In addition to the safety efforts usually employed in atomic test operations, considerable
forethought and planning were required in the handling of liquified hydrogen. The Ivy
operation overseas and its preparation in the ZI involved the handling of liquified hydrogen
in quantities not previously encountered. The safety aspects of engineering design and operating procedures were continuously reviewed by LASL personnel who retained as safety
consultants recognized Jeaders in the commercial field.
In the development of experience with this product a conservative approach was adopted.
Standard safety techniques for combustible gases were used and modified as experience and
circumstances indicated. Although liquified hydrogen is recognized as the most energetic
chemical fuel, it has desirable properties that facilitate simple safety techniques. For example, although the mixtures of hydrogen gas and air do have a wide explosive range, they re-
quire a relatively high concentration of hydrogen as a lower explosive limit, which means
that, compared to most other combustible gases, a larger quantity of hydrogen must be free
for a risk to be present. In addition, although liquid hydrogen has a low heat of vaporization,
it also has a high rate of diffusion and thus is easily dissipated. Both these characteristics, a
high lower explosive limit and a rapid upward diffusion rate, make the problems of safe
handling not too difficult. Adequate ventilation was readily incorporated in the designs and
operating procedures so that the prevailing conditions were continuously safe, with minimum
risk even in the case of untoward incidents. These safety features were incorporated for all
operations of TU 2, 3, and 4.
The primary roll-up of equipment for TU 3 was completed prior to Mike Shot. Virtually
all equipment, except three Dewars and several “transportainers,” was ready for evacuation by
M-—3 days. This left only a very small amount of equipment and materials to be handled after
Mike Shot.
The over-all storage efficiency of the TU 3 Dewars, from the time of receiving liquid .
hydrogen until itwas emptied from the Dewars, and including all losses of every kind (from
normal heat leaks, from accidents, from Dewar-to-Dewar transfers, from some experiments,
and from malfunction of the equipment) was 95 per cent over a period of approximately 2!
months. Since the one completely critical commodity, for which TU 3 was responsible, was
deuterium, it is interesting to note that, of
stored by TU 3 over a period of
36 days, the total loss was 0 liters.
4.4
TASK UNIT 4, MIKE ASSEMBLY
TU 4 was organized to prepare for shipment and to assemble the complete Mike device.
CTU 4 coordinated the Mike assembly at all points for all groups and contractors. These
groups consisted of personnel of American Car and Foundry (ACF) and CMR, GMX, and W
Divisions, LASL. Each of these groups was responsible for various specific assembly
operations. For example, ACF was responsible for the mechanical assembly of the device;
CMR was responsible for the cryogenics system,
and W-1 was responsible for all nuclear components.
Prior to the assumpcion by CTG 132.1 of operational control of the device, TU 4 maintained efficient liaison with all the diversified groups of the Laboratory concerned with the
development of the Mike device.
The Mike device was shipped to Eniwetok aboard the USS Curtiss, and after the arrival of
TU 4 personnel in the Forward Area in mid-September the Mike assembly program began with
the components being unloaded as necessary from the USS Curtias to the cab on Elugelab
Island. Prior to departure for the Forward Area, a schedule of operations for assembly of the
device, and for other installation within the cab after commencement of the device assembly,
was decided upon. This schedule took into account not only the predicted assembly time of the
57