http://www.nature.com/news/modernize-radiation-measurements-to-save-lives-1.20579
Nature - International Weekly Journal of Science
Modernize radiation measurements to save lives
The US refusal to use SI radiation units is confusing and dangerous.
Its time to make the switch.
13 September 2016
There are two types of nation: those that use the metric system and those
that have put a man on the Moon. The reliance of the United States on feet
and pounds, along with its refusal to embrace metres and kilograms,
baffles outsiders as much as it warms the hearts of some American
patriots. But it is time for the country to give up on the curie, the
roentgen, the rad and the rem.
Instead, US regulators and scientists should adopt the appropriate SI
units for the measurement of radioactivity. They should do so not only for
the sake of international harmony, but also to protect the health and
safety of US citizens.
After years of wrangling, on 29September the National Academies of
Sciences, Engineering, and Medicine will hold a workshop to discuss
whether the United States should adopt the international system of units
for radiological measurements. The negotiations will affect everyone from
NASA astronauts and air crews to emergency responders.
The rest of the world signed up some time ago. In the 1970s, the
International Committee for Weights and Measures adopted a clear set of SI
units to describe radiation exposure. The curie, an inspiringly named but
clunky measure of radioactivity, was replaced with the becquerel. The
roentgen, describing air ionization, became a measurement in coulombs per
kilogram. The rad, which quantifies absorbed dose, was superseded by the
gray. And the rem, which describes thedose that causes the same amount of
biological damage as a rad, was replaced by the sievert.
In case of a nuclear accident, this last quantity is the most crucial.
Sieverts capture how peoples immediate radiation exposure might translate
to future health effects. In 2011, after a tsunami swamped the Fukushima
Daiichi nuclear power plant in Japan, the International Atomic Energy
Agency and Japanese authorities used sieverts to describe releases of
radiation from the three failed reactors.
As fear spread and the public and media clamoured for information, the
last thing anybody needed was a load of complicated conversions. It was
hard enough for most to sort out the difference between millisieverts and
microsieverts, never mind then having to convert those to rems. Yet US
officials insisted on generating hazard maps using rems. And that meant
that people, including those in the danger zone, could not tell at a
glimpse what was really happening. In the middle of a radiation incident,
should emergency-response officials need to whip out their calculators?
Yes, it is possible to use both sets of measures, and to follow the rem
numbers with the sievert numbers in brackets. In practice, this is what
many US regulatory agencies do. But it is simply too awkward. The
Australian government has publicly criticized the US system for creating
confusion.
In the middle of an international nuclear-radiation incident, should
emergency-response officials huddled in a situation room really need to
whip out their calculators? Remember NASAs Mars Climate Orbiter, which was
lost in 1999 when someone forgot to convert between imperial and metric
units (even though they had plenty of time to check) the spacecraft broke
apart in the Martian atmosphere rather than smoothly entering orbit.
Imagine if such an embarrassing error involved the life and safety of
millions of people here on Earth.
Many US experts know that they need to make the switch. Officially, the
government encourages agencies to use SI units. And unlike with everyday
measures of distance and mass, Americans dont have a deep and lasting
emotional bond with radiological measures, and could easily be brought to
understand sieverts. During Fukushima, many US news agencies gave up on
even trying to convert, and simply used the international sievert
measures.
So why not make the change? The US nuclear industry claims it will be
expensive, with millions of dollars needed to update software and hardware
and to retrain workers. (In 2012, the countrys Nuclear Regulatory
Commission, which technically oversees the industry but is widely
sympathetic to it, quashed an effort to switch to SI units.) But the US
nuclear industrys suppliers also sell to European manufacturers, and so
are well equipped to adapt.
In the eighteenth century, French scientists proposed the metric system,
and then French officials imposed it. US researchers should follow their
lead, and then US regulators should make the change, and require the
industry to follow.
In 1914, an article in Nature bemoaned the fact that the metric system was
slow in catching on: Why do people go on agitating? Well, the reason is
the necessity for such a system. A century on, the United States is
running out of reasons not to bring its radiation measurement into the
modern era.
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