Neutron spectrometry and dosimetry study at two research nuclear reactors using Bonner sphere spectrometer (BSS),...

Area of Science:

• Nuclear Engineering
• Radiation Detection and Measurement

Background:

• Neutron fields require accurate characterization for safety and research.
• Different reactor designs and measurement locations significantly influence neutron spectra.

Purpose of the Study:

• Compare neutron spectrometry results from three distinct instruments.
• Quantify neutron fields at the McMaster Nuclear Reactor (MNR) and AECL Chalk River National Research Universal (NRU) Reactor.

Main Methods:

• Utilized a Bonner sphere spectrometer (BSS), cylindrical nested neutron spectrometer (NNS), and rotational proton recoil spectrometer.
• Conducted measurements at specific locations within the MNR (reactor pool base) and NRU (top of reactor plate).

Main Results:

• Observed significantly different neutron spectral shapes between MNR and NRU reactors.
• MNR showed a large thermal neutron fluence component due to extensive shielding, while NRU had negligible thermal neutrons.
• Neutron ambient dose rates varied: 0.03-0.06 mSv/h at NRU TOR, and 0.07-2.8 mSv/h at MNR beam ports.

Conclusions:

• Reactor type and measurement location critically impact neutron field characteristics.
• The BSS instrument exhibited a slight over-response, likely due to an uncalibrated response matrix.
• Accurate neutron dosimetry is essential for understanding and managing radiation fields in nuclear facilities.