NEA Nuclear Data High Priority Request List, HPRL

HPRL Main High Priority Requests (HPR) General Requests (GR) Special Purpose Quantities (SPQ) New Request SGC/HPRL Documents


Request ID10 Status of the request General request
TargetReaction and processIncident EnergySecondary energy or angleTarget uncertaintyCovariance
 79-AU-197 (n,tot) SIG  5 keV-200 keV  5 
FieldSubfieldDate Request createdDate Request acceptedOngoing action
 Science,Fusion Dosimetry 18-MAY-07 06-JUN-07 

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Requester: Dr Roberto CAPOTE NOY at IAEA, AUT
Email: roberto.capotenoy@iaea.org

Project (context): Dosimetry

Impact:
INDC(NDS)-0507 Summary Report of Consultants’ Meeting Review the Requirements to Improve and Extend the IRDF library (International Reactor Dosimetry File (IRDF-2002)), IAEA Headquarters, Vienna, Austria 20-21 April 2006, prepared by L.R. Greenwood and Alan L. Nichols (IAEA, Vienna, January 2007)

Accuracy:
5%

Justification document:
Gold is an extremely important material in nuclear applications: the capture on gold is a standard neutron cross-section, gold has been proposed as a high energy neutron dosimeter (see below), Au-197(n,2n) is a reactor dosimetric reaction considered in all recent IRDF files, etc. Reactions on gold are also of interest for nuclear model code testing as gold is a mono-isotopic element being amenable to detailed calculations.
Taken from INDC(NDS)-0507 "... proposed high energy dosimetry reactions 197Au(n,2n)196Au, 197Au(n,3n)195Au, and 197Au(n,4n)194Au require the extension of the gold evaluation up to 60 MeV"
To our surprise we found large discrepancies in the measured total cross section data of gold in the 5-200 keV energy range (URR) as can be seen from the attached plots. The only existing evaluation (Young et al in red in the figures) has been carried out in the early nineties and has been adopted for all subsequent libraries with minor modifications. This evaluation follows the Seth et al. data measured in 1965, which is in contradiction with several new measurements (for example Purtov 1994 and Wishak 1995-2006). The spread of the Wishak measurements is puzzling.

Comment from requester:
A new dispersive coupled-channel optical model potential (5 keV - 200 MeV) derived using the requested data (plus the existing database above 200 keV) will have a direct impact on future evaluations of neutron induced reactions on gold.

Comments from evaluator/experimentalist:
While considerable data exist for the 5-200 keV total cross section, there is considerable scatter in these data. The measurement range is well suited for time-of-flight facilities and may also be accessed with quasi-monoenergetic beams using the Li(p,n) neutron source reactions. For a transmission measurement optimal conditions are obtained with a transmission factor close to 0.5, which implies that getting a sample might be costly, but purity and chemical issues should not be concerns. A measurement which overlaps with the region of the Au capture standard (200 keV to 2.5 MeV) would be of interest to allow a consistency check.

Comments for achieved accuracy:

Review comment:

Additional file attached: AU197_NTOT_RECENT.ps
Additional file attached: AU197_WISHAK.ps