Nuclear Data Section
International Atomic Energy Agency
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Memo CP-D/541

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30 December 2008
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N. Otsuka,

Subject:
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Fission neutron distribution (41516.002-008)
Memo 4C-4/173

Concerning 41516 (PRELIM.4145), A. S. Vorobyev et al. [1] gives angular andenergy distribution of prompt neutrons from thermal neutron induced fission to study
contribution of prompt neutrons emitted by a fissioning nucleus (“scission neutron”)
and by fission fragments. For this purpose, neutron emission angle θ is measured fromdirection of light fission fragment momentum (as mentioned under REACTION infree texts).
REACTIONs and unit codes are used in PRELIM.4145 are summarized below:
Sub#.002.003.004,.005
.006
.007
.008

REACTION(92-U-235(N,F),PR,NU/DA)(92-U-235(N,F),PR,AKE/DA,N)(92-U-235(N,F),PR,NU/DA/DE)//(92-U-235(N,F),PR,NU/DA/DE))(92-U-235(N,F),PR,NU/DA/DE)(92-U-235(N,F),PR,NU/DE,LF,REL)(92-U-235(N,F),PR,NU/DE,HF,REL)

Unit
PRT/FIS/SR
MEV
NO-DIM
NO-DIM
NO-DIM
NO-DIM

1. Heading and unit codes
The following corrections would be proposed:
Sub #002-003
004-005006

Comment
Use ANG-RL instead of ANG.
Use new heading codes ANG-RL-** instead of ANG-**.
Use a new unit code P/FS/MEVSR instead of NO-DIM

Dictionary 24 (Data headings)
ANG-RL-DN
Relative angle in denominator
ANG-RL-NM
Relative angle in numerator
Dictionary 24 (Data units)
PRT/FIS/SR(update of unit family: 1/A → FYDA)
P/FS/MEVSR
particle/fission/sr/MeV (unit family: FYAE)

Dictionary 26 (Unit families)
FYDA
per-cent per fission per solid angle
FYAE
per-cent per fission per solid angle per energy(These codes are added when they are used in the final TRANS.4145 without
objections from other centers.)

2. Quantity codes(1) 41516.002-006
Differential prompt neutron multiplicity (not cross section) with respect toindependent variables of neutron has been coded by PR,D*,N rather
than PR,NU/D* (* = A, E,…). The latter has been used to define prompt fission
neutron multiplicity at a given variables of fission fragments. If we stick thisconvention, the following modification should be applied to 41516.002-006:
Sub #002003004006

In PRELIM.4145
PR,NU/DA
PR,AKE/DA,N
PR,NU/DA/DE

A possible solution
PR,DA,N+LF (new code)
PR,AKE/DA,N/N+LF (new code)
PR,DA/DE,N+LF/N (new code)(2) 41516.007-008
There is a code
PR,DE,N,MXD prompt neutron spectrum relative to Maxwell distribution ofgiven temperature
in dictionary 236. However, source of prompt neutron (emitted by light fragment orheavy fragment) cannot be given on the basis of this quantity code because SF7 isoccupied by N (neutron). So a possible solution is PR,DE,N,MXD/MSC instead of
PR,NU/DE,*F,REL.
Outgoing light particles from fission are often measured in coincidence with fission
fragments. We would introduce new branch or modifier codes which mean “measuredin coincidence with light/heavy fragment”. Further comprehensive investigation isnecessary.
Reference[1] V.G. Vorobyev et al., Nucl. Instrum. Meth. A 598(2009)795

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