Teste | Abstract: 111-1 | ||||
Abstract:The International Commissions on Radiation Units and Measurements (ICRU) and on Radiological Protection (ICRP) have published a joint report, as ICRU Report 95, which recommends new operational quantities for use in radiological protection [1]. The current set of operational quantities used for external radiation ambient dose equivalent, H* (10), and personal dose equivalent Hp(d, α), are defined in the ICRU sphere which bears no resemblance to the reference anthropomorphic phantoms used to define the protection quantity effective dose, E. Furthermore, the choice of the depth d of 10 mm for ambient and personal dose equivalent led to a considerable overestimation of effective dose at low photon energies (Ep < 70 keV). For these reasons, the ICRU Report 95 proposes a new operational quantity for area monitoring, called Ambient Dose (H*), which is defined on the same ICRP anthropomorphic phantoms as the protection quantities. The objective of this study was to evaluate the impact of this new quantity on the response of several survey meters that are commonly used in radiation protection in medicine, research and industry. The study was conducted at the Ionizing Metrology Laboratory of the Nuclear Energy Department of the Federal University of Pernambuco in Brazil, which provides calibration services using gamma and X-ray radiation. The laboratory is accredited under the ISO :17025:2017 standard. In this study it was evaluated 16 survey meters from different manufacturers and models, with Geiger Muller detector. The response was evaluated for S-Cs and ISO-N X ray beam from N-40 to N-200. The dependence of the energy response, for each survey meter, was evaluated in both quantity H*(10) and H*. The reference dose rate was determined by multiplying the air kerma rate by the conversion coefficient (H*(10) or H*) available from ISO 4037 [2] and Behrens, R. and Otto, T [3]. The results demonstrated the monitor response for H* presented different behavior depending of the model, indicating that some detectors will be overestimated or underestimated the H* values for low energy, requiring redesign of the instruments. Some equipment showed similar energy dependence response for H* and H*(10) requiring recalibration. In conclusion, before the use of the survey meters to measure this new quantity it is necessary to evaluate and adjust their energy dependence response. Keywords: survey monitors, new operational quantities, ICRU Report 95 |