Proton induced activity in graphite - comparison between measurement and simulation

TL;DR

This study compares measured radionuclide activities in graphite targets exposed to 590 MeV protons with Monte Carlo simulations to improve understanding of activation processes for waste disposal.

Contribution

It provides a detailed comparison between experimental measurements and simulation models for proton-induced activation in graphite targets.

Findings

Measured activities generally agree with simulations within uncertainties.

Simulation models show strengths and limitations in predicting long-lived isotopes.

Results inform safety assessments for radioactive waste disposal.

Abstract

The Paul Scherrer Institut (PSI) operates the Meson production target stations E and M with 590 MeV protons at currents of up to 2.4 mA. Both targets consist of polycrystalline graphite and rotate with 1 Hz due to the high power deposition (40 kW at 2 mA) in Target E. The graphite wheel is regularly exchanged and disposed as radioactive waste after a maximum of 3 to 4 years in operation, which corresponds to about 30 to 40 Ah of proton fluence. For disposal, the nuclide inventory of the long-lived isotopes (T(1/2) > 60 d) has to be calculated and reported to the authorities. Measurements of gamma emitters, as well as 3H, 10Be and 14C, were carried out using different techniques. The measured specific activities are compared to Monte Carlo particle transport simulations performed with MCNPX2.7.0 using the BERTINI-DRESNER-RAL (default model in MCNPX2.7.0) and INCL4.6/ABLA07 as nuclear reaction models.