After a reactor shuts down, 15% of the rated capacity of the reactor is released as delayed heat due to the decay of short lived radioactive byproducts. This delayed heat must be dissipated into the environment to keep the structure of the reactor from damage.
The Indians have designed and are implementing a nuclear reactor that can passively dissipate this delayed heat production after reaction shutdown has been triggered. This passive heat dissipation design uses heat pipes specifically reserved for this purpose. These pipes carry heat unaided into the environment. Such heat pipes can operate unpowered in air and/or completely submerged in water. The contents of the reactor core are totally sealed from the outside environment which includes these heat pipes. Nevertheless, uncontaminated delayed heat can be passively carried into the environment cooling the reactor without any possibility of core compromise. The pebble bed reactor design is also passively cooled and can dissipate the delayed heat load without external power. The point, many nuclear reactor designs exist that can be deployed on the coast, underground or under the sea without the possibility of shutdown failure. Early on, the decision to go with the light water reactor design was a political one born within internal governmental political in-fighting in preference to safer type designs. The decision makers in the nuclear industry both in government and in industry will stay with the light water design for their own reasons. Today in the American led orthodox view, nuclear safety lies in maintaining ages old tried and true technology that maintain safety by relying on ultimate human intervention and control. Some question that view as foolish. But other countries are going in other directions including fail safe engineered passive control. On Sun, Apr 1, 2012 at 11:17 PM, Jed Rothwell <[email protected]> wrote: > David Roberson <[email protected]> wrote: > > This information does not build up my confidence in nuclear reactors >> located on shorelines. >> > > They are all on the shoreline in Japan. They use ocean water for cooling. > > > >> Perhaps a need exists for some form of absolute kill mechanism that can >> be called upon in such an emergency. >> > > Reactors are SCRAM'ed of course, but it is physically impossible to keep > them from generating heat. You have to cool them down for many days. > > I think the problem can be addressed by putting emergency generators far > above the waterline, perhaps in the second story of the reactor building. > The Fukushima disaster was caused by the tsunami destroying the Diesel fuel > tanks. The tsunami did not destroy the reactor itself, although water did > get into the buildings I think. If the fuel tank and generator had survived > there would have been no disaster. > > The disaster was made worse by a mistake made a few days into the > disaster. They brought in an emergency Diesel. It ran out of fuel during > the night. No one noticed. That sounds like an incredibly stupid mistake, > but it is understandable. The people were working under extreme duress, > similar to soldiers in a battlefield. They were facing extreme peril, with > intense radiation and explosions all around them. They had gone without > sleep for days. > > - Jed > >
