hoses

calculated by the Langley code (Wilson et al. 1970) and Armstrong et al. (1969) at Oak Ridge National Laboratory
using the High Energy Transport Code (HETC). The results in the figure use the maximum surface dose equivalent
conversion factors for a 30-cm tissue slab geometry. Dose equivalent averaged over the 30-cm slab is
approximately a factor of 2-3 lower for solar particle events (Foelsche et al. 1974). It was clear from these results
that exposures to crew and passengers on high-latitude routes of the SST flying at 58 g/cm would be unacceptable
unless descent to subsonic altitudes was possible to minimize exposures during such a large event. The importance
of such events is limited to the Polar Regions.

The main concem of these early studies 108
was the potential prenatal injury in high-altitude i
flight especially during such a possible large ibs
solar event since crew and passengers included a3 165]
women of childbearing age. It is seen in Fig.3 32 a
that flights from the US northeast to Europe fly $e
along the edge of the polar region and are # aot

subject to solar particle event exposures {Wilson
et al. 1995). An advisory committee to the
Federal Aviation Administration (FAA 1975)
recommended that a satellite early-
warning/monitoring system be established,
active onboard monitoring devices be included
in the aircraft design, and that operational
procedures be developed to insure that
exposures on a given flight be limited to 5 mSv.

B 3%

‘monitor inorement,
(on ground), percent
a %

Oo 8 6 2M 8 16 BO
‘UT, br

16

Although many ground level events occur, only
a few have been of such intensity as to be of
concern to near term high-altitude air traffic.
The second largest ground level event observed

8 [is of & 16 24 8 16
1 A2o13, 1 "eb, 23, 1956-9

Fig. 6 . Energetic solar events measured on the ground and
at SST altitude.

30-31, 1969

over the last 60 years is the event on September

29, 1989. This event was similar to the February 23, 1956 event in its time course and spectral content but of an
order of magnitude lower intensity (on the order of 1 mSv/hr) and of less concern to supersonic operations. Since
the February 23, 1956 event is the only outstanding event, it leaves a heavy operational overhead requirement for
such an unlikely occurrence. Yet, it is likely such an event will occur again and pethaps an even larger event. It is
fortunate that high-altitude aircraft requirements are largely met by the space program and weather service
requirements providing potential cost sharing (Wilson 1981).

RECENT AIR STUDIES

Many factors relative to aircraft exposures have ——— rare
changed over the last decade as recounted in the introduction. oO HETC
There are continued studies of a possible hypersonic air ‘Upper limat
transport, which will bring a host.of new issues as.reviewed _ 30
elsewhere (Wilson 2000). Two key events had an important
impact on requirements for atmospheric ionizing radiation
research over the last decade: the ICRP (1991) included
aircrew among the defined occupationally exposed and NASA
initiated a technology assessment for a possible second-
generation supersonic transport (High Speed Civil Transport,
SCT). 7) °

Although a consistent data set over much of the
Earth’s surface and most of solar cycle 20 has been measured
by the LaRC SST program, many of the individual
components were not resolved due to instrument limitations at rot i n 3
the time of measurement (circa 1964) and the major portion of ° 00 on _ 300
the neutron spectrum depended on theoretical calculations for Fig, 7 Calculated upper and lower limits for
proton interactions with the atmosphere (Foelsche et al. 1974). dose equivalent rate at high latitude for the
Hewitt et at. (1978) measured the neutron spectrum using 2 Feb 93. 1956 event

5

103

Lower lieut



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J Linsley 1984 J. Phys. G: Nucl. Phys. 10 L191-L195

Sab-luminal pulses from cosmic-ray air showers

LLinsley
Dept. of Phys, & Astron., Univ. of New Mexico, Albuquerque, NM, USA.
Print publication: Issue 8 (August 1984)

Abstract. Some signals produced by air showers of energy greater than 1019 eV in
scintillators at impact parameters greater than 1 km possess a distinctive feature, a ’sub-
Inminal pulse’ (SLP) following the normal one with a time delay of approximately 1.5 r/c.
The average amplitnde of the SLP corresponds to an energy deposit of about 50 MeV,
three times as much as is deposited by 2 vertical minimum ionising muon. The SLP
account for approximately 5% of the energy deposited in the etmosphere by such air
showers at these distances.

doi. 10 1088/0305-4616/10/8/005
URL: http //stacks.iop org/0305-4616/10/L191

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Table 4. Dose (D) and Dose Equivalent (H) for 1989 Large Solar Particle Events

Behind Slab Shield Amounts (2)
D, cGy Ficrp2s SV
Material x, gfom? [~“Com San dem Som

‘Lumar regolith T 3761.76 | 20809 | 743522 | 30624
2 158695 | 16396 | 279231 | 239.48
5 391.73 88.28 615.87 | 127.24
10 109.88 39.65 164.00 57.03
15 1361 7.6 271 1168
50 175 1.22 3.13 2.24
5 0.40 032 0.89 0:70
Water I 283031 | 19852 | 509928 | 291.77
2 117681 | 150.11 | 192211 | 21856
5 276.48 73.68 41137 | 105.56
10 7368 30.07 105.56 42.88
25 322 4.90 12.00 7129
Magnesia i 3286.85 | 20437 | 616685 | 300.69
@ hydride 2 1383.24 | 15776 | 233636 | 230.15
5 333/30 81:26 50818 | 116.74
10 91.02 3493 132.66 49.99
25 10.89 6.28 16.19 9.45
Polyethylene I 2587.62 | 195.67 | 4552.52 | 28747
2 106536 } 145.79 | 1706.01 } 21210
5 24581 69:35 360.31 99.23
10 64.21 2742 90.89 39.05
25 691 423 10.02 6.30
cam. | | ee) BS | SSS Tee

poly. ie .3' 69 .. 5
5 295.16 7687 439.73 | 110.38
10 79:37 31.96 113.69 45.72
7 _ : 25 «9.03. 535__|  -13.18. 799.
Lithium hydride 1 2822.50 | 199.70 | 497957 | 294.08
2 118439 | 15150 | 1903.08 | 221.22
5 282.09 74.90 415.17 | 107.75
10 75.67 | 30.71 107.58 43.97
25 3.49 499 12.27 739



A2tpq

Although not a study of commercial aircrew, the report of the National Economic Council (NEC) Panel on
Occupational Hazards Associated with Nuclear Weapons Production (NEC 2000) has important implications for
commercial aviation. The US President requested the NEC to assess “whether there is evidence of occupational
illness in current and former contract workers at the US Department of Energy (DOE) from exposures to
occupational hazards unique to nuclear weapons production and evaluate the strength of that evidence.” The NEC
Panel (Task Group 1) found only modest average annual exposures of the DOE contractor workforce, 1.5 to 2 mSv
to 1960, a slow decline from 1.5 mSv to 1 mSv in 1978 through 1988, followed to a rapid decline to a few tenths of
a mSv past 1990 (compared to an estimated annual aircrew exposure (e.g., Chicago-to-NY) of 2.72 mSv, Friedberg
et al, 2002). Mortality studies among the DOE contractors showed a healthy worker effect but increased standard.
mortality and incident ratios (SMRs, SIRs) with 90-95 percent confidence intervals above unity (statistically
significant) for cancer of the thyroid, breast, pharynx, esophagus, stomach, small intestine, pancreas, bile ducts, gall
bladder, and liver as well as leukemia, multiple myeloma, and lymphomas (except Hodgkin’s) as identifiable work
related illnesses as concluded by the panel. A compensation program for this entire list of illnesses was set up with
some limitations related to possible causality. Furthermore, several cancer sites showed positive correlations with
radiation exposures while other cancer sites were assumed to be related to other environmental factors. As a result,
the NEC recommended legislation for worker compensation for this restricted list of ilinesses which were found
with statically significant elevated SMRs and SIRs, leading to the Energy Employees Occupational Illness
Compensation Program Act of 2000 passed by the US Congress and signed into law.

A few studies of populations in high-altimde cities have concluded an inverse effect with radiation
exposure although Weinberg et al. (1987) argues that oxygen effects may be the source of decreased adverse health
tisks at high altitudes. Mote recently studies of US Air Force pilots showed statistically significant elevated risks
of cancer in genitals, testis, and urinary systems (Grayson and Lyons 1996). A recent study of mortality among US
commercial pilots and navigators found statistically significant elevations of kidney and pelvic cancers (Nicholas et
al. 1998). Many European epidemiological studies on health outcomes of aircrew have been in progress for several
years (see e.g. Rafnsson et al. 2000, 2001, Ballard et al. 2002, and for reviews Ballard et al. 2000, De Angelis et al.
2001a, 2001b) and provide additional concern for the need for further studies in the US. It is well established that
elevated standard mortality and incidence ratios with 90 to 95 percent confidence intervals above unity is observed
among European aircrew as shown in Table 1 along with limited US studies. Even so, one might argue that the
SMR and SIR depend on the control group and there are even regional differences as observed in the DOE
contractor studies (NEC 2000) and the data still rests on relatively few occurrences in many cases (Friedberg et al.
2002). Still, establishment of policy and science are different issues and the data in Table 1 meets the selection
criteria of the NEC panel for compensation (NEC 2000). It is anticipated that US crews who fly generally closer to
the magnetic pole than European crews will have both different radiation exposure patterns and distribution of
cancers with elevated SMRs. It appears the situation justifies that US aircrews are probably due illness
compensatory legislation but insufficient data exists on which to write such legislation. It is imperative that US
aircrew epidemiological studies are expanded to correct the current Jack of data on cancer incidence and mortality
among US aircrew in preparation of required legislation. This impetus follows since, “it is clear that there are
health risks associated with a career of flying.”

(Friedberg et al. 2002) iby rn
~~ a Chenareatines SA grea? 1 Os ah Rg oe?
CONTINUING US ACTIVITY ast me | acclnses
Three issues continue to be addressed 2 {
within the US: development of the basic AIR 4 FE j 4 |
model incliding experimental validation, testing 2 Ht } 3 }
of potential aircraft material transmission 23" A i A \
properties, and epidemiological studies. The = gai ; ‘\ j i. ‘ 4
extent of the ongoing activity will be briefly 3 | i \ | vo t
reviewed in this section. a eo i 1 ogee , 4
The continued analysis of the ER-2 flight A Tf \
data has concentrated on establishing corrections oe a Ee
to the neutron spectrum due to packaging into the Neutron Energy (eva

flight racks and the surrounding aircraft structure . .
(Goldhagen et al. 2003). This will be followed by Fig. 12 Comparison of the augmented FLUKA evaluated

analysis of the other instruments used on the neutron spectra at the northern extreme of June 1997 ER-2
flights including the high-pressure ion chamber,  {ieht measurements.

q


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the corresponding first version space radiation

code (ref. 3). The peripheral and central limits (curves)
are the unitary limits on the projectile fragmentation
which ensure charge and mass conservation, not includ-
ing the direct target knockout contributions to the trans-
titted fluence (ref. 4). The NUCFRG2 (curve) is the
revised database that resulted from the 600 4 MeV
experiments at the Bevalac facility (ref. 5). The two
upper curves (labeled hard specirum and soft spectrum)
inchude improved nuclear data for the knockout of light
fragments from projectile and target nuclei and the
uncertainty in their production spectra (ref. 6). These
data encompass our best current estimate of the attenua-
tion of dose equivalent in aluminum. Clearly, large
changes in the nuclear data and transport procedures
have occurred in the last several years. Only the comple-
tion of the transport code with the as yet neglected radia-
tion components (with added laboratory and flight
testing) will allow a final evaluation of the expected
astronaut exposure.

In retuming to the Moon, we first note that in addi-
tion to great changes in technology, our understanding of
space radiation protection practice has improved since
the first lunar missions. The Apollo program was recog-
nized as a high risk, exploratory venture in which the
radiation risks were a direct trade-off against the other
mission risks (ref. 8). As a result, the protection stan-
dards were mainly concemed with early biological
effects associated with high exposures that may directly
impact mission safety. The late biological effects such as
cancer induction and cataract formation were of second-
ary concem. Thus, the low level galactic cosmic rays
(GCR) were neglected in the design process. The inspor-
tant solar particle events (SPE) of the time were those of
solar cycle 19, including 23 February 1956, 16 July
1959, and 12-13 November 1960, for which it was esti-
mated that serious exposures could impact mission
safety, but that early lethality was unlikely. During the

. ions 16 and 17, the
This event had signifi-
cantly higher exposures within typical space structures
than prior events, bringing to mind the potential lethality
of solar particle events (ref. 9). In addition to an
improved knowledge of the environment, the whole tex-
ture of the space program changed with the development
of the Skylab and shuttle operations, in which access to
space became routine, and the need for revised space
radiation standards developed (ref. 10). As a result of the
routine access to space, the neglect of the galactic cosmic
ray background was reevaluated and identified as a criti-
cal element in future NASA radiation concems (ref. 11).
No standards have been established to protect astronauts
from the high charge and energy (HZE) patticles of
galactic cosmic rays. In addition to changes in protection

2

A27p

practices, the technology base has improved, and mission
costs may change radically as the result of new space
transportation methods, the use of a space-based staging
area (provided by the developing Intemational Space
Station), and new spacecraft materials. Such new materi-
als may provide added ion compared with an
equal mass of aluminum (the standard construction mate-
tial in the Apollo program).

