Generator systems radioisotopes from

The AEG sponsored research ia the program known as Systems for Nuclear AuxiHary Power (SNAP) as early as the 1950s. Most of the systems developed iavolved the radioisotope plutonium-238 as a heat source for a thermoelectric generator. Such electrical suppHes permitted radio transmission to earth from spacecraft such as Pioneer and l qyager. 

Radiation gauging pertains to the use of penetrating radiation, in particular as emitted from radionuclides or radioactive isotopes, for the measurement of particular properties of a material or system. Such properties may include density, thickness, mass, volume, composition, uniformity, etc. In addition to the use of nuclear radiation from radioisotopes instead of X-rays from machine generators, the other distinguishing difference from Radiography is that electronic detectors are employed instead of flhn to measure the transmitted or scattered radiation... 

Such systems are called radioisotope generators. Rn is sometimes used for the radiotherapeutic treatment of cancer. This product is isolated by separating it as a gas from the parent substance Ra which is normally in the form of solid or a solution of RaBr2. Rn grows into the radium sample with a half-life of 3.8 d. After a 2-week period, following a separation of radon from radiiun, approximately 90% of the maximum amount of radon has grown back in the radium sample. Consequently, it is useful to separate Rn each 2 weeks from the radium samples since further time provides very little additional radioactivity. The Rn is an a emitter the ther utic value comes from the irradiation of the tissue by the y-rays of the decay daughters Pb and Bi which reach radioactive uilibrium extremely rapidly with the Rn. 

The basis of any XRF technique is the photoelectric fluorescence of characteristie secondary x-rays from a sample. These are stimulated by irradiation with suitable primary photons. In isotope souree systems, primary photons are provided by radioisotopes that emit photons in the x-ray energy band. In tube source instruments, x-rays are generated by accelerating electrons onto a suitable target in the tube. In both cases, energies of the secondary x-rays... 

A radioisotope thermionic generator uses the decay heat of a radioactive element. The design is usttally modttlar. A module includes the radioisotope fuel, its encapsttlation, a thermionic converter, heat transfer paths (for coupling heat from the fuel to the converter and from the converter to the radiator), hermetically sealed housing, and thermal insulation. A variety of design concepts have been considered (planar and cylindrical converters, heat pipe and conduction coupling, and several radioisotopes), and a few fueled systems have been brrilt. However, no report of an operational irse of a radioisotope thermionic generator has yet been made. 

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