ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
obtained from subsequent analyses of fuel samples,
together with the known amounts of concentrate
added.) While the total amount of uranium (U235)
added to the system in order to make the reactor
critical was approximately 135 Ib, because of the
amounts withdrawn from the system for samples
and in trimming the pump level, the uranium
concentration at criticality was 23;7 Ib/ft3; or,
since the calculated volume of the 1300°F core
was 1.37 ft3, the “cold,” clean critical mass of
the reactor was 32.5 Ib of UZ3’.
Low-Power Experiments
Several “experiments” were performed on the
critical reactor at low power, including reactor
power and rod calibrations. In addition, the
effects of the process system parameters on re-
activity were noted, and a preliminary measure-
ment of the temperature coefficient was under-
taken. The tests were started on the morning of
November 4 and were completed by noon on
November 8.
The regulating rod was calibrated both by the
addition of fuel and by a determination of the
resultant pile period upon withdrawing the rod
.- c
0*04 1
c
\
y 0.02
a
12
0.01 t
0 L
A
X
(as derived from the inhour equation). The value
of the rod was first obtained by noting the amount
of rod insertion required to maintain a constant
power level as a finite amount of fuel was added
to the system. This information, together with
a calculated value of the mass reactivity coef-
ficient (Ak/k)/(Am/m) of 0.232, permitted a de-
termination of the value of the rod. The technique
of rod calibration by pile period was also employed
both at design fuel flow (48 gpm) and with no fuel
flow. The data from each of these tests are
presented in Fig. 1.2. Although there is con-
siderable scatter, the data from the different rod
calibration techniques appear to be mutually con-
firmatory, and a rod value of 0.032 Ak/in. obtained
from the data was used throughout the remainder
of the experiment. It should be noted, however,
that the period calibration with no flow is believed
to give the best data, since the inhour equation
is applicable without correction and the resultant
value of the rod is not dependent’on a reactivity
coefficient .
The reactor power was first estimated from the
fission chamber counting rate, but attempts were
made to confirm the estimate by operating the
A FUEL ADDITION
0 PILE PERIOD ZERO FLOW
3i?cnm
OR NL - LR - D WG 39 008
X PILE PERIOD 48gpm FLOW
0 2 4 6 8 io 12 14
ROD POSITION (in.)
Fig. 1.2. Calibration of Regulating Rod,