December 21, 1954

With regards to your letter of December 16, 1954, I would like to provide the
following data:
On Friday morning, December 17, 1954, in order to check the operation of the
system pressure measuring system, a small amount of air was allowed to bleed into
the recombiner system via the recombiner pump bleedein connection. This carried
sufficient activity into the first barrel of the gas holding system to raise the
radiation level to 300 mr/hr at 4 inches from the first barrel, 40 mr/hr at the
grate and 5 mr/hr on top of the 4" concrete slab immediately above the first barrel.
These measurements were made with no shielding water in the pool.

Since the pressure gauge showed no change with the initial bleed-in, this in-
dicated the system was greatly below -20" H2O pressure, the actual pressure in the
recombiner-gas disposal system was found by taking a measurement with the mercury
manometer on the sampling panel. The pressure measurement showed a pressure of
-50" H2O.

It was decided after consultation with the deputy director to bleed-in the
additional air required to lower the pressure to approximately -15" H2O at the
holding tanks rather than at the recombiner pump in order to not carry additional
radioactive gas into the tanks. Valves 3, 26, and 30 at the holding tanks were
opened to accomplish this.

The final pressure at this time was adjusted to approximately -17" H2O.

It was decided at this time to fill the pool with the shielding water.

The pool was given a quick cleaning job which was made difficult by the fact that
the pool drain was repeatedly clogged by the mud and debris in the pool. The pool
was then tilled to within one foot of the top, --7' of water depth, --4' over the top
of the barrels.

The pressure in the gas system rose to -7" H2O due to the relatively high temperature
of the shielding water compared to the existing ambient temperature. As the water
gradually cooled, the system pressure has drooped back to -12" H2O

Dr. Beck
December 21, 1954

It is calculated that the gas system pressure will vazy approximately 1.4" H2O
per degree centigrade change in water temperature in the pool.

No change in system pressure with changes in temperature of the reactor itself
should be expected as long as the recombine gas system is connected directly to the
holding barrels as long as the temperature remains constant. The volume of the re-
combiner system is approximately 8 liters compared to 2000 liters in the barrels.

Of the two vacuum collecting barrels, one is at complete vacuum and one is at
half vacuum. No gas has been bled off to the stock since last summer and that had
only a very slight activity.

No radiation can be detected at any point around the pool. This is perhaps a
combination of the shielding water and the relatively short half-life of the gas
activity.