ORAU Team Document Number: ORAUT-TKBS-0006-3 Dose Reconstruction Project for NIOSH Effective Date: 04/11/2005 Revision No.: 01 Hanford Site - Occupational Medical Dose Controlled Copy No.: ________ Page 1 of 28 Subject Experts: Vernon E. Shockley and Ronald L. Kathren Supersedes: Document Owner Approval: Signature on File Date: 04/07/2005 Edward D. Scalsky, TBD Team Leader Revision No.: 00 Approval: Signature on File Date: 04/07/2005 Judson L. Kenoyer, Task 3 Manager Concurrence: Signature on File Date: 04/07/2005 Richard E. Toohey, Project Director Approval: Signature on File Date: 04/11/2005 James W. Neton, Associate Director for Science TABLE OF CONTENTS Section Page Record of Issue/Revisions ................................................................................................................... 3 Acronyms and Abbreviations ............................................................................................................... 4 3.1 Introduction ................................................................................................................................. 5 3.2 Technical Factors Affecting Diagnostic X-Ray Dose ................................................................... 5 3.2.1 Applied Kilovoltage and Filtration .................................................................................... 5 3.2.2 Current and Exposure Time ............................................................................................. 7 3.2.3 Distance .......................................................................................................................... 8 3.2.4 Collimation and Waveform Characteristics ...................................................................... 8 3.2.5 Screens, Grids, and Other Factors Potentially Affecting Worker Dose ............................. 9 3.3 Diagnostic X-Ray Doses to Hanford Workers, 1943 to Date ....................................................... 9 3.3.1 Doses From 14” × 17” PA Chest Radiography ............................................................... 12 3.3.2 Lateral 14” × 17” Chest Radiography ............................................................................. 16 3.3.3 Chest Photofluorography ............................................................................................... 19 3.4 Uncertainty Analysis for Hanford Radiography Doses ............................................................... 20 References ........................................................................................................................................ 23 Glossary ............................................................................................................................................ 26 Effective Date: 04/11/2005 Revision No. 01 Document No. ORAUT-TKBS-0006-3 Page 2 of 28 LIST OF TABLES Table Page 3-1 Relationship of beam intensity and various technical factors .................................................. 9 3-2 Analogous of IREP organs not included in ICRP 34 ............................................................. 11 3-3 Frequency of Occupational x-rays at Hanford ....................................................................... 12 3-4 Summary of beam parameters for 14" × 17" PA chest radiography ...................................... 14 3-5 Average absorbed chest X-ray dose (mGy) for selected organs for 1 Gy entrance kerma (air kerma without backscatter) for a beam quality of 2.5 and 4.0 mm aluminum HVL ......................................................................................................... 16 3-6 Organ dose estimates for Hanford chest radiographs from before 2/1/1946 to present ............................................................................................................................. 17 3-7 Average absorbed dose from chest photofluorography (mGy) for selected organs for 1 Gy entrance kerma (air kerma without backscatter) for a beam quality of 2.5 mm aluminum HVL .......................................................................................... 20 3-8 Organ dose estimates for Hanford photofluorography March 1945 to 1/31/1962 ............................................................................................................................. 20 Effective Date: 04/11/2005 Revision No. 01 Document No. ORAUT-TKBS-0006-3 Page 3 of 28 RECORD OF ISSUE/REVISIONS ISSUE AUTHORIZATION EFFECTIVE REV. DATE DATE NO. DESCRIPTION 09/16/2003 08/29/003 00 Original draft technical basis document, Section 3, for the Hanford Site. Initiated by Edward D. Scalsky Draft 10/18/2004 01-A Draft revision to incorporate numerical changes in tables and to add additional tables. Initiated by Edward D. Scalsky. Draft 04/04/2005 01-B Incorporates NIOSH review comments. Initiated by Edward D. Scalsky. Draft 04/06/2005 01-C Incorporates additional NIOSH review comments. Initiated by Edward D. Scalsky. 