Inspection Surveys of X-Ray Inspection Systems: Results of Five Years and Implications on Future Management of Radiation Risks

Abstract

Purpose: Until the mid-1980s, federal inspectors performed radiation surveys annually on individual x-ray inspection systems which were operated for security screening purposes in federal facilities nationwide, and problems identified were corrected. The surveys were undertaken because of perceived high radiation risks and a need to ensure worker and public external exposures were minimized. The x-ray inspection systems are federally regulated under the Radiation Emitting Devices(RED) Act and, initially they were assessed by model type against the design, construction and performance criteria specified in the applicable RED regulations (Schedule II, Part IV) and were found compliant. A subsequent study not only demonstrated a much lower radiation risk attributed to a combination of technological advances in x-ray system design with narrow primary beams, high efficiency detectors and image processing capability, but also stressed the need for proper equipment maintenance and continued education of operators and maintenance personnel. Survey frequency was thus reduced to once every 2-3 years in accordance with a 1993 federal operational standard (SafetyCode 29). The radiation protection principles in Safety Code 29 are similar to those of the 1996International Atomic Energy Agency (IAEA) Basic Safety Standards for the protection against ionizing radiation and the safety of radiation sources. The purpose of this study was to assess inspection-survey data from 1993 through 1997 to elicit guidance toward the future management of radiation risks associated with the operation of such x-ray systems. Materials and methods: Data were retrieved from an inspection database containing survey records and problems identified on individual x-ray inspection systems operated in federal facilities for 1993 through 1997 inclusive. Problems identified in the records were divided into three groups: hazardous elements which included x-ray system's components or operational conditions or unsafe practices deemed to compromise safety and potentially increase risks; inactions of x-ray inspection systems' owners/users to promote safety and minimize risks; and problems not resolvable through the operational standard.Results and discussions: Cumulatively from 1993 to 1997, 314 surveys were performed on specific x-ray inspection systems deployed nationwide in various federal facilities, and 115/314 (3 7%) x-ray inspection systems presented 128 problems. Re-surveys were done on a number of x-ray systems during that time, implying that survey distribution was neither equal annually nor geographically.Recurring problems were observed on some x-ray inspection systems, implying that the respective user facilities were probably incapable of resolving such problems, or there was a lack of post inspection survey follow-up, or a combination of both. Of the problems identified in the 5-yearperiod,54/128 (42%) were attributed to unavailability of the operational standard, or its improper use or consultation by x-ray systems' operators and facility personnel; 32/128 (25%) were linked to missing or unclear view of x-ray warning signs; 17 /128 (13 %) were associated with malfunctioning or blocked x-ray warning lights; 11/128 (9%) were identified as mechanically-related to the lead drapes, or conveyor, or foot-mat switch, or anode/cathode attachment components; 6/128 (5%) were attributed to unsafe acts committed by x-ray systems' operators; 5/128 (4%) were linked to improper functioning of interlocks and switches; and 2/128 (2%) were associated with stray x-radiation emissions not in accord with the regulatory limit, but which did not create any risk to the operator or the public. The most frequent problem identified, including those related to the committed unsafe acts strongly suggest that user facilities need to strengthen their use and consultation of the operational standard in order to prevent an increased risk of radiation exposure. The remaining problems were related to maintenance activities which are inextricably coupled to the x-ray system owner/user responsibilities and which are resolvable through Safety Code 29. Only one x-ray system presented 3 problems, eleven x-ray systems were identified with 2 problems, and the remaining ( 103)presented 1 problem each. No x-radiation exposure hazard was found, and no adverse safety condition was revealed for which Safety Code 29 did not apply. In terms of problem distribution by facility, 95/314 (30%) x-ray systems were located in airports, and 9% found for each of the years1993 and 1995; 8/314 (3%) were found at penitentiaries; 6/314 (2%) were operated in military establishments; 3/314 (1%) were found at customs centers; and 1/314 (<1%) each existed at apolitical site, an international business site and a postal depot. This facility-problem distribution, when coupled with the problems identified, does not support the misconceived notion that safety is being extensively compromised in federal facilities that use such x-ray inspection systems, thereby, elevating radiation risks. On the contrary, fewer problems were identified in recent years, suggesting 1) improved user responsibility to achieve conformity with the operational standard, and 2) a need to work closer with some user facilities and promote more use of the operational standard in developing good administrative, operating and maintenance practices to ensure radiation risks remain low in the workplace. Overall, the evidence does not support a need for federal inspectors to continue inspection surveys, respecting the routine operation of x-ray inspection systems. Instead, it suggests a quality system to be established and implemented by user facilities for the ongoing operation and maintenance of such x-ray systems with appropriate guidance from the regulatory agency. Auditing would constitute part of the process to ensure risks are kept low.Conclusion: There were no unusual hazards identified or undue risks of x-radiation exposure posed to the x-ray system workers or to the public. The identified problems that could compromise safety were generally related to maintenance activities, which are the x-ray system owner/user responsibilities; fewer problems were found in recent years and are resolvable through Safety Code29 which promotes good operating and maintenance practices. Safety Code 29 contains the administrative and technical requirements necessary to effectively manage the radiation risks potentially associated with the future operation of these x-ray inspection systems. Based on the results of this review, inspection surveys of such x-ray inspection systems by federal inspectors appear tenuous or unwarranted, and a quality system for the ongoing operation and maintenance of such xray systems appear feasible. Regulatory guidance and audits are necessary to assure radiation risks remain low in the workplace in accordance with the operational standard.