248
20 Remediation
level of about 10 Bq cm
2 . The equates to 1000 Bq for every 100 cm
2 , which
corresponds to 60,000 dpm for every 100 cm
2 ; this is significantly higher than
the 5000 dpm limit for total contamination that is usually used as a limit in
the US. And, while causing very low risk, this level of contamination, and
the corresponding count rate when surveying, would likely be alarming to
members of the public.
In general radiation dose rate—and long-term dose and risk—is directly proportional to the contamination levels in the area in which one is living. If contamination
levels are increased by a factor of, say, five then the dose rate also increases by a
factor of five, the total dose increases by a factor of five, and the risk (assuming that
risk is directly proportional to dose at all levels of exposure) increases by a factor of
five.
So now consider a hypothetical contaminated area in which contamination levels
drop linearly with distance, in all directions. Since the volume of a sphere (or, in this
case, a half-sphere) is proportional to the radius cubed, the volume to be remediated
in this scenario will increase with the cube of the degree of remediation to be accomplished. In other words, reducing the contamination levels (and dose) by a factor of
two will require excavating eight times as much soil with a corresponding increase
in cost. Thus, reducing risk by a factor of two increases the expense of remediation
by a factor of as much as eight [4]. This is the fundamental tension when developing
cleanup levels—the ever-increasing cost of further remediation that must be balanced
by the ever-diminishing reduction in risk “purchased” with these expenditures.
Of course, cost is not the only trade-off. Excavating contaminated soil, demolishing contaminated buildings, loading contaminated materials into containers and
shipping those containers hundreds or thousands of kilometers, then unloading and
burying them at the other end … all of these carry their own risks and at some point
the added risks these activities generate might well be greater than the risks they help
to avert.
To the remediation and transportation risks we must add the risks that arise simply
from spending the public’s money. There have been a number of studies (e.g.Keeney
[5]) that have concluded that large costs distributed across society can have a negative effect because, in order to pay higher taxes (or utility bills or other necessary
expenses) the public has to take money from other risk-reduction measures. They
might delay replacing worn tires, be unable to pay for medications, choose not to see
a physician, and so forth. Keeney noted a rate of one anticipated fatality for about
$25 million in cost distributed across society; thus, a billion-dollar remediation might
lead to as many as 40 premature deaths. If the contamination that was remediated
produced only a very small radiation dose, simply funding the remediation might
cost more lives than the contamination would have.
20 Remediation
level of about 10 Bq cm
2 . The equates to 1000 Bq for every 100 cm
2 , which
corresponds to 60,000 dpm for every 100 cm
2 ; this is significantly higher than
the 5000 dpm limit for total contamination that is usually used as a limit in
the US. And, while causing very low risk, this level of contamination, and
the corresponding count rate when surveying, would likely be alarming to
members of the public.
In general radiation dose rate—and long-term dose and risk—is directly proportional to the contamination levels in the area in which one is living. If contamination
levels are increased by a factor of, say, five then the dose rate also increases by a
factor of five, the total dose increases by a factor of five, and the risk (assuming that
risk is directly proportional to dose at all levels of exposure) increases by a factor of
five.
So now consider a hypothetical contaminated area in which contamination levels
drop linearly with distance, in all directions. Since the volume of a sphere (or, in this
case, a half-sphere) is proportional to the radius cubed, the volume to be remediated
in this scenario will increase with the cube of the degree of remediation to be accomplished. In other words, reducing the contamination levels (and dose) by a factor of
two will require excavating eight times as much soil with a corresponding increase
in cost. Thus, reducing risk by a factor of two increases the expense of remediation
by a factor of as much as eight [4]. This is the fundamental tension when developing
cleanup levels—the ever-increasing cost of further remediation that must be balanced
by the ever-diminishing reduction in risk “purchased” with these expenditures.
Of course, cost is not the only trade-off. Excavating contaminated soil, demolishing contaminated buildings, loading contaminated materials into containers and
shipping those containers hundreds or thousands of kilometers, then unloading and
burying them at the other end … all of these carry their own risks and at some point
the added risks these activities generate might well be greater than the risks they help
to avert.
To the remediation and transportation risks we must add the risks that arise simply
from spending the public’s money. There have been a number of studies (e.g.Keeney
[5]) that have concluded that large costs distributed across society can have a negative effect because, in order to pay higher taxes (or utility bills or other necessary
expenses) the public has to take money from other risk-reduction measures. They
might delay replacing worn tires, be unable to pay for medications, choose not to see
a physician, and so forth. Keeney noted a rate of one anticipated fatality for about
$25 million in cost distributed across society; thus, a billion-dollar remediation might
lead to as many as 40 premature deaths. If the contamination that was remediated
produced only a very small radiation dose, simply funding the remediation might
cost more lives than the contamination would have.