Memorandum from Raymond L. Murray to Clifford Beck
April 6, 1953
April 6, 1953
to: C K Beck
from: R L Murray
Subject: Control and Safety Rods
In answer to your questions:
- 1. What are exact dimensions of Boron Column in Control and Safety Rod?
- length 12.0" (three 4.0" cylinders)
- outside diameter 0.630"
- inside diameter 0.183"
- 2. What is Volume of Boron?
- 18.7 cm³ per cylinder, total 74.8 cm³
- 3. density of Boron?
- 4. density of Boron containing material
- 5. Total weigh of Boron per rod
- 6. Total weight of boron Containing Material
- 7. What, if anything, is present besides B4C?
- Comparing theoretical percentage B with actual, discrepancy of 0.6%. No
information on what this is, but may be carbon. Does not matter, however.
Critical condition will be achieved with solution at temperature
of cooling water, with one rod completely out (safety) and one
rod completely in (control). As one rod is removed, [delta]k increases,
the power rises, and the temperature rises. The rod value as best
we can compare with Los Alamos is 80 grams of U-235 or 0.016 [delta]k.
If either this rod is dropped or the safety rod falls, the reaction is
suppressed. The average change in reactivity is, for 5"/min removal
0.016/2 minutes = 0.008/min or 0.00013/sec
The maximum rate of change of reactivity is approximately twice
this value, when the rod is half way out.