Moderator, in nuclear reactor

On a larger scale, deuterium oxide has been used as a moderator in nuclear reactors, having some advantages over graphite. 

Heavy water (p. 39) is now manufactured on the multikilotonne scale for use both as a coolant and neutron-moderator in nuclear reactors its absorption cross-section for neutrons is much less than for normal water [Pg.623]

It was detected by Urey, Brickwedde and Murphy in 1932. It occurs in all natural compounds of hydrogen including water, as well as in free hydrogen molecules at the ratio of about one part per 6,000 parts hydrogen. The principal application of deuterium is in tracer studies for measuring rates and kinetics of chemical reactions. It also is used in thermonuclear reactions and as a projectile in cyclotrons for bombardment of atomic nuclei to synthesize isotopes of several transuranium elements. Deuterium oxide, D2O, or heavy water is used as a neutron moderator in nuclear reactors. 

In a typical experiment, reduction of the water s volume from 2400 L to 83 mL yields 99% pure D20. Large amounts of D20 (about 160 tons per year in the United States) are manufactured by this method for use as a coolant and a moderator in nuclear reactors. 

Denterinm is invariably prepared from heavy water, which itself is mannfactnred by the electrolytic emichment of water, and is available for use as a moderator in nuclear reactors. D2O is useful as a source of deuterium in deuterium-labeled compounds. Deuterium compounds such as heavy water have been extensively studied. In Table 3, a number of physical properties of normal water and heavy water are compared. 

Beryllium oxide is used as a reflector and moderator in nuclear reactors. In addition to its low neutron-capture cross section, BeO has physical, mechanical, and chemical properties that allow its use at elevated temperatures, but its high cost and propensity to damage under irradation have limited its applications " ... 

USE Source of neutrons when bombarded with alpha particles according to the equation jBe + JHe J C + jn This yields about 30 neutrons per million alpha particles. Also as neutron reflector and neutron moderator in nuclear reactors. In beryllium copper and beryllium aluminum alloys (by direct reduction of beryllium oxide with carbon in the presence of Cu nr Al). In radio tube parts. In aerospace structures. In inertial guidance systems. 

USE To study chemical reaction rates and mechanisms. The cross section of deuterium for the capture of thermal neutrons is very low which makes it useful, in the form of heavy water> as a neutron moderator in nuclear reactors. Produces a considerable decrease in neutron energy per collision. 

Deuterium oxide is available in ton quantities and is used as a moderator in nuclear reactors, both because it is effective in reducing the energies of fast fission neutrons to thermal energies and because deuterium has a much lower capture cross-section for neutrons than has hydrogen and hence does not... 

The major use for zirconium is in the nuclear industry. Zirconium alloys (zircaloys) are used extensively as a cladding for nuclear (uranium oxide) fuel rods in water cooled reactors. Zircaloys were favoured over stainless steel cladding because they had a considerably lower neutron cross-section, appropriate thermal conductivity and both corrosion and mechanical resistance. As indicated, hafnium is an impurity in nearly all zirconium ores. Hafnium, however, has a much higher neutron cross-section than zirconium and, as such, the two elements must be separated prior to using zirconium in fuel rod cladding. For many years the separation was very difficult due to the chemical similarity of the two elements. Zirconium hydride is used as a moderator in nuclear reactors. 

RESEARCH ON THE USE OF ORGANIC COOLANTS AND MODERATORS IN NUCLEAR REACTORS. 

RESEARCH ON THE USE OF ORGANIC COOLANTS AND MODERATORS IN NUCLEAR REACTORS. //ENGLISH TRANSLATION OF ISSLED. PO PRIMENENIYU ORGANICHESKIKH TEPLONOSITELEY-ZAMEDLITELEY V YADERNYKH REAKTORAKH 611-, 1964.//... 

Precaution Flamm. solid powd. mod. fire hazard as powd. or dust or when exposed to flame si. explosion hazard as dust incompat. with halocarbons reacts incandescently with fluorine and chlorine reacts with Li, P Hazardous Decomp. Prods. Heated to decomp, in air, emits very toxic fumes of BeO NFPA Health 3, Flammability 1, Reactivity 0 Uses Structural material in space technology moderator In nuclear reactors source of neutrons windows for x-ray tubes in gyroscopes, computer parts, inertial guidance systems additive in solid-propellant rocket fuels beryllium-copper alloys aircraft brakes neutron reflectors... 

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