Standard Sources for Health Physics Instrument Calibration

Abstract

A basic review of radioactive and machine sources of ionizing radiation useful for health physics instrument calibration, with particular emphasis on the needs of the applied health physicist. Topics considered include standards terminology and hierarchy; alpha, beta, electromagnetic and neutron sources; and accuracy limits under laboratory and field conditions. Detailed characteristics of common sources and their salient physical characteristics are tabulated. TOWARDS A MORE EXACT TERMINOLOGY

Characteristics of beta detection and dose measurement at Department of Energy facilities

“…Current practices for instrument ca 1 i brati on with an uranium slab require placement of the survey instrument with its window in contact with the slab. Beta dose rates are constant only for a few millimeters above the slab surface (Kathren 1975) and fall off to only 4% of their surface value at 10 em from the slab. Unless the detector's sensitive 18 • • • • • volume is only a few millimeters deep~ the radiation field in the sensitive volume will not be uniform.…”

“…One further problem is that the uranium slab emits gamma radiation as well as beta radiation. This contributes about 10% of the dose rate at the surface of the uranium slab and increases to approximately 20% at 10 em (Kathren 1975). Because of this nonuniform photon contribution, accurate compensation factors are difficult to determine, and in most cases none have been made.…”