Passive nondestructive burnup monitoring of MNSR irradiated fuel by measuring photoneutrons produced within fission products

A passive nondestructive method for monitoring of Syrian miniature neutron source reactor (MNSR) fuel burnup is introduced. The inner irradiation site design inside the Be reflector was exploited to measure the generated photoneutrons induced by fission products hard gamma radiation in the subcritical state. The photoneutron flux was measured using gold foils as a function of cooling time and operation power. For cooling time ranges between 10 and 25 d, experiments show that 140Ba is the extremely dominating inducer of photoneutrons and the measured flux is proportional to the accumulated 140Ba. This result forms a new method base for MNSR fuel burnup monitoring. It might be used also as a safeguards technique to check the operator declared information.