ORNL-2106 - the Molten Salt Energy Technologies Web Site

A NP PROJECT PROGRESS REPORT
TABLE 421. SOME CALCULATED DESIGN PARAMETERS OF THE VERTICAL IN-PILE LOOP DESIGNED
FOR OPERATION IN POSITION C46 OF THE LlTR
Fuel
NaF-ZrF4-UF4 Shallow4
(53.5-4 0.6.5
mole %I
Reynolds Numbers Fuel Temperature Maximum Air
Loop Differential Temperature
Position Fuel Air
(OC) (OC)
Deep'
NaF-KF-LiF-UF4 Shallowu
(1 1.2-4 1-45.3
mole %I
Deepc
1,500
3P00
6,000
10,000
1,500
3,000
6,000
10,000
1,500
3,000
6,000
10,000
1,500
3,000
6,000
10,000
32.000
22,000
10,000
20,000
74,000
50,000
44,000
42,000
19,000
16,000
15,000
15,000
32,000
26,000
24,000
23,000
fip of loop at position of maximum thermal-neutron flux.
bBased on earlier calculations.
12
CTip of loop at bottom of active lattice.
factor from about 11 in the "shallow" position to
about 6 in the "deep" position.
FA ST-N E UT RD N D E T E C T OR S
D. Binder
A great variety of radiation-damage studies require
a knowledge of the fast-neutron flux of the
reactor being used for the irradiations. For
instance, changes in the mechanical and electrical
properties of metals and insulators are dependent
on the shape of the neutron-energy spectrum. As
the neutron energy increases, the number of atoms
displaced increases until a critical energy is
reached at which the effect saturates.22 Therefore,
it is essential to know the number of neutrons
per unit energy up to about five times the critical
energy and the integrated flux above this energy.
The energy spectra in two types of reactors from
thermal to 100 ev or 1 kev and from 0.7 to 8 Mev
22G. H. Kinchin and R. S. Pease, Reps. Progr. in
~hys.
18, 152 (1955).
242
135
65
33
33
103
56
30
17
125
65
33
20
94
50
27
16
380
410
5 10
520
250
450
530
550
450
550
580
600
3 80
410
460
480
Air Flow
Rate (cfm)
41
30
28
28
100
70
60
59
27
23
21
21
45
36
33
32
have been investigated by Tri~e.~~,~~ For the
remaining investigation, that is, the 1-kev to
0.7-Mev region, a detector must be developed with
which to study the variation of displacements with
neutron energy. The development of useful detectors
is dependent on a knowledge of this variation,
and vice versa. The first step therefore is
to calculate a known case based on simple assumptions.
Germanium was selected as the material to be
studied because it is sensitive to neutrons and
the relationship between the solid-state effect and
the number of displacements is known. From the
work of Cleland et aZ.25 at low temperatures, it is
known that five electron traps are introduced per
23J. B. Trice, Fast Neutron Flux Measurements in
E-25 o/ the Brookhaven Graphite Reactor, ORNL CF-
55-7-130 (July 27, 1955).
24J. B. Trice, A Series of Thermal, Epithermal and
Fast Neutron Measurements in the MTR, ORNL CF-
55-10-140 (Oct. 28, 1955).
25J. W. Cleland, J. H. Crawford, Jr., and J. C. Pigg,
Pbys. Rev. 98, 1742 (1955).
a
It
.
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