So I’m sitting in my cube,
minding my own business when this guy walks in and introduces himself as one of
the engineers that works with the ALARA program. For those of you non-nuclear
engineers out there, ALARA stands for As Low As Reasonably Achievable. The
appropriateness of using the word ‘reasonable’ in this context is going to be
the focus of this blog post. But that’s for later, right now let’s get back to
the story. So this dude tells me that the station missed its dose goals last
month and so they’re talking to everybody who picked up any dose to understand
why we got dose and I received 1 mRem of dose while working in the fuel
building. There are two problems with this. First, the monthly dose goal is a
station wide goal, it doesn’t care if one person gets all of the dose or if 500
people get 1/500 of the dose. Ridiculous. Second, I didn’t get 1 mRem of dose.
Monthly dose accounting is based on data from electronic dosimeters (EDs) that
are checked out before each entry into the radiological controlled area (RCA)
which is the part of the plant that contains all of the pipes that carry
radioactive water and thus the only part of the plant where we would expect to receive
dose above background levels. These EDs display our dose down to the nearest
0.1 mRem, but the computer system only records data to the nearest whole mRem.
This means that two separate RCA entries resulting in 0.4 mRem each, even if
they occur just minutes apart from each other, would be recorded by the system
as 0 mRem while a single entry of 0.5 mRem would be recorded as 1 mRem. Six
other people did the job with me the day I got that dose. We were all in the
same place, exposed to the same conditions, for the same amount of time, but I
was the only with the ALARA engineer on my case. My coworkers all exited the
RCA with 0.3 or 0.4 mRem and turned in their EDs in time to be recorded as a
big old 0. I, on the other hand, managed to pick up a single particle of
radioactive cobalt on my pants that prevented me from passing through the
radiation detectors to exit the RCA. As I sat in the health physics office
(wearing disposable scrubs) for nearly two hours while they located the
particle and removed it from my pants. This office was not in the plant and far
removed from any excess sources of radiation, but just on the wrong side of the
radiation monitors for me to be able to process out my ED. As I sat there, I
watched as normal background radiation pushed my ED from 0.4 to 0.5 mRem and
just like that I was on the bad boy list.
If you’re like me, you’re
probably thinking this whole scenario is just a little bit ridiculous. The
truth is over-protection from radiation can have some pretty serious
consequences. Decreasing marginal returns mean more and more money being spent
on smaller and smaller dose savings. So much focus on radiological hazards can
at best make workers less efficient and at worst distract them from more
imminent industrial safety risks. And a race to the bottom can create some behavior
that is just plain unethical, like having crews stop work and exit the RCA
after 0.4 mRem, only to immediately reenter and continue the same job. So with
those questions in mind we have to ask the question, “Is it worth it?”
Let’s quickly catch up on how the
industry got to this point. When America’s nuclear program was in its infancy,
it was pretty clear that radiation could have some serious health effects and
some type of protection would have to be put in place. The linear no threshold
(LNT) theory was put forth which basically assumes that there is a linear
health response to dose at all levels and even low levels will have some effect
even if it’s very small. Considering the lack of knowledge on the topic at the
time this was a conservative, prudent model to use, but still the DOE rejected
it for lack of evidence. Despite the DOE’s rejection, in 1954 the National
Council on Radiation Protection and Measurements (NCRP) decided there was
enough evidence and promoted the theory as truth. Remember though, at this time
the vast majority of data on the health effects of radiation came from the
survivors of the two Japan bombings which were extraordinarily high doses. The
NCRPs decision was based off of extrapolating a linear response at higher dose
levels down to lower ones. The LNT theory has been pushed by regulatory bodies
ever since. Despite setting clear upper limits, regulation calls for ALARA to
be applied which effectively drive the race to the bottom and actual dose
limits end up well below the limit called out by law.
More recent evidence shows that
negative health effects below 10 Rem in a year are non-existent. You read that
right, 10 Rem. In my story from work, we were squabbling over mRem or
thousandths of a Rem. And it doesn’t matter if that 10 Rem comes all at once or
spread out over the year. At first this was merely empirical data with no
physical cause. We realized that the average person receives about 300 mRem a
year in background radiation, but environmental effects like altitude, eating
habits, and proximity to certain manmade sources could send that number well
over 600 mRem and yet the people getting more were just as healthy as those
getting less. Then tests were done on people who got known acute doses of
various magnitudes. Small changes in blood chemistry that were unaccompanied by
any other symptoms occurred approaching 10 Rem and any other observable effects
didn’t start occurring until over 10 Rem. The EPA charts these health effects here (about 1/3 of the way down the page). Critics argued that the observed data didn’t
make any sense and wasn’t backed up by any physical reason for why radiation in
low doses didn’t cause any damage. That was until several studies gave us the
answer including this one performed by medical
doctors who use radiation to treat patients and aren’t linked to the nuclear
industry in any way. For those of you who are like me and don’t like big
biology and medical words, the gist of it is that when life was first
developing on Earth, our planet was crazy radioactive so early cells evolved
built in defense mechanisms. These defense mechanisms prevent low levels of
radiation from causing any damage but eventually at much higher doses the
defenses are overwhelmed and the flood gates open.
That upper regulatory limit that
I mentioned earlier is 5 Rem per year, which is still half of what we now know
to be safe levels of radiation. I get about 4-5 mRem in a year from work.
Driving down dose levels to these extreme levels has a large economic impact on
nuclear power plants every year and has the potential to backfire in the other
ways I listed above.
What do you think? Has the
nuclear industry taken radiation protection too far or is it worth it at any
cost?
A lecture from former ANS
president Eric Loewen that makes a lot of the same points as me in much greater
detail and ends with a newspaper article that covers the danger of letting
juries of laymen decide what ALARA means when we should be using the hard and
fast regulatory limit as a guide:
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