Correspondence COMMENT ON GEANT4 CALIBRATION OF GAMMA SPECTROMETRY EFFICIENCY FOR MEASUREMENTS OF AIRBORNE RADIOACTIVITY ON FILTER PAPER Dear Editors: ALREFAE’S ARTICLE, “GEANT4 Calibration of Gamma Spectrometry Efficiency for Measurements of Airborne Radioactivity on Filter Paper” (Alrefae 2014), includes an Appendix with a very helpful discussion and derivation of a method for generating points randomly distributed on the surface of a disk with radius rdisk. There is a mistake, however, between eqn (A5) and eqn (A6). The expression for probability density p as a function of polar coordinate r should be p(r) =2r/r2disk. This is the only error; subsequent equations (eqns A6–A8) are correct as stated, as are the formulae for the pgenerating ffiffiffiffiffiffiffi points (ri,φi) in polar coordinates: ri = rdisk δ 1;i (eqn A8; Alrefae 2014) and φi = 2πδ2,i (eqn A3; Alrefae 2014), where the δ’s are random numbers between 0 and 1. The author declares no conflicts of interest. JIM BOGARD Senior Health Physicist/Radiation Safety Officer Dade Moeller & Associates 704 S. Illinois Ave. Oak Ridge TN 37830 REFERENCE Alrefae T. GEANT4 calibration of gamma spectrometry efficiency for measurements of airborne radioactivity on filter paper. Health Phys 107:435–441; 2014.
RESPONSE TO COMMENT ON GEANT4 CALIBRATION OF GAMMA SPECTROMETRY EFFICIENCY FOR MEASUREMENTS OF AIRBORNE RADIOACTIVITY ON FILTER PAPER Dear Editors: MANY THANKS to Jim Bogard for carefully reading the article “GEANT4 Calibration of Gamma Spectrometry Efficiency for Measurements of Airborne Radioactivity on Filter Paper” (Alrefae 2014). The reader pointed out a typographical 0017-9078/15/0 Copyright © 2015 Health Physics Society DOI: 10.1097/HP.0000000000000264
error in one of the equations of the article’s Appendix and confirmed the validity of all the other equations in the Appendix. Apologies to the readers, for this error went unnoticed despite rounds of revisions. Although such typographical errors seldom have any effect on the results and findings, it is important for authors to present and for readers to receive accurate information. The author declares no conflict of interests. TAREQ ALREFAE Kuwait University Khaldia, Kuwait
REFERENCE Alrefae T. GEANT4 calibration of gamma spectrometry efficiency for measurements of airborne radioactivity on filter paper. Health Phys 107(5):435–441; 2014.
AIRCRAFT CREWMEMBER DOSES SHOULD BE MEASURED Dear Editors: FRASCH ET AL. (2014) analyzes German aircraft crewmember (ACM) radiation doses from exposure to galactic cosmic radiation (GCR) in 2004–2009. They say the dose trend was up due to increasing airline business and decreasing solar cycle (SC) 23 activity, 2009 doses were upper limits as SC 23 activity reached a minimum then, and GCR anticorrelates with that activity. However, GCR is not the only source of radiation in flight. ACM can also receive dose from solar proton events (SPE), solar neutron events (SNE), solar gamma ray events (SGE), terrestrial gamma-ray flashes (TGF) thundercloud gamma rays (TGR), radioactive cargo, and medical exams required for airline work. Frasch et al. (2014) ignores the sources listed above except for SPE, which they dismiss believing SPE add little dose, seldom occur, and were not observed in 2008–2011 by two aircraft flying with dose rate gauges. With regard to SPE, Beck et al. (2009) review literature on in-flight dose measurements during solar storms and say it is possible for ACM to get 3 mSv during a single major SPE. In the U.S., the Space Weather Prediction Center (SWPC) tracks sun activity by near-Earth satellites that have proton detectors aimed at the sun for continuous counting (NOAA 2013). SWPC reported 16 and 8 SPE in 2004–2009 and 2008– 2011, respectively. In 1999–2003 when SC 23 was active, it reported 68 SPE plus the Halloween Space Weather 557
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Copyright © 2015 Health Physics Society. Unauthorized reproduction of this article is prohibited.
