SYMPOSIA PAPER Published: 01 January 2001

Metal Discs as Very Low Thermal Neutron Flux Monitors in Reactor Environment


Metal discs of pure materials like Au, W, Ta, Dy, Sm, In, Re and Mn can be used as monitors of very low thermal neutron fluxes. In order to reach low detection limits, the discs were activated for about 3 half-lives and measured with ultra low-level gamma-ray spectrometry for another 3 half-lives in an underground laboratory located at a depth of 225 m. The minimum detectable activity for these discs is in the range 0.5 mBq to 50 mBq, which was found through calibration to correspond to thermal neutron fluxes in the range 10-4 to 10-2 cm-2 s-1.

The discs were calibrated in the well defined neutron flux of the 1-m diameter large cavity facility located in the thermal column of the BR1 reactor at SCK•CEN. Thermal and 235U fission spectrum neutron standard fields were used in the calibration procedure.

The objectives of this technique, the calibration results as well as the first monitoring of thermal neutron fluxes at work places outside the BR1-reactor are presented.

Author Information

Martínez Canet, MJ
EC-JRC-IRMM Retieseweg, Geel, Belgium
Hult, M
EC-JRC-IRMM Retieseweg, Geel, Belgium
Köhler, M
EC-JRC-IRMM Retieseweg, Geel, Belgium
Aït Abderrahim, H
SCK•CEN, Mol, Belgium
Marloye, D
SCK•CEN, Mol, Belgium
Price: $25.00
Contact Sales
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Developed by Committee: E10
Pages: 761–768
DOI: 10.1520/STP13667S
ISBN-EB: 978-0-8031-5450-6
ISBN-13: 978-0-8031-2884-2