In this report, we examine the attenuation character-
istics of potential shield materials for use in the early
return to the Moon and assess the shield requirements
that protect the astronauts,

Radiation Protection Standards

Currently, uo radiation limits have been accepted or
However, for planning purposes only, the National
Council on Radiation Protection (NCRP) suggests that
the limits established for astronauts in low-Earth orbit
(LEO) may be used as guidelines for other missions if
the principle of ALARA (as low as reasonably achiev-
able) is followed (ref. 7). LEO exposure limits are cur-
rently given as dose equivalents to specific organs for
short-term (30-day) exposure, annual exposure, and total
career exposure. LEO limits for the skin are 150, 300,
and 600 cSv (1 cSv = 1 rem), respectively. LEO limits
for the ocular lens are 100, 200, and 400 cSv, respec-
tively. LEO limits for the blood-forming organs (BFO)
are 25, 50, and 100 to 400 cSv, respectively (with career
limits, depending on age and gender). Note that the expo-
sure limits for the BFO reflect the exposure limitation to
prevent all cancer, assuming that the BFO dose is indica-
tive of whole body exposure. The NCRP is currently
revising the LEO recommendations as a result of larger
estimates of cancer risk coefficients (ref. 12).

The current limits are based on a 3-percent lifetime
excess fatal cancer risk, which is comparable to the fatal
tisk of moderately safe occupations (ref. 7). A lower
acceptable risk may be required due’ to thé iniproved
safety record, in recent years, of these moderately safe
industries. Furthermore, it is unlikely that special high
tisk limits for exploratory class missions will be
approved in the current social context. In the current con-
text, risk management for Human Lunar Return (LR)
may be even more restrictive and may lead to more strin-
gent, or at best unchanged, shield requirements.

Even if designs are adequate for protection from a
solar event, an accidental exposure could occar. In the
event of accidental exposure, methods to deal with the
potential astronaut health problems must be part of the
plaming process, and there must be reasonable assump-
tions as to the worst case scenario to allow for medical

treatment plans and to provide adequate dosimetry to


A 32e.2

5

ry 8 Ey 1S eye 25

Figure 1a. Jonization rate in the month of June, 1997, at 19.8 KM near polar region.
Atmospheric pressure = 55.2 mb.

fight s7-108

Figure Ib. Predicted and measured values of Air Ionization Rate as function of time for Flight 108.

3


A2ztph

Bonner sphere set up at subsonic altitudes and analyzed the data assuming a simple power spectrum and confirmed
the importance of the high-energy neutrons but left the exact nature of the spectrum uncertain due to limitations of
the analysis methods. Ferenc Hajnal of the DOE Environmental Measurements Laboratory developed new analysis
techniques for unfolding Bonner sphere neutron spectral data and found important structural features in Hewitt’s
data near 100 MeV (See Fig. 8) that have important implications for aircraft exposures (Hajnal and Wilson 1991,
1992). A quick survey of published atmospheric neutron spectra shows considerable uncertainty in our knowledge
and the impact of these uncertainties are analyzed elsewhere (Wilson et al. 1995, Wilson 2000). The status of
knowledge of atmospheric ionizing radiation was 100,
reviewed by the NCRP (1996) providing a basis for
continued studies in support of the HSCT
technology assessment activity.

Further studies were started at the Langley Br
Research Center. An instrument package was
developed in accordance with the NCRP
recommendations through an international guest
investigator collaborative project, thereby ensuring
the availability of the numerous instruments
required measuring the many components of the
radiation spectra and providing a calibration
platform for dosimetry. Selection criteria included:
(a) the instruments had to fit within the cargo bay
areas of the ER-2 airplane and be able to function
in that environment, (b) the instruments had to be ‘Nentron exergy, logic B, MeV

Provided at no cost to meet budget constraints, (c) Fig. 8 Hajnal unfolded neutron spectrum from Hewitt data

each instrument must have a principal investigator -
with independent resources to conduct data measured at 17.46°N at 23.5 km compared to Hess et al.

analysis, and (d) the instrument array must be able (1961) spectrum.

to measure all significant radiation components for

which the NCRP (1996) had established minimal requirements. Also, the flight package had to be operational and
the first flight to occur before or near the maximum in the galactic cosmic ray intensity (spring/summer 1997) and
continued through the next cosmic ray minimum.

The flight package was a collaboration of fourteen institutions in five countries and consisted of eighteen
instruments able to separate the various physical components and tested various dosimeters (Goldhagen et al.
2000). The flight plan was established using the first AJR model (Tai et al. 1998) and concentrated on north/south
surveys with an altitude profile at the northern extremity. The first flight series in June 1997 met with considerable
success with the loss of only one instrument in the 15
data flow. The flight program ended with the
decision that technology was not ready to develop a —— North, 0.8 GV cutoff
competitive high-speed civil transport but the data __
analysis continues. to this day. including corrections = South, 12.GY cutoff.
for the ER-2 flight platform structure. Preliminary
neutron spectra (Goldhagen et al. 2002} are shown
in Fig. 9 and tend to confirm the results of Hajnal’s
analysis (Fig. 8). Note that the neutron spectra of
the northem and southern flight extremes, where the
geomagnetic cutoffs differ by more than an order of
magnitude, are similar in spectral content with
different magnitude. This corresponds well with the 0.0
more limited results of Foelsche et al, (1974), who 10°8 10° 104 i092 10° 102 10
likewise concluded that the spectrum has negligible Neutron Energy (MeV)
differences in the upper atmosphere as a function of . .
altimde and latitude. Fig. 9. Cosmic-ray neutron spectra measured at the 2

‘A preliminary comparison of the first AZR Rother end (54'N, 117°W, 0.8 GV cutoff, 56 g em

* prehminary comp: * ‘atmospheric depth) and at the south end (19°N, 127°W, 12
model with the high-pressure argon ion chamber is GV cutoff; 54 g cm atmospheric depth). The south
given in Fig. 10. This was approximately a six and spectrum is multiplied by 8.

&

Neubionsiem?, see
T
a an

o

B x dE/dE (cm? sec)!
iJ
aq



A2ep fe

Foelsche, T., R. Mendel], J.W. Wilson, R.R. Adams, Measured and calculated neutron spectra and dose
equivalent rates at high altitudes: relevance to SST operations and space research, NASA TN D-7715, 1974.

Friedberg, W., D.N. Faulkner, L. Snyder, E.B. Darden, K. O'Brien, Galactic cosmic radiation exposure and
associated health risks for air carrier crewmembers. Aviat Space Environ Med 68, 1104-1108, 1989.

Friedberg, W., K. Copeland, F.E. Duke, J.S. Nicholas, E.B. Darden, K. O’Brien, Radiation exposure of aircrews.
Occupational Medicine: State of the Art Reviews 17, 293-309, 2002.

Frier, P., E.J. Lofgren, E.P. Ney, and F. Oppenheimer, The heavy component of the primary cosmic rays. Phys.
Rev. 74, 1818-1827, 1948.

Goldhagen, P., Overview of aircraft radiation exposure and recent ER-2 measurements. Health Phys.79: 526-544,
2000.

Goldhagen, P., M. Reginatto, T. Kniss, J.W. Wilson, R-C. Singleterry, 1.W. Jones, W. Van Steveninck,
Measurement of the energy spectrum of cosmic-ray induced neutrons aboard an ER-2 high-altitude airplane.
Nucl. Inst. & Meth. A 476, 42-51, 2002.

Goldhagen, P., J.M. Clem, J.W. Wiilson, Recent results on measurements of the energy spectrum of cosmic-ray
neutrons aboard 2 ER-2 airplane and on the ground. Ady. Space Res. This issue, 2003.

Grajewski, B., E.A. Whelan, M.A. Waters, J.S. Kesner, and T.M. Schnorr, Overview of the proposed NIOSH-FAA
study of reproductive disorders in femal flight attendants. Paper presented at the 424 Annual Meeting of the
Radiation Research Society, Nashville, TN, April-May 1994.

Grayson, J.K., T.J. Lyons, Cancer incidence in United States Air Force aircrew, 1975-89. Aviat. Space Environ.
Med 67, 101-104, 1996.

Gundestrup, M., and H.H. Storm, Radiation-induced acute myeloid jeukaemia and other cancers in commercial jet
cockpit crew: A population-based cohort studies, Lancet, 354, 2029-2031, 1999.

Hajual, F., and J.W. Wilson, High-altitude cosmic-ray neutrons: a significant contributor to the radiation exposures
at aircraft altitudes. Seventh Symposium on Neutron Dosimetry, Berlin, October 14-18, 1991,

Hajnal, F., and JW. Wilson, High-altitude cosmic ray neutrons: probable source for the high energy protons at the
earth’s radiation belts. In proc. 8th Congress Intl. Radiat. Prot. Assoc. Montreal, p 1620, 1992.

Haldorsen, T., J. Reitan, and U. Tveten. Cancer incidence among Norwegian airline pilots. Scand. J. Work.
Environ. Health 26, 106-111, 2000.

Haldorsen, T., J. Reitan, and U. Tveten. Cancer incidence among Norwegian airline cabin attendants. Int.
_J.Epidemiol. 30, 825-830, 2001. .

Hammar N, Linnersjo A, Alfredsson L, Dammstrom B-G, Johansson M, Eliasch H. Cancer incidence in airline and
military pilots in Sweden 1961 - 1996. Aviat Space Environ Med 73, 2-7, 2002.

Hess, V. F., and J. Eugster, Cosmic Radiation and Its Biological Effects, Fordham University Press, New York,
1949,

Hess, W. N., E.H. Canfield, and R.E, Lingenfelter, Cosmic-ray neutron demography. J. Geophys. Res. 66, 665-667,
1961.

Hewitt, J. E., L. Hughes, J.W. Baum, A.V. Kuehner, J.B. McCaslin, A. Rindi, A.R. Smith, L.D. Stephens, R.H.
Thomas, R. V. Griffith, and C.G. Welles, Ames collaborative study of cosmic ray neutrons mid-latitude flights.
Health Phys. 34, 375-384, 1978.

ICAO “Annex 6: To the converntion on International Civil Aviation, Part I: International Commercial Air
‘Transport-Aeroplanes” International Standards and Recommended Practices. Sixth Edition of Part J, July 1995.
International Civil Aviation Organization, 1995.

ICRP Task Group, Radiobiological aspects of the supersonic transport. Health Phys. 12, 209-226, 1966.

ICRP The 1990 Recommendations of the International Commission for Radiological Protection, 1CRP Report 60,
Pergamon Press, Oxford, UK, 1991.

ICRU The quality factor in radiation protection. ICRU Rep. 40, Bethesda, M_D., 1986.

ED


A 25 pr

found that the radiation levels varied by up to 30 percent within the aircraft cabin space. These results give
incentive to evaluation of aircraft materials as a means to providing limited control of the interior environment.
Evaluation of aircraft design alternatives requires a physics-based AIR model for which the transmission properties
of aircraft materials can be folded into the design process.

POLICY & EPIDEMIOLOGY

Aside from the question of more restrictive regulatory requirements resulting in a FAA advisory
(McMeekin 1990) there is increased concem for potential health outcomes among the crew in commercial aviation.
The health outcomes are undoubtably related to environmental factors including radiation. Studies continue to
expand giving greater statistical resolving power (De Angelis et al. 2001a). Although as a group the health risks of
this select group of individuals are low (healthy worker effect, for the specific case of aircrew members, see De
Angelis et al. 2001b), Band (1990) found increased risks of several types of cancer among Canadian commercial
pilots. Further concern for some of the most sensitive occupants of commercial aircraft, the US National Institute
for Occupational Safety and Health continues a study of early pregnancy outcomes armong commercial flight
attendants (Grajewski et al. 1994, Whelan 2002).

Table 1. Cancer Sites with significant positive association for civilian airline flight personnel
crewmembers. Confidence limits are 90 or 95 percent depending on study.

