• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Heat Generation Summary
Calculation of Decay Heat - h1012v2_75

Thermodynamics Heat Transfer and Fluid Flow Volume 2 of 3
Page Navigation
  50    51    52    53    54  55  56    57    58    59    60  
DECAY HEAT Heat Transfer DECAY HEAT Decay heat production is a particular problem associated with nuclear reactors. Even though the reactor is shut down, heat is produced from the decay of fission fragments.  Limits for each particular reactor are established to prevent damage to fuel assemblies due to decay heat. EO 2.7 DEFINE the term decay heat. EO 2.8 Given the operating conditions of a reactor core and the necessary formulas, CALCULATE the core decay heat generation. EO 2.9 DESCRIBE  two  categories  of  methods  for  removing decay heat from a reactor core. Reactor Decay Heat Production A problem peculiar to power generation by nuclear reactors is that of decay heat.   In fossil fuel facilities, once the combustion process is halted, there is no further heat generation, and only a relatively small amount of thermal energy is stored in the high temperature of plant components. In a nuclear facility, the fission of heavy atoms such as isotopes of uranium and plutonium results in  the  formation  of  highly  radioactive  fission  products.    These  fission  products  radioactively decay  at  a  rate  determined  by  the  amount  and  type  of  radioactive  nuclides  present.    Some radioactive atoms will decay while the reactor is operating and the energy released by their decay will  be  removed  from  the  core  along  with  the  heat  produced  by  the  fission  process.    All radioactive materials that remain in the reactor at the time it is shut down and the fission process halted will continue to decay and release energy.   This release of energy by the decay of fission products is called decay heat. The amount of radioactive materials present in the reactor at the time of shutdown is dependent on the power levels at which the reactor operated and the amount of time spent at those power levels.   The amount of decay heat is very significant.   Typically, the amount of decay heat that will be present in the reactor immediately following shutdown will be roughly 7% of the power level  that  the  reactor  operated  at  prior  to  shutdown.    A  reactor  operating  at  1000  MW  will produce  70  MW  of  decay  heat  immediately  after  a  shutdown.    The  amount  of  decay  heat produced  in  the  reactor  will  decrease  as  more  and  more  of  the  radioactive  material  decays  to some stable form.  Decay heat may decrease to about 2% of the pre-shutdown power level within the  first  hour  after  shutdown  and  to  1%  within  the  first  day.    Decay  heat  will  continue  to decrease  after  the  first  day,  but  it  will  decrease  at  a  much  slower  rate.    Decay  heat  will  be significant weeks and even months after the reactor is shutdown. HT-02 Page 52 Rev. 0







Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.