ANSI HPS N43.17-2009 Radiation Safety for Personnel Security Screening Systems Using X-Ray or Gamma Radiation.pdf

1、ANSI/HPS N43.17-2009 American National Standard Radiation Safety for Personnel Security Screening Systems Using X-Ray or Gamma Radiation Approved: August 2009 American National Standards Institute, Inc. iiPublished by Health Physics Society 1313 Dolley Madison Blvd. Suite 402 McLean, VA 22101 Copyri

2、ght 2009 by the Health Physics Society. All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States of America iiiThe Health Physics Society N43.17 Stan

3、dards Subcommittee responsible for the development of N43.17-2002 had the following members: Frank Cerra (chair), Martin Annis, Edgar Bailey, Terry Brayer, Larry Cothran, Daniel Kassiday, Andy Kotowski, Roy Lindquist, William Passetti, Richard Schueller, Timothy Scroggins, Gerald Smith, Steve Smith,

4、 Richard Whitman, Pamela Zaresk. The N43.17 Subcommittee responsible for the current revision had the following members: Frank Cerra, Co-Chair, National Institute of Standards and Technology Daniel Kassiday, Co-Chair, Food and Drug Administration Martin Annis, Annistech Paul Bergstrom, National Inst

5、itute of Standards and Technology Jack Burroughs, L-3 Security NCRP Commentary 16; 2003. AMERICAN NATIONAL STANDARD ANSI/HPS N43.17-2009 1 Radiation Safety for Personnel Security Screening Systems Using X-Ray or Gamma Radiation 1.0 Scope This standard applies to the manufacture and operation of secu

6、rity screening systems that are intended to expose humans to primary beam x-rays, gamma radiation, or both. This standard does not address neutron-based systems. Examples of screening practices covered by this standard include the following: Direct screening of humans to detect objects hidden within

7、 an individuals body or clothing. Knowingly exposing human occupants to the primary beam when screening vehicles or structures. Screening of orthopedic casts and prosthetic devices while being worn. The standard provides requirements specific to the ionizing radiation safety aspects of both the desi

8、gn and operation of these systems. It does not include electrical safety guidelines or any other safety, performance, or use considerations outside the realm of radiation safety. The limits in this standard are not intended to apply to stowaways not authorized to be in the area and not known to be p

9、resent prior to scanning. It is recognized that the need for security might sometimes call for exceeding the dose limits set in this standard. This should be based on an analysis demonstrating that the security benefit outweighs the risk from the radiation exposure incurred by the individuals screen

10、ed. This standard does not address the evaluation of the societal benefit of security screening. Therefore, screening operations that exceed this standards dose limits are beyond the scope of this standard and shall not claim compliance with this standard. Medical diagnostic systems should be used u

11、nder medical supervision and are not covered by this standard. 2.0 Definitions The following are terms that are either of key significance or have a specific meaning in this standard that might differ from the terms usage elsewhere. This is not meant to be a comprehensive glossary of terms used in r

12、adiation protection. The discussion in Annex C contains additional information on radiation quantities and units. Access panel: Any panel designed to be removed or opened for maintenance or service purposes that when removed or opened affects the radiation leakage pattern or allows intrusion into th

13、e radiation field. ADAP: see Ambient Dose Equivalent Area Product Administrative control: A documented, compulsory, routine procedure aimed at controlling the radiation exposure received by individuals and ensuring that the appropriate dose limits are not exceeded. Air kerma: The total initial kinet

14、ic energy transferred to charged particles per mass of air as a result of irradiation. The unit of air kerma is the joule per kilogram or gray (Gy). (1 Gy air kerma corresponds to approxi-mately a 114-roentgen exposure). ALARA: As Low As Reasonably Achievable, economic and social factors being taken

15、 into account. Aluminum-equivalent filtration: The thickness of aluminum affording the same attenuation of the x-ray beam as the material in question under specified conditions. Ambient dose equivalent area product (ADAP): The product of the ambient dose equivalent, H*(10), and the scan area at a de

16、fined distance (used only for partial-body scanners). Ambient dose equivalent, H*(d): The dose equivalent at a point in a radiation field produced by the corresponding expanded and aligned field in the ICRU sphere (ICRU ANSI/HPS N43.17-2009 2 1998) at a depth d on the radius opposing the direction o