Cancer Site Sex | Job Type | Confidence | Source
Limits
All Sites* M CA SR_ [13 [2.2 Haldorsen et al. (2001)
| Bone F_|CA SIR {18 | 54.4 | Pukkala et al. (1995)
Brain M P SIR_ [12 |7.9 Band et al. (1990) _
Brain M P SMR | 1.4 195 | Band etal. (1990)
Breast F CA SIR_ | 12 | 22 Pukka et al. (1995)
Breast F CA Sm {10 | 43 Wartenberg et al. (1998, 1999)
Breast F [CA SIR | 1.09 [1.83 | Reynolds et al. (2002)
Esophagus M CA SIR_|2.7 | 11.4 | Haldorsen et al. (2001)
Hodgkin Lymphoma M P SIR_{ 1.2 | 11.7 _| Band et al. (1990)
Kidney and Pelvis MtF | P PMR | 1.18 | 3.06 _| Nicholas et al. (1998)
Leukemia — AML M P SIR_ | 2.1 193 Band et al. (1996) _
Leukemia — Myeloid M P SIR_ | 1.4 15.5 Band et al. (1996)
Liver* M CA SIR (1.3 [39.2 | Haldorsen et al. (2001)
Prostate M P SIR_ 114 125 Band et al, (1996)
Rectum M P SMR [1.2 | 11.2 | Bandet al. (1990)
(Skin — Melanoma M_ (Pe SMR (1.5 163 | Irvine & Davies (1999)
Skin ~ Melanoma M PE SIR | Ll | 2.7 Haldorsen et al. (2000)
Skin - Melanoma M P SIR | 5.0 | 36.5 | Rafnsson et al. (2000) _
Skin - Melanoma M CA SIR {Ll [64 | Haldorsen etal. (2001)
Skin - Melanoma M Pp SIR__|.2.85 | 4.23 | Nicholas et al. (2001)
Skin - Melanoma FE CA SIR_ | 1.2 167 Rafnsson et al. (2001)
Skin—Melanoma M P SIR | 1.27 | 4.54 | Hammar et al. (2002)
Skin--Melanoma F CA SIR__| 1.28 | 4.38 | Reynolds et al. (2002)
Skin ~ Other Cancers M P SIR_ ji) 122 Band et al. (1990)
Skin ~ Other Cancers M PE (jets) | SIR [2.1 14.2 | Gundestrup & Storm (1999) _
Skin - Other Cancers M P SIR_ ]13 | 4.0 Haldorsen et al. (2000)
Skin - Other Cancers* M CA SIR_ | 45 | 18.8 | Haldorsen et al. (2001)
Prostate# M PR SHR {1.19 | 2.29 | Ballard et al. (2000) _
Skin — Melanoma# M P SMR |} 1.02 | 3.82 | Ballard et al. (2000) _

*cancer outcome possibly related to lifestyle only; # results from meta-analysis of previous studies, then adjusted
for socio-economical status; AML = Acute Myeloid Leukemia; CA = Cabin Attendants;

P= Pilots only; PE = Pilots and flight Engineers; PMR = Proportional Mortality Ratio;

‘SIR = Standardized Incidence Ratio; SMR = Standardized Mortality Ratio

x


—?

References

1, T. Foelsche, R. B. Mendeli, J. W. Wilson, and R. R. Adams, Measured and calculated neutron spectra
and dose equivalent rates at high altitudes: Relevance to SST operations and space research, NASA TN
D-7715, 1974

2. FAA Advisory Committee on the Radicbiclogical Aspects of the Supersonic Transport, Cosmic
radiation exposure in the Supersonic and subsonic flight. Aviat, Space & Environ. Med. 46:1170-1185;
1975

3. HL J. Schaefer, Public health aspects of galactic radiation exposures at supersonic transport altitudes.
Aerosp. Med. 39:1298-1303; 1968.

4. K. OBrien and W. Friedberg, Atmospheric cosmic rays at aircraft altitudes. Environ. Intern. 20:645-
663; 1994.

5. W. Friedberg, L. Snyder, D. N. Faulkuer, E. B. Darden, and K. O'Brien, Radiation Exposure of
Aircrew Members II, Washington DC, DOT/FAA/AM-92/2, 1992.

6. W. J. White, Crewmember training on in-flight radiation exposure, FAA Advisory Circular, AC 120-
61, May 19, 1994,

7. ICRP, Recommendations of the Intemational Commission on Radiological Protection. ICRP Publ. 26,
1977

8. Comm. On Biological Effects of Ionizing Radiations: Health Effects of Exposures to Low Levels of
Tonizing Radiation: BEIR V. Natl. Acad. Press, 1990.

9. United Nations Scientific Committee Effects Atomic Radiation: Sources, Effects and Risks of Ionizing
Radiation _1988 Report to the General Assembly, With Annexes. United Nations, 1988

10. ICRP, 1990 recommendations of the International Commission on Radiological Protection, ICRP
Publ. 60, Pergamon Press, 1991

11. NCRP, Limitation of exposure to ionizing radiation, NCRP Rep. No. 116, 1993.

12. G. Reitz, K. Schnuer, K. Shaw (ed), Radiation Exposure of civil Aircrew, Radiat. Prot. Dos. 48, no.
1, 1993.

13. F, Fiorino, Airline outlook, Radiation Limits, Aviat, Week and Space Tech. p. 23, June 3, 1996,

14. J. W. Wilson, J. E. Nealy, F. A. Cucinotta, J. L. Shinn, F. Hajnal, M. Reginotto, and P. Goldhagen,
Radiation safety aspects of commercial high-speed flight transportation. NASA TP 3524, May 1995.

15. NCRP, Radiation Exposure and High-Altitude Flight. NCRP Commentary No. 12, July21, 1995.

A 32 edt


Cruiser) with operating altitudes from 45,000-
51,000 ft (Boeing 2002). In recognition of the

w

potential impact of several of these factors on a
present day crew exposures, the Commission of 3
the European Communities organized a Py
Workshop on Radiation Exposure of Civil #32
Aircrew (Reitz et al. 1993). The workshop EP
conclusions (mainly for subsonic exposures) are z=
that the environment is not adequately known for a5
reliable estimates of dose equivalent resulting 321
mainly from uncertainty in the neutron spectra at as
high energies and a re-evaluation of the heavy ion a
component should be made. More recently the s
Intemational Civil Aviation Organization (ICAO) 0

has recommended that “Aj} airplanes intended to
be operated above 15 000 m (49 000 ft) shail
carry equipment to measure and indicate
continuously the dose rate of total cosmic

A2sps

10

rol

2

2

8 10

*

5

81071

£

10

103 a

we wt iw? igh te? 108

‘Neutron energy, MeV

Fig. 2 Neutron spectrum at 70,000 ft over Ft. Churchill on
Augast 3, 1965.

sadiation being received (i¢., the total of ionizing and neutron radiation of galactic and solar origin) and the
cumulative dose on each flight. The display unit of the equipment shall be readily visible to a flight crew member”
(ICAO 1995). More recently Japanese flight crews have requested from their governtuent, health benefits on the basis that
their exposures are "far greater than the exposure of the average nuclear power plant worker" (Fiorino 1996). Added
emphasis comes from epidemiological studies of health outcomes among Depastment of Energy contractors (NEC

2000) leading to the Energy Employees Occupational
iliness Compensation Program Act of 2000, Finally, it is
clear that the development of advanced high-altitude
commercial aircraft (such as the HSCT) requires some
attention to the past concems of high-altitude flight but in
terms of current day knowledge and uncertainty in that
knowledge (Wilson et al. 1995). In a prior report, we
reviewed the status of knowledge of human occupational
exposures and related uncertainties in health risks (Wilson
2000). It was clear that exposures among aircrew were
generally higher than other terrestrial occupationally
exposed groups and the aircrew risk uncertainties were
high since a large fraction of the exposure is from high-
LET radiations.

In this paper we will review key historical
developments in our understanding of atmospheric
ionizing fadiation. and, its. impact. on commercial
operations. Although such a review cannot be made
without reference to work outside the US, we leave the
thorough review of European research to O’Sullivan et al.
(2003) in this issue. A brief overview of ongoing
research in the US is given with special emphasis on
future requirements.

PAST AIR STUDIES

The primary concern for commercial aircraft
radiation exposures began with the Supersonic Transport
with a projected high operating altitude (20-km) for
service on transoceanic flights. Foelsche raised concem
on vulnerability on the high-latitude routes from the US
easter seaboard to Europe where extraterrestrial particles
easily penetrate the geomagnetic field and intense solar

3

H, mSv/1000 br at 40 000 ft

Fig. 3 Background exposure levels (AJR model) in
atmosphere at solar minimum (1965).


17, Shinn, J. L.; Cucinotta, F A.; Wilson, J. W.; Badbwar, G. D.;
O'Neill, P. M; and Badavi, F. F: Effects of Target
Fragmentation on Evaluation of LET Spectra From Space
Radiation in Low-Earth Orbit (LEO) Environment—Impect
on SEU Predictions. JEEE Trans. Nucl. Sci., vol. 42, no. 6,
pt. 1, Dec, 1995, pp. 2017-2025.

18, Wilson, John W.; Badavi, Francis F; Cucinotia, Francis A;
Shinn, Judy L.; Badhwar, Gautam D.; Silberberg, R.; Tsao,
C.H; Townsend, Lawrence W.; and Tripathi, Ram K;
HZETRN: Description of a Free-Space Ion and Nucleon

A227 pie

‘Transport and Shielding Computer Program. NASA TP-3495,
1995.

19, Wilson, John W.; and Badavi, F. K: Methods of Galactic
Heavy Ton Transport. Radiat. Res., vol. 108, 1986,
pp. 231-237.

20. King, Joseph H.: Solar Proton Fluences for 1977-1983 Space
Missions. J. Spacecr. & Rockets, vol. 11, no. 6, June 1974,
pp. 401-408,


; /
a
g

Ty mene ni an re

J. W. Wilson!, P. Goldhagan”, D. L. Maiden’, H. Tai’
'NASA Langley Research Center, Hampton, Virginia
2DOCE Environmental Measurements Laboratory, New York, New York

‘The Langley Research Center (LaRC) performed atmospheric radiation studies under the SST
development program in which important ionizing radiation components were measured and extended by
calculations to develop the existing atmospheric ionizing radiation (AIR) model. In that program the
measured neutron spectrum was limited to less than 10 MeV by the available 1960-1970 instrumentation.
Extension of the neutron spectrum to high energies was made using the LARC PROPER-3C monte carlo
code. It was found that the atmospheric neutrons contributed about half of the dose equivalent and
approximately half of the neutron contribution was from high energy neutrons above 10 MeV. Further-
more, monte carlo calculations of solar particle events showed that potential exposures as large as 10-100
mSv/hr may occur on important high latitude routes but acceptable levels of exposure could be obtained if
timely descent to subsonic altitudes could be made. The principal concern was for pregnant occupants
onboard the aircraft [1]. As a result of these studies the FAA Advisory Committee on the Radiobiological
Aspects of the SST recommended [2]:

1. Crew members will have to be informed of their exposure levels.

2. Maximum exposures on any flight to be limited to 5 mSv

3. Airborne radiation detection devices for total exposure and exposure rates

4. Satellite monitoring system to provide SST aircraft real-time information on atmospheric

radiation levels for exposure mitigation

5. A solar forecasting system to warn flight operations of an impending solar event for flight

scheduling and alert status
These recommendations are a reasonable starting point to requirements for the HSCT with some
modification reflecting new standards of protection as a result of changing risk coefficients,

One result of the SST studies was the realization that subsonic aircrew members are among the
most high occupationally exposed groups [1,3] which prompted the FAA to develop methods to further
study exposures resulting in the CARI exposure estimation code (named after the Civil Aeronautical
Research Institute) based on the LUIN transport model (developed by the DOE Environmental Measure-
ments Laboratory) to generate the database [4]. The estimated risk of serious illness to the child of a
subsonic aircrew member during pregnancy is on the order of 1.3 per thousand [5] and the FAA
recommended thet air carriers begin a program of training of their employees on the risks of inflight
subsonic exposures [6]. The dose rates at the HSCT altitudes are a factor of 2-3 higher than for subsonic
operations and the HSCT crew annua! flight hours will have to be reduced by this same factor to maintain
exposure levels comparable to the subsonic crews.

Regulations on exposure limitation are based mainly on the estimated cancer risk coefficients.
These coefficients have increased. significantly over the last decade as solid tumor appearance is higher
among ‘the’ WW2~ nuclear “weapons siirvivors than’ initially aiticipatéd’ [7-10]. Asa result, new
recommendations for reducing regulatory limits have been made by national and international advisory
bodies [10,11]. Whereas subsonic crew exposures were well under the older regulatory limits, the
substantial reductions (by factors of 2.5 to 5) in exposure limitations recommended by these advisory
bodies resulted in the need to improve aircrew exposure estimates [12]. Hence, a workshop on Radiation
Exposure of Civil Aircrew held in Luxembourg on June 25-27, 1991 was sponsored by the Commission of
the European Communities Directorate General XI for Environmental Nuclear Safety and Civil Protection
[12]. To be noted in the workshop is the closure of the gap between subsonic aircrew exposures and the
newly recommended regulatory limits and in fact some concern that limits may be exceeded in some
cases. Thus uncertainty in exposure estimates becomes a critical issue and emphasis on the numbers of
and spectral content of high energy neutrons as well as the penetrating muitiple charged ions were
identified as a critical issue for subsonic flight crews. More recently Japanese flight crews have requested
from their government, health benefits on the basis that their exposures are "far greater than the exposure
of the average nuclear power plant worker" [13]. The issues for HSCT commercial air travel are
compounded by the higher operating altitudes (higher exposure levels) and the possibility of exposures to

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dose within hours. Twenty minutes after the optical flare
and radio noise were seen at Earth, energetic particles
arrived from the February 1956 event. From the ground-
based measurements, the event's intensity was seen to
have peaked 30 minutes later, followed by a decay witha
mean time of 1 hour (ref. 15). Thus, the entire flare lasted
only a few hours. Crew members would have had signifi-
cantly less time to reach a flare shelter before limits were
exceeded (compared with the October 1989 event). The
time development of the February 1956 event was also
characteristically very different from the other recorded
large flares of November 1960 (ref. 15) and August 1972
(ref. 9).