558
Health Physics
Storms of 2003 that damaged spacecraft, degraded communications, and caused power outages (NOAA 2004). SWPC reports rise time to peak proton flux, and rise time averaged 13.5 h for the 55 SPE with times >1 h. Decay time is typically longer than rise time. Thus, ACM might have received dose from SPE on average during one day of every month in 1999–2003. The German approach to ACM radiation safety is admirable and markedly superior to that of the U.S., which recognizes its ACM as radiation workers but does not require dosimetry. The approach follows from a European Union (EU) Directive that member nations establish protection against substantially increased exposures to natural radiation. The German agency responsible for air safety implemented the EU Directive by requiring its airlines to report ACM doses, and a separate agency maintains dose records in a Registry. The Registry ACM doses are done by computer program calculations for GCR alone. Frasch et al. (2014) analyzed Registry data for 2004–2009 considering the inflight measurements made in 2008–2011. It says 95% of measurements made over 18,345 h were within ±30% of calculation. So, if the average flight was 8 h, 115 flights had doses outside the 30% limit. A plausible explanation for actual doses larger than expected is sources of exposure other than GCR. In the U.S., radiation workers (other than ACM) are required to have performance-tested dosimetry (ANSI/HPS 2009). The requirements would not be met if dose were by a computer program that did not account for all sources of exposure. Bramlitt and Shonka (2015) discuss SPE, SNE, SGE, and TGF as natural sources that expose ACM. During SC 23, SPE detections by near-Earth satellite were 5.7 times greater than on Earth by neutron monitors. SNE and SGE radiations have been measured on Earth at the GeV level, but intensity is greatest at flight levels and subsolar points (0°± 23.5° latitude). TGF are pulses by thunderstorms and lightning. Satellites detect TGF gamma rays, and Dwyer et al. (2010) reports TGF dose to ACM and passengers could reach 100 mSv in 1 ms. Tierney et al. (2013) uses Fermi satellite data for a global annual frequency of 1,200 ± 100 TGF per day. TGR last longer than TGF and are detected from mountain locations. Tsuchiya et al. (2012) saw TGR >40 MeV for ~40 min. Frasch et al. (2014) concludes ACM make up a nonhomogeneous population for GCR dose due to professional and social status linked with age and gender. A subgroup of ACM with the highest GCR dose is employed by business aviation airlines. Frequent flyers are a subgroup whose dose is not assessed, yet visitors who enter radiation areas at nuclear facilities on the ground are normally monitored. Ionizing radiation at flight levels is nonhomogeneous in time and place. ACM on polar routes may get dose from
May 2015, Volume 108, Number 5
SPE, while those on equatorial routes in daylight may get it from SNE and SGE. ACM may get dose from TGF by merely flying over thunderstorms and from TGR by flying in or near thunderclouds. Lufthansa ACM may get dose from SNE, SGE, TGF, and TGR on its flights south of the equator to 10 African nations, including one with the most lightning on Earth. ACM doses in the Registry are good estimates for the GCR source, as GCR has been extensively studied and is relatively well understood. But a European Commission evaluation of programs for GCR dose indicates