Evaluation of the in-situ performance of neutron detectors based on EJ-426 scintillator screens for spent fuel characterization
| Autor: | Linus Ros, Per Kristiansson, Ulrika Bäckström, Mikael Elfman, H. Perrey, Anders Sjöland |
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| Rok vydání: | 2021 |
| Předmět: |
Physics
Nuclear and High Energy Physics Photomultiplier Physics - Instrumentation and Detectors Physics::Instrumentation and Detectors business.industry Astrophysics::High Energy Astrophysical Phenomena Detector FOS: Physical sciences Instrumentation and Detectors (physics.ins-det) Scintillator Clab Neutron temperature Optics Neutron flux Neutron detection Neutron Nuclear Experiment (nucl-ex) business Nuclear Experiment Instrumentation |
| Zdroj: | Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 1020:165886 |
| ISSN: | 0168-9002 |
| Popis: | The reliable detection of neutrons in a harsh gamma-ray environment is an important aspect of establishing non-destructive methods for the characterization of spent nuclear fuel. In this study, we present results from extended in-situ monitoring of detector systems consisting of commercially available components: EJ-426, a 6Li-enriched solid-state scintillator material sensitive to thermal neutrons, and two different types of Hamamatsu photomultiplier tubes (PMT). Over the period of eight months, these detectors were operated in close vicinity to spent nuclear fuel stored at the interim storage facility CLAB, Oskarshamn, Sweden. At the measurement position the detectors were continuously exposed to an estimated (moderated) neutron flux of approx. 280 n/s cm 2 and a gamma-ray dose rate of approximately 6 Sv/h. Using offline software algorithms, neutron pulses were identified and characterized in the data. Over the entire investigated dose range of up to 35 kGy, the detector systems were functioning and were delivering detectable neutron signals. Their performance as measured by the number of identified neutrons degrades down to about 30% of the initial value. Investigations of the irradiated components suggest that this degradation is a result of reduced optical transparency of the involved materials as well as a reduction of PMT gain due to the continuous high currents. Increasing the gain of the PMT through step-ups of the applied high voltage allowed to partially compensate for this loss in detection sensitivity even when the detectors were highly irradiated. The integrated neutron fluence during the measurement was experimentally verified to be in the order of 5 × 10 9 n cm −2 . The results were interpreted with the help of MCNP6.2 simulations of the setup and the neutron flux. |
| Databáze: | OpenAIRE |
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