Note especially :
Doses can be calculated on-line for a wide variety of flights at www.sievert-system.org (in French).
Jaro
NUCLEONICS WEEK - April 4, 2002
WORRIED BY RADIATION?
FRENCH SITE FIGURES YOUR AIR TRAVEL EXPOSURE
Members of the public can calculate their radiation exposures
during air travel on an Internet site opened to the public
last week by the French Civil Aviation Administration (DGAC).
The site, which features a new software program called
Sievert developed to help airline companies manage exposures
of air crews, is funded by DGAC and managed by the
Institute of Radiological Protection & Nuclear Safety (IRSN).
The 1996 Euratom "basic safety standards" directive
requires Euratom member states to evaluate the exposure to
cosmic radiation of air crew members and, if individual dose
exceeds 1 milliSievert (mSv, equivalent to 100 millirem), to
take measures to reduce exposure as far as possible, to inform
personnel of the risks of exposure, and to avoid exposure of
unborn infants to more than 1 mSv.
All Euratom member states have either transposed the
1996 regulations into national law or are in the process of
doing so, and are laying plans to comply with the requirements.
Many other countries, including the U.S., have not
adopted the new regulations, which are based on International
Commission on Radiological Protection (ICRP) recommendations
of 1990. The previous (1977) ICRP recommendations,
the last adopted in the U.S., didn't cover occupational exposure
of non-radiation workers such as air crews. But French
officials said U.S. airlines are nevertheless taking steps to
evaluate air crew exposure and reduce unnecessary exposure,
and especially to inform personnel of risks they incur.
Jean-Francois Bottollier, project director for Sievert at
IRSN, said the French system is the only one in the world to
consider solar eruptions, thanks to measures IRSN's predecessor,
IPSN, made during flights of Air France's Concorde
supersonic aircraft, whose flight path is much higher than that
of subsonic aircraft. According to the measurements of those
and other flights during 1991-98, exposure during a Paris-New
York in Concorde flight averaged 0.08 mSv, while Paris-
San Francisco gave a dose of 0.14 mSv, Paris-Fairbanks-Tokyo
0.15 mSv, and Paris-Buenos Aires 0.1 mSv. Doses
increase with altitude, but Concorde spends less time in flight
due to its speed. However, if there is a solar eruption, the
effective dose can triple or more, experts said.
According to IRSN, a person residing 17 months in Paris
or 9 months in the uranium-rich central French region of
Limousin would get a dose of 1 mSv, from a combination of
telluric and cosmic radiation. During air travel, only cosmic
radiation comes into play.
Bottollier said Sievert is the only system so far to be truly
operational, in that air personnel-and now, the public-can
calculate the real dose they received on a given flight on a
given day. Values for a normal trip are based on calculations
of dose rates for 265,000 sections of airspace according to
altitude, longitude and latitude, but it takes the Paris Observatory
and IRSN several weeks to calculate real doses for flights during a solar eruption.
Bottollier said that based on measurements during a solar
eruption last April 15, the dose rate during a Concorde flight
at 11 kilometers' altitude between Paris and New York was
doubled during the eruption, from 6 microSv/hour to 12 mi-croSv/h,
and for the entire trip it was 30% higher than normal.
The "worst case" observed in the past, said the Observatory's
Pierre Lantos, generated a dose for a Concorde crew of 26
mSv for a single trip. But the eruptions, which average one a
year, don't make much difference in air personnel's annual
dose, Bottollier noted.
Pierre Dessarps, manager of the project for DGAC,
said that traditional land-based means of monitoring doses,
such as individual dosimeters and ambient dosimetry during
flights, have been used in Concorde from the beginning but
proved unwieldy for managing the "thousands of flights" the
authority must oversee in France. Alain Biau of IRSN added
that the on-board measurements for Concorde "weren't very
precise" and were useful mainly for alerting pilots to solar
eruptions at a trigger reading of 500 millirem, so the plane
can immediately drop to a lower altitude.
Pierre Blanchard, a former Air France flight crew member
who is overseeing the Sievert project for the French airline,
said that signal had been given only once since the company
began Concorde flights in 1976. The monitoring in principle
applies to flights above 15,000 meters, but British Airways
obtained an exemption from the monitoring for its Concorde crews, he said.
With the Sievert system in place, airlines send data about
their flight crew personnel to the system and receive individual
calculated doses the next day, project managers told journalists
at a March 28 briefing. The system has been open to
airlines since October. IRSN's Bottollier said that results so
far show that real doses, calculated according to flight paths
effectively taken, corroborate well with the standard doses
predicted by earlier IRSN measurements. "We are not under-estimating
the risk," he said.
Dessarps said some 20 airlines have already asked to
register on the Sievert site. The operating cost of Sievert is
about 100,000 euros a year.
A question not yet resolved is what will happen if air
personnel are found to receive more than 6 mSv/y. Under
French regulations, the dose limit for a member of the public
is 1 mSv/y. An individual receiving an occupational dose of
more than 1 mSv/y from cosmic radiation should be monitored
and potentially classified as a radiation worker. For a
dose above 6 mSv/y, he or she must be classified as a category
A worker, with a statutory dose limit of 50 mSv/y.
Air France's Blanchard said that in any case, the company
transfers pregnant women to ground jobs. For other cases,
union leaders have asked that personnel receiving over 1mSv/year
be classified as radiation workers, but the issue is
still under discussion. He said Air France would apply the
Alara (as low as reasonably acceptable) principle in managing
crew members, notably pilots who can't readily be transferred
between different types of aircraft. If one type of aircraft leads
to higher doses than the average, Air France will take action
to lower them, he said. But if doses throughout the fleet are at
5 mSv, he said, "We'll live with it."
Doses can be calculated on-line for a wide variety of
flights at www.sievert-system.org (in French).
-Ann MacLachlan, Paris