PACER

From Encyclopedia Jr, free information reference for Kids

For the US government documentation system, see PACER (law)

The PACER project, carried out at Los Alamos National Laboratory in the mid-1970s, explored the possibility of a fusion power system that would involve exploding small hydrogen bombs (fusion bombs)—or, as stated in a later proposal, fission bombs—inside an underground cavity.

The proposed system would absorb the energy of the explosion in a molten salt, which would then be used in a heat exchanger to heat water for use in a steam turbine. In the original fusion-bomb proposal, a huge cavity would be emptied in a salt dome, but further developments used engineered cavities instead. A typical design called for a 4 m thick steel alloy blast-chamber, 30 m (100 ft) in diameter and 100 m (300 ft) tall, to be embedded in a cavity dug into bedrock in Nevada. Hundreds of 15 m (45 ft) long bolts were to be driven into the surrounding rock to support the cavity. The space between the blast-chamber and the rock cavity walls was to be filled with concrete; then the bolts were to be put under enormous tension to pre-stress the rock, concrete, and blast-chamber. The blast-chamber was then to be partially filled with molten fluoride salts to a depth of 30 m (100 ft), a "waterfall" would be initiated by pumping the salt to the top of the chamber and letting it fall to the bottom, and while being surrounded by this falling coolant, a 1-kiloton fission bomb would be detonated; this would be repeated every 45 minutes. The fluid would also absorb neutrons to avoid damage to the walls of the cavity.

Another example: a 2-kiloton bomb; this produces an energy of 8 TJ (8 × 10¹² joules), which would be absorbed by 2,000 metric tons of flibe (a mixture of lithium and beryllium fluorides), i.e. 4 MJ/kg; the energy the coolant absorbs per mass for heating and evaporation is the same as the energy value of TNT, hence the amount of coolant has to be the same as the TNT-value of the bomb.

As an energy source, the system is the only one that could be demonstrated to work using existing technology. However it would also require a large, continuous supply of nuclear bombs, making the economics of such a system rather questionable. The production of thermonuclear, or even just nuclear, bombs requires high immediate capital expenses, and also has long-term environmental costs. Additionally, the political effects of beginning a large-scale production of nuclear bombs could potentially be large, and with increasing bomb numbers, increased security measures would be necessary. The entire system—fissile material production, bomb fabrication, and power generation—could be carried out in a single well-guarded site, but only for great development costs that would likely never be recovered by generating energy.

[edit] See also

• Nuclear pulse propulsion

[edit] References

• Garwin, Richard L.; Charpak, Georges (2001). Megawatts and Megatons: A Turning Point in the Nuclear Age? Knopf. ISBN 0-37-540394-9.

[edit] External link

• Determination of main reactor parameters for flibe (Li2BeF4) cooled peaceful nuclear explosive reactors (PACER) (pdf)