Nuclear experiments

Oil Contamination of Helium Gas. For more than 20 years, helium gas has been used in a variety of nuclear experiments to collect, carry, and concentrate fission-recoil fragments and other nuclear reaction products. Reaction products, often isotropically distributed, come to rest in helium at atmospheric concentration by coUisional energy exchange. The helium is then allowed to flow through a capillary and then through a pinhole into a much higher vacuum. The helium thus collects, carries, and concentrates products that are much heavier than itself, electrically charged or neutral, onto a detector... 

In the previous article (1) on heteronuclear double resonance in this series it was suggested that such experiments would soon vie for importance with homonuclear ones. In fact, there has been an almost total eclipse partly as a result of the use of proton decoupling in all work, partly because of improved methods of frequency generation and control which have made experimental distinctions between the two types of experiment much less important. The present review therefore deals with both homo- and hetero-nuclear experiments and includes multiple resonance work also. The seven years up to mid-1978 are covered, although it has been impossible to mention every experiment. Emphasis is laid upon new ideas and developments of technique, with some preference for the more recent work. The Chemical Society specialist reports on NMR spectroscopy have included regular articles on multiple resonance (2,3) and a number of reviews deal with various aspects of the subject. (4-19) It has been decided to omit work on the solid state. 

Information from a number of sources, including the open scientific literature, was consulted in addition to that provided by the French authorities. Reports on three independent scientific missions to the atolls that are available in the public domain were consulted—the Scientific Mission of French Polynesia (Tazieff mission) of June 1982, the New Zealand, Australia and Papua New Guinea Scientific Mission of Mururoa Atoll (Atkinson mission) of October 1983, and the Scientific Mission of the Calypso to the Site of the Nuclear Experiments at Mururoa Atoll (Cousteau mission) of June 1987. 

Two dimensional experiments can also show correlations between different types of nuclei. These hetero-nuclear experiments have the advantage that nuclei such as and N have much wider chemical shift ranges, and therefore the 2D experiments achieve a tremendous reduction in spectral crowding. The HETCOR (HETeronuclear CORrelation) experiment was the first 2D experiment developed to provide... 

Angel RJ, McCammon CA, Woodland AB (1998) Structure, ordering and cation interactions in Ca-free P2i/c clinopyroxenes. Phys Chem Minerals 25 249-258 Arthur J (1996) How to do resonant nuclear experiments with synchrotron radiation. II Nuovo Cimento Soc ItalFis 180 213-220... 

Of the 112 known elements, only about 90 occur naturally on Earth. The remainder are synthesized, usually in barely detectable amounts, in high-energy nuclear experiments. Less than half of the 90 naturally occurring elements are abundant enough to play a significant role in the chemistry of everyday stuff. 

Then followed an 11-inch machine which produced one million-volt protons, and these were used, actually, in some nuclear experiments. Indeed, the first cyclotron-produced nuclear disintegrations were produced by this 11-inch cyclotron. 

Seaborg and his colleagues conducted various nuclear experiments calculated to produce element 95 or element 96. Then they followed lengthy and complicated chemical procedures trying to isolate and identify microscopic traces of these new forms of matter. 

Radioactive Natural sources, mining of ra-substances dioactive ores, fission processes, nuclear experiments... 

The success of an irradiation experiment depends to a large extent on the target considerations. In many nuclear experiments as much time has to be devoted to the target preparation as to the rest of the experiment. If the purpose is to produce a radionuclide for a simple tracer experiment, the consideration in this section may be sufficirait. If, however, the requirements are a product of extreme purity, very high specific activity, or very short half-life, special techniques must be used, which are discussed in 15.5-15.7. 

In 1790 Adair Crawford and William Cruikshank first detected non-radioactive strontium in the mineral strontianite in Scotland. Metallic strontium was isolated in 1808 by Sir Humphry Davy. Radioactive Sr-90, like many other radionuclides, was discovered in the 1940s in nuclear experiments connected to the development of the atomic bomb. 

