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15 Initial Emergency Response Efforts
15.3.2 Radiation Dose Management
If high levels of radioactivity are involved in the attack and radiation dose rates
are high then managing radiation dose to the emergency responders will become
a significant task. Part of dose management involves insuring that no individual
exceeds a radiation dose limit, that the total dose of all workers combined is as low
as reasonably achievable (ALARA), and that dose is balanced as much as possible
rather than “burning out” a few people while others receive little or no dose.
The best way to accomplish this is by using dosimetry—ideally, every worker who
enters the Hot Zone will have their own dosimeter, but this is not always possible.
If there are insufficient dosimeters such that not every person can be issued one, it
might be necessary to use group dosimetry, to be able to account for the location(s),
time in each location, and dose rate at that location for each worker, or to use other
dose estimation methods [10]. If possible, the dosimeters should be accredited by
the National Voluntary Laboratory Accreditation (NVLAP) program, although if
NVLAP-accredited dosimeters are not available, any type of dosimeter will suffice,
including PRDs that record the total dose in addition to the dose rate.
Individual dosimetry involves issuing a dosimeter to each person entering the
Hot Zone, and reading the dosimeter when that person exits. If there are insufficient
NVLAP-accredited dosimeters to provide one for each person it is also acceptable
to issue electronic dosimeters or PRDs that have a total dose feature that can be used
to record the person’s dose while in the Hot Zone. Either way, the most accurate
reading will occur if the dosimeter is read or is zeroed out before the wearer enters
the Hot Zone. If this is not possible, the wearer should read (and record) the total
dose prior to entry and the difference between these readings represents their dose
during that particular entry.
If there are insufficient dosimeters or instruments to provide to all persons entering
the Hot Zone then group dosimetry should be considered. Group dosimetry involves
providing an individual dosimeter for at least one person in each working group (e.g.
firefighting hose team, rescue team, etc.) entering the Hot Zone, and the dose to that
one individual is assigned to all members of their team. For group dosimetry to be
relatively accurate the members of the group must be working in relatively close
proximity in an area in which radiation dose rates are relatively constant from place
to place (i.e. no person is likely to be standing in a localized hot spot).
In the absence of sufficient dosimeters for group dosimetry, it might be possible to
calculate radiation exposure if the location of a person (or group) can be determined,
as well as the amount of time spent in each location. A person (for example) who
spent ten minutes in an area with radiation levels of about 60 mGy hr
−1 should receive
a dose of about 10 mGy from their work in that area. If they spend an additional six
minutes in an area with a dose rate of 200 mGy hr
−1 then an additional 20 mGy can
be added to their dose for a total of 30 mGy for that entry. Assigning a radiation
dose based on such calculations is possible, but this is not the preferred method for
determining exposure.
15 Initial Emergency Response Efforts
15.3.2 Radiation Dose Management
If high levels of radioactivity are involved in the attack and radiation dose rates
are high then managing radiation dose to the emergency responders will become
a significant task. Part of dose management involves insuring that no individual
exceeds a radiation dose limit, that the total dose of all workers combined is as low
as reasonably achievable (ALARA), and that dose is balanced as much as possible
rather than “burning out” a few people while others receive little or no dose.
The best way to accomplish this is by using dosimetry—ideally, every worker who
enters the Hot Zone will have their own dosimeter, but this is not always possible.
If there are insufficient dosimeters such that not every person can be issued one, it
might be necessary to use group dosimetry, to be able to account for the location(s),
time in each location, and dose rate at that location for each worker, or to use other
dose estimation methods [10]. If possible, the dosimeters should be accredited by
the National Voluntary Laboratory Accreditation (NVLAP) program, although if
NVLAP-accredited dosimeters are not available, any type of dosimeter will suffice,
including PRDs that record the total dose in addition to the dose rate.
Individual dosimetry involves issuing a dosimeter to each person entering the
Hot Zone, and reading the dosimeter when that person exits. If there are insufficient
NVLAP-accredited dosimeters to provide one for each person it is also acceptable
to issue electronic dosimeters or PRDs that have a total dose feature that can be used
to record the person’s dose while in the Hot Zone. Either way, the most accurate
reading will occur if the dosimeter is read or is zeroed out before the wearer enters
the Hot Zone. If this is not possible, the wearer should read (and record) the total
dose prior to entry and the difference between these readings represents their dose
during that particular entry.
If there are insufficient dosimeters or instruments to provide to all persons entering
the Hot Zone then group dosimetry should be considered. Group dosimetry involves
providing an individual dosimeter for at least one person in each working group (e.g.
firefighting hose team, rescue team, etc.) entering the Hot Zone, and the dose to that
one individual is assigned to all members of their team. For group dosimetry to be
relatively accurate the members of the group must be working in relatively close
proximity in an area in which radiation dose rates are relatively constant from place
to place (i.e. no person is likely to be standing in a localized hot spot).
In the absence of sufficient dosimeters for group dosimetry, it might be possible to
calculate radiation exposure if the location of a person (or group) can be determined,
as well as the amount of time spent in each location. A person (for example) who
spent ten minutes in an area with radiation levels of about 60 mGy hr
−1 should receive
a dose of about 10 mGy from their work in that area. If they spend an additional six
minutes in an area with a dose rate of 200 mGy hr
−1 then an additional 20 mGy can
be added to their dose for a total of 30 mGy for that entry. Assigning a radiation
dose based on such calculations is possible, but this is not the preferred method for
determining exposure.