Airport Passenger Screening Using Backscatter X-Ray Machines Compliance with Standards (2015) / Chapter Skim
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1 Introduction
1 Introduction
Pages 9-26
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TSA started deploying AITs in 2008 for use as a secondary2 screening of airport 1 Government Accountability Office, Transportation Security Administration: Progress and Chal lenges Faced in Strengthening Three Key Security Programs, Statement of Stephen M Lord, Director, Homeland Security and Justice Issues, Testimony Before the Committee on Oversight and Government Reform and Committee on Transportation and Infrastructure, House of Representatives, released March 26, 2012, http://oversight.house.gov/wp-content/uploads/2012/03/3-26-12-Joint-TI-LordTestimony.pdf.
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Although the amount of energy is quite small, the patterns of ionization create localized damage that can cause malfunctions in inanimate objects such as microelectronics or injury to biological systems. For purposes of radiation protection in humans, the exposure to ionizing radiation is mea sured in terms of effective dose termed a sievert (Sv)
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SOURCE: Data from National Council on Radiation Protection and Measurements, NCRP Report No. 160: Ion izing Radiation Exposure of the Population of the United States, Bethesda, Md., 2009.
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For example, TSA decided neither to save nor transport the images acquired from screening, and it eventually isolated the operator viewing the images from the individuals being screened. In 2011, in response to ongoing privacy concerns, TSA piloted a program for manufacturers to develop automatic target recognition (ATR)
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(b) FIGURE 1.1 Advanced imaging technologies deployed by TSA: (a)
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X-ray backscatter AIT (b) millimeter wave AIT.
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(b) FIGURE 1.3 Images from a millimeter wave AIT equipped with automatic target recognition.
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SAFETY CONCERNS RELATED TO X-RAY BACKSCATTER AIT Although it was privacy concerns and lack of ATR that led to the removal of the Rapiscan X-ray backscatter AITs from the airports, another concern relates to their safety. X-ray backscatter systems emit ionizing radiation.
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Frequent flyers and airline and airport staff whose cumulative dose, and therefore risk, increases because they are screened more frequently compared to the general population. At the societal level, the concern about risks from exposure17 to the X-ray backscatter AIT systems is as follows: Even though the dose to an individual from screening with the X-ray backscatter AITs may be small, and therefore the risk of developing cancer for that particular individual is also small, the collective dose18 to the more than 815 million passengers traveling annually within the United States19 and likely to be screened with this technology may be high.
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24 Johns Hopkins University Applied Physics Laboratory, Radiation Safety Engineering Assessment Report for the Rapiscan Secure 1000 in Single Pose Configuration, NSTD-09-1085, Version 2, Laurel, Md., August 2010.
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The five investigations mentioned above showed that a single screening with the Rapiscan Secure 1000 SP (single pose) 29 unit is associated with an effective dose to a person being screened, roughly in the range of one-twenty-fifth to one-eighth of the standard limit (11 to 33 nSv)
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:1112-1115. 34 See, for example, Cerra, Assessment of the Rapiscan Secure 1000 Body Scanner for Conformance with Radiological Safety Standards, 2006; JHU/APL, Radiation Safety Engineering Assessment Report for the Rapiscan Secure 1000 in Single Pose Configuration, 2009.
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For these cases, each AIT software design includes a "maintenance mode" or "engineer ing mode" that is restricted to trained and certified maintenance personnel. THE STUDY REQUEST Congress introduced legislation calling for an independent investigation of the safety of the X-ray backscatter AIT systems.40 In response to this call, in No vember 2011, TSA made a commitment at the Senate Homeland Security and Governmental Affairs Committee hearing that it would conduct an independent 36 In their April 6, 2010, letter, Sedat et al.
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Specifically, it was not to address the following: 1. The issue of justification of the use of X-ray backscatter AIT systems when an alternative technology that does not use ionizing radiation exists, or 2.
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As part of the NRC independent evaluation, DHS requested that the NRC subcontract with an appropriate testing organization or qualified consultants to conduct field studies to measure the radiation emitted by the AIT systems as they are used. According to the DHS-NRC agreement, the work of the subcontractors would be overseen by the NRC.
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Instead, they had access to two AIT systems: 1. A Rapiscan Secure 1000 unit located at NIST, Gaithersburg, Maryland, that was previously deployed at LaGuardia Airport.
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• Chapter 4 describes dosimetric considerations for measurements of ionizing radiation emitted by the X-ray backscatter AITs. • Chapter 5 provides an overview of the pertinent radiation standards.
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For the analysis of the previous studies in Chapter 6, the committee focused on the methodologies used to measure radiation emitted by the AIT systems as well as on the results reported. For the reports or papers in which assessments of the effective dose are based on estimates of AIT system characteristics rather than measurements, the committee provides a summary at the end of Chapter 6.
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