Radioisotopic thermoelectric generators

Table 2. Summary of Radioisotope Thermoelectric Generators Successfully Launched by the United States from 1961 to 1990...

Skrabek, E.A., High temperature insulations for radioisotope thermoelectric generators. In Proc. of 13th Intersociety Energy Conv and Eng Conf, vol. 2, ASME, New York, 1978, pp. 1712 1716. 

Radioisotope thermoelectric generators (RTGs) are sometimes used as power sources for space systems. In April 1964, a United States RTG navigational satellite, SNAP 9A, reentered the atmosphere and burned up at high altitude over the Mozambique Channel, releasing 629 trillion becquerels (TBq), equivalent to 17,000 Ci, of Pu and 0.48 TBq of Pu (Whicker and Schultz 1982a Richmond 1989). In January 1978, a Soviet RTG satellite, Kosmos 954, reentered the atmosphere over Canada and spread radiouranium across parts of that country (Richmond 1989). The amount of radioactive materials in space applications is expected to increase (Richmond 1989). 

The primary use for plutonium (Pu) is in nuclear power reactors, nuclear weapons, and radioisotopic thermoelectric generators (RTGs). Pu is formed as a by-product in nuclear reactors when uranium nuclei absorb neutrons. Most of this Pu is burned (fissioned) in place, but a significant fraction remains in the spent nuclear fuel. The primary plutonium isotope formed in reactors is the fissile Pu-239, which has a half-life of 24 400 years. In some nuclear programs (in Europe and Japan), Pu is recovered and blended with uranium (U) for reuse as a nuclear fuel. Since Pu and U are in oxide form, this blend is called mixed oxide or MOX fuel. Plutonium used in nuclear weapons ( weapons-grade ) is metallic in form and made up primarily (>92%) of fissile Pu-239. The alpha decay of Pu-238 (half-life = 86 years) provides a heat source in RTGs, which are long-lived batteries used in some spacecraft, cardiac pacemakers, and other applications. 

The n-type PbTe as a thermoelctric material whose carrier concentration n is controlled to have around 3.0 x 10 m is commonly used in the temperature range of a hot side electrodes between 600 and 950 K.[l] The thermoelectric figure of merit Z has a maximum value of 1.4 X 10 K at 700 K and the dimensionless thermoelectric figure of merit ZT attains to almost unity. Then, PbTe and its solid solutions are utilized such as a solar thermoelectric generator (STG) and a radioisotope thermoelectric generator (RTG).[1,2]... 

USE 238Pu as heat source as radioisotope thermoelectric generator in radionuclide batteries for pacemakers with Be as neutron source. in atomic weapons in power reactors. Caution Radiation hazard concentrates in bone. 

FIGURE 3.12 Results of radioisotope thermoelectric generators (RTG) microprobe and RTG diffraction analyses at 2663 h (a), 5020 h (b), and 11,192 h (c). (From Balajka J., Gas-Side Corrosion in Oil-Fired Boilers, Research Power Institute, Bratislava, CSSR, 1983. With permission.)... 

A thermionic space reactor system does not suffer a radiological safety disadvantage compared with a thermoelectric space reactor system since both systems are laimched cold and neither reactor is started until a nuclear safe orbit has been achieved. The radiological hazards associated with the launch of a cold reactor system without a fission product inventroy are significantly less than those of a launch of a radioisotope thermoelectric generator. 

Thermoelectric devices are traditionally fabricated by assembling small blocks of n-type and p-type material in an array, intercoimected in series with electrodes. A successful system implementation is the radioisotope thermoelectric generator (RTG) for deep space probes. Microfabrication technologies for thermoelectric materials are however being developed to create low-cost integrated power and cooling microsystems. 

Radioisotope thermoelectric generators (RTGs) Irradiators Teletherapy sources Fixed, multi-beam teletherapy (gamma knife) sources AID > 1000... 

The use of these devices is based on more than thirty years of operation experience on space vehicles of various types. As an example, the US Department of Energy (DoE) has up to now suppUed 44 radioisotope-powered thermoelectric generator systems, used in 24 space missions. The most recent thermoelectric generator built by the DoE, the General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG), (Fig. 26-1), produces 290 W of electric energy with less than 11 kg of plutonium dioxide. Three units are installed on the Cassini vehicle for the exploration of Saturn,... 

The nuclear reaction that powers the radioisotope thermoelectric generator shown in the... 

This is a highly exothermic nuclear reaction producing 0.54 kW kg plutonium and is used in the so-called RTG (radioisotope thermoelectric generator) power units in interplanetary space probes (e.g., Cassini space probe) as well as in some experimental-type pacemakers. Think of the following problem a newly manufactured Pu94-powered pacemaker is surgically implanted into a patient. Keeping in mind that the Pu-238 half-life is 87.74 yr calculate how much Pu-238 fuel is needed in order to maintain a minimum of 100 jlW output for 25 years ... 

This capsule with the radioactive material is called a radiation heat source (RHS). Heat may be produced in dynamic or static cycles using the temperature difference between RHS and environment. Similar to the reactor sources, static conversion systems, particularly thermoelectric ones, were widely used both in the USSR and in the USA. Systems on their basis have been named as radioisotope thermoelectric generators (RTG). 

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