Ionizing Radiation Metrology

The importance of accurate and reliable measurement is crucial in various domains such as national and international trade, health, industry, safety, and regulatory affairs. The initial system of measurement, based on human morphology, was later replaced by nature-based standards due to inconsistencies. The globalization of trade necessitated a common measurement standard, leading to the establishment of international organizations, including the CGPM, CIPM, and BIPM, through the ‘Metre Convention’ treaty. To address the demand for quality products within a comparable system, the CIPM formulated the ‘Mutual Recognition Arrangement’ (CIPM-MRA). This arrangement allows the recognition of calibration certificates issued by one economy by others, provided they adhere to CIPM-MRA guidelines. In metrology, economies are represented by their Metrology Institutes (National Metrology Institute, NMI, and Designated Institute, DI), responsible for maintaining national standards, providing traceable calibration, and coordinating with international organizations. This chapter focuses on ionizing radiation metrology, specifically within the framework of CIPM. The Consultative Committee for Ionizing Radiation (CCRI) oversees dosimetry, radionuclide measurements, and neutron measurements. These measurements are integral to scientific research, medicine (diagnostic radiology, cancer treatment), radiation protection, and radiation processing. Primary measurement standards, maintained by BIPM and NMIs/DIs of various countries, play a crucial role in realizing accurate measurements. The chapter discusses primary standards in dosimetry (Free air ionization chamber, cavity ionization chamber, calorimeter, and Fricke dosimeter), radionuclide measurements (proportional counter, liquid scintillator, plastic scintillator-based coincidence counting systems), and neutron measurements (Manganese bath system, proton recoil telescope, standard thermal assembly in graphite). Countries with no primary standards, in any specific area, maintains secondary standards, calibrated against established primary standards from other countries or BIPM. Overall, this chapter aims to bring out the significance of international cooperation in metrology and the role of standards in ensuring accurate and reliable measurements across diverse applications.