X-10 reactor

Activation analysis X-10 reactor, LITR reactor, neutron flux neutron flux 5xl0"cm-2s l 10 3cm-2s Emission spectroscopy (Cupspark) Flame photometry... 

Figure A4-W is a plot of the neutron flux along the vertical centerline of the active lattice, starting at the bottom of the lattice and continuing up to the shim rod electromagnets. The flux at the magnets is seen to be too low to give good counting statistics. To check this measurement, the neutron atte.nuation curve from the X-10 reactor lid tank was normalized and plotted with the curve from the Mock-Up, considering the top of the Mock-Up lattice to be the source plate.

The actual design of the shuttle is, of c ourse, best done by the MTR operator or the experimenter. If a shuttle design similar to that of the hydraulic rabbit system of the X-10 reactor is used, the. tubes should have a minimum radius of curvature of 48 in. The rabbit tube positions at the east end of the reflector will accommodate 1.190-in.-O.D. tubes, and the regulating rod holes will accommodate 1.500-in.-0.D. tubes. The inside diameters of these tubes have been set at 1.000 in. end 1.310 in., respectively. 

Gadolinium s extremely high cross section for thermal neutrons, 4.6 x 10 (46,000 bams) per atom, is the reason for its extensive use in the nuclear energy (see Nuclearreactors). It is used as a component of the fuel or control rods, where it acts as a consumable poison, a trap for neutrons in the reactor (39). 

The purified raw gas goes to a Synthol (Eischer-Tropsch) unit for catalytic conversion of CO and H2 to Hquid fuels. The tars and oils obtained from quenching the raw gas from the gasifiers go to a Phenosolvan plant to provide tar products for the refinery and ammonia for fertilizer. The Synthol plant has seven reactors, each with 1.9 x 10 m /h (1.6 x 10 ft /d) gas feed. Annual plant production is 1.5 x 10 t motor fuels, 185 x 10 t ethylene,... 

World annual uranium requirements in 1993 were estimated at about 58,382 t natural uranium equivalent. Reactor-related requirements are expected to rise about 1015 t/yr on the average, reaching 75,700 t U total requirements in the year 2010. The cumulative aggregate world uranium requirements for the period 1993—2010 are estimated to be about 1.185 X 10 t U metal (29). 

Boron-10 has a natural abundance of 19.61 atomic % and a thermal neutron cross section of 3.837 x 10 m (3837 bams) as compared to the cross section of 5 x 10 m (0.005 bams). Boron-10 is used at 40—95 atomic % in safety devices and control rods of nuclear reactors. Its use is also intended for breeder-reactor control rods. 

By contrast, uranium fuels for lightwater reactors fall between these extremes. A typical pressurized water reactor (PWR) fuel element begins life at an enrichment of about 3.2% and is discharged at a bum-up of about 30 x 10 MW-d/t, at which time it contains about 0.8 wt % and about 1.0 wt % total plutonium. Boiling water reactor (BWR) fuel is lower in both initial enrichment and bum-up. The uranium in LWR fuel is present as oxide pellets, clad in zirconium alloy tubes about 4.6 m long. The tubes are assembled in arrays that are held in place by spacers and end-fittings. 

Account must be taken in design and operation of the requirements for the production and consumption of xenon-135 [14995-12-17, Xe, the daughter of iodine-135 [14834-68-5] Xenon-135 has an enormous thermal neutron cross section, around 2.7 x 10 cm (2.7 x 10 bams). Its reactivity effect is constant when a reactor is operating steadily, but if the reactor shuts down and the neutron flux is reduced, xenon-135 builds up and may prevent immediate restart of the reactor. 

Many redundant safety features were provided at the SRP. These included a moderator dump tank, gadolinium nitrate solution as emergency absorber, continuously mnning diesel generators, and a 95 x 10 -L (25 x 10 -gal) elevated water tank for each reactor, for assurance of cooling. 

The Natural Reactor. Some two biUion years ago, uranium had a much higher (ca 3%) fraction of U than that of modem times (0.7%). There is a difference in half-hves of the two principal uranium isotopes, U having a half-life of 7.08 x 10 yr and U 4.43 x 10 yr. A natural reactor existed, long before the dinosaurs were extinct and before humans appeared on the earth, in the African state of Gabon, near Oklo. Conditions were favorable for a neutron chain reaction involving only uranium and water. Evidence that this process continued intermittently over thousands of years is provided by concentration measurements of fission products and plutonium isotopes. Usehil information about retention or migration of radioactive wastes can be gleaned from studies of this natural reactor and its products (12). 

