aluminum nitrate needed as salting agent was provided when the fuel was dissolved in nitric acid. The plutonium content of the fuel was too low to warrant recovery. Plutonium was made trivalent and inextractable before solvent extraction and thus routed to the aqueous high-level waste. 

Ensuring that the mass is always below the critical level by limiting the quantity present this may be as small as a few tens of kilograms for low enriched uranium. Such a system has the disadvantage of requiring an elaborate system of managerial control combined with a system of mechanical interlocks to ensure that specified quantities never are exceeded. 

Highly Active Liquor high-efficiency particulate air filter high(ly) enriched uranium High Enriched Waste Concentrates High-level liquid waste high-level waste heavy metals... 

Enriched uranium. Uranium in which the proportion of U has been increased above the natural level of 0-7% by weight. 

Releases from the nuclear fuel cycle may occur during reactor operations, nuclear fuel reprocessing, UFg conversion, uranium enrichment, uranium fuel fabrication, high-level waste solidification, high-level and low-level waste disposals. The enrichment process, with a significant aimual release through liquid discharges to the sea, is considered as the key contributor. So far, the total release of Tc to the... 

Kazakhstan has a nuclear scientific-industrial complex which was set up as a part of a nuclear infrastructure of the former USSR. More than 50% of the uranium resources of the former Soviet Union are in Kazakhstan, with seven uranium mines. Two UO2 plants produced up to 35% of the total uranium in the USSR in 1990. There are extensive facilities for producing UO2 pellets for VVER fuel elements from Russian enriched uranium. Kazakhstan has several research reactors and one operating nuclear power plant, the BN-350 fast reactor, which started operation in 1973 with a design life of 20 years. Work on its lifetime extension has the intention of bringing it into compliance with current safety standards. 1995 and 1996 were devoted to this work. In October 1996. experimental investigation on accident-proofdecay heat removal by natural circulation was carried out. The reactor BN-350 was restarted in February 4, 1997 at a power level of 420 MW(th). 

In late summer 1943 it was decided that K-25 would play a lesser role than ori ally intended. Instead of producing fully enriched uranium-235, the gaseous diffusion plant would now provide around fifty percent enrichment for use as feed material in Y-12. This would be accomplished by eliminating the more troublesome upper part of the cascade. Even this level of enrichment was not assured since a barrier for the diffusion plant still did not exist. The dedsion to downgrade K-25 was part of the... 

Indonesia Research center May 1994 Low levels of fission and activation products were seen in water and vegetation. Swipe samples taken in buildings showed low and high-enriched uranium particles from research and medical isotope production activities... 

An important consideration in the safe transportation or processing of enriched-uranium solutions in ordinary equipment is solution crystallization, which may cause the uranium concentration to exceed the safe Untits established by the isotopic level.- Process operations require solution stability, which caii be maintained by temperature control. In the transportatton of solutions, the free-acid concentration may be adjusted to ensure that should crystallization occur, the maximum aranium concentration of the solution will never exceed the. safe limit. 

Depleted uranium foils (0.2% enrichment, S-mils thick by l-ln. diam) and foils (93% enrichment, 4.5-mils thick by i-in. diam) were placed at corresponding locations about the center of the two halves of the llPR-6 machine. Foils were placed among the adjoining surfaces of the plates. In another experiments a 2- >< 2- x -in. plate of 93% enriched uranium and a 2- x 2- X -in. plate of depleted uranium (0.2% enriched) that are normally in the core were replaced by packets of foils equivalent in weight and enrichment to the two plates. All foils were irradiated for one hour at a power level of about 50 W and, subsequently counted for fissiim fragments. jbi the case of the packets, only l-in.-diam foils punched out from the... 

At one of toe larger LWR fuel fabrication facilities, very large containers of low enriched uranium contam inated scrap are assayed using gamma rays (from Pa, a daughter of with large Nal detectors, prior to volume reduction by incineration. These assays provide a measure of the total uranium input into the incinerator. Thus incinerator cleanout is required only when the uranium content reaches toe level specified by criticality procedures. Thid results in fewer incinerator shutdowns for cleanout. 

There has been considerable need for neutron irradiation units with high neutron fluxrfor use in research, industry, and education. Sources of various types have been used lor this purpose for maiiy years, but have lacked the intensity and volume, with level flux, for larger sample irradiation. While the research reactor can produce the desirable neutron flux, construction and operation is rather costly. A neutron multiplier has been described. .using a subcritical lattice of enriched uranium rods,with a central cylindrical flux trap. A Cf. source is used to provide the initial neutrons to drive the unit. This lattice unit was loaded at the Critical Mass Laboratory to study aspects of criticality including keff and effects of temperature, voids, and added material. 

For most of the world s reactors, enriched uranium is required as fuel. Enrichment increases the proportion of the U-235 isotope from its natural level of 0.7% to 3%-5%. This enables greater technical efficiency in reactor design and operahon, particularly in larger... 

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