17、f the aligned field. Dose equivalent is the product of the absorbed dose D at a point in tissue (i.e., the mean energy imparted per unit mass) and the quality factor Q at that point. The unit of dose equivalent, H, and of ambient dose equivalent, H*(d), is the joule per kilogram (J kg1), with the sp

18、ecial name sievert (Sv, 1 Sv = 100 rem). Backscatter system: A security screening system that makes use of radiation scattered or deflected from an object or person to form an image of the scattering object or person. Beam exit surface: The surface of the outer system assembly from which the direct

19、x-ray or gamma ray beam emanates. This may be a flat surface or the outer surface of a port or collimator. The subject being scanned is exposed through this surface. Systems with more than one radiation source may have more than one beam exit surface. Beam stop: A radiation shield meant to intercept

20、 the direct beam of radiation. Bystander: Any person other than the individual being screened who is not directly associated with operation of the system. Effective dose: A summation of the equivalent doses in tissues or organs each multiplied by the appropriate tissue weighting factor as defined by

21、 the International Commission on Radiation Units and Measurements (ICRU 1998). The tissue weighting factors were modified by the International Commission on Radiological Protection in its Publication 103 (ICRP 2007). The unit of effective dose is joule per kilogram, and its special name is sievert (

22、Sv, 1 Sv = 100 rem). Engineering control: A safety component of the system design that prevents improper operation or unintended radiation exposure. Examples of engineering controls include one-way turnstiles, interlocked motion sensors, etc. Equivalent dose: The absorbed dose in an organ or tissue

23、multiplied by the appropriate radiation weighting factor. The unit of equivalent dose is joule per kilogram, and its special name is sievert (Sv, 1 Sv = 100 rem). See ICRU (1998). External surface: The outside surface of the enclosure containing all associated ionizing radiation sources. Facility: S

24、ee Operating facility. General-use system: A personnel screening system that delivers a reference effective dose equal to or less than 0.25 Sv (25 rem) per screening as defined in this standard. Given proper justification and certain restrictions, general-use systems may be operated without specific

25、 controls that would limit the number of individuals scanned or the number of scans per individual in a year. Ground fault: An accidental electrical grounding of an electrical conductor. Half-value layer (HVL): The thickness of specified material that attenuates the radiation beam such that the air-

26、kerma (or exposure) rate is reduced to one-half of its original value. The HVL is determined in such a way that scattered radiation, other than that initially present in the beam, is excluded (i.e., in narrow-beam geometry). High radiation area: An area, accessible to individuals, in which radiation

27、 levels could result in an individuals receiving a dose equivalent in excess of 1 mSv (100 mrem) in 1 hour at 30 cm from a beam exit surface. The ambient dose equivalent at 10 mm, H*(10), shall be used for determining the potential dose to individuals. Inspection zone: The general area established b

28、y the operating institution for the purpose of limiting or controlling access to the area where the screening will be performed. This includes but is not limited to any ingress, egress, gate, portal, traffic path, and areas, access to which is restricted due to the presence of radiation. The ambient

29、 dose equivalent, H*(10), outside of the inspection zone shall not exceed 20 Sv (2 mrem) in any 1 hour. Institution: See Operating institution. ANSI/HPS N43.17-2009 3 Limited-use system: A personnel screening system that is capable of delivering a reference effective dose greater than 0.25 Sv (25 re

30、m) per screening but shall not exceed a reference effective dose of 10 Sv (1 mrem) per screening as defined in this standard. Limited-use systems require additional controls and documentation to ensure that annual individual dose limits are not exceeded. Mode of operation: A selectable set of techni

31、que factors or machine settings that is pre-determined by the manufacturer for a specific purpose. Multiple source system: A system utilizing more than one source of radiation. NID: Negligible Individual Dose. An annual effective dose lower than or equal to 0.01 mSv (1 mrem). Occupancy factor: The f

32、raction of time relative to 2,000 hours per year (full occupancy) that a maximally exposed individual is expected to remain in a given area. Operating facility (also facility): A location of use where one or more screening systems may be installed. Operating institution (also institution, user, end

