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Aircraft Human Radiation Exposure Christopher J. Mertens NASA Langley Research Center Hampton, VA.

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Presentation on theme: "Aircraft Human Radiation Exposure Christopher J. Mertens NASA Langley Research Center Hampton, VA."— Presentation transcript:

1 Aircraft Human Radiation Exposure Christopher J. Mertens NASA Langley Research Center Hampton, VA.

2 Radiation Storms: Impact on Air Travel Radiation Exposure to Commercial Aircrew and Passengers – The ICRP classify commercial aircrew as occupational radiation workers – The NCRP reported that flight crews receive the largest annual effective dose among occupational radiation workers – Current guidelines for maximum public and prenatal exposure can be exceeded (1 mSv) on high-latitude commercial routes during a single solar radiation storm event or for frequent flyer exposure to high-latitude background levels (~ 10 flights/yr during solar minimum) Increased Number of Commercial Polar Routes – United Airlines flew 12 demo polar flights in 1999 – United Airlines flew 1832 polar flights in 2007

3 Radiation Storms: Impact on Air Travel Summary of DOC (NOAA/SWPC) Report [2004] – Typical cost savings from US-China cross-polar route ~ $35k-$45k per flight compared to previous non-polar route – However, rerouting polar flight can cost up to $100k per flight is fuel stops and layovers are necessary – FAA issued radiation advisory during Halloween 2003 storm and one major airline rerouted six polar flights, which included fuel stops. This cost the airline as much as $600k Other Reroutes – United rerouted 26 polar flights during January 2005 storm period and 5+ polar flights during the December 2006 storm period – Delta Airlines rerouted 8 polar flights during January 2012 storm period and 8+ polar flights during March 2012 storm period. The Emerging Commercial Space Transportation Industry and Space Tourism

4 Nowcast of Atmospheric Ionizing Radiation (NAIRAS) Model What Does NAIRAS Provide? – Real-time effective dose rates from physics-based models – GCR and SEP sources – 1x1 lat/lon geographic grid, km with 1 km vertical resolution, 1-hr time cadence – Geomagnetic influences from solar-wind / magnetosphere coupling – Various graphical displays of effective dose rates and representative high-latitude flight-accumulated effective dose.

5 NASA’s NAIRAS Model Predictions During March 2012 Solar Storm Events Public Web site: (or google NAIRAS)http://sol.spacenvironment.net/~nairas/

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7 ESWE Workshop: An Aviation Radiation Perspective What constitutes an extreme space weather event (Tuesday morning session)? – Any event that would require airlines to reroute flights in order to avoid ICRP public/prenatal exposure limits from being reached/exceeded – What are the radiation effects on microelectronic systems for commercial air/spaceflight? What recent space weather event(s) to include in “campaign” analysis (Tuesday afternoon session)? – January 20, 2005 SEP event: (1) “challenging” ion spectra, (2) high anisotropy – Neutron monitor site at Tibet (~ 14 GV) measured GLE of 2.4%, indicating sufficiently large number of ~ 14 GeV protons! – Peak incident SEP ion flux and subsequent atmospheric radiation dose occurred in southern hemisphere in first few hours of the event

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9 Backup Slides

10 Real-time Neutron Monitor Data (e.g., IZMIRAN and LOMNICKY) Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) Model HZETRN + Dosimetry Fit to Climax HP Badhwar+O’Neill GCR Model NOAA/GOES +NASA/ACE Data Spectral Fitting Magnetospheric Magnetic Field (e.g., T05) Effects on Cutoff Rigidity Cutoff Rigidity (IGRF) Atmospheric Density NCEP/GFS Atmospheric Dose and Dose Equivalent NASA/ACE Solar Wind and IMF Data

11 Carrington Event SEP Spectral Fluence [Smart et al., 2006; Townsend et al., 2006] – Five measured spectral shapes considered o August 1972 (soft) o September 1989 (hard) – Spectral shapes normalized to >30 MeV proton fluence determined by impulsive NOy deposition in polar ice cores [McCracken et al. 2001] – Lack of detectable increase in annual 10 Be deposition in polar ice favors a soft spectrum

