When a reactor runs, gamma rays are emitted in extraordinary quantity. These gammas tend to heat the graphite in thermal MSRs, as experienced at the MSRE, and make the graphite's steady temperature quite a bit hotter than then the salt. ORNL found that gamma heating in graphite is nearly uniform over the core since gammas have a long mean free path. In addition, the gamma heating is proportional to the average fission heat. This kernel computes local gamma heating as a function of average fission heat and a user-defined proportionality factor (usually between 2 and 10 percent).
Gamma can define a form factor for the gamma heating. That is, gamma heating can be set to be cosinusoidal or Bessel.
