20.3 Decontamination Standards for Homes, Businesses, Public Spaces, etc.
251
Another factor to consider is how much remediation is required. Consider, for
example, a 40-story office building with extensive contamination on the exterior
surfaces. How much of the exterior should be decontaminated or replaced?
It is reasonable to decontaminate or replace exterior surfaces on the ground floor
because people can be exposed to radiation from embedded or affixed contamination.
It might make sense to decontaminate the second story as well for the same reason.
But should the 20th story be decontaminated if dose rates on the building’s interior
are acceptable? At a height of 60 or 70 m above the ground the contamination would
produce little or no dose at ground level; does it make sense to spend millions—even
tens or hundreds of millions—of dollars to decontaminate or replace contaminated
windows and exterior walls that produce little or no risk? Remediation or decontamination can be expensive and might produce little or no risk reduction; or will
the contamination pose a sufficient risk to window-washers, or to members of the
public as rain and weathering brings it down to street level, to justify the expense of
cleanup or removal? There are circumstances in which it might be most sensible to
simply leave the contamination in place rather than spending vast sums of money on
remediation that will accomplish little or no actual reduction in risk (for example, a
2019 contamination accident at the University of Washington is estimated to have a
remediation cost in excess of $60 million—Leone [6]).
There are national and international recommendations regarding the acceptable
dose to those living in an area to help determine when an area should be evacuated
and when the population should be permitted to return; in the US these are referred
to as Protective Action Guides (PAGs). The US Environmental Protection Agency
(EPA), for example, recommends evacuating from areas where even those sheltering
in place are expected to receive a dose in excess of 10 mSv during the first four days if
evacuation will produce a lower dose than sheltering. The EPA further recommends
relocating members of the public if the projected dose in the first year will be 20 mSv
with 5 mSv in any subsequent year [13]. At the same time, a 2014 NCRP report
notes “The RDD/IND Planning Guidance (from DHS [11]) does not include specific
cleanup criteria for RDD or IND incidents. Rather it recommends that decisions for
late-phase response be made using a site-specific optimization process which is a
decision-making process intended to take into account the many potential attributes
or factors that can affect overall public welfare and restoration decisions” (NCRP
[8] (Fig. 20.1).
20.4 Decontamination of Buildings, Infrastructure,
and Areas
Decontamination, even of radioactivity, is not a mysterious process. The author has
performed decontamination of tools, soils, concrete, metal, and even his own skin,
generally using the same “decontamination” techniques that are used to remove dust,
grease, or spilled food. Loose surface contamination can simply be wiped up and
251
Another factor to consider is how much remediation is required. Consider, for
example, a 40-story office building with extensive contamination on the exterior
surfaces. How much of the exterior should be decontaminated or replaced?
It is reasonable to decontaminate or replace exterior surfaces on the ground floor
because people can be exposed to radiation from embedded or affixed contamination.
It might make sense to decontaminate the second story as well for the same reason.
But should the 20th story be decontaminated if dose rates on the building’s interior
are acceptable? At a height of 60 or 70 m above the ground the contamination would
produce little or no dose at ground level; does it make sense to spend millions—even
tens or hundreds of millions—of dollars to decontaminate or replace contaminated
windows and exterior walls that produce little or no risk? Remediation or decontamination can be expensive and might produce little or no risk reduction; or will
the contamination pose a sufficient risk to window-washers, or to members of the
public as rain and weathering brings it down to street level, to justify the expense of
cleanup or removal? There are circumstances in which it might be most sensible to
simply leave the contamination in place rather than spending vast sums of money on
remediation that will accomplish little or no actual reduction in risk (for example, a
2019 contamination accident at the University of Washington is estimated to have a
remediation cost in excess of $60 million—Leone [6]).
There are national and international recommendations regarding the acceptable
dose to those living in an area to help determine when an area should be evacuated
and when the population should be permitted to return; in the US these are referred
to as Protective Action Guides (PAGs). The US Environmental Protection Agency
(EPA), for example, recommends evacuating from areas where even those sheltering
in place are expected to receive a dose in excess of 10 mSv during the first four days if
evacuation will produce a lower dose than sheltering. The EPA further recommends
relocating members of the public if the projected dose in the first year will be 20 mSv
with 5 mSv in any subsequent year [13]. At the same time, a 2014 NCRP report
notes “The RDD/IND Planning Guidance (from DHS [11]) does not include specific
cleanup criteria for RDD or IND incidents. Rather it recommends that decisions for
late-phase response be made using a site-specific optimization process which is a
decision-making process intended to take into account the many potential attributes
or factors that can affect overall public welfare and restoration decisions” (NCRP
[8] (Fig. 20.1).
20.4 Decontamination of Buildings, Infrastructure,
and Areas
Decontamination, even of radioactivity, is not a mysterious process. The author has
performed decontamination of tools, soils, concrete, metal, and even his own skin,
generally using the same “decontamination” techniques that are used to remove dust,
grease, or spilled food. Loose surface contamination can simply be wiped up and