12 Carrington Event Geomagnetic Storm [Li et al., 2006] – H-component depression measured in India and taken as Dst – Solar wind shock velocity: determined from time between flare and magnetic disturbance – Temerin and Li [2002] Dst model fits measured H- component depression o Interplanetary Ey = VxBz determine maximum Dst depression o Large solar wind density (to calculate dynamic pressure) needed to reproduce rapid recovery

13 Carrington 1859

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18 Aircraft Radiation Exposure Medical Research Cosmic rays can directly break DNA strands in biological tissue, or produce chemically active radicals in tissue that alter the cell function [Wilson et al., 2005, 2003] – Both can lead to cancer Other adverse health effects include, but are not limited to, reproductive disorder and prenatal injury [Lauria et al., 2006; Waters et al., 2000; Aspholm et al., 1999] Because aircrew total career dose is received is low doses per flight, and accumulated slowly over the length of a flying career, the direct evidence that a person can develop cancer as a result of cosmic radiation is inconclusive – Other lifestyle risk factors exist over a flying career However, radiation protection community accepts the Linear No Threshold (LNT) theory – Every radiation exposure will have an effect on human health

19 NIOSH Exposure Assessment of US Commercial Pilots Poster 6/10 Soc Epi Res; manuscript in review FIRST STUDY OF US commercial pilot career exposure profile from individual flight segments: Cosmic radiation Solar energetic particle events Chronic circadian disruption FINDINGS A median pilot incurred 34.4 mSv GCR and flew through 6 SEPs in 28 y flying 1.92 mSv in the last study year Exposure metrics increased markedly IMPLICATIONS No dose limits for US crew Median pilot would trigger EU radiation monitoring (>1mSv/y) A pregnant female pilot could exceed ICRP guidelines for pregnant radiation workers High-exposed pilots at increased risk Image courtesy of Kanzelhöhe Observatory

20 Aircraft Radiation Exposure Recommendations and Actions Europe – EU Directive 96/29/EURATOM (1996) – Legal regulations on radiation protection of aircrew implemented into national law with EU member states by 2000 – Exposures must be assessed if 1 mSv/yr is likely to be exceeded – 6 mSv/yr “action level” (ALARA principle) o Individual record keeping and medical surveillance required – Monitoring recommended under 6 mSv/yr – German implementation o Operational GCR radiation exposure assessment using approved code o No approved operational SEP radiation exposure assessment o Some airlines interested in concomitant radiation measurements Japan – State regulations recommend airlines try to keep aircrew exposure below 5 mSv/yr, which is the exposure dose limit for other occupationally exposed workers in Japan

21 Aircraft Radiation Exposure Recommendations and Actions USA – ICRP recommendations (< 20 mSv/yr, < 1 mSv during pregnancy) – Pregnant crewmember no more than 0.5 mSv in any month (FAA recommendation) Current development of SpWx/aircraft radiation requirements ICAOWMO SpWx User Requirements CPWG SpWx User Needs FAA SpWx AWG User Needs FAA NOAA/ SWPC Radiation assessment Radiation measurements/predictions ICAO: International Civil Aviation Organization

22 SEP Aircraft Radiation Exposure High-Latitude Flights Roughly three SEP events per solar cycle with sufficient flux and energy to significantly increase atmospheric radiation above GCR February 1956 Event (Wilson et al., 1995) – Commercial: ~ 5 mSv October 1989 Event (AMS & SolarMetrics, 2007) – Commercial: ~ 2 mSv Halloween 2003 Event (Mertens et al., 2010) – Commercial (11 km, 10-hr): ~ 0.2 mSv – Executive (15 km, 10-hr): ~ 0.4 mSv January 2005 Event (NAIRAS; Copeland et al., 2008) – Commercial (11 km, 10-hr): ~ 1 mSv – Executive (15 km, 10-hr): ~ 4 mSv


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