04/11/2005 04/11/2005 01 Approved issue of Revision 01. Initiated by Edward D. Scalsky. Effective Date: 04/11/2005 Revision No. 01 Document No. ORAUT-TKBS-0006-3 Page 4 of 28 ACRONYMS AND ABBREVIATIONS Al aluminum cm centimeter DCF dose conversion factor EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000 ESE entrance skin exposure Gy gray HVL half value layer ICRP International Commission on Radiological Protection ICRU International Commission on Radiological Units IREP Interactive RadioEpidemiological Program kVp peak kilovoltage, applied kilovoltage LAT lateral mA milliampere mAs milliampere-second mm millimeter NCRP National Council on Radiation Protection and Measurements NIOSH National Institute for Occupational Safety and Health PA posterior-anterior R roentgen RMS root mean square s second SID source to image distance SSD source to skin distance Effective Date: 04/11/2005 Revision No. 01 Document No. ORAUT-TKBS-0006-3 Page 5 of 28 3.1 INTRODUCTION Diagnostic x-ray procedures were an additional contributor to the occupational radiation exposure of Hanford workers. In general, the dose from these exposures was neither measured nor considered or included as part of the overall occupational exposure of the employee, although it clearly was occupationally related. With the passage of the Energy Employees Occupational Illness Compensation Program Act of 2000 (EEOICPA), diagnostic medical x-rays administered in conjunction with routine or special physical examinations required for employment were recognized as a valid source of occupational exposure. Unlike occupational exposures incurred during normal work processes, individual diagnostic medical x-ray exposures were not monitored, necessitating reconstruction of the doses acquired in this manner. This report describes the technical aspects of dose reconstruction from medical x-rays administered prior to employment and periodically thereafter as a condition of employment. Technical Basis Documents and Site Profile Documents are general working documents that provide guidance concerning the preparation of dose reconstructions at particular sites or categories of sites. They will be revised in the event additional relevant information is obtained about the affected site(s). These documents may be used to assist NIOSH in the completion of the individual work required for each dose reconstruction. In this document, the word “facility” is used as a general term for an area, building or group of buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons employer facility” or a “Department of Energy facility” as defined in the Energy Employee Occupational Illness Compensation Program Act of 2000 (42 U.S.C. § 7384l (5) and (12)).” 3.2 TECHNICAL FACTORS AFFECTING DIAGNOSTIC X-RAY DOSE A number of factors determine the dose to workers from a diagnostic x-ray procedure. For a more or less standard medical radiographic (i.e., diagnostic) unit with a tungsten target (anode) and focal spot of 1-2 mm, these include the basic machine settings used for the exposure, which include the applied kilovoltage of the beam (kVp), beam current (mA), time of exposure (s), distance, waveform, amount and kind of filtration used, collimation or use of diaphragms, tube housing characteristics, type and speed of the film, development procedure, screens, grids, and the size of the worker. While this list of factors looks formidable, in the absence of direct measurements of the beam itself, which are rarely available, the dose to the worker can be estimated with a reasonable degree of accuracy with knowledge of only the three basic machine parameters (applied kilovoltage, current, and time) and assumptions about filtration, collimation, and waveform characteristics. The implications of these factors to worker dose are discussed below. 3.2.1 Applied Kilovoltage and Filtration The energy of the x-ray beam is determined by the applied kilovoltage and the filtration, and is sometimes referred to as beam quality. X-rays, as produced in a typical medical x-ray tube, are bremsstrahlung and, as such, are a distribution or spectrum of energies ranging from zero to the applied kilovoltage, which refers to the potential between the anode and cathode of the tube. For a typical unfiltered x-ray spectrum, the average energy is about one-third of the peak energy, or applied kilovoltage. Hence, most of the x-rays produced are much lower in energy than the applied kilovoltage of the beam, and are attenuated by the torso or other portion of the body being radiographed and never reach