mostly from the residual cloud samples, particularly with regard to particle
size distributions and radioactivity, these data having been correlated to a
great extent. Other information from shots has been developed by several
investigators.
Initiation of this project is particularly timely. Since the effective cessation of nuclear testing resulting in releases of radioactivity into the atmosphere many years ago, the community of individuals who are familiar with
debris sampling and analysis, and with the systematics of physical, chemical,
and radiochemical properties of the debris has become well-dispersed and has
effectively decreased considerably,
In addition, the selection and availability
of such samples has decreased.
If additional work with samples stili available
is to be accomplished, such work should not be postponed.
The substrate or medium also varies considerably.
distinguish between:
On this basis, one may
Underwater bursts (of no interest);
Water surface bursts (Pacific Proving Grounds--of marginal interest);
Shallow-water surface bursts, on a barge (Pacific Proving Grounds--of
interest only for evaluation of Marshall Islands);
Bursts on coral (with or without a steel tower);
Bursts in or on alluvium (NTS, with or without a steel tower):
Bursts on hard rock.
DEVICE SHOTS
In some cases,
the substrate {s partially modified by the presence of large
quantities of added materials,
The nature and properties of the particulates formed as a result of explosions
involving nuclear materials depend on the type of device, but mostly on the
detonation conditions and the substrate. Thus, one may distinguish tests on
the basis of the height of burst (HOB), or better, on the basis of the scaled
height of burst (SHOB). Although not entirely correct, one may use a
(yield)-'/3 - scaling law, so that the scaled height of burst is:
(SHOB) = (HOB) (Yield) ~ 1/3
where the height of burst may be expressed either in meters or in feet, and
where the yield may be expressed in kilotons or in megatons TNT-equivalent.
On the basis of height-of-burst (depth-of-burst) differences, one may distinguish
such as concrete or steel.
The properties of the particulates are also affected by the nature of the
shot:
Nonnuclear events involving nuclear materials; actual nuclear detonations
involving fission or fusion or both.
Device composition also is a variable.
The overall radionuclide spectrum is
{neutron spectrum) and the fissionable material used.
In addition, however,
the specifics of the resulting transuranic distribution depends to some extent
on whether Pu was present in the device as fuel, or formed from U through Np
by neutron capture.
between:
SAMPLING
Underground (fully contained) bursts (of no interest, except when early
Venting occurred);
Cratering (partially contained) bursts, including very shallow bursts;
surface bursts (HOB})<5 m, scaled to 1 kt);
Since the validity of an analysis can be no better than the sample analyzed,
sampling must be considered in some detail.
Near-surface bursts (5 m <(HOB <130 m, scaled to 1 kt including tower
shots and many balloon shots);
A great variety of sampling methods and of samplers has been used, sometimes
deployed in specific arrays. What was used depended upon the type of sample
desired, but also upon the state of the art.
A survey of samplers and sampling
methods used over the years is shown in Table 1.
All of the samples taken
constituted only a very small fraction of the cloud, or of the total amount
of
radioactive and nonradioactive debris lifted.
Fallout samples from Bravo, an
approximately 1L0-Mt ground-surface shot of the 1954 Castle series, may have
Free airbursts (HOB >130 m, scaled to 1 kt; of no interest) including
upper atmosphere bursts (no surface material swept into the cloud.)
*This quotation is from the unclassified abstract of the series.
contained as little as 107!2 or less of the amount lifted. Cloud samples
collected by aircraft may have contained from 10°! to 10-]4 o£ the total
cloud.
Thus, no sample taken was likely to be completely representative
of
the cloud or of the fallout.
The considerable inhomogeneities that exist in
chouds arse would generally preclude representative samples from
having been
obtained.
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