more is needed if sudden changes in local dose rates become known (Bottollier-Depois et al. 2012). SPE, SNE, SGE, TGF, TGR, and TNF are sudden events that warrant consideration. ACM dose calculations are incomplete without consideration of natural radiations from the sun and from Earth, as well as radioactive cargo and required medical exams involving radiation. True doses are needed for ACM protection, especially as TGF alone may cause doses over limits. The need can be met by active dose measurements. Frasch et al. (2014) with Bramlitt and Shonka (2015) provide a sound rationale for all nations with major airlines to require valid ACM dosimetry. The authors declare no conflicts of interest. EDWARD T. BRAMLITT 8813 Camino Osito NE Albuquerque, NM 87111 [email protected]
JOSEPH J. SHONKA 119 Ridgemore Circle Toccoa, GA 30577 [email protected]
REFERENCES American National Standards Institute/Health Physics Society. American national standard for dosimetry: personnel dosimetry performance and criteria for testing. McClean VA: Health Physics Society; ANSI N13.11; 2009. Beck P, Dyer C, Fuller N, Hands A, Latocha M, Rollet S, Spurny F. Overview of on-board measurements during solar storm periods. Radiat Protect Dosim 136:297–303; 2009. DOI: 10.1093/rpd/ncp208. Bramlitt ET, Shonka JJ. Radiation exposure of aviation crewmembers and cancer. Health Phys 108:76–86; 2015. Bottollier-Depois JF, Beck P, Latocha M, Mares V, Matthia D, Rühm W, Wissmann F. Comparison of codes assessing radiation exposure of aircraft crew due to galactic cosmic radiation. Luxembourg: Publication's Office of the European Union; European Commission Report RP 173; 2012. DOI: 10.2768/22100. Dwyer JR, Smith DM, Uman MA, Saleh Z, Grefenstette B, Hazelton B, Rassoul HK. Estimation of the fluence of high energy electron bursts produced by thunderclouds and the resulting radiation dose received in aircraft. Geophys Res Atmosphere 112:206–216; 2010. DOI:10.1029/2009JD0I2039.
www.health-physics.com
Copyright © 2015 Health Physics Society. Unauthorized reproduction of this article is prohibited.
Correspondence
Frasch G, Kammerer L, Karofsky R, Schlosser A, Stegemann R. Radiation exposure of German aircraft crews under the impact of solar cycle 23 and airline business factors. Health Phys 107: 542–553; 2014. DOI:10.1097/HP.0000000000000150. NOAA. Halloween space weather storms of 2003. NOAA technical memorandum OAR SEC‐88; Boulder, CO: Space Environment Center; 2004. NOAA. Solar proton events affecting the earth’s environment. Boulder, CO: Space Weather Prediction Center; 2013. Available at http://swpc.noaa.gov/ftpdir/indices/SPE.txt. Accessed 17 December 2013. Tierney D, Briggs MS, Fitzpatrick G, Chaplin VL, Foley S, McBreen S, Connaughton V, Xiong S, Byrne D, Carr M, Bhat PN, Fishman GJ, Greiner J, Kippen RM, Meegan CA, Paciesas WS, Preece RD, von Kienlin A, Wilson-Hodge C. Fluence distribution of terrestrial gamma-ray flashes observed by the Fermi gamma-ray burst monitor. Geophys Res Space Phys 118:6644–6650; 2013. DOI:10.1002/jgra.50580. Tsuchiya H, Hibino K, Kawata K, Hotta N, Tateyama N, Ohnishi M, Takita M, Chen D, Huang J, Miyasaka M, Kondo I, Takahashi E, Shimoda S, Yamada Y, Lu H, Zhang JL, Yu XX, Tan YH, Nie SM, Munakata K, Enoto T, Makishima K. Observation of thundercloud-related gamma rays and neutrons in Tibet. Menlo Park, CA: SLAC National Accelerator Laboratory; arXiv 1204.2578, KIPAC, SLAC PUB‐153; 2012.
