Pebble Bed
This technology claims a dramatically higher level of safety and efficiency. Instead of water, it uses pyrolytic graphite as the neutron moderator, and an inert or semi-inert gas such as helium, nitrogen or carbon dioxide as the coolant, at very high temperature, to drive a turbine directly. This eliminates the complex steam management system from the design and increases the transfer efficiency (ratio of electrical output to thermal output) to about 50%. Also, the gases do not dissolve contaminants or absorb neutrons as water does, so the core has less in the way of radioactive fluids and is more economical than a light water reactor.
The technology was first developed in Germany[1] but political and economic decisions were made to abandon the technology. [2] In various forms, it is currently under development by MIT, the South African company PBMR, General Atomics (U.S.), the Dutch company Romawa B.V., Adams Atomic Engines, INL, and the Chinese company Huaneng [3].
In June 2004, it was announced that a new PBMR would be built at Koeberg, South Africa by Eskom, the government-owned electrical utility[4]. There is considerable opposition to the PBMR from groups such as Koeberg Alert and Earthlife Africa, the latter of which has sued Eskom to stop development of the project [5].
