Richard Jernigan -> RE: nuclear crisis in Japan (Mar. 30 2011 20:12:01)
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ORIGINAL: Ron.M If you de-couple the generator from the steam source, then the source just gets hotter and hotter since there is nothing to take the energy away. Leaving the generators with no-load has the same effect. You cannot shut down a Nuclear reaction in 5 minutes or at the turn of a key. It takes days and that energy has to be dissipated, whether in useful energy of not, otherwise you will get a heat overload and eventual explosion. This is what Pimientito was on about. cheers, Ron But see the following, from http://en.wikipedia.org/wiki/Load_following_power_plant "Boiling water reactors Boiling water reactors (BWR) and Advanced Boiling Water Reactors can use a combination of control rods and the speed of recirculation water flow to quickly reduce their power level down to under 60% of rated power, making them useful for overnight load-following. In markets such as Chicago, Illinois where half of the local utility's fleet is BWRs, it is common to load-follow (although less economic to do so). Pressurized water reactors Pressurized water reactors (PWR) use a chemical shim in the moderator/coolant (see nuclear reactor technology) to control power level, and so normally do not load follow. (In most PWRs, control rods are either fully withdrawn or fully inserted - variable control is difficult, partly due to the large bundle sizes.) In France, however, nuclear power plants use load following. French PWRs use "grey" control rods, in order to replace chemical shim, without introducing a large perturbation of the power distribution. These plants have the capability to make power changes between 30% and 100% of rated power, with a slope of 5% of rated power per minute. Their licensing permits them to respond very quickly to the grid requirements." end quote I wonder what the specific technology is at Fukushima? I was wondering why they didn't just shove in the control rods when things started to go bad. Did the sudden power outage disrupt control? Did the earthquake take the emergency batteries off line? At any rate, people (including me) are going to be very skeptical of nuclear plant safety for quite a while. Here's the San Onofre plant in Southern California, sitting on the coast and near a major fault. RNJ
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