Only minor doses in free space were predicted by
space weather forecasters for the August 1972 event;
however, it was the largest event ever observed for space
exposures. By 0700 Universal time (UT), the accumu-
lated dose at a 1-cm depth was 2.7 cGy, climbing rapidly
to 10 Gy over the next several hours (1400 UT). Astro-
nauts (nominaily shielded in free space) would have had.
only ~3.5 hours to reach a storm shelter from the time of
particle onset at 1 AU (astronomical unit) to the time that
30-day exposure limits (assuming LEO limits) were
exceeded {ref. 9). Clearly, very high levels of exposure
can be received in a short time (a few hours) with possi-
bly inadequate wanting, leading to the possibility of
early radiation syndrome. Some attention needs to be
given to the prediction and control of biological effects
which could occur during such an accidental exposure
(ref. 13).

Radiation Protection From Various Shielding
Thicknesses

Estimates of exposures made in 1992 by using the
galactic cosmic ray CREME model and the sum of the
1989 flare events (October, September, and August) are
substantially different from the exposure estimates of
more recent models of the GCR by Badhwar and O’Neill.
(ref. 14).and the.recent reevaluation of the nuclear data-
bases in the HZETRN code (ref. 18). The solar flare
results have changed mainly because of reevaluation of
the particle fluence. New tables for GCR exposures
behind regolith and polyethylene shields are shown in
tables 1 and 2 for solar minimum and maximum,
respectively.

Overall, the dose and the dose equivalent are sub-
stantially higher because the CREME model underesti-
toated the fluence of important components (ref. 14). In
addition to the more intense environmental model, the
cross sections for fragmentation and particle production
are substantially greater than those represented in prior
codes (fig. 1). Also, the atomic interactions are more
accurately accounted for than in the Letaw, Silberberg,

4

A27p1

and Tsao procedure (ref. 1) and in Wilson and Badavi
(ref. 19), All these factors compound to increase the esti-
mated astronaut exposure with the latest values given in
tables 1 and 2. A factor-of-three reduction in exposures is
seen near solar maximum for moderate-to-thin shielding.
This ratio of solar minimum to solar maxinnum decreases
to slightly over two at large depths.

We have recalculated the dose and the dose equiva-
lent for the solar particle event of 4 August 1972 with the
BRYNTRN code. The results are presented in table 3.
We have used two representations of the 4 August 1972
event spectra: one prepared by King (ref. 20) and the
other by Wilson and Denn (ref. 9). The relative advan-
tage of a hydrogenic polymer, as opposed to regolith, is
clearly apparent in the table. The geometry used is a
spherical shell with a tissue sample within a 0-cm and a
5-em radius. Reducing the values by a factor of 2 approx-
imates self-shielding provided by the human geometry
for the skin or lens (0 cm) or the BFO (5 cm). These val-
‘ues are in reasonable agreement with the older values by
Simonsen, Nealy, Sauer, and Townsend (ref. 16) and are
in good agreement with Wilson and Denn for polyethyi-
ene (ref. 9). Doses to the lens or to the skin on the lunar
surface are further reduced to about a factor of 4 smaller
than the 0-cm values, and the BFO is about a factor of 4
smaller than the 5-cm value given in table 3.

Galactic Cosmic Ray Dosage for 16-Day
Exploration Missions

Compared with the ofher inherent risks of space-
flight, the risks of a 16-day exposure to galactic cosmic
fays would not be a concem. We use the following
assumptions in estimating GCR exposure:

* 6 days in free space and 10 days on the lunar
surface

“5 g/om? aluminum shield typical of, ‘Apollo-type

* estimate of blood-forming organ dose as 5-cm
water depth dose

The GCR dose estimate would be 1.3 to 3.4 cSv to
the skin and 1 to 2.4 cSv to the BFO when the range of
values depends on whether the mission is at solar
maxinnm or solar minimum. (Using a computerized
anatomical man mode! would lower these estimates, but
mates.) These estimates could be compared with the
annual allowed exposure of 50 cSv or the 30-day allowed
exposure of 25 cSv used for the space station, although
these limits do not apply strictly for these radiations. If
the mission is planned for 2001, the environment will be


diagnose the expected severity for medical intervention
during the course of the mission. This planning requires
the specification of adequately complex dosimetry sys-
tems capable of estimating organ dose rates. Well-
established biological response models must be validated
for treatment planning in the space environment (ref. 13).

Radiation Environmental Models

For exploration calculations of radiation effects in
free space, we use environmental input models and two
transport codes. For galactic cosmic ray (GCR) environ-
ments, we now use the model of Badhwar and O’Neill
(ref. 14). Our carlier work during the Space Exploration
Initiative (SEI) time period used the CREME model
(ref. 1) for the GCR environment and an earlier version
of the HZETRN code that was developed at Langley
Research Center (LaRC) (ref. 2). For solar proton event
environmental data, we use a variety of inputs: the flu-
ence (time integrated flux) of the four largest flares that
have occurred during the last 40 years—February 1956,
November 1960, August 1972, and October 1989
(refs. 9, 15, and 16); flux data from the GOES-7 satellite
for a series of 1989 flares, including October 1989; and
IMP-5 aud IMP-6 data for the August 1972 event. in
addition, we have inputs of smaller flare data from
IMP-7 and IMP-8 satellites.

For the transport of GCR and solar proton events
through various materials, LaRC has developed
HZETRN and BRYNTRN, respectively. The transport
codes and the database are tested in laboratory experi-
ments performed by the Lawrence Berkeley Laboratory
and others. Both codes are well-known and are used
widely in the radiation community. We also model the
effects of biological response and electronic response to
the radiation environment for incorporation inte the
transport code analysis systems.

Our engineering design tools can model various cov-
figurations of spacecraft/habitats to determine the shield-
ing -that-is-provided: by the-structure;~the internal and
external equipment, and the consumables. Those results,
combined with the transport results, will provide us an
estimate of the radiation environment within the
SpacecrafVhabitat, Then we can investigate the optimum
placement of equipment to minimize parasitic shield
requirements, We are currently validating this procedure
with detectors onboard the LEWIS spacecraft that will be
launched in May 1997 (ref. 17).

Currently, large uncertainties exist in biological
response, spacecraft shielding properties, and transport
Properties of body tissues to HZE (high charge and
energy) particles, such as those which comprise the
galactic cosmic rays. The uncertainty in astronaut risk to
HZE particles consists of the biological response with

A27 eb

uncertainties up to a factor of ~5 and to the transport
properties of materials with uncertainties up to a factor of
~2 (fig. 1). The NASA Life Sciences Division is funding
projects to reduce these factors. Uncertainties in the GCR
background environment ate estimated to be about 10 to
15 percent, while the solar event spectra are variable, and
the appropriate design spectrum is controversial. For this
analysis, we will use the 4 August 1972 event as the most
hazardous single event for space exposures yet observed.

Statistical Odds of Encountering a Major
Solar Proton Event

Although the statistical odds of encountering a major
solar proton event such as the February 1956, July 1959,
November 1960, August 1972, or October 1989 event is
Statistically very low, with only 5 major events in the last
40 years (probability for a 16-day mission is about 1 in
200). Serious exposures to the crew would occur if no
provisions for a major solar event were provided. For
example, the 30-day exposure limit of 25 cSv is greatly
exceeded by any of these events without special provi-
sion. Some have suggested that early lethality may occur
within 45 or more days after an extremely intense event.
Clearly, such an event cannot be ignored on the basis that
it is unlikely. One need only to recall that with a slight
change in schedule, either Apollo 16 or Apollo 17 would
have encountered the August 1972 event, which is the
most important event ever observed with regard to space
radiation safety. Furthermore, one must consider the neg-
ative impact on the developing space program if ade~
quate provision is not made to protect the astronauts from
a potentially debilitating injury.

If the solar particle event can be predicted from solar
observation, crew members will have a minimum warn-
ing time of 20 minutes before the arrival of energetic par-
ticles (ref. 15). The October 1989 flare came in three
smnain pulses and lasted about 10 days (ref. 16). The limit-
ing dose for the October 1989 flare was the 30-day ocular
tens--dose- (assuming “LEO - limits); which~-would “be
reached only 17 hours after receiving warning (assuming
that the crew member on the hmar surface was wearing 2
space suit), In comparison, one extravehicular activity
(BVA) shift may last between 6 and 8 hours. For flares
such as the October 1989 event, crew members will have
a number of hours to seek shelter before any of the
30-day limits are exceeded. These time limits would
determine the safe distance for a crew member to venture
from the protection of the habitat or storm shelter. For
example, during the August 1972 event, the ocular lens
limit would have been reached in about 7 to 8 hours
(ef. 9).

The time development of the particle fluence can be
very different. The February 1956 event delivered its

3


4 2% ef

particle events could induce unacceptable exposures on a single high-altitude flight. It was assumed that the
neutrons produced in nuclear reactions with atmospheric nuclei would play an important role in carrying the dose
equivalent deeper into the atmosphere and potentially contribute to background exposures. A measurement
program was initiated by NASA at the Langley Research Center (LaRC) to resolve these issues in July 1964.

The LaRC commissioned over 300 flights over most of the duration of solar cycle 20 on high-altitude
aircraft and balloons to study both background radiation levels over the solar cycle and to make measurements

during a solar particle event. The Langley flight package
consisted of 2 1-10 MeV neutron spectrometer, tissue
equivalent ion chamber, and nuclear emulsion for
nuclear reaction rates in tissue. Monte Carlo
calculations (Wilson et al. 1970, Lambiotte et al. 1971)
for incident GCR protons were used to extend the
neutron spectrum to high energies (Fig. 2). Also shown
in Fig. 2 are the contributions to dose and dose
equivalent from neutrons on individual energy decades.
The measured data was integrated into a parametric
Atmospheric Ionizing Radiation (4/R) model scaled
with Deep River neutron monitor count rate and
geomagnetic vertical cutoff rigidity (Wilson et al. 1991).
The solar mimimum global exposures are shown in Fig.
3 at two altitudes, Over half of the neutron dose is from
neutrons above 10 MeV and an accurate knowledge of
the high-energy neutron quatity factors is critical to
evaluation of dose equivalent. About half of the dose
equivalent is from neutrons as shown in Fig. 4.
Additional high-LET components come from the
nuclear reactions caused by the charged hadrons so that
well over half of the exposures in commercial
operations are from high-LET events which leaves large
uncertainties in the associated health risks (Wilson
2000, Cucinotta et al. 2001) even if the radiation levels
are accurately known.

The only solar particle events of interest are
those capable of ground level observations with ion
chambers (Fig. 1) or neutron monitors. The rates of
occurrence of such events (Shea and Smart 1993) are
shown in Fig. 5. The ground level events vary greatly in
intensity and only the most intense events are important
to high-altitude aircraft protection. The largest ground

_ level event yet observed occurred.on Feb. 23, 1956 in

which neutron count rates rose to 3,600 percent above
background. Two of the afore mentioned over 300
Mights were made ovt of Fairbanks, Alaska during the
event of March 30-31, 1969 with results shown in Fig.
6. Ifthe ground level increase for the March 1969 event
is used to scale other historical ground level events, we
conclude that high-levels (1 cSv or more) of radiation
exposure were present at aircraft altitudes in the past.
The uncertainties in the proton spectra for the Feb. 1956
event are large but upper and lower bounds estimated by
Foelsche result in dose equivalent rates from Monte
Carlo calculations (Foelsche et al. 1969, Wilson et al.
1970, Armstrong et al. 1969) in qualitative agreement
with those derived from simply scaling the March 1969
data. The Monte Carlo results are shown in Fig. 7 as

4

‘Smagothed sunspot number »

Fig. 4 Fraction of dose equivalent ( {AIR model) due
to neutrons at solar minimum (1965).

fe Cycle 19 —np-— Cycle 20 ——ate~ Cyele 21 —t~ Cycle 22-

et Sass

Number of events
even

too

Boe swans thE :
1938 15001965970) i978 1880 1585

Fig. 5 Temporal distribution of ground level solar
particle events for the past 40 years. (Shea and Smart


protection will be derived from materials and equipment
that is onboard the spacecraft for other purposes. The
choice of materials used to construct the spacecraft sys-
tems is very important, and some attention should be
given to materials that will be used in future spacecraft
technology. For example, materials designed primarily
for water and food storage also could be useful for other
purposes. Removable polymeric flooring and other
equipment could be temporarily rearranged for protec-
tion from a solar event. Parasitic shielding is expensive,
but polyethylene is a good material if added shield mate-
rial is required. However, polyethylene has limited mate-
tial properties and poses a flammability issue that must
be resolved. Polymer composites are the next most useful
matetials, but the preferred material would have a high
binder-to-fiber ratio to maintain a high hydrogen content.
Careful consideration should be given to the other
onboard materials.

