Abstract
.Ampoules of amorphous 99.5% enriched 13C were irradiated at the PF1b neutron beam line at the high-flux ILL research reactor in order to produce 14C atoms. The precise ratio of 14C/13C was subsequently measured at the VERA Accelerator Mass Spectrometer, allowing the 13C(n, gamma)14C thermal cross section to be accurately determined. This is the first measurement of this cross section at sub-eV energies via this technique and the result of 1.52 pm 0.07 mb for the thermal cross section is in good agreement with other recent measurements which were performed via Prompt Gamma-ray Activation Analysis.
Highlights
Introduction and motivationAccelerator mass spectrometry (AMS) offers a highly sensitive method for determining the number of nuclear reactions that have occurred in certain suitable cases and is being used more frequently to extract accurate cross sections for these reactions
The result is in agreement with the most recent value measured via Prompt Gamma-ray Activation Analysis (PGAA) [10] which uses fully independent experimental and analytical methods
Details of the first measurement of the 13C(n, γ) thermal cross section using neutron irradiation and AMS have been presented and the results confirm the precise values obtained using PGAA giving confidence to nuclear waste calculations carried out using the major evaluations
Summary
Accelerator mass spectrometry (AMS) offers a highly sensitive method for determining the number of nuclear reactions that have occurred in certain suitable cases and is being used more frequently to extract accurate cross sections for these reactions. The 13C neutron absorption cross section is suitable for being measured by this technique due to the wealth of experience through the use of AMS for carbon dating. This cross section is of importance to both nuclear energy applications [1,2] and the slow neutron capture process in nuclear astrophysics [3]. In the UK, irradiated graphite makes up 23% of the intermediate level nuclear waste, amounting to a volume of approximately 67,000 m3 weighing 83,000 metric tonnes with a further 14,000 tonnes classed as low level nuclear waste [4]. To avoid expensive destructive measurement techniques, one relies on the nuclear data for the four main production routes; 13C(n, γ)14C, 14N(n, p)14C, 17O(n, α)14C and 18O(n, n α)14C in order to predict the amount of 14C present in irradiated graphite
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