sp-fispact2001 - ENEA AFS Cell

2. htape3x int=int2 outt=resid
(„int2‟ is the input file for HTAPE3X with the options IOPT=108 and KOPT=0. „resid‟ is the
output containing the residual nuclei).
Here is an example for int2:
Residual nuclei
in 25 cells
108,,,,0,25,,,,/
15,20,25,30,44,46,48,52,54,56,58,60,62,64,92,94,96,98,104,
106,108,110,112,114,116
Until now this is just a standard MCNPX procedure.
SP-FISPACT2001 will read the values of „resid‟ (stable and metastable isotopes) and subtract
these values from „elast‟ to obtain the residual nuclei per source proton; finally it will create
the preliminary file COLLAPX with the new pseudo cross-sections.
3.2 Preparation of the preliminary input COLLAPX
The file FLUXES for FISPACT needs to be prepared with the values of the flux spectrum
under 20 MeV as provided by MCNPX.
In order to prepare properly the preliminary input „collapx.i‟ for SP-FISPACT, the user must
specify before the code word COLLAPSE: the value of the flux under 20MeV irradiating the
material, the source proton current used, the material irradiated and the number of atoms of
this material. Five new code words have been introduced for this purpose: CURRENT,
TARGET, ATTARGET, HCOLLAPSE, TCOLLAPSE.
The file collapx.i has to be prepared following these steps:
1. Input the integrated flux under 20MeV using the code word FLUX (this is a standard
FISPACT code word, but it has to be specified also in the preliminary input and not only in
the main input). If activation calculations are needed only above 20MeV then enter in any
case a value of the flux as well as a spectrum of the flux in the file FLUXES. These will be
fictitious values without any consequence for the results. Use a realistic value, such as FLUX
1E15 (see WARNINGS n. 5 at page 14).
Example: if there is a flux under 20MeV of 10 14 neutrons/cm 2 sec, then write: FLUX 1E14.
2. Input the proton current (in mA) used as source particles in MCNPX. Since the results in
MCNPX are, as stated above, provided as residual nuclei per source particle, the value of the
current has to be fixed in order to provide the correct number of residual nuclei per second.
The new code word is CURRENT.
Example: if the proton current of the accelerator is 3mA, then write: CURRENT 3.
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