Management of Commercially Generated Radioactive Waste - U.S. ...

Issue
267
GEOLOGIC CONSIDERATIONS
Radiolysis will cause hydrogen and oxygen to form in a bedrock cavern, thus creating a
potentially explosive atmosphere. Should an explosion occur inside the cavern, the conse-
quences are really unknown. It will place stress on the cavern and the aquifer and increase
the chances of water movement, thus increasing the potential for additional contamination
of the aquifer. The authors fail to address such possibilities. (97)
Response
The consequences of an explosion were not addressed because the probability of one
occurring after emplacement of waste is considered to be infinitesimally small. The explo-
sive range for hydrogen in air is 4.1 to 74.2 volume percent. Mixtures in this range will
ignite and burn if the temperature is above the ignition point, 1085 0 F (585 0 C) (Perry 1950).
Temperatures will never be this high. Below this temperature, a spark could cause an explo-
sion in mixtures in the explosive range. This will never be achieved in an open storage
room (e.g., in salt; 5.5 m x 6.7 m x 1070 = 39,400 m 3 ), because a production of 1615 m 3
(0.041 x 39,400) of H 2 would be required. Production of this much hydrogen would require
the complete radiolysis of 1300 liters of water with no recombination or the total corrosion
of 3,000 kg of iron by an aqueous corroding medium.
Preliminary estimates of the quantities expected by radiolysis of brine (or water) in
the backfill surrounding waste packages were performed by Jenks (Jenks 1980). His work
indicates that such accumulations will not approached by even an order of magnitude. Jenks
(Jenks 1979) also made estimates of corrosion accelerated by radiolysis which also indicates
that adding hydrogen produced by aqueous corrosion will still not cause the quantity to
approach that needed for the explosive range.
The explosive range could possibly occur in voidage in the backfill surrounding the
waste package. Sparks are not likely in this location. In any case, the reaction could not
be propagated through the backfill because the baffling effect of the backfill particles.
Issue
Additional geologic background information should be provided in the Statement, and the
discussion of tectonic effects should be expanded. (10)
Response
This Statement is generic in nature, and the geologic history of formations (salt,
basalt, granite, shale) and plate tectonics are discussed in general terms. Detailed dis-
cussions would be more appropriate and will be included in future site-specific EISs.