Heat, Damage, and Photon Source

The photon source from neutron reactions is also an interesting response that can be obtained with the special edit name GAM. Decay photons, such as the 1.779-MeV photon from the Al-28 $\beta\bar{~~}$ decay mentioned above, can also be added into the photon source as shown in the next sample problem.

  TEST 6 -- HEAT, DAMAGE, PHOTON SOURCE
  0  1  0  1  1  1  0  3  0  0
  30  2  47  0  0  1  1  1  14  4
  AL-27
  ALUM/
  1  1  AL27/
  HEAT  DPA  GAM  GAM  GAM  GAM  GAM
   GAM  GAM  GAM  GAM  GAM  GAM  GAM
  1  HEAT/
  1  NG  1.125E6/
  2  DAME  .02/
  11  NG/
  STOP

The 12 occurrences of GAM reserve spaces for the 12 photon groups. Group 9 (1-2 MeV) is in position 11, and the last edit specification adds the equilibrium 1.779-MeV photon production rate into that group (one such delayed gamma is produced per capture event). Note also that damage energy is converted to DPA in position 2 using 25 eV for the displacement energy ${ 0.02 = [1/(2*25)] }$. Most SN codes could use these cross sections and print out steady-state photon source vectors by region to be used in a subsequent photon transport calculation.

Coupled sets, like the one defined in Sample Problem 3, can also be prepared including steady-state radioactive decay contributions. Putting a negative sign on JEDPOS defines the gamma group in the coupled set that will receive the contributions defined by that edit specification. The Problem 3 input would become

  TEST 3A -- COUPLED SET WITH STEADY-STATE DECAY
  0  3  0  3  1  1  0  3  0  0
  42  2  46  0  0  1  1  2  1  2
  AL-27
  * */
  1  1  AL27/ 
  HEAT
  1  HEAT/  NN AND NG PART
  1  GHEAT/  GG PART
  1  NG  1.125e6  AL27 / DELAYED HEAT AND GAMMAS FOR AL27
 -8  NG  1.       AL27
  1  NP  3.2e5    AL27
-10  NP  .72      AL27
 -9  NP  .28      AL27
  STOP

Delayed heat and photon production edit specifications for some important materials are given in the DELAY12 and DELAY24 files included in the TRANSX distribution. As an example, the 12-group data for U-238 are repeated below:

  1  N2N 0.060E+6  U238
  1  NG  0.160E+6  U238
  1  NF  8.580E+6  U238
 -4  NF  5.995E-4  U238
 -5  NF  4.072E-3  U238
 -6  NF  2.036E-2  U238
 -7  NF  9.226E-2  U238
 -8  NF  3.033E-1  U238
 -9  NF  1.442E+0  U238
-10  NF  3.384E+0  U238
-11  NF  4.726E+0  U238
-12  NF  1.514E+0  U238

The heating part (position 1) includes the beta decay heating for Pu-239 and Np-239; thus, it includes all the heat up to the appearance of the final Pu-239 product. The contributions to heating and photon production from fission come from the decay of the fission products.

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