RESPONSE TO BRAMLITT AND SHONKA Dear Editors: BRAMLITT AND Shonka responded to our paper “Radiation Exposure of German Aircraft Crews under the Impact of Solar Cycle 23 and Airline Business,” recommending that aircraft crewmember (ACM) doses should be measured. We appreciate their critical acclaim and comments. We would like to clarify some criticized aspects and shed light on the practical problems of implementing official dose measurement of aircrews. Route doses that aircraft crews receive are composed of a systematic dose component that occurs inevitably on every flight from high altitude radiation and of components that contribute only stochastically to route doses; e.g., solar particle events in solar storms or terrestrial gamma flashes in tropical thunderstorms. The systematic component is the major contributor to the accumulated annual dose of ACM and can be calculated with sufficient accuracy for the purpose of official occupational dose monitoring. Exposures from the stochastic components require elaborate inflight measurements. Because of their small probability of occurrence and the route mix of the aircrew personnel, they contribute far less to the annual occupational dose compared to the systematic component. We concede that, in rare cases of solar storms, significant additional doses cannot be excluded. However, constant in-flight measurements in two Airbus 340s from 2008–2011 did not give any hint of enhanced route doses caused by solar particle events or terrestrial gamma flashes. The official German dose monitoring of occupational exposure from cosmic radiation is based on German
559
law and transposes the European Council Directive 96/29 EURATOM. It has to focus explicitly on the systematic component of cosmic radiation as the dominant contributor to the annual dose of aircrew personnel. It also has to exclude, per definition, potential exposures from any other civilian or natural radiation sources such as medical x ray, radioactive cargo or terrestrial gamma flashes. Bramlitt and Shonka quoted a possible dose of 3 mSv during a single major solar particle event. This refers to a supersonic flight via pole route (Beck et. al. 2009). As German airlines do not operate supersonic aircraft, this scenario is irrelevant for Germany. We agree that dose measurements can provide for more confidence in occupational dose monitoring than dose calculations under the precondition that adequate measurement and dosimetry are performed. From the perspective of official radiation protection, we support the idea of a graded approach by measuring route doses, but only in long-range aircrafts. One reason is to register stochastically-occurring doses from solar particle events or terrestrial gamma flashes, not so much because we expect substantial dose contributions but to preserve evidence. The other and, from our perspective, stronger reason lies in the application of the optimization principle in radiation protection: Measured ambient equivalent dose rates can give immediate feedback to pilots and could allow them to optimize a route dose during the flight (e.g., by abstaining from the last step climb, etc.). However, this requires the use of radiation detection systems on board that cover the energy spectra of all relevant particles, calculate valid dose rates and route doses from the measurements, and provide the results instantly visible within the set of instruments enabling the pilots to act. To call for in-flight dose measurements is one thing; to put this into the praxis of official dose monitoring is another (not trivial) task. Any attempts to convince airlines to implement cost-intensive dose rate instruments in their aircraft on a voluntary basis and to develop flight operational procedures for pilots in order to react on measured dose rates will be in vain as they increase costs. The airline business is under strong pressure financially from international competition. It was very difficult to implement official aircrew monitoring on the basis of route dose calculation programs in European Union Member States. Meanwhile, some European countries monitor aircraft crews fairly well for 10 to 15 y, while other highly industrialized nations have not even begun. Thus, official in-flight dose measuring can only be implemented on a legal basis with international consensus, and it will be a stony way. On the other hand, the history of radiation protection teaches us that all occupational dose monitoring started small and emerged more or less rapidly. This applies for the dosimetry technique as well as for the monitored groups
www.health-physics.com
Copyright © 2015 Health Physics Society. Unauthorized reproduction of this article is prohibited.
RESPONSE TO COMMENT ON GEANT4 CALIBRATION OF GAMMA SPECTROMETRY EFFICIENCY FOR MEASUREMENTS OF AIRBORNE RADIOACTIVITY ON FILTER PAPER Dear Editors: MANY THANKS to Jim Bogard for carefully reading the article “GEANT4 Calibration of Gamma Spectrometry Efficiency for Measurements of Airborne Radioactivity on Filter Paper” (Alrefae 2014). The reader pointed out a typographical 0017-9078/15/0 Copyright © 2015 Health Physics Society DOI: 10.1097/HP.0000000000000264
error in one of the equations of the article’s Appendix and confirmed the validity of all the other equations in the Appendix. Apologies to the readers, for this error went unnoticed despite rounds of revisions. Although such typographical errors seldom have any effect on the results and findings, it is important for authors to present and for readers to receive accurate information. The author declares no conflict of interests. TAREQ ALREFAE Kuwait University Khaldia, Kuwait
REFERENCE Alrefae T. GEANT4 calibration of gamma spectrometry efficiency for measurements of airborne radioactivity on filter paper. Health Phys 107(5):435–441; 2014.