33、user): A government or private organization that controls the deployment of screening systems at one or more facilities. Operator: Any employee associated with the operation of the system whose responsibilities include at least one of the following: initiating or stopping the scan, verifying the sys

34、tem is operating correctly, providing information and instructions to the screened individuals, and controlling access to the inspection zone. This does not include other employees, such as individuals who may be remotely viewing the image results but are not directly responsible for the other funct

35、ions. Personnel security screening system: A system designed for the detection of contraband and weapons concealed on a person or in a vehicle while being occupied by one or more people (in the body of this standard also referred to as “screening system” or “system”). Primary beam: The beam of radia

36、tion emanating from the system intended to reach the target being scanned. This excludes scattered radiation and radiation transmitted through shielding. Portal system: A system designed to image persons who move through the inspection zone under their own control, by a moving walkway, or within a v

37、ehicle. It does not include systems that move the individual through the inspection zone in a controlled manner, such as a moving platform on which the subject is normally required to remain still (see Stationary-subject system). Qualified service provider: As it pertains to radiation surveys, a per

38、son having the knowledgeas demonstrated by documen-ted training and experienceto properly measure ionizing radiation and analyze the results relative to the requirements of this standard. As it pertains to radioisotope maintenance, a person having the necessary training and experience to safely main

39、tain and repair the system and who is registered or licensed according to regulatory requirements at the location where the service is being performed. Radiation area: An area, accessible to individuals, in which radiation levels could result in an individuals receiving a dose equivalent in excess o

40、f 0.05 mSv (5 mrem) in 1 hour at 30 cm from a beam exit surface. The ambient dose equivalent at 10 mm, H*(10), shall be used for determining the potential dose to individuals. Reference effective dose, EREF: A quantity based on measurable parameters used by this standard for setting dose limits. It

41、is derived from the effective dose to the average adult as defined in ICRU Report 57 (ICRU 1998) and as modified by ICRP Publication 103 (ICRP 2007). It is obtained from air kerma (or exposure) and HVL measurements as described in Section 6.1.3 of this standard, “Determination of the Reference Effec

42、tive Dose.” ANSI/HPS N43.17-2009 4 Safety interlock: A device that is intended to automatically prevent or interrupt the radiation hazard whenever safety is compromised by access to the interior of the system, unauthorized access to a radiation area, or by an operational malfunction. Scan: The opera

43、tion necessary to produce one image (e.g., front view) from one radiation source. One radiation source simultaneously producing multiple images also constitutes one scan. Two sources simultaneously producing two images constitute two scans. In some cases several scans may be required for a single sc

44、reening of the subject. Scan area: The total area on the reference plane that is covered by the primary beam as it scans. The reference plane is the plane containing the reference measuring point and is perpendicular to the beam direction at the reference point (used only for partial-body scanners).

45、 Screening: The sum of radiation exposures or scans necessary to image objects concealed on all sides of the body as intended by the system design under normal conditions. Examples: 1) for backscatter systems a screening typically consists of four scans, one from each side; 2) for transmission syste

46、ms a screening typically consists of one scan; 3) for portal systems a screening consists of a complete pass through the inspection zone. Shall: The word “shall” is used to indicate a requirement. Should: The word “should” is used to indicate a provision that is not required but is recommended as go

47、od practice. Shutter: A means of turning a radiation beam on and off by blocking the beam with a suitable thickness of shielding material. This may be accomplished by moving the shield in front of the radiation source or by moving the radiation source behind the shield. Sievert (abbreviated Sv): The

48、 unit of equivalent dose, ambient dose equivalent, and effective dose. One sievert represents one joule of photon energy absorbed in each kilogram of irradiated tissue. Stationary-subject system: A system designed to image a person who remains stationary while a scan is occurring. This includes syst

49、ems that move the individual through the inspection zone in a controlled manner, such as a moving platform on which the subject is normally required to remain still. Structure: Any physical enclosure containing humans that might be inspected. Includes but is not limited to vehicles, cargo containers, walls, wheelchairs, buildings, etc. Technique factors: The x-ray settings, including 1) the peak kilovoltage applied to the x-ray tube, 2) the electric current passing through the x-ray tube, and 3) the scan time. Transmission system: A security screening