Article

Parameter of neutron calibration field in Viet Nam following international standard

Institute for Nuclear Science and Technology, 179 Hoang Quoc Viet − Cau Giay, Hanoi, Viet Nam

^* Corresponding author: LnThiem@vinatom.gov.vn

Received: 12 January 2024
Accepted: 27 May 2024

Abstract

This paper presents the technical parameters of neutron calibration fields available in Viet Nam for calibrations of neutron measuring meters (i.e., neutron ambient dose equivalent/rate meters and/or neutron personal dose equivalent/rate meters − referred to neutron meters). The technical parameters of neutron calibration fields, in this work, consist of physical quantity (i.e., the integrated neutron fluence rate over a neutron spectrum, ϕ); operational dosimetric quantities (i.e., ambient dose equivalent rate, Ḣ^*(10)) and radiation quantities (i.e., fluence-spectrum-averaged energies, Ē; fluence-to-ambient dose equivalent conversion coefficient, h*). The technical parameters of neutron reference fields were reported for different radiation beam qualities following the ISO-8529 and the ISO-12789 series (i.e., for direct neutron component from a neutron reference fields of a bare ²⁴¹Am-Be, complied with the ISO-8529 series criteria; and for total neutron component from simulated workplace neutron reference fields of a  ²⁴¹Am-Be source moderated by different polyethylene spheres and from a neutron reference field of a bare ²³⁹Pu-Be source, complied with the ISO-12789 series criteria). The technical parameters of the ISO-8529 neutron reference field of the bare ²⁴¹Am-Be source were theoretically calculated based on the total neutron source strength and presented for direct neutron component. In addition, the technical parameters of the ISO-12789 simulated workplace neutron reference fields of the ²⁴¹Am-Be source moderated by different polyethylene spheres as well as of the ²³⁹Pu-Be source were characterized using the Bonner sphere spectrometer system accompanying with the FRUIT neutron spectrum unfolding code for the total neutron component. The technical parameters as well as their combined standard uncertainties of neutron fields were also presented in conjunction with different distances from the sources’ centers.