AIRCRAFT CREWMEMBER DOSES SHOULD BE MEASURED Dear Editors: FRASCH ET AL. (2014) analyzes German aircraft crewmember (ACM) radiation doses from exposure to galactic cosmic radiation (GCR) in 2004–2009. They say the dose trend was up due to increasing airline business and decreasing solar cycle (SC) 23 activity, 2009 doses were upper limits as SC 23 activity reached a minimum then, and GCR anticorrelates with that activity. However, GCR is not the only source of radiation in flight. ACM can also receive dose from solar proton events (SPE), solar neutron events (SNE), solar gamma ray events (SGE), terrestrial gamma-ray flashes (TGF) thundercloud gamma rays (TGR), radioactive cargo, and medical exams required for airline work. Frasch et al. (2014) ignores the sources listed above except for SPE, which they dismiss believing SPE add little dose, seldom occur, and were not observed in 2008–2011 by two aircraft flying with dose rate gauges. With regard to SPE, Beck et al. (2009) review literature on in-flight dose measurements during solar storms and say it is possible for ACM to get 3 mSv during a single major SPE. In the U.S., the Space Weather Prediction Center (SWPC) tracks sun activity by near-Earth satellites that have proton detectors aimed at the sun for continuous counting (NOAA 2013). SWPC reported 16 and 8 SPE in 2004–2009 and 2008– 2011, respectively. In 1999–2003 when SC 23 was active, it reported 68 SPE plus the Halloween Space Weather 557
www.health-physics.com
Copyright © 2015 Health Physics Society. Unauthorized reproduction of this article is prohibited.
558
Health Physics
Storms of 2003 that damaged spacecraft, degraded communications, and caused power outages (NOAA 2004). SWPC reports rise time to peak proton flux, and rise time averaged 13.5 h for the 55 SPE with times >1 h. Decay time is typically longer than rise time. Thus, ACM might have received dose from SPE on average during one day of every month in 1999–2003. The German approach to ACM radiation safety is admirable and markedly superior to that of the U.S., which recognizes its ACM as radiation workers but does not require dosimetry. The approach follows from a European Union (EU) Directive that member nations establish protection against substantially increased exposures to natural radiation. The German agency responsible for air safety implemented the EU Directive by requiring its airlines to report ACM doses, and a separate agency maintains dose records in a Registry. The Registry ACM doses are done by computer program calculations for GCR alone. Frasch et al. (2014) analyzed Registry data for 2004–2009 considering the inflight measurements made in 2008–2011. It says 95% of measurements made over 18,345 h were within ±30% of calculation. So, if the average flight was 8 h, 115 flights had doses outside the 30% limit. A plausible explanation for actual doses larger than expected is sources of exposure other than GCR. In the U.S., radiation workers (other than ACM) are required to have performance-tested dosimetry (ANSI/HPS 2009). The requirements would not be met if dose were by a computer program that did not account for all sources of exposure. Bramlitt and Shonka (2015) discuss SPE, SNE, SGE, and TGF as natural sources that expose ACM. During SC 23, SPE detections by near-Earth satellite were 5.7 times greater than on Earth by neutron monitors. SNE and SGE radiations have been measured on Earth at the GeV level, but intensity is greatest at flight levels and subsolar points (0°± 23.5° latitude). TGF are pulses by thunderstorms and lightning. Satellites detect TGF gamma rays, and Dwyer et al. (2010) reports TGF dose to ACM and passengers could reach 100 mSv in 1 ms. Tierney et al. (2013) uses Fermi satellite data for a global annual frequency of 1,200 ± 100 TGF per day. TGR last longer than TGF and are detected from mountain locations. Tsuchiya et al. (2012) saw TGR >40 MeV for ~40 min. Frasch et al. (2014) concludes ACM make up a nonhomogeneous population for GCR dose due to professional and social status linked with age and gender. A subgroup of ACM with the highest GCR dose is employed by business aviation airlines. Frequent flyers are a subgroup whose dose is not assessed, yet visitors who enter radiation areas at nuclear facilities on the ground are normally monitored. Ionizing radiation at flight levels is nonhomogeneous in time and place. ACM on polar routes may get dose from