A number of pool, also called swimming pool, reactors have been built at educational institutions and research laboratories. The core in these reactors is located at the bottom of a large pool of water, 6 m deep, suspended from a bridge. The water serves as moderator, coolant, and shield. An example is the Lord nuclear reactor at the University of Michigan, started in 1957. The core is composed of fuel elements, each having 18 aluminum-clad plates of 20% enriched uranium. It operates at 2 MW, giving a thermal flux of 3 x 10 (cm -s). The reactor operates almost continuously, using a variety of beam tubes, for research purposes. 

Uranium oxide [1344-57-6] from mills is converted into uranium hexafluoride [7783-81-5] FJF, for use in gaseous diffusion isotope separation plants (see Diffusion separation methods). The wastes from these operations are only slightly radioactive. Both uranium-235 and uranium-238 have long half-Hves, 7.08 x 10 and 4.46 x 10 yr, respectively. Uranium enriched to around 3 wt % is shipped to a reactor fuel fabrication plant (see Nuclear REACTORS, NUCLEAR FUEL reserves). There conversion to uranium dioxide is foUowed by peUet formation, sintering, and placement in tubes to form fuel rods. The rods are put in bundles to form fuel assembHes. Despite active recycling (qv), some low activity wastes are produced. 

Water as coolant in a nuclear reactor is rendered radioactive by neutron irradiation of corrosion products of materials used in reactor constmction. Key nucHdes and the half-Hves in addition to cobalt-60 are nickel-63 [13981 -37-8] (100 yr), niobium-94 [14681-63-1] (2.4 x 10 yr), and nickel-59 [14336-70-0] (7.6 x lO" yr). Occasionally small leaks in fuel rods allow fission products to enter the cooling water. Cleanup of the water results in LLW. Another source of waste is the residue from appHcations of radionucHdes in medical diagnosis, treatment, research, and industry. Many of these radionucHdes are produced in nuclear reactors, especially in Canada. 

The accident at the Three Mile Island (TMI) plant in Pennsylvania in 1979 led to many safety and environmental improvements (4—6). No harm from radiation resulted to TMI workers, to the pubHc, or to the environment (7,8), although the accident caused the loss of a 2 x 10 investment. The accident at the Chernobyl plant in the Ukraine in 1986, on the other hand, caused the deaths of 31 workers from high doses of radiation, increased the chance of cancer later in life for thousands of people, and led to radioactive contamination of large areas. This latter accident was unique to Soviet-sponsored nuclear power. The Soviet-designed Chemobyl-type reactors did not have the intrinsic protection against a mnaway power excursion that is requited in the test of the world, not was there a containment building (9—11). 

Cost and Value of Plutonium. The cost of building all U.S. nuclear weapons has been estimated as 378 biUion in 1995 dollars (24). If half of this sum is attributed to U.S. weapons-grade plutonium production (- lOOt), the cost is 1.9 x 10 /kg of weapons-grade Pu. Some nuclear weapons materials (Be, enriched U, Pu) also have value as a clandestine or terrorist commodity. The economic value of reactor-grade plutonium as a fuel for electric power-producing reactors has depended in the past on the economic value of pure 235u... 

A large number of radiometric techniques have been developed for Pu analysis on tracer, biochemical, and environmental samples (119,120). In general the a-particles of most Pu isotopes are detected by gas-proportional, surface-barrier, or scintillation detectors. When the level of Pu is lower than 10 g/g sample, radiometric techniques must be enhanced by preliminary extraction of the Pu to concentrate the Pu and separate it from other radioisotopes (121,122). Alternatively, fission—fragment track detection can detect Pu at a level of 10 g/g sample or better (123). Chemical concentration of Pu from urine, neutron irradiation in a research reactor, followed by fission track detection, can achieve a sensitivity for Pu of better than 1 mBq/L (4 X 10 g/g sample) (124). 

Total reserves of thorium at commercial price in 1995 was estimated to be >2 x 10 metric tons of Th02 (H)- Thorium is a potential fuel for nuclear power reactors. It has a 3—4 times higher natural abundance than U and the separation of the product from Th is both technically easier and less expensive than the enrichment of in However, side-reaction products, such as and the intense a- and y-active decay products lead to a high... 

Zirconium is used as a containment material for the uranium oxide fuel pellets in nuclear power reactors (see Nuclearreactors). Zirconium is particularly usehil for this appHcation because of its ready availabiUty, good ductiUty, resistance to radiation damage, low thermal-neutron absorption cross section 18 x 10 ° ra (0.18 bams), and excellent corrosion resistance in pressurized hot water up to 350°C. Zirconium is used as an alloy strengthening agent in aluminum and magnesium, and as the burning component in flash bulbs. It is employed as a corrosion-resistant metal in the chemical process industry, and as pressure-vessel material of constmction in the ASME Boiler and Pressure Vessel Codes. 

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