| B N C
Experimental Report |
Experiment title Neutron flux measurements in reactor channels used for radiation damage studies |
Proposal No. Local contact A. Simonits |
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Principal proposer: F. Gillemot, Á. Griger Experimental team: A. Simonits |
Date of Experiment: 1999 Date of Report December 16, 1999 |
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Objectives
Foil activation technique and gamma-ray spectrometry has been applied to
characterize so-called “fast neutron channels” in BNC.
Results
Overall neutron flux characterizations have been performed in several vertical channels
(“Bagira”, 353, 555, 147, etc.) of the Budapest Research Reactor constructed for neutron damage
studies. Due to the extreme experimental conditions (> 5·1013 thermal and fast fluxes, 100÷
3000 h irradiation periods, etc.) special dosimetry foils developed at IRMM-Belgium (Al-0.01%
Co, etc.), as well as high-rate gamma-ray spectrometry (Loss-free counting with Dual Spectrum
Option) were used. Thermal and epithermal neutron fluxes were determined by 1/v- and
resonance detectors (Fe, Al-Au, Al-Co, Nb, etc.) where the actual epithermal flux was
approximated by the 1/En1+α function (Table 1). Fast fluxes were determined with a number of
threshold reactions covering the 2-10 MeV energy range (Fe, Cu, Ti, Nb, Zr, etc.). As shown, the
actual fast neutron flux distribution did not deviate from the fission flux with more than 5 % in
channels investigated. The overall accuracy for thermal and fast integral fluxes approached 1-3 %.
The method will be refined to monitor the required 0 – 18 MeV energy range more evenly.
| Reaction used | Ethres MeV |
Term. flux (n/cm2s) |
? (1/E1+?) |
Fast flux (n/cm2s) |
| 63Cu(n,α)60Co | 10 | -0.03 | 4.52 1013 | |
| 58Fe(n,γ)59Fe | - | 3.99 1013 | - | |
| 54Fe(n,p)54Mn | 2.8 | 4.60 1013 | ||
| 59Co(n, ?)60Co | - | 4.00 1013 | <||
| 94Zr(n, ?) 95Zr | - | 4.05 1013 | ||
| 90Zr(n,2n) 89Zr | 13 | 4.73 1013 | ||
| 47Ti(n,p) 47Sc | 2.2 | 4.38 1013 | ||
| 46Ti(n,p) 46Sc | 4.4 | 4.46 1013 | ||
| 48Ti(n,p) 48Sc | 6.9 | 4.50 1013 | ||
| Weighted averages: | 4.00 1013 | 4.50 1013 | ||
Table 1. Neutron flux parameters determined in reactor channel position 147/3
References
Future prospects
A. Simonits, F. De Corte, S. Van Lierde, S. Pommé, P. Robouch, M. Eguskiza: “The k0 and Q0
values for the Zr isotopes: a re-investigation ” Paper presented on the 10th Conf. on MTAA,
Washington, April 19-23, 1999 (in print, J. Radioanal. Nucl. Chem. Articles)
Neutron spectrum adjustments are being performed with the aid of the SANDBP code.
(in co-operation with BME, Budapest)