May 2015, Volume 108, Number 5
SPE, while those on equatorial routes in daylight may get it from SNE and SGE. ACM may get dose from TGF by merely flying over thunderstorms and from TGR by flying in or near thunderclouds. Lufthansa ACM may get dose from SNE, SGE, TGF, and TGR on its flights south of the equator to 10 African nations, including one with the most lightning on Earth. ACM doses in the Registry are good estimates for the GCR source, as GCR has been extensively studied and is relatively well understood. But a European Commission evaluation of programs for GCR dose indicates more is needed if sudden changes in local dose rates become known (Bottollier-Depois et al. 2012). SPE, SNE, SGE, TGF, TGR, and TNF are sudden events that warrant consideration. ACM dose calculations are incomplete without consideration of natural radiations from the sun and from Earth, as well as radioactive cargo and required medical exams involving radiation. True doses are needed for ACM protection, especially as TGF alone may cause doses over limits. The need can be met by active dose measurements. Frasch et al. (2014) with Bramlitt and Shonka (2015) provide a sound rationale for all nations with major airlines to require valid ACM dosimetry. The authors declare no conflicts of interest. EDWARD T. BRAMLITT 8813 Camino Osito NE Albuquerque, NM 87111 [email protected]
JOSEPH J. SHONKA 119 Ridgemore Circle Toccoa, GA 30577 [email protected]
REFERENCES American National Standards Institute/Health Physics Society. American national standard for dosimetry: personnel dosimetry performance and criteria for testing. McClean VA: Health Physics Society; ANSI N13.11; 2009. Beck P, Dyer C, Fuller N, Hands A, Latocha M, Rollet S, Spurny F. Overview of on-board measurements during solar storm periods. Radiat Protect Dosim 136:297–303; 2009. DOI: 10.1093/rpd/ncp208. Bramlitt ET, Shonka JJ. Radiation exposure of aviation crewmembers and cancer. Health Phys 108:76–86; 2015. Bottollier-Depois JF, Beck P, Latocha M, Mares V, Matthia D, Rühm W, Wissmann F. Comparison of codes assessing radiation exposure of aircraft crew due to galactic cosmic radiation. Luxembourg: Publication's Office of the European Union; European Commission Report RP 173; 2012. DOI: 10.2768/22100. Dwyer JR, Smith DM, Uman MA, Saleh Z, Grefenstette B, Hazelton B, Rassoul HK. Estimation of the fluence of high energy electron bursts produced by thunderclouds and the resulting radiation dose received in aircraft. Geophys Res Atmosphere 112:206–216; 2010. DOI:10.1029/2009JD0I2039.
www.health-physics.com
Copyright © 2015 Health Physics Society. Unauthorized reproduction of this article is prohibited.
Correspondence
Frasch G, Kammerer L, Karofsky R, Schlosser A, Stegemann R. Radiation exposure of German aircraft crews under the impact of solar cycle 23 and airline business factors. Health Phys 107: 542–553; 2014. DOI:10.1097/HP.0000000000000150. NOAA. Halloween space weather storms of 2003. NOAA technical memorandum OAR SEC‐88; Boulder, CO: Space Environment Center; 2004. NOAA. Solar proton events affecting the earth’s environment. Boulder, CO: Space Weather Prediction Center; 2013. Available at http://swpc.noaa.gov/ftpdir/indices/SPE.txt. Accessed 17 December 2013. Tierney D, Briggs MS, Fitzpatrick G, Chaplin VL, Foley S, McBreen S, Connaughton V, Xiong S, Byrne D, Carr M, Bhat PN, Fishman GJ, Greiner J, Kippen RM, Meegan CA, Paciesas WS, Preece RD, von Kienlin A, Wilson-Hodge C. Fluence distribution of terrestrial gamma-ray flashes observed by the Fermi gamma-ray burst monitor. Geophys Res Space Phys 118:6644–6650; 2013. DOI:10.1002/jgra.50580. Tsuchiya H, Hibino K, Kawata K, Hotta N, Tateyama N, Ohnishi M, Takita M, Chen D, Huang J, Miyasaka M, Kondo I, Takahashi E, Shimoda S, Yamada Y, Lu H, Zhang JL, Yu XX, Tan YH, Nie SM, Munakata K, Enoto T, Makishima K. Observation of thundercloud-related gamma rays and neutrons in Tibet. Menlo Park, CA: SLAC National Accelerator Laboratory; arXiv 1204.2578, KIPAC, SLAC PUB‐153; 2012.
