a
»
0
NN
below 40 pCi/g.
2.
Reduce the average concentration of the "defined
regicn’’ to some lower number which shall be determined by cost-benefit
considerations, but will usually not be belowlocal background.
(4) Condition D:
An assay area whose average Pu concentration
is any 5 ca thickness of soil below the surface layer when measured®
(at the 67 percent confidence level) to exceed 400 pCi/g will be
excavated end measured iteratively until its average Pu concentration.
in the new S cm layer is found by measurement (at the 50 percent confidence level) to be reduced in the defined region to some lower number
which shall be determined by cost - benefit considerations, but will
|
usually not be below local background.
Footnotes:
A
Assay Area.
The field of view of the in situ detector in its
normal operating position; typically a 28 meter diameter circle of
3 - 5 cm in cepth.
Scattered measurement can be used to estimate average
concentrations between such measurements by means of a linear estimator
progran known as "'Krigging."
P Statistically, two-thirds of the time the actual concentration will
be below the guide number.
One-third of the time the actual concentration
may exceed the number by some percentage which must be empirically deter-
mined (up to 20-30 percent, as an estimate).
—
This is similar to using a - ~
50 percent confidence level with a mmerical guide 20-30 percent (estimated)
lower.
If a 90 percent confidence level were used with the numerical
guide, the equivalent guide at a 50 percent confidence level would