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RADIOISOTOPE THERMOELECTRIC
GENERATOR
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INTRODUCTION
 A radioisotope thermoelectric generator
(RTG, RITEG) is an electrical generator that
obtains its power from radioactive decay.
 In this device, the heat released by the decay
of a suitable radioactive material is converted
into electricity by the See beck effect using an
array of thermocouples.

CONSTRUCTION & DESIGN
 The design of an RTG is simple by
the standards of nuclear technology
the main component is a sturdy
container of a radioactive material
(the fuel).
 Thermocouples are placed in the
walls of the container, with the
outer end of each thermocouple
connected to a heat sink.
 Radioactive decay of the fuel
produces heat which flows through
the thermocouples to the heat sink,
generating electricity in the process.

Desirable Characteristics of
Fuel For RTG
 High energy output
 Easy absorption and conversion into thermal
radiation
 Long half life
 High specific power output
 Low shielding requirements
A PLUTONIUM238Pu
PELLET

FUELS(ISOTOPES)
 Plutonium-238
 curium-244
 strontium-90
 polonium-210
 promethium-147,
 caesium-137,
 cerium-144, ruthenium-106, cobalt-60, etc..

Potential Fuels for RTG
238Pu 90Sr 210Po 241Am
Shielding
(mm of lead)
2.5 16 100 18
Half life (years) 87.7 28.78 0.38 432.7
Specific Power
(Wg-1)
0.448 0.128 17.81 0.089

LIFESPAN
 Most RTGs use 238Pu, which
decays with a half-life of 87.7
years. RTGs using this material
will therefore diminish in power
output by 0.787% of their
capacity per year. 23 years after
production, such an RTG will
have decreased in power by
16.6%, i.e. providing 83.4% of its
initial output.Thus, with a
starting capacity of 470W, after
23 years it would have a capacity
of 392W.

EFFICIENCY
 Higher efficiency means less radioactive fuel is
needed to produce the same amount of power and
therefore a lighter overall weight for the generator.
 Thermocouples used in RTGs are very reliable and
long lasting, but are very inefficient.
 So efficiency above 10% have never been achieved
and most RTGs have efficiency between 3 to 7 %.

SAFETY
 RTGs may pose a risk of
radioactive contamination:
if the container holding the
fuel leaks, the radioactive
material may contaminate
the environment.
 Iridium cladding
 Graphite aero-impact shell
 Composite covering
 Alloying

Applications
 Used as power sources in satellites, space probes
and unmanned remote facilities.
 Used as power sources for navigation beacons,
radio beacons, light houses and weather
stations.
 Used at places where solar cells are not viable.
 Most desirable power source for unmanned and
unmaintained situations needing a few 100 watts
or less of power of durations too long for fuel
cells, batteries and generators.

Challenges
 Low overall efficiencies (6 - 7%)
 Degradation of thermoelectric elements
 Design of effective thermal path
 Breakdown of insulators

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