Reactor Decay Heat Production

A problem strange to power generation by nuclear reactors is that of the decay heat. In fossil fuel amenities, once the combustion procedure is stopped, there is no further heat generation, and only a comparatively small quantity of thermal energy is stored in the high temperature of plant components. In a nuclear facility, the fission of weighty atoms likes isotopes of uranium and plutonium outcomes in the formation of highly radioactive fission products. Such fission products radioactively decay at a rate established by the quantity and kind of radioactive nuclides present. A few radioactive atoms will decay whereas the reactor is operating and the energy discharged by their decay will be eliminated from the core all along with the heat generated by the fission procedure. All radioactive materials which stay in the reactor at the time it is shut down and the fission procedure stopped will continue to decay and discharge energy. Such release of energy by the decay of fission products is termed as decay heat.

The quantity of radioactive materials present in the reactor at the time of shutdown is based on the power levels at which the reactor operated and the quantity of time spent at those power levels. The quantity of decay heat is very important. Usually, the quantity of decay heat which will be present in the reactor instantly following shutdown will be around 7% of the power level which the reactor operated at preceding to shutdown. The reactor operating at 1000 MW will generate 70 MW of decay heat instantly after a shutdown. The quantity of decay heat generated in the reactor will reduce as more and more of the radioactive material decays to few stable form. Decay heat might reduce to around 2% of the pre-shutdown power level inside the first hour after shutdown and to 1% in the first day. Decay heat will continue to reduce after the first day, though it will reduce at a much slower rate. The decay heat will be important weeks and even months after the reactor is shutdown.

The design of the reactor should permit for the elimination of this decay heat from the core by some means. When sufficient heat elimination is not available, decay heat will raise the temperatures in the core to the point which fuel melting and core damage will take place. Fuel which has been eliminated from the reactor will also need some technique of eliminating decay heat when the fuel has been exposed to an important neutron flux. Each reactor facility will contain its own technique of eliminating decay heat from both the reactor core and also any irradiated fuel eliminated from the core.