Reactor neutron sources

Radiation source leak checks can be performed including the reactor neutron source and sealed gamma sources. 

Reactor neutron source (1) Thermo-electric converter (5)... 

Uses of Plutonium. The fissile isotope Pu had its first use in fission weapons, beginning with the Trinity test at Alamogordo, New Mexico, on July 16, 1945, followed soon thereafter by the "Litde Boy" bomb dropped on Nagasaki on August 9, 1945. Its weapons use was extended as triggers for thermonuclear weapons. This isotope is produced in and consumed as fuel in breeder reactors. The short-Hved isotope Tu has been used in radioisotope electrical generators in unmanned space sateUites, lunar and interplanetary spaceships, heart pacemakers, and (as Tu—Be alloy) neutron sources (23). 

Beryllium has a high x-ray permeabiUty approximately seventeen times greater than that of aluminum. Natural beryUium contains 100% of the Be isotope. The principal isotopes and respective half-life are Be, 0.4 s Be, 53 d Be, 10 5 Be, stable Be, 2.5 x 10 yr. Beryllium can serve as a neutron source through either the (Oi,n) or (n,2n) reactions. Beryllium has alow (9 x 10 ° m°) absorption cross-section and a high (6 x 10 ° m°) scatter cross-section for thermal neutrons making it useful as a moderator and reflector in nuclear reactors (qv). Such appHcation has been limited, however, because of gas-producing reactions and the reactivity of beryUium toward high temperature water. 

Since the recognition in 1936 of the wave nature of neutrons and the subsequent demonstration of the diffraction of neutrons by a crystalline material, the development of neutron diffraction as a useful analytical tool has been inevitable. The initial growth period of this field was slow due to the unavailability of neutron sources (nuclear reactors) and the low neutron flux available at existing reactors. Within the last decade, however, increases in the number and type of neutron sources, increased flux, and improved detection schemes have placed this technique firmly in the mainstream of materials analysis. 

Two types of sources are used. Originally developed in the 1940s, nuclear reactors provided the first neutrons for research. While reactors provide a continuous source of neutrons, recent developments in accelerator technology have made possible the construction of pulsed neutron sources, providing steady, intermittent neutron beams. 

At the end of the irradiation, the samples are withdrawn from the reactor and y-ray spectroscopy is carried out. Most often the laboratory performing the y-ray spectroscopy is located in a different city, in which case the samples are shipped and the reactor serves as a neutron source only. Many reactors also have y-ray spectroscopy capability so that measurements can be made at the reactor site as well. 

The following sources and instruments dominate studies in the area of liquids and amorphous materials. Although there are a number of sources available, each is optimized for a particular class of experiment. The sources can be split into two types pulsed neutron sources and reactor sources... 

Howitzer (Trademark of Reactor Experiments, Inc). The assembly is a 6-cu ft cylindrical Lucite tank filled with distilled water and containing three access ports (Fig 3). The large spherical container on the right is the shielded storage cask for the 2S2Cf neutron source when not in use... 

Reactors are sources of neutrons, and thus most reactor-produced radionuclides are neutron-rich ft emitters. Reactor-produced radionuclides are of relatively low specific activity if the target nucleus is the same element as the product radionuclide, because the target and the product cannot then be chemically separated. 

The most sensitive method for determining trace amounts of technetium is the neutron activation . The Tc sample is irradiated by slow neutrons. The radioactive isotope Tc with a half-life of 15.8 s is formed by the reaction Tcfn, y) Tc, the neutron capture cross section of which is comparatively large (20 bams), so that it is possible to determine amounts < 2x 10 " g of Tc. However, the method is not widely used since the half-life of Tc is very short. Moreover, this method is only convenient when a reactor or a neutron source is available. 

Californium is a synthetic radioactive transuranic element of the actinide series. The pure metal form is not found in nature and has not been artificially produced in particle accelerators. However, a few compounds consisting of cahfornium and nonmetals have been formed by nuclear reactions. The most important isotope of cahfornium is Cf-252, which fissions spontaneously while emitting free neutrons. This makes it of some use as a portable neutron source since there are few elements that produce neutrons all by themselves. Most transuranic elements must be placed in a nuclear reactor, must go through a series of decay processes, or must be mixed with other elements in order to give off neutrons. Cf-252 has a half-life of 2.65 years, and just one microgram (0.000001 grams) of the element produces over 170 mhhon neutrons per minute. 

WBNS Water Boiler Neutron Source (Reactor)... 

The minor and trace elements in coals are currently determined by several techniques, the most popular of which are optical emission and atomic absorption spectroscopy. Neutron activation analysis is also an excellent technique for determining many elements, but it requires a neutron source, usually an atomic reactor. In addition, x-ray fluorescence spectroscopy, electron spectroscopy for chemical analyses (ESCA), and spark source mass spectroscopy have been successfully applied to the analyses of some minor and trace elements in coal. 

Traditional neutron sources for SANS have been nuclear reactors, such as the High Flux Reactor at Institut Laue-Langevin (ILL), Grenoble. As a neutron source, it is necessary that a reactor should have a high neutron flux, not necessarily a high power. 

Studies of the effect of neutron irradiation are divided into three groups slow or thermal neutrons, fission products and reactor neutrons. The slow neutrons are obtained from a radioactive source or high energy neutrons that are produced by deuterium bombardment of a beryllium target in a cyclotron and slowed down passing thru a thick paraffin wax block. The fission products in one case are produced when a desired sample is mixed or coated with uranium oxide and subsequently irradiated with slow neutrons. The capture of neutrons by U23S leads... 

A nuclear reactor is usually the source of fast and thermal neutrons. These reactor neutrons are always accompanied by a gamma-ray field so that a material exposed in a reactor is subjected to the accumulated radiation effect—... 

Radioisotopes that decay by spontaneous fission with the direct accompanying release of neutrons are usually associated with the natural elements of uranium and thorium and the manmade element plutonium. However, the rate of decay of these elements by fission is so slow that it is only by incorporating them into large nuclear piles or chain reactors that they can be utilized as intense neutron sources. In the US Dept of Energy National Transplutonium Program, small quantities of elements heavier than plutonium are produced for basic research studies and to discover new elements with useful properties. One of these new elements, californium-252 (2S2Cf), is unique in that it emits neutrons in copious quantities over a period of years by spontaneous fission... 

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