RESPONSE TO BRAMLITT AND SHONKA Dear Editors: BRAMLITT AND Shonka responded to our paper “Radiation Exposure of German Aircraft Crews under the Impact of Solar Cycle 23 and Airline Business,” recommending that aircraft crewmember (ACM) doses should be measured. We appreciate their critical acclaim and comments. We would like to clarify some criticized aspects and shed light on the practical problems of implementing official dose measurement of aircrews. Route doses that aircraft crews receive are composed of a systematic dose component that occurs inevitably on every flight from high altitude radiation and of components that contribute only stochastically to route doses; e.g., solar particle events in solar storms or terrestrial gamma flashes in tropical thunderstorms. The systematic component is the major contributor to the accumulated annual dose of ACM and can be calculated with sufficient accuracy for the purpose of official occupational dose monitoring. Exposures from the stochastic components require elaborate inflight measurements. Because of their small probability of occurrence and the route mix of the aircrew personnel, they contribute far less to the annual occupational dose compared to the systematic component. We concede that, in rare cases of solar storms, significant additional doses cannot be excluded. However, constant in-flight measurements in two Airbus 340s from 2008–2011 did not give any hint of enhanced route doses caused by solar particle events or terrestrial gamma flashes. The official German dose monitoring of occupational exposure from cosmic radiation is based on German
559
law and transposes the European Council Directive 96/29 EURATOM. It has to focus explicitly on the systematic component of cosmic radiation as the dominant contributor to the annual dose of aircrew personnel. It also has to exclude, per definition, potential exposures from any other civilian or natural radiation sources such as medical x ray, radioactive cargo or terrestrial gamma flashes. Bramlitt and Shonka quoted a possible dose of 3 mSv during a single major solar particle event. This refers to a supersonic flight via pole route (Beck et. al. 2009). As German airlines do not operate supersonic aircraft, this scenario is irrelevant for Germany. We agree that dose measurements can provide for more confidence in occupational dose monitoring than dose calculations under the precondition that adequate measurement and dosimetry are performed. From the perspective of official radiation protection, we support the idea of a graded approach by measuring route doses, but only in long-range aircrafts. One reason is to register stochastically-occurring doses from solar particle events or terrestrial gamma flashes, not so much because we expect substantial dose contributions but to preserve evidence. The other and, from our perspective, stronger reason lies in the application of the optimization principle in radiation protection: Measured ambient equivalent dose rates can give immediate feedback to pilots and could allow them to optimize a route dose during the flight (e.g., by abstaining from the last step climb, etc.). However, this requires the use of radiation detection systems on board that cover the energy spectra of all relevant particles, calculate valid dose rates and route doses from the measurements, and provide the results instantly visible within the set of instruments enabling the pilots to act. To call for in-flight dose measurements is one thing; to put this into the praxis of official dose monitoring is another (not trivial) task. Any attempts to convince airlines to implement cost-intensive dose rate instruments in their aircraft on a voluntary basis and to develop flight operational procedures for pilots in order to react on measured dose rates will be in vain as they increase costs. The airline business is under strong pressure financially from international competition. It was very difficult to implement official aircrew monitoring on the basis of route dose calculation programs in European Union Member States. Meanwhile, some European countries monitor aircraft crews fairly well for 10 to 15 y, while other highly industrialized nations have not even begun. Thus, official in-flight dose measuring can only be implemented on a legal basis with international consensus, and it will be a stony way. On the other hand, the history of radiation protection teaches us that all occupational dose monitoring started small and emerged more or less rapidly. This applies for the dosimetry technique as well as for the monitored groups
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Copyright © 2015 Health Physics Society. Unauthorized reproduction of this article is prohibited.