Liquid-hydrogen/solid-air explosions have been carried out in a closed volume to assess the possible hazards of an explosion in an in-pile nuclear experiment. At A.E.R.E. Harwell there are a number of current and prospective nuclear-physics experiments that use chambers adjacent to the reactor core, filled with liquid hydrogen in order to moderate the reactor neutron flux and produce collimated beams of low-energy neutrons. These moderator chambers are generally surrounded by a vacuum tube of up to 7 ft in length and 4 to 12 in. in diameter. 

After completion of this "mechanical program in September, 1949, it appeared that much could be learned by converting the Mock-Up into equipment for low-power nuclear experiments such as critical mass determination, ueutron-and gamma-flux measurements, and operation of the control system. These studies occupied the period Trom February, 19S0 to September, 1950. 

Full-scale test of the servo mechanism as an automatic control device was accomplished during the low—power nuclear experiments described in Section A4.5.7. The system performed satisfactorily for several months at power levels from 100 watts to 175 kilowatts. 

Erosion and desertification can be studied, e.g., by determining changes in cesium-137 levels in surface soil, the origin of cesiiun-137 being the fallout of early nuclear experiments. 

Resonance detectors are also useful for Coulomb-excited nuclear experiments and for in situ implantation experiments using short-lived Mn as parent nuclide to produce Fe... 

V.V. Dolgov, M.E. Minashin, V.N. Sharapov, Operating Experience with the Biiibino Dual-Purpose Electricity and Heat Nuclear Plant in the Far North , Nuclear Experience. v.2, IAEA-CN-42/235, Vienna (1983). 

A computerized library ot references to integral neutron eiq )eriment8 has b n developed at tiie Lawrence Radiation Laboratory at Livermore. This library serves as a data base for the systematic retrieval of documents describing diverse critical and bulk nuclear experiments. The evaluation and reduction of the physical parameters of tee experiments to a standard numerical format, and their comparison with calculated results using Monte Carlo computer codes and established libraries of neutron cross sections, will make routine appraisal euler, and also make possible improvement of neutron trwsport cal culations. 

Industry Experience is more blurred. It may be considered acceptable for someone with aerospace avionics experience to work on elements of a rail signalling system and vice versa. However, the nuclear industry requires nuclear experience. An organization could break into a new industry by employing new staff with relevant experience and providing evidence of infrastructure, culture, processes and procedures (perhaps through professional accreditation schemes). 

The genetically significant radiation exposure of the population (Table 7.4) by natural sources (approximately 110 mrem/a) is roughly twice as much as the mean radiation exposure by artificial sources. The radiation load through X-ray diagnosis constitutes the major part of the artificial radiation the population is exposed to. The contribution from fallout from nuclear experiments is less than 1% of the natural radiation exposure. Exposure through nuclear facilities is assumed to be of the same magnitude. 

Results were presented from ID solid-state NMR MAS exchange nuclear experiments aimed to investigate the influence of the side-chain length on the main- and side-chain dynamics in selected members of the poly- -acrylates series, poly( -hexylmethacrylate) and poly(n-butylmethacrylate). The molecular dynamics of the different molecular sub-units in the slow-motion region was... 

For high-temperature operations, materials, and fuels are key technologies. There is a century of large-scale experience in the use of fluoride molten salts. Aluminum is made by electrolysis of a mixture of bauxite and sodium aluminum fluoride salts at 1000 C in large graphite baths. Fluoride salts are compatible with graphite fuels. A smaller nuclear experience base exists with molten fluoride salts in molten salt reactors. Nickel alloys such as modified Hastelloy-N have been qualified for service to 750 C. A number of metals and carbon-carbon composites have been identified for use at much higher temperatures however, these materials have not yet been fully developed or tested for such applications. 

Safety reviews should be conducted in sufficient depth to ensure that all issues and questions raised by the review can be satisfactorily resolved. Safety review activities should be performed by personnel who have sufficient education, nuclear experience, expertise and training to allow a thorough understanding and evaluation of the items reviewed. 

Since assuming responsibility for SRS, WSRC has also brought in senior managers and many new line managers with previous experience in the commercial nuclear industry and has significantly augmented the professional staff with people who have commercial or naval nuclear experience. 

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