Concluding Remarks

For the short-term missions to the Moon, the shield-
ing against the galactic cosmic ray (GCR) background is
negligible. Longer missions (to establish a permanent
base) will be limited by the GCR exposures, and the lat-
est results on shielding properties will require added
shield mass over prior estimates. The solar energetic par~
ticle events require special consideration and protection
of at least 10 g/cm” of water or polyethlene during transit
to the Moon and 5 g/cm” on the Moon’s surface. The
shield mass requirements to protect astronauts from a
solar event are about 40 percent higher if regolith or alu-
minum is used. In the event of an accidental exposure by
a solar event, some provision for medical treatment
needs to be provided. The accurate prediction of acciden-
tal exposure levels is necessary to allow proper prognosis

and-medical-treatment.-Appropriate design‘ criteria for —

protection against solar events are still lacking.

NASA Langley Research Center
Hampton, VA 23681-2199
May 6, 1997

References

1. Letaw, J. R,; Silberberg, R.; and Tsao, C. H.: Radiation Haz-
ards on Space Missions Outside the Magnetosphere. Adv.
Space Res., vol. 9, no. 10, 1989, pp. 285-291.

2. Wilson, John W.; Townsend, Lawrence W.; and Badavi, F. E:
A. Semiempirical Nuclear Fragmentation Model. Mucl.
Instrum. & Methods Phys. Res., vol. B18, no. 3, Feb. 1987,
pp. 225-231.

3. Wilson, John W.; Townsend, Lawrence W.; and Badavi,
Forooz F.: Galactic HZE Propagation Through the Earth’s

A27P7

Atmosphere. Radiat. Res., vol, 109, no, 2, Feb. 1987,
pp. 173-183.

Townsend, L. W; Cucinotta, F. A.; and Wilson, J. W.: HZE
Reactions and Data-Base Development. Biological Effects and
Plysics of Solar and Galactic Cosmic Radiation,
C. 2. Swenberg, G. Horneck, G. Stassinopoulos, eds., Plenum,
Press, 1993, pp. 787-809.

. Wilson, J. W.; Shinn, J. L.; Townsend, L. W.; Tripathi, R. K5
Badavi, F. F.; and Chun, S. ¥.: NUCFRG2: A Semiempirical
Nuclear Fragmentation Model. Nuci. Instrum. Phys. Res. B,
vol. 94, 1994, pp. 95-102.

6. Cucinotta, F.A.; Townsend, L. W.; Wilson, J. W.; Shinn, J. L5
Badhwer, G. D.; and Dubey, R. R.: Light fon Components of
the Galactic Cosmic Rays—Nuclear Interactions and Trans-
port Theory. Adv Space Res., vol. 17, no. 2, 1996,
Pp. (2)77-(2)86.

7, National Council oa Radiation Protection and Measurements:
Guidance on Radiation Received in Space Activities. NCRP
Rep. No. 98, July 31, 1989.

Billmgham, John; Robbins, Donald E.; Modisette, Jerry L;
and Figgins, Peter W.: Status Report on the Space Radiation
Effects on the Apallo Mission, Second Symposium on Protec-
tion Against Radiations in Space, Arthur Reetz, Jr, ed., NASA.
SP-71, 1965, pp. 139-156.

‘Wilson, J. W, and Denn, F. M.: Preliminary Analysis of the
Implications of Natural Radiations on Geostationary Opera-
tions. NASA TN D-8290, 1976.

>

ww

tad

°

10. National Academy of Science: Radiation Protection Guides
and Constraints for Space-Mission and Vehicle-Design Stud-
ies Involving Nuclear Systems. NAS Rep. CR-128872, 1970.

LL. Grabn, Douglas, ed.: HZE-Particle Effects in Manned Space-
Fight. NAS, 1973.

12. Smith, H., ed.: 1990 Recommendations of the International
Commission on Radiological Protection. ICRP Publ. 60, Nov.
1990.

13. Wilson, J. W.; Cucinotta, F. A’; Jones, T. E.; and Chang, C. K.:
Astronaut Protection From the 4 August 1972 Solar Event.
NASA TP-3643, 1997.

14, Badbwar, G. D,; and O’Neill, P, M.: Gelactic Cosmic Radia-
tion Modet and Its Applications. Adv Space Res., vol. 17,
20.2, 1996, pp. (2)742)17-

15. Foelsche, Trutz; Me B,; Wilson, John W.; and
Adams, Rickard R.z Calculated Ne

tra and Dose Equivalent Rates at High Altitudes; Relevance to

SST Operations and Space Research, NASA TN D-7715,

Br

16, Simonsen, Lisa C5 Nealy, John E; Saner, Herbert H; and
Townsend, Lawrence W.: Solar Flare Protection for Manned
Lamar Missions: Analysis of the October 1989 Proton Flare
Event. SAE Tech. Paper Ser. 911351, July 1991.


h2sp-t0

the various scintillators, and particle telescopes. Collaboration with the Bartol Research Institute at the University
of Delaware and their unique augmentation of FLUKA to include collisional source terms for multiple charged ions
is being evaluated for use in deriving a new physics-based AJR model (Clem et al. 2003). Preliminary comparisons
of the altitude survey at the northern extreme of the ER-2 flight shown in Fig. 12 are encouraging. The new AIR
model will include a dynamic geomagnetic transmission model for years 1945 to 2020 including geomagnetic
storm effects (De Angelis et al. 2003), The fundamental model will be for the particle fields allowing introduction
of aircraft geometry and human geometry-for final exposure evaluation. One use of the model will be to evaluate
single event effects on avionics in future aircraft design. With the historic variation of the geomagnetic
transmission factors, the model will enable exposure assessment in retrospective health outcome studies.

The transmission properties of materials in such a complicated environment are poorly understood. The
effects of the surrounding aircraft materials and payload on the exposures within the cabin space and on the flight
deck are largely unknown. As a result we have designed a flight experiment for the ER-2 aircraft for evaluation of
material effects on the local radiation environment. The experiment uses cross-calibrated TEPCs to measure effects
on the lineal energy spectra as a fumction of material type. One rack of the basic apparatus is shown in Fig. 13.
There are two such racks that fill the two well-isolated superpod tailcones mounted on the midwings of the ER-2.
The measured change in tineal energy spectral =
content as a function of shield material will give us a
degree of measure of the change in the physical
fields within the shielded region to evaluate
computational shielding models. Fundamental to
this usage is an improved understanding of the TEPC
response in such mixed radiation fields (Shinn et al.
2001).

The NIOSH/FAA Study of Reproductive
Disorders in Female Flight Attendants remains as the
only US led epidemiological effort of which we are
aware, The study is in three parts: data on
reproductive outcomes by questionnaire, ovulation
function study using hormone testing, and an
environmental assessment of the cabin space
(Whelan 2002). Primary school teachers of the same
age distribution are being used as a control group for Fig. 13 Aircraft shield materials experiment rack
the study. being prepared for ER-2 flight.

CONCLUDING REMARKS

_ ..,. SST related studies of atmospheric ionizing radiation quantified.the exposure fields, established-neutrons-as
the dominant component of radiation health hazard, and identified solar particle event exposures of pregnant
occupants as a major health issue. Even then it was recognized that background exposures of commercial aircrew
placed them among the most highly exposed occupational groups. As cancer risk coefficients were revised to
greater values and corresponding new safety standards implemented, concem over potential health risks led to a
number of studies of the radiation environment and corresponding studies of health risks at subsonic commercial
transport altitudes. Although unrelated, identifiable added health risks were found in epidemiological studies of
nuclear weapons workers, who were generally less exposed to ionizing radiation than commercial aircrew. The
resulting legislation for the US nuclear weapon contractors has strong implications for aircraft safety. Extensive
studies of European aircrews have resulted in a database adequate for compensation ‘of European aircrew.
However, the corresponding database on US aircrew is lacking. An accurate physics based A/R model is required
to evaluate reference exposures for epidemiological studies and evaluation of potential design features of future
aircraft to improve safety. The development of such a model has been the focus of the NASA Langley Research
Center for the last several years. A comprehensive flight measurements program is required to validate the AIR
mode] and evaluate the transmission properties of aircraft materials.

REFERENCES

Allkofer, O. C., W. Heinrich, Measurement of galactic cosmic ray nuclei at supersonic transport altitudes and their
dosimetric significance. Health Phys. 27, 543-551, 1974.

/0


NASA Technical Paper 3662

Radiation Analysis for the Human Lunar
Return Mission

J. W. Wilson, L. C. Simonsen, J. L. Shinn, R. R. Dubey, W. Jordan, and M. Kim

September 1997


Table 2. Annual Dose (D) and Dose Equivalent (#) for Galactic Cosmic Rays
Behind Slab Shield Amounts (x) at the 1970 Solar Minimum

Lunar regolith, D, cGy/yr at—~ Hep, CSv/y at—

x, gem? Om Som Ocm Som
f) 6.12 6.97 37.90 34.47
1 7.21 7.02 44.01 33.66
2 744 7.06 43.33 32.87
5 VIA TAS 40.55 30.72
10 793 7.24 36.42 27.84
3 8.04 736 28.98 22.80
50 7.94 737 24.77 20.02

‘) TI2 7.25 23.76 19.43

[ Polyethylene, D, cGylyr at— gp, cSv/yr at—

2, g/om Ocm Som Ocm Som
i) 6.12 6.97 37.90 34.47

1 6.63 6.94 39.09 32.77

2 6.69 6.90 37.07 31.21

5 6.66 6.80 31.40 27.25

10 6.51 6.66 2451 22.59

25 6.23 6.41 15.36 16.47

50 6.03 6.16 12.35 14.39

75 5.77 5.83 11.69 — 13,71

A27 pi


A27e!

Table 1. Annual Dose (D) and Dose Equivalent (H) for Galactic Cosmic Rays
Behind Slab Shield Amounts (x) at the 1977 Solar Minimum

Lunar regolith, D, cGy/yr for— “Heo, Sviyr for—
x, gem? Ocm Som Ocm Som
0 19.44 20.41 120.13 A683
1 21.92 20.37 132.26 91.06
2 22.20 20.33 126.62 87.16
5 22.25 20.17 111.38 79.43
10 21.94 19.91 93.74 69.36
25 20.93 19.20 68.66 53.89
50 19.46 18.10 56.32 45.18
15 18.05 16.99 52,54 43.21
[ Polyethylene, D, cGylyr at— “Hep, CSv/yr at—
x, gfe? Ocm Sem Om Som
0) 19.44 20.41 120.13 94.63
1 20.52 20.18 118.39 88.63
2 20.39 19.96 108.86 83.33
5 19.71 19.40 36.61 10.78
10 18.79 18.69 64.09 57.30
2s 1727 1738 38.92 ALIS
50 15.84 15.88 30.82 35.20
15 14.45 1438 2818 | 32.43



Cail Phrase: MC 110

Historical / Biographical Note:

Sergei Alexander Korff was born in Helsingfors, Finland, in 1906. Immigrating to the
United States with his family in 1917, he became a citizen in 1927. Korff attended
Princeton receiving his A.B. in 1928, M.A. in 1929 and Ph.D. in 1931. Between 1932
and 1940, he completed research fellowships at the Mt. Wilson Observatory, the
California Institute of Technology, the Carnegie Institute of Washington, and the Bartol
Research Foundation. Collaborating with eminent physicists in his early work, Korff
investigated topics such as optical dispersion, proportional counters and neutron
Measurements in cosmic radiation. Korff began his tenure at New York University in
1941, and continued there until his death in 1989. He helped train at least three
generations of students, taking many on research expeditions as far away as the North
Pole and the South Seas.

In addition to his teaching and research, Korff lent his efforts to the international
scientific community. He compiled the report of the Joint Commission on High Altitude
Research for ICSU-UNESCO; served on the Cosmic Ray Technical Panel for the
International Geophysical Year, 1957-58; organized the pole-to-pole Rockwell Scientific
Round-the-World Flight in 1965; and encouraged and secured support for scientific
work around the world, particularly in Central and South America. Notable among his
numerous professional affitiations were his terms as president of the Explorer's Club
(1955-1958); the American Geographical Society (1966-1971); and New York Academy
of Science (1972). For his efforts to transfer surplus scientific equipment to the
decimated laboratories of France after World War II, in 1952 Korff was decorated

®@ Chevalier of the Legion of Honor. For the contribution of his radiation detection devices
to the study of cancer, he was awarded the Curie Medal of the Internationa! Union
Against Cancer.

