In situ measurement of neutron temperature for the extended k0 NAA at FRM II

Abstract

The neutron temperature at different irradiation positions in the research reactor FRM II was measured using thermometer labels together with lutetium standards. This was the first time to measure the local temperature at the irradiation positions with this combination. The simplified Westcott formalism was used to calculate the neutron temperature using Lu and g(Tn) factors from different data sources. The results showed agreement between neutron temperature according to the Lu method and the temperature showed on the labels. They can be used as a reliable alternative to determine the neutron temperature instead of using Lu standards in the extended k0 NAA.

Measurement of k0 values for europium, lutetium and iridium at FRM II with a very well thermalized neutron spectrum

“…These results were in accordance with the temperatures monitored by the reactor control system at different places in the reactor. A detailed description of the in situ temperature measurement can be found in another publication [7]. The g(T n ) factors were calculated according to Eq.…”

“…The g(T n ) factors of Holden (1999) and Choi and Trkov (2007) are quite close to each other, although they used different input databases of ENDF/B-V and EAF-99, but they are about 4% higher than the other three g(T n ) data sets. This would lead to different results of the k 0 determination or temperature determination (up to 10 °C), if Lu is used as the temperature monitor [7]. Holden used in his 1999 paper the…”

“…by using temperature readings of the reactor moderator measured by thermocouples [6]. At FRM II, a method using irreversible thermometer labels was developed to measure the temperature at the irradiation positions in situ [7] and applied to determine the k 0 values of some non-1/v nuclides in this work.…”