Field radiography using 100 Ci of Co-60 without interrupting adjacent manufacturing operations

Abstract

Radiography is the primary method of Nondestructive Examination recognized by the ASME B and PV Code as providing objective evidence of volumetric examination of the pressure boundary welds that are present in the Clinch River Breeder Reactor Program (CRBRP) Steam Generator. In order to support the steam generator production schedule, the radiographic examinations must be performed without interrupting any other manufacturing or inspection operations taking place within a 20-ft radius from the source. This condition imposes rigorous radiation safety requirements since the gamma radiation sources chosen to be used for examination of the pressure boundary welds, Co-60 and Ir-192, are very energetic. Co-60 gamma ray energy is 1.17 and 1.33 MeV and Ir-192 gamma ray is .6 MeV. The hazard of using such a high energy sources in the immediate vicinity of working personnel has necessitated the need for a thorough evaluation of methods of protection. Personnel protection from penetrating radiation, both x-ray and gamma ray, is accomplished by ingenious use, singly or in combination, of two factors which reduce radiation intensity. These factors are distance and shielding. In all radiographic operations the primary consideration is for personnel safety. The maximum radiation dose rate limit will be 0.002 rem/hr. This document describes how the factors of distance and shielding have been used to assure personnel safety at all times