Korff's Counter Project and Cosmic Ray Project attracted numerous students to NYU;
many tater achieved prominence as physicists. The project also brought the university
substantial funding from government agencies, such as the National Air and Space
Agency and the National Science Foundation. Author of over 150 scientific papers and
books, as well as a number of works on exploration, geology and stamps, Korff's
contributions to science went beyond the study of cosmic rays. His ability to render
complex scientific issues exciting and clear to the general public in ieee and

Scope and Content Note

The collection reflects the work and perspective of a scientist whose life work was
devoted to understanding the universe and sharing that knowledge with as wide an
audience as possible. The Korff Collection documents the work of a prominent cosmic
ray physicist active in academic, governmental and international settings. The
collection contains 10 linear feet of correspondence, notes, photographs, manuscripts,
and printed material documenting research grants, academic activities, professional

r ) organizations, conferences, and publications. Korff's work from 1928 to 1989 is
reflected; the bulk of the material representing the period 1950-1980. There is a
largely undocumented area in this collection: the first is Korff's work prior to his
affiliation with NYU, while the second coincides with World War II.

http://dlib.nyu.edu:8083/archead/servlet/SaxonServiet?source=/korffxml&style=/saxon01... 4/24/2005


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Phys. Rev. C 9, 1718 (1974): Radin et al, - Alpha-spallation cross ...
=. members of the Cosmic Ray Group at New York University for their hn
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argument?
... know the mechanism, that was left to the jor Mendell, a monk, .
re tly id partly because she ...

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Phys. Rev. C ~ Volume: Page/Article: Retrieve

Phys. Rev. C 2, 793-798 (1970)

{Issue 3 — September 1970 ]

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View Page Images, PDF (1083 kB), or Buy this Article See Also: Erratum

Cross Section for C!( alpha , alpha n)C1 at 920 MeV

Jonathan Radin
New York University, Brom, New York 10453 .

Received 30 October 1969; revised 21 May 1970

Plastic scintillators were exposed in the external 920-MeV alpha -particle beam at the 184-in. cyclotron at Lawrence
Radiation Laboratory. The beam-flux monitor was [ford 100- LA pellicles. The cross section for C!( alpha , alpha n)C!!
‘was found to be 49.4 + 1.8 mb.

©1970 The American Physical Society

URL: http://link.aps.org/abstract/PRC/v2/p793
DOK: 10.1103/PhysRevC.2.793

View Page Images, PDF (1083 kB), or Buy this Article
[ Previous article | Next article | Issue 3 contents ]
See Also:

Erratum: J. Radin, Cross Section for C!2( alpha, alpha n)C!! at 920 MeV, Phys. Rev. C4, 1010 (1971).

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http://prola.aps.org/abstract/PRC/V2/3/p793_1 4/24/2005


near solar Maxinmm, and the minimum GCR environ-
ment is appropriate.

Crew Dosage Expected on Lunar Missions
During Past Solar Proton Events

The October 1989 event was a series of particle
increases lasting 10 days. Exposure estimates (ref. 16)
for the October 1989 event during the 3-day trip to or
from the Moon, behind a shield thickness of 2 cm of
water (lightly shielded module) in free space is between
65 and 80 cSv to the blood-forming organ (BFO) (by
using a 5-cm depth dose as the estimated BFO exposure).
By using the same assumptions for a 10-cm water shield
{typical of a storm shelter), the dose equivalent to the
BFO is estimated to be between 10 and 17 cSv. For 2
Tunar surface stay, assuming a 2-cm water shield for the
entire 10-day fluence, in which the lunar surface pro-
vides additional protection, the estimated BFO dose
equivalent is 50 to 65 cSv. For 10 cm of water shielding
on the lunar surface for the 10 days, the estimated dose
equivalent to the BFO is 8 to 14 cSv. The shielded vol-
‘umes are assumed to be cylindrical.

In estimating the dose equivalent to the BFO, the
lens, and the skin for the August 1972 event, we have
used self-shielding factors which substantially reduce the
organ dose by about a factor of 2 and an average quality
factor of 1.3 (ref. 9), In addition, there is a further reduc-
tion on the Junar surface to a factor of 2 because of the
Junar shadow. The dose equivalent from the August 1972
event is somewhat higher and is accumulated over a
shorter period of time (about 10 to 16 hours). During the
three-day transit time, the August 1972 event would
result in exposures within a simple pressure, vessel

~ (approximately 1 g/cm? equivalent water) 6 Sv
(skin and lens) and 2.2 Sv (BFO). By moving into an
equipment related area (5 g/cm” equivalent water, com-
pared to the Apollo command module of 4.5 gen), the

are 2 Sv (skin and lens) and 0.46 Sv (BFO).
To meet the 30-day limit, one will require a storm shelter
(about 10 g/cm?) in which 0.6 Sv (skin and lens) and
0.2 Sv (BFO) would have been received.

Ina space suit on the lmar surface, the accumulated
exposure is about 13 Sv (skin and lens) and 1.1 Sy to the
BRO. Moving into a simple pressure vessel on the sur-
face (minimam habitat wall of approximately 1 g/cm?)
Teduces the estimated exposures to 7.8 Sv (skin and lens)
and 0,85 Sv (BFO). The exposures in an equipment room
(5 g/cm) within the habitat are still lower, yielding I Sv
(skin and lens) and 0.23 Sv (BFO), which satisfy the
30-day exposure limitation requirements for the LEO

N27 pe

Using the ALARA principle (keeping exposure as
low as reasonably achievable), one would attempt to pro-
vide as much shielding as reasonably possible. The fol-
lowing requirements are necessary to meet currently
accepted space station limits as applied to this mission:

a storm shelter of at least 10 g/cm? of water equiv-
alent shield during transit to the Moon {note that
this is equivalent to about 14 g/cm” of aluminum)

+ a region that has at least 5g/om” water equivalent
shielding (7 g/cm? of alaminum) that all astronauts
can reach in a timely fashion (within 2 few hours)
during lunar operations

* improved biological understanding that could pos-
sibly relax the current 30-day limit, result in great
reductions in the shield requirements, and reduce
mission costs

+ exploration of dynamic shielding concepts in
which movable equipment and materials can be
used to make the most effective temporary use of
onboard mass

Radiation Protection Properties of Materials

The GCR background during a 16-day mission is not
more than 3.4 cSv. The primary protection problem for
the HLR is that the possibility of solar particle event
exposures may be quite large, with a 0.5-percent proba-
dility within a 16-day mission. Although the probability
of occurrence is small, the potentially serious illness
which could result is a cause for concern. There are two
important parameters in determining space shield proper-
ties in a solar particle event: stopping the low energy pro-
tons by atomic collision, and to a lesser extent, stopping
the ion of particles in collision with the shield
nuclei ith respects, hydrogen is @ préferréd material
constituent; the higher the hydrogen content per unit
mass of material, the better the shield properties (both the
atomic and nuclear properties). Thus, polyethylene, other
polymers, water, compressed methane (a possible rocket
fuel), and LiH are all good materials. Shield attenuation
Tesults are shown in table 4 for several materials for the
October 1989 event (ref. 16). Of the materials listed, only
the regolith contains no hydroges-bearing molecules.
Water and magnesium hydride are likely materials for
life support systems. Polyethylene is used as a high per-
formance shield and shows significant advantage over
regolith. Adding boron to the polyethlene to deplete the
low energy (thermal) neutrons appears to be counterpro-
ductive because the added production of secondaries and
the change in the atomic cross sections usually increase
the dose. Lithinm hydride is probably a better alternative.

Protecting the astronaut from space radiation is
dependent on the local distribution of materials. Much

5


- event.

one-half hour flight starting June 13, 1997

northem, western, and southern headings.

h2ee7

at 15:52 from NASA Ames Research Center on a prescribed sequence of
This was the second northern flight and the aim was to approximately

repeat the radiation measurements as a function of geomagnetic latitude to as far north as possible with altitude
excursions along a constant-radiation, geomagnetic latimde line near Edmonton, Canada. During the westward

portion of the flight, an altitude excursion

was made as an altitude survey as evident in the figure. The AIR model

using the recorded flight trajectory is shown in the figure for comparison with the measured flight data.

A preliminary summary of
European activity is given by
McAulay et al. (1996). Further
study of the atmospheric neutron
spectrum lead by H. Schraube of
GSF in Neuherberg has been
funded by the Directorate General
XII. The experimental component
consists of a Bonner sphere
spectrometer with a 7He
proportional counter (Schraube et
al. 1998) on a mountaintop
(Zugspitze). The theory portion of
the study uses the FLUKA code,
currently maintained at CERN, and
the known cosmic rays incident on
the atmosphere (the multiple
charged ions are assumed to be
dissociated into nucleonic
constituents (Roesler et al. 1998).
It is interesting to note that the
structure expected from the
analysis of Hajnal at 100 MeV
(Fig. 8) appears in both the

41
a6 ome
si
pe tresy

za
8 Nemuast ae
os
calf

oS » oa ps a ea ae a ot ae

van te nec

Fig. 10 Predicted and measured value of Air Ionization Rate as function of
time for Flight 97-108, Fume 13, 1997.

measurements and the FLUKA calculation (see Fig. 11). Note that this feature was absent from the LUIN code
available at the time of the study. LUIN then depended on the Hess et al. (1961) spectrum for guidance as to the
shape of the neutron spectrum at low energies. Thus the LUIN code is not a basic physics model in that it contains
information outside the basic LUIN transport model (O’Brien and Friedberg 1994). Schraube et al. (1998) showed

that the neutron ambient dose equivalent
contributions are from high-energy
neutron interactions with tissue nuclei
resulting in an array of high-LET
reaction products at each collision
LUIN99. and. LUIN2000
(O’Brien et al., 2003) address this issue
by using Rosier et al. (1998) neutron-
spectrum results. Very little biological
data exist on such radiations (Wilson et
al. 1990, Wilson 2000, Cucinotta et al.
2001).

It was determined by Foelsche
et al. (1974) using simultaneous flight
measurements with a research aircraft
and a balloon that local neutron
production in materials of a small
research aircraft added 10 percent to the
measured neutron field. Later
measurements by Wilson et al. (1994)
onboard commercial subsonic transports

is about a factor of two larger than that estimated by LUIN; the added

935,
‘Nentron fluence rate at Zugspitze (700g/em)

Remy

rena

‘ ae ee ee oe
10-7 10 yq-5 104 q-3 10 gt 10° jt

Neutron eaergy, E, GeV

Fig. 11 Spectral neutron fluence rate obtained by measurements and

calculations on top of Zugspitze (by permission of Schraube et al.
1998).

oe
10°22, 1110710, 5-9 19-8


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‘Title: The War Years: An Interview with Bernard Hamermesh

Authors: Mendell, Rosalind B.

Journal: Frontiers in Cosmic Physics; Symposium in memory of Serge Alexander Korff, held on September
13, 1990, in New York, NY. Edited by Rosalind B. Mendell and Allen I. Mincer. Published by
Annals of the New York Academy of Sciences, Volume 655, New York, NY, 1992, p.22
Publication Date: 06/1992

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Irvine, D., and D. Davies, British Airways flightdeck mortality study, 1950-1992”. Aviat. Space Environ. Med. 70,
548-555, 1999,

Siang, T.-N., B.L. Lord, J.H. Hendry, Alpha particles are exwemely damaging to developing hemopoiesis
compared to gamma irradiation. Radiat. Res. 137, 380-384, 1994.

Lambiotte, J. J., IW. Wilson, and T.A. Filipas, PROPER-3C: A Nucleon-Pion Transport Code, NASA TM X-
2158, 1971.

- Lebuser, H. J. Round table discussion. Radiat. Prot. Dosim. 48, 136-138, 1993.

McAulay, I. R., D.T. Bartlett, G. Dietze, H.G. Menzel, K. Schnuer, and U.J. Schrewe, Exposure of air crew to
cosmic radiation. European Radiation Dosimetry Group, EURADOS report 1996-01, 1996.

McMeekin, R. R. Radiation exposure of air carrier crewmembers. FAA Advis. Circ. No. 120-52, Mar. 1990.
NCRP Limitation of exposure to ionizing radiation. NCRP Rep. 116, Bethesda, MD., 1993.

NCRP Radiation exposures and high-altitude flight. NCRP commentary No. 12, NCRP, Bethesda, MD., 1996.
NEC http://www.eh.doe.gow/benefits/nec/necreport! pdf, 2000.

Nicholas, J.S., D.T. Lackland, M. Dosemeci, L.C. Mohr Jr., J.B. Dunbar, B. Grosche, and D.G. Hoel. Mortality
among US commercial pilots and navigators. J. Occup. Environ. Med. 40, 980-985, 1998.

Nicholas et al., G.C. Butler, D.T. Lackland, G.S, Tessier, L.C. Mohr Jr., and D.G. Hoel. Health among commercial
airline pilots, Aviat. Space Environ. Med. 72, 821-826, 2001.

