ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
injury for any radiation schedule no matter how
irregular. The expression is
where
I(t) = injury at time t in units of maximum safe
injury (MSI) which is just that allowed for
training by the ANP-MAG (t >= t ‘),
dD
-- - dose rate, rem per unit time, at time t”
dt ” (0 < t ” < t ’).
It may be noted that the half life of the reparable
injury is about one year and that this component
appears to constitute 90% of the total.
Other formulations are suggested to take account
of other phenomena, such as enhancement of sensi-
tivity by previous doses. Nothing basic to the
biology of the problem is intended; rather, it is
suggested that if the restrictive planning chart is
satisfactory for airplane design and strategic plan-
ning, then the formulation should also be satis-
factory from a biological point of view. Since it
is much more flexible than the chart, it would be
much more useful for interpretation of actual radia-
tion schedules in terms of injury.
This same model predicts that the AEC laboratory
tolerance doses administered over a 30-year period
give the same injury as does an instantaneous
dose of about 60 rem. These numbers are not in-
consistent with presently accepted concepts.
ANALYSIS OF SOME PRELIMINARY
DIFFERENTIAL EXPERIMENTS
M. F. Valerino”
In order to investigate the adequacy of simple
analytical models proposed for describing some of
the neutron transport processes involved in the
aircraft divided-shield concept, some of the data
obtained in the preliminary differential experiment~’~
at the TSF have been examined. Only
thermal-neutron measurements have been made.
130n loan to Tower Shielding Facility from National
Advisory Committee for Aeronautics, Cleveland, Ohio.
14C. E. Clifford et al., Preliminary Study of Fast Neu-
tron Ground and Air Scattering at the Tower Shielding
Facility, ORNL CF-54-8-95 (Aug. 23, 1954).
146
The thermal-neutron flux measured at the rear of
the detector tank as a function of the angle 8 (angle
between the reactor axis of symmetry and the
source-detector axis) for a 65-ft reactor-detector
separation distance and a 195-ft altitude is shown
in Fig, 12.6. The flux is plotted relative to that
for 8 = 0 deg and is compared with a curve of the
direct beam flux to be expected at the detector, as
calculated on the basis of the total water thickness
between the reactor surface and the detector. In
the calculation of the direct beam flux the leakage
neutrons were assumed to have a cosine distribu-
tion at the reactor surface, and the attenuation
lengths were based on Lid Tank Shielding Facility
(LTSF) data corrected to give the point-to-point
material attenuation kernel. The calculated curve
agrees well with the experimental curve for angles
up to 45 deg. Beyond the 45-deg angle, the calcu-
lated flux drops off rapidly, and at 90 deg the direct
beam is gone. The measured flux for 8 = 90 deg
must hence be presumed to be due to air-scattered
neutrons only. Single-scatter theory calculations
have not yet been performed for the case of a beam
whose axis of symmetry is at an angle with the
source-detector axis, and hence it was not possible
to calculate the magnitude of the air scattering to
be expected.
In order to estimate the air scattering into the
rear of the detector tank, the air-scattered flux
40
05
02
O‘I
- 005
“0
4 0.02
0.01
0005
0002
0.001
2-01-056-2-T7
Fig. 12.6. Comparison of Calculated and Meas-
ured Fluxes in Rear of Detector Tank.
0
a
-
-