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Design and Stress Analysis of Extraterrestrial ... - The Black Vault

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In designing a source it is necessary to reduce this pressure to<br />

permissible values.<br />

Frequently the isotope must be alloyed with other metals to<br />

improve its<br />

heat conductivity <strong>and</strong> strength.<br />

Curium-2 1 12 is<br />

obtained a'tifically by bombarding americium-241<br />

with neutrons. <strong>The</strong> specific thcrmal capacity is 122 W/g. It can<br />

be used in generators with a service period from 3 to 6 months.<br />

<strong>The</strong> problems <strong>of</strong> protection during the use uf this isotope are related<br />

to the suppression <strong>of</strong> incidental a-decay <strong>of</strong> neutron <strong>and</strong> y-radiations.<br />

In decay curium-242 changes into plutonium-238, which causes<br />

the severe corrosion <strong>of</strong> ordinary stainless steels; only tantalum is<br />

not corroded. Curium-242 is used as an alloy with americium-241<br />

(45% Cm <strong>and</strong> 55% Am) <strong>and</strong> is further alloyed with a stabilizing metal,<br />

for example, gold (1 part Cm + Am + 5 parts An), which improve<br />

heat transfer in the alloy.<br />

Helium is separated as a result <strong>of</strong> the decay <strong>of</strong> curium-242. If<br />

we place an isotope in a hermeticaL.y sealed ampoule without extra<br />

space, by the end <strong>of</strong> the service period the pressure <strong>of</strong> the helium<br />

accumulating in the ampoule rises to 550 daN/cm 2 (2110 days after<br />

closing the isotope in the ampoule).<br />

Table 2.3 presents data on the main isotopes used in extraterrestrial<br />

power plants.<br />

As is apparent from the table, we can design a source which<br />

will operate for different periods <strong>of</strong> time. Short-life sources<br />

are used for research purposes.<br />

sources.<br />

Let us examine the structural diagrams <strong>of</strong> isotopic energy<br />

190

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