O’Brien, K., and W. Friedberg, Atmospheric cosmic rays at aircraft altitudes. Environ Internat’! 20, 645-663,
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O'Brien, K., D.F. Smart, M.A. Shea, E. Felsberger, U. Schrewe, W. Friedberg, and K. Copeland. “World-wide
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O’Sullivan, D., The DOSEMAX Team, The radiation field at aircraft altitudes-A decade of progress. Adv, Space
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B


A2red

Abstract

An analysis of the radiation hazards that are anticipated on an early Human
Lunar Return (HLR) mission in support of NASA deep space exploration activities is
presented. The HLR mission study emphasized a low cost lunar return to expand
human capabilities in exploration, to answer fundamental science questions, and to
seek opportunities for commercial development. As such, the radiation issues are cost
related because the parasitic shield mass is expensive due to high launch costs. The
present analysis examines the shield requirements and their impact on shield design.

Introduction

The Human Lunar Retum (HLR) study examined the
basic rationale, the required technologies, and the mis-
sion development for a return to the Moon. The basic
thrust of the HLR mission study is to make humanity a
multi-planet society, to open new opportunities for com-
mercialization, and to answer fundamental questions
about Earth and solar system science. Since these goals
are mainly futuristic in orientation, the attempt is to lay
the foundation for human space activity over the next
three decades, The near term objectives will hinge
mainly on the current cost of space exploration and
emphasize the possibility of a low cost return to the

1.0 r~

Moon. Radiation protection systems (shielding, monitor-
ing, and medical supplies) impact mission cost, and
‘uncertainty in past shield databases is inadequate for the
present design study. Recent advances in shield design
technologies require a regeneration of the necessary
design database (refs. 1 through 6). For example, a pro-
gression of aluminum shield attenuation characteristics is
shown in figure 1. The lower curve is that generated by
the code of Letaw, Silberberg, and Tsao (ref. 1) and was
used in the National Council on Radiation Protection
(NCRP) report 98 (ref. 7). The nuclear fragmentation
(NUCFRGI) curve used the first generation of the
Langley Research Center (LaRC) database (ref. 2) and

2B
EI
2
3
FE
z Database
z
g Soft spectrum
A Peripheral
NUCFRG2
NUCFRG1
Central
2 | | J Letaw et al.
0 10 20 30 40 50
Aluminum shield thickness, g/cm?

Figure 1, Shield attemsation for solar minimum galactic cosmic ray dose equivalent resulting from muclear fragmentation (NUCFR) models

Gi and G2.


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jo TLE AND SUBTLE
Radiation Analysis for the Human Lunar Retum Mission,

s. ORE
7, W, Wilson, L- C. Simonsen, J. L. Shinn, RR. Dubey, W. Jordan, and
|. Kim

S. FUNDING NUMBERS
WU 199-45-16-11

NIZATION

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[&- PERFORMING ORGANIZATION
REPORT NUMBER

L-17613

[S. SPONSORINGIMONITORING AGENCY NAME(S) AND ADDRESSES)

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AGENCY REPORT NUMBER
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71. SUPPLEMENTARY NOTES.
Wilson, Simonsen, and Shinn: Langley Research Center, Hampton, VA;

Dubey and Jordan: Old Dominion|
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design.

An analysis of the radiation hazards that are anticipated on an early Human Lunar Return (HLR) mission in support
of NASA deep space exploration activities is presented. The HLR mission study emphasized a low cost lunar return}
to expand human capabilities in exploration, to answer fundamental science questions, and to seck opportunities for,
commercial development. As such, the radiation issues are cost related because the parasitic shield mass is expen-
sive due to high launch costs. The present analysis examines the shield requirements and their impact on shield!

7% SUBJECT TERMS — —_ ” ” ~ ~ [15 NUMBER OF PAGES
Human Lunar Return; Radiation protection; Solar particle events; Galactic cosmic’ 15
rays; Shield design fic PRRECObE
A03
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A2spe

and was correlated with solar disturbances (Hess and Eugster 1949). Observed large increases in the ionization
rates would be attributed to particles coming directly from the solar events (Fig. 1). More modest decreases over a
few days, as seen for the July-August 1946 event, were attributed to disturbance of the local interplanetary medium
by which approaching cosmic rays were excluded from the local Earth environment (Forbush decrease). It was
now Clear that extraterrestrial radiation from both the sun and the galaxy were contributing to the atmospheric
ionization levels. The next-to-last piece of important evidence from a human exposure perspective was the
discovery of heavy ion tracks by Phyllis Frier and coworkers (1948) using nuclear emulsion track detectors in high
altitude balloon flight. Although the initial emphasis of this discovery was the ability to sample cosmic matter,
attention would turn to the possibility of human exposure by these ions in high-altitude aircraft and future space
travel (Armstrong et al. 1949, Schaefer 1950, 1952, 1959, Altkofer and Heinrich 1974).

When the possibility of high-altitude supersonic commercial aviation was first seriously proposed, Foelsche
brought to light a number of concerns for the associated atmospheric radiation exposure due to penetrating cosmic
rays (CR) from the galaxy (GCR) and the sun (SCR, also referred to as solar particle events, SPE) including the
secondary radiations produced in collision with air nuclei (Foelsche 1961, Foelsche and Graul 1962, Foetsche
1965). Subsequently, a detailed study of the atmospheric ionizing-radiation components at high altitudes was
conducted from 1965 to 1971 at

PUT
the NASA Langley Research AE eR eect
Center (LaRC) by Foelische et al. l6rr ar a THT Ca 180 r
(1969, 1974). Prior to that study 2 RAE at e807 sudden Godhava
the role of atmospheric neutrons cogent a 160
é or 48 ofthemagnetic ew #
in radiation exposure was § oom 2 8 8 ol 3 3 0
generally regarded as negligible § 4[—| eee (Genamm| 2 E
(ICRP 1966). The LaRC studies $ 9) ‘Godhava. 28 40 3 B 220 t
revealed the neutron radiation to & t ne 5 Los § roo (| C=
be the major contributor to io se & i
commercial aircraft GCR 2-8 4 a8 Ogg %
exposure. Still the exposure g [ & i Busntayo | $ 2
levels were comfortably below § Pye a og g° g3°
allowable exposure limits for the 2 9 422 20 i 0
block hours typical of airline a cal 3A a q a
crews of that time except during 4 U Hoancayo . 0 20
a possible solar particle event ser +1 Christehurch ol
(less than 500 block hours were 2 Uw 2% 2B 39 1 3 18 20 22 3 20 2
typical of the 1960’s although July-August 1946 ‘November 1949 November 1949

regulations allowed up to 1000 F ig. 1 Ground level ion chamber observations of solar particle events of
hours)... As -a result, the US . 1946 and 1949. From Foelsche.et al. 1974). .

Federal Aviation Agency (FAA)

Advisory Committee on the Radiobiological Aspects of the SST issued recommendations that crew members will
have to be informed of their exposure levels, maximum exposures on any flight be limited to 5 mSv, development
of airborne radiation monitors, development of a satellite monitoring system, and development of a solar event
forecasting service (FAA 1975, see also Foelsche et al. 1974).

Several factors have changed since those early studies: (a) the highly ionizing components are found to be
more biologically damaging than previously assumed and the associated quality factors for fatal cancer have been
increased (ICRU 1986, ICRP 1991); (b) recent studies on developmental injury in mice embryo indicate larger
quality factors are required for protection in prenatal exposures (Jiang et al. 1994); (c) recent epidemiological
studies (especially the data on solid tumors) and more recent A-bomb survivor dosimetry have resulted in higher
radiation risk coefficients for y rays (UNSCEAR 1988, BEIR V 1990, ICRP 1991) resulting in lower proposed
permissible limits (ICRP 1991, NCRP 1993); (d) "an urgent need is recognized for better estimates of the risk of
cancer from low levels of radiation" (anon. 1993); (e) subsequent to deregulation of the airline industry, flight
crews are logging greatly increased flight hours (Bramlett 1985, Wilson and Townsend 1988, Friedberg et al. 1989,
Barish 1990); (2 a new class of long haul commercial aircraft is being developed on which personnel for two crew
shifts will be simultaneously aboard a single flight leading to increased exposures for a fixed number of flight duty
hours (Lebuser 1993); (g} US airline crew members are now classified as radiation workers (McMeekin 1990,
ICRP 1991); (h) NASA is developing technology for a High Speed Civil Transport (HSCT) to begin service in the
twenty-first century; and (g) there are plans to introduce a revolutionary commercial transport (Mach 0.98 Sonic

a


A271 e3

Available electronically at the following URL address: hitp//techreports.larc.nasa.gov/Itrs/ltrs. him!

Printed copies available from the following:

‘NASA Ceater for AeroSpace Information National Technical Information Service (NTIS)
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(301) 621-0390 (703) 487-4650


Phys. Rev. C __. Volume: Page/Article: _ Retrieve

Phys. Rev. C 9, 1718-1729 (1974)
{Issue 5 —- May 1974]

| Previous article | Next article | Issue 5 contents }

View Page Images, PDF (1847 kB), or Buy this Article

Alpha-spallation cross sections at 920 MeV (230 MeV/N) in 27Al, 160, !2C, and Be, and
application to cosmic-ray transport

Jonathan R. Radin®
Tel-Aviv University, Department of Physics & Astronomy, Ramat Aviv, Israel

Alan R. Smith and Nickey Little
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720

Received 29 November 1973

We investigated the effects on cosmic rays from spallation reactions between cosmic rays and interstellar helium. The
spallation cross sections were measured by exposing thin-sandwich targets to the 920-MeV (230-MeV/N) external aipha -
particle beam of the 184-in. cyclotron at Lawrence Berkeley Laboratory. Cross sections were measured for the production:

from 27A] of 8F (12.5+0.5 mb); from !60 of 150 (46.442.7 mb), !3N (6.75+0.5 mb), 'C (18.540.9 mb), and 7Be (18.541.3
mb); from 12¢ of 7Be (20.0+1.2 mb); and from Be of 7Be (12.6:+0.8 mb), We constructed spallation cross-section ratios for
the ratio of alpha -particle-induced to proton-induced reactions (= Sigma pha ‘p) We parametrized this ratio by the nucleon
difference ( Delta A) between the target initial and final states and we fitted this ratio [ Sigma “pha  o{ Delta A)) to a linear
fanction i in Delta A, We used this function [ Signa alpha pDelta A) to obtain all of the alpha -particle-spallation cross.

‘sections from the corresponding proton- spallation cross sections for targets and products in the elemental range 3 <= Z <= 8,
and we applied these cross sections to a cosmic-ray transport calculation wherein we investigated the sensitivity of the
cosmic-ray L / Mratio [-(Li + Be + B) / (C + N + O)} and of the abundances of the Z and M elements to the helium fraction
of the interstellar gas.

[NUCLEAR REACTIONS 27 AX alpha ,x)!8F; 160, alpha x)!50, 13N, UC, 7Be; 12C( alpha x)’Be; *Be( alpha ,x)’Be,
E=920 MeV; measured sigma ; Nal detector. Examined effect interstellar He on cosmic rays.}

©1974 The American Physical Society

URL: http:/link.aps.org/abstract/PRC/v9/p1718
DOI: 10.1103/PhysRevC.9. 1718

* Work performed in part while at New York University, Department of Physics, New York City, N. Y. 10003.

View Page Images, PDF (1847 kB), or Buy this Article

http://prola.aps.org/abstract/PRC/v9/i5/p1718_1 4224/2005


A2épil
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2001a.

De Angelis,-G.,_M. Caldora; M. Santaquilani; R. Scipione, and: A. Verdecchia. Health risks from radiation exposure
for civilian aviation flight personnel: a study of Italian airline crew members, Radiat. Res. 156, 689-694, 2001b.

De Angelis, G., J.M. Clem, P. Goldhagen, J.W. Wiilson, A new dynamical atmospheric ionizing radiation (AIR)
model for epidemiological studies. Adv. Space Res. This issue, 2003.

FAA Cosmic radiation exposure in supersonic and subsonic flight. Aviat, Space, & Environ. Med. 46, 1170-
1185, 1975.

Fiorino, F. Airline outlook, radiation limits, Aviat. Week and Space Tech. p, 23, June 3, 1996.
Foelsche, T. Radiation Exposure in Supersonic Transports. NASA TN D-1383, 1961.
Foelsche, T., and E.H. Graul, Radiation exposure in supersonic transports, Atompraxis, 8, 365-380, 1962.

Foelsche, T. SST report on the space radiation effects on the Apollo mission. Second Symposium on Protection
Against Radiations in Space, Arthur Reetz, ed., NASA SP-71, 139-156, 1965.

Foelsche, T., R. Mendell, R.R. Adams, J.W. Wilson, Measured and Calculated Radiation Levels Produced by
Galactic and Solar Cosmic Rays in SST Altitudes and Precaution Measures to Minimize Implecations at
Commercial SST-Operations. NASA paper prepared for the French-Anglo United States Supersonic Transport

VII Meeting, Paris, France, Mar. 3, 1969.



A27pz

NASA Technical Paper 3662

Radiation Analysis for the Human Lunar
Return Mission .

