Underground Reactors Revisited

Most of my ideas are not original. At least not in the sense that I was the first person who thought of them. This is most certainly the case for underground reactors. I thought about first underground reactor siting three years ago, primarily because I speculated that it would cost less than an above ground containment dome. Both Andrei Sakharov, and Edward Teller suggested underground reactor siting before I thought of the idea, and a lively discussion of the use of underground Teller's original idea was to bury reactors deep underground, but late in his life Ralph Moir persuaded Teller that it would be more practical and almost as effective to bury them closer to the surface. There was a considerable discussion of underground reactor placement during the 1970's, but no reactor manufacturer seems to have been interested in the underground placement approach.

In his last paper Edward Teller, togeather with Raloh Moir, proposed

a new combination including non- proliferation features, undergrounding, limited separations, and long-term, but temporary, storage of reactor products also underground. All these ideas are intended to make the plant economical, resistant to terrorist activities, and conserve resources in order to be available to greatly expand nuclear power if needed as envisioned by Generation IV reactor requirements.

Teller and Moir preferred a silo type design, a vertical tube that would contain a Molten Salt Reactor with drain tanks underneath, and a conventionally placed generator turbine at surface level.

Recent thinking about underground placement has focused on near surface placement. It cost money to dig a deep hole although it is not hugely expensive. Under ground reactor placement has to compete economically with above ground containment structures in cost. If the underground approach is not cost competitive with above ground structures, what is the point?Near surface placement lowers costs some, and near surface placement allows the locations of non-radioactive components of electricity generation system above ground. Thus the reactor can be located under the turbine hall. An aircraft attack might at least temporarily disable the turbine, but it would not damage the buried reactor.

Another solution to the cost issue is to place reactors in pre existing mines. Salt mines would be potentially useful, and are often located in surprising places. There is, for example, a giant salt mine located over 1000 feet under Detroit, Michigan. This mine includes over 100 miles of roads, and excavated portions are used to business and industrial purposes. Transport trucks operating within the mine are already powered by electricity. as can be seen in the photograph to to the right. Another huge underground salt mine exists in Hutchinson, Kansas.

Numerous salt domes have been excavated by pumping water into them and then drawing out brine. Hundreds of these salt caverns are then used for natural natural gas storage. Such caverns might also be used for underground reactor placement. Underground salt formations, often hundreds and even thousands of feet underground, are scattered all over the United States. For example "the panhandle" of West Virginia has in its basement a 50' layer of salt, 5000 or more feet underground. Salt formations under not only Detroit, but much of Michigan. Other salt formations stretch from Kansas to New Mexico. West Texas has numerous large salt formations in its geological basement.

In addition to salt mines, numerous natural and excavated underground structure can be found all over the country. Example include a large underground rock quarry is located under the Louisville, Kentucky Zoo, an old limestone mine near Kansas City, caves near St. Louis now used for warehouse space by a brewing company, a limestone mine in Indiana, now used as warehouse space.

There are over 500,000 abandoned mines in the United States. Most would undoubtedly be useless as reactor sites, but a some, located in geologically stable regions, well constructed, dry and readily accessible to areas where electricity is in demand, could prove useful as underground reactor placement sites.

Past studies have suggested the following advantages for underground reactor placement:

# Higher Resistance to...

– Terrorist attack

– Aircraft impacts

– Proliferation

– Sabotage and vandalism

– Conventional warfare effects

# Higher Levels of...

– Protection against severe weather effects

– Landscape aesthetics

# Greater containment capability relative to a surface-sited plant...

– Reduced public health impacts from extreme hypothetical accidents

Past research suggested that cost of excavating underground facilities would be higher than building conventional facilities, but these studies looked at excavations to depths of more than 300 feet, far more than would be required to obtain the safety and security advantages of underground nuclear placement. When a silo type structure is used to house smaller underground reactor, a relatively small area would need to be excavated. In addition, the use of salt domes and other salt formations was not considered by past studies of underground nuclear placement, despite the low cost of underground salt excavation, and the widespread extent of underground salt formations.

In many cases, costly excavations for deep underground nuclear placement can be avoided by using existing caves and mines, and relatively shallow reactor placement. Large existing salt mines would be attractive locations for existing reactor parks.