J. W. Wilson, L. C. Simonsen, J. L. Shinn, and M. Kim
Langley Research Center « Hampton, Virginia

R.R. Dubey and W. Jordan
Old Dominion University » Norfolk, Virginia

National Aeronautics and Space Administration

@ Langley Research Center * Hampton, Virginia 23681-2199

September 1997


Aszpz

a large solar particle event wherein annual exposure limits could be greatly exceeded on a single flight
[1,14].

As a result of the higher expected exposures in high altitude flight, the US congressionally
chartered federal advisory agency on radiation protection, NCRP, examined the data on atmospheric
radiation and made recommendations [15] on the need for future studies as follows:

1, Additional measurements of atmospheric ionizing radiation components with special emphasis

on high energy neutrons

2. A survey of proton and neutron biological data on stochastic effects and developmental injury

for evaluation of appropriate risk factors

3. Develop methods of avoidance of solar energetic particles, especially for flight above 60,000 f

4, Develop an appropriate radiation protection philosophy and radiation protection guidelines for

commercial flight transportation, especially at high altitudes of 50,000 to 80,000 ft
Clearly, these recommendations must be addressed before the HSCT goes into commercial service to
ensure the safety of the crew and passengers. The current effort in this assessment is the use of an
experimental flight package to reduce the uncertainty in AIR models in direct response to the NCRP
recommendations.

An instrument package was developed in accordance with the NCRP recommendations through
an international guest investigator collaborative project to acquire the use of existing instruments to
measure the many components of the radiation spectra. Selection criteria was established which included:
(@) the instruments had to fit into the cargo bay areas of the ER-2 airplane and able to function in that
environment (Some high quality laboratory instruments were rejected because of their large size or
inability to operate in the ER-2 environment.), (b) the instrument had to come at no-cost for use by the
project to meet budget constraints, (c) the instrument must have a principal investigator with their own
resources to conduct data analysis, and (d) the array must include all significant radiation components for
which the NCRP had made minimal requirements. The flight package must be operational and the first
flight occur before or near the maximum in the galactic cosmic ray intensity (ca. spring/sunamer 1997)
and extend through the next cosmic ray minimum.

The flight package developed uses all of the available space in the ER-2 cargo areas. The
primaty instruments in the package consist of neutron detectors, scintillation counters, and an ion
chamber from the DOE Environmental Measurements Laboratory and charged particle telescopes from
Institute of Aerospace Medicine of Deutsche Forschungsanstalt fur Luft- und Raumfahrt (DLR), and
Johnson Space Center. Ten other instruments from Germany, Italy, the United Kingdom, and Canada
make up most of the remainder of the flight package. These include passive track detectors from Institute
of Aerospace Medicine, DLR, and University of San Francisco; TEPCs from Boeing and Defence
Research Establishment Ontario; and dosimeters from Boeing, Royal Military Academy in Ontario and
National Radiological Protection Board (NRPB) in the UK. The existing primary instruments and data
system were modified for operation on the ER-2. A data acquisition system was incorporated to control
operation of the entire instrument package, and to record data from the primary instruments during flight.
Data from the other instruments are recorded separately by each instrument and recovered after a flight.
‘The AIR model was modified for diurital and solar rotational Corrections as shown ini figure 1a with the
tesults for the ion chamber in 2 northern flight into Canada shown figure lb, The dosimetry of the
neutron component is being updated with ambient dose and dose equivalent for comparison with the
TEPC data. Preliminary bonner sphere functions are likewise being used for preliminary flight
comparisons.


New York University Archives

Guide to the Papers of Serge A. Korff
1928-1989

New York University Archives.

Elmer Hofmes Bobst Library

70 Washington Square South

New York, NY 10012

Phone: (212) 998-2646

Fax: (212) 995-4070

Email: nancy.cricco@nyu.edu

© 2003 New York University Archives . All rights reserved.
New York University Libraries, Publisher

Processed by: Susan Aprill, 1994

Machine-readable finding aid created by Brian Stevens - derived from an XML finding aid,
2003. Description is in English.

2003korff converted from EAD 1.0 to 2002 by one2two.xsl.

Descriptive Summary

Creator: Korff, Serge Alexander, 1906-

Title: Papers.

Dates: 1928-1989

Abstract: "Serge A. Korff was a prominent cosmic ray physicist active in

academic, governmental and international settings whose tenure at
NYU was from 1941-1989. The collection encompasses Korff's
professional career and includes correspondence with leading
American, South American and European physicists, graduate
students and post-doctoral fellows, academicians from other
disciplines, professional scientific organizations, government
agencies, military personnel, commercial equipment suppliers, and
publishing concerns. Also included in the collection is information on
research projects and expeditions; grant proposals and reports;
TMateriats on scientific conferences; students’ theses and
dissertations; administrative records pertaining to NYU and its
physics department; and reprints of scholarly articles by Korff and
others.

Quantity: 12 linear feet (8 boxes)

http://dlib nyu.edu:8083/archead/servlet/SaxonServiet?source=/korffxml&style=/saxon01... 4/24/2005


A2ep.d

Shea, M. A., and D.F. Smart, “History of energetic solar protons for the past three solar cycles including cycle 22
update.” Biological Effects and Physics of Solar and Galactic Cosmic Radiation, C. E. Swenberg, G. Horneck,
G. Stassinopoulos, eds. Plenum Press, 37-71, 1993.

Shinn, J.L., J.W. Wilson, M.S. Xapsos, 4n improved Analytical Model for Microdosimeter Response. NASA/TP-
2001-21 1040, 2001.

Tai, H.; J.W. Wilson, and D.L. Maiden, " Anmospheric Ionizing Radiation (AIR) ER-2 Preflight Analysis, NASA
Technical Paper 1998-208422, June 1998.

UNSCEAR, United Nations Scientific Comm. on Effects of Atomic Radiation: Sources, effects and risks of
ionizing radiation-1988 report to the General Assembly, United Nations, 1988.

Wartenberg D, Stapleton CP. Risk of breast cancer is also increased among retired US female airline cabin
attendants. BMJ 316, 1902, 1998.

Wartenberg D, Stapleton CP. Risk of breast cancer among female airline cabin attendants. BMJ 318, 126, 1999.

Weinberg, C. R., K.G. Brown, D.G. Hoel, Altitude, radiation, and mortality from cancer and heart disease. Radiat.
Res. 112, 381-390, 1987.

Whelan, E.A. The Working Women’s Health Study: The NIOSH/FAA Study of Reproductive Disorders in Female
Flight Attendants. National Institute for Occupational Safety and Health, Status Reports Q2 2002.

Wilson, J. W., J.J. Lambiotte, T. Foelsche and T.A. Filippas, Dose Response Functions in the Atmosphere Due to
Incident High-Energy Protons with Application to Solar Proton Evenis. NASA TN D-6010, 1970.

Wilson, J. W., Solar radiation monitoring for high altitude aircraft. Health Physics 41, 607, 1981

Wilson, J. W., L.W. Townsend, Radiation safety in commercial air traffic: A need for further study. Health Phys.
55, 1001-1003; 56, 973-974, 1988.

Wilson, J. W., J.L. Shinn, and L.W. Towsend, Nuclear reaction effects in conventional risk assessment for
energetic ion exposures. Health Phys. 58, 749-752, 1990.

Wilson, J. W., L.W. Townsend, W. Schimmerling, G.S. Khandelwal, F. Khan, J.E. Nealy, F.A. Cucinotta, L.C.
Simonsen, J.L. Shinn, J. W. Norbury, Transport methods and interactions for space radiation, NASA RP-1257,
1991.

Wilson, J. W., J.E. Nealy, F.A. Cucinotta, J.L. Shinn, F. Hajnal, M. Reginatto, and P.Goldhagen, Radiation safety
aspects of commercial high-speed flight transportation, NASA TP-3524, 1995.

Wilson, J.W. Overview of radiation environments and human exposures. Health Phys. 79, 470-494, 2000.

Wilson, O.J., B.F. Young, and C.K. Richardson, Cosmic radiation doses received by Austrlian commercial flight
crews and the implications of ICRP 60. Health Phys. 66, 493-502, 1994.


10

A27p

Table 3, Dose (D) and Dose Equivalent (H) for 4 August 1972 Event Spectra by King and LaRC

D, cGy H, Sy D, cGy H, cSy
Lunar regolith, King King LaRC LaRC
x, go” Ocm Som Oem | Sem Oan Som Om Som
1 3250.5 242.55 | 5696.6 332.73 {2613.7 254.1 4ADLA 346.57
2 1722.2 183.48 | 2843.8 251.55 | 1472.7 198.02 | 23913 269.98
5 495.2 36.0 TI2S 119.0 480.84 | 100.66 740.36 | 137.84
10 117.2 29.10 179.7 413 13259 38.20 200.75 53.57
25 6.08 2.39 11.27 469 9.34 3.96 16.04 6.91
50 0.2932 0.23 1.42 0.95 0.5 0.35 1.79 1.92
75 0.0732 0.083 0.5232 0.39 0,099 | 0.12 0.61 0.47
D, Gy H, Sy D,cGy H Sy
Polyethylene, King King LaRC LaRC

x, g/cm? Ocm Sem Ocm 5em Ocm 5cm Ocm Sem

1 24374 | 221.82 37144 | 322.20 {2013.4 234.63 | 3022.5 338.18

2 1188.7 155.5 1727.9 | 225.36 | 1055.0 170.84 | 1515.8 245.76

5 287.4 6041 401.09 88.0 295.83 7348 410.2 106.09

10. . $5.31.) 16.1 76.14) 2444 67.96 2255 | 93.77-} 3354

25 1.96 0.874 3.27 2.03 3.33 1.56 5.20 3.09

50 0.125] 0.0898 0.36 0.367 0.18 0.13 0.49 0.47

718 0.04 0.0317 0.13 0.13 0.054 0.04 0.16 0.17



doc A.zw

OVERVIEW OF ATMOSPHERIC IONIZING RADIATION (AJR)
RESEARCH: SST-PRESENT

LW. Wilson’, P. Goldhagen’, V. Rafasson’, J. M. Clem’, G. De AngelisTM® W. Friedberg”

'NASA Langley Research Center, Hampton VA 23681 USA
DOE Environmental Measurements Laboratory, New York NY 10014 USA
University of Iceland, Reykjavik, Iceland

“Bartol Research Institute, University of Delaware, Newark DE 19716 USA
v 50ld Dominion University, Norfolk VA 23508 USA
‘stituto Superiore di Sanita’, Rome, Italy
BN "Civil Aerospace Medical Institute, FAA, Oklahoma City, OK 73125 USA

ABSTRACT

The Supersonic Transport (SST) program, proposed in 1961, first raised concern for the exposure of pregnant
occupants by solar energetic particles (SEP), and neutrons were suspected to have a main role in particle
propagation deep into the atmosphere. An eight-year flight program confirmed the role of SEP as a significant
hazard and of the neutrons as contributing over half of the galactic cosmic ray (GCR) exposures, with the largest
contribution from neutrons above 10 MeV. The FAA Advisory Committee on the Radiobiological Aspects of the
SST provided operational requirements. The more recent (1990) lowering of recommended exposure limits by the
International Commission on Radiological Protection with the classification of aircrew as “radiation workers”
renewed interest in GCR background exposures at commercial flight altitudes and stimulated epidemiological
studies in Europe, Japan, Canada and the USA. The proposed development of a High Speed Civil Transport
(HSCT) required validation of the role of high-energy neutrons, and this resulted in ER-2 flights at solar minimum
(June 1997) and studies on effects of aircraft materials on interior exposures. Recent evaluation of health outcomes
of DOE nuclear workers resulted in legislation for health compensation in year 2000 and recent European aircrew
epidemiological studies. of health outcomes bring renewed interest. in aircraft.radiation exposures. .As.improved
radiation models become available, it is imperative that a corresponding epidemiological program of US aircrew be
implemented.

INTRODUCTION

After the discovery of radiation emanating from certain materials, the source of background radiation
observed in the atmosphere was thought to have exclusively originated from the ground, however Hess’s series of
balloon flights from 1911-1913 showed that an additional component originating from the sky was also present in
this background. in 1925, Millikan coined this newly discovered radiation as cosmic rays.

The fact that the cosmic rays consisted in part of charged particles was directly demonstrated by
coincidence experiments using Geiger-Mueller tubes and resolving individual charged particle tracks within a
Wilson cloud chamber. The cloud chamber lead to the discovery of the positron as part of the cosmic rays,
followed by the discovery of the charged mesons, and further shed light on the important neutron component of
cosmic radiation in the atmosphere (Bethe et al. 1940). Worldwide surveys of cosmic ionization during the years
1931-1932 were made by several groups and Hess of Austria studied time variations associated with solar activity
cycle on a mountaintop from 1931-1937. Global radiation levels correlated well with the expected effects of the
geomagnetic deflection of cosmic radiation. A worldwide network of stations began to develop leading to observed
short-term fluctuations in the global ionization rates simultaneously in both the southern and northern hemispheres

i