The Myers-Mahar paper offers important insights into the future of nuclear power station siting, nuclear cost reduction and nuclear safety. The "Underground Siting" abstract reads,
Small modular reactors (SMRs) sited 100 to 300 meters deep in underground chambers constructed in bedrock having favorable geotechnical properties could be both cost effective and provide superior levels of safety and physical security. The bedrock adjacent to and enclosing the reactor chamber would become the functional equivalent of a conventional containment structure, but one with increased margins of safety for design- basis accidents, reduced risks for beyond-design-basis accidents, and a high level of inherent physical protection against external threats. In addition, seismic safety could be enhanced at lower cost because seismic waves are generally attenuated with depth in bedrock. Nominal steel and concrete around the reactor would be required as would sealing of tunnels and other penetrations into the reactor chamber. Nonetheless, the net result in capital cost savings could potentially more than offset the cost of underground excavation. For a hypothetical granitic bedrock site with SMRs at a nominal depth of 100 meters, preliminary excavation cost estimates for single- and four-unit installations constructed by drill-and-blast range from around $90 million to $45 million per reactor, respectively, and for a twelve-unit installation constructed by tunnel boring machine from $25 to $15 million per reactor. Specialized applications for bedrock-sited SMRs include collocation at underground hydropower stations, test and demonstration facility for prototype SMR designs, and deployments in regions at risk of terrorist or military attack.One of the long term objections to underground reactor siting has been that it would increases reactor siting and housing costs, but advances in excavation technology and Alvin Weinberg's idea of building large numbers of multi reactor parks could potentially lower nuclear costs, while dramatically increasing nuclear safety. The Myers-Mahar paper makes clear exactly how dramatic the cost savings of underground reactor housing might turn out to be. They argue,
1) Reduce per-reactor capital cost of underground construction by siting multiple reactors in a single location, thereby allowing the cost of the common access shafts and tunnels to be shared among more than one reactor.In addition,
2) Reduce capital cost by restricting siting to those locations in bedrock of such high quality that excavated openings would be largely self-supporting and the rock overlying and enclosing the reactor chamber would act as a low-cost, passive, natural containment structure---and in addition would attenuate seismic motion and protect against aircraft impact, bombs and related threats.
3) Reduce capital cost and shorten the schedule for underground construction by taking advantage of advances in equipment, technology, and techniques for underground construction that have occurred since the 1970s such as underground excavation using hard-rock tunnel boring machines.
4) Reduce life-cycle cost by using in-place decommissioning.
5) Collocate waste management and other fuel cycle facilities underground in proximity to the reactors as a means to both reduce waste management cost and provide a new concept for nuclear waste management.Myers and Mahar reference a paper. "Cost Advantages of Large Underground Nuclear Parks," by K.M. Giraud, J.F. Junze, and J.M. Mahar, to argue that a 10% reduction of electrical generation costs from large single unit reactors is possible through underground siting with an even larger savings possible through multi-unit nuclear parks.
Public concerns about nuclear safety may have their irrational components, but nuclear power will not be acceptable until the public is sure that nuclear power plants do not pose a threat to their safety and well being. Once the public feels confident about nuclear safety, the case against nuclear power will weaken significantly. It is not enough to build safer reactors, an accomplishment which reactor manufactures have already accomplished, the public must be assured by the designed in safety improvements. Underground reactor siting hold the potential of boosting public confidence in reactor safety, to the point where opposition to nuclear power is no longer acceptable. If underground housing of power reactors increases confidence in nuclear safety, while lowering nuclear housing costs, then we will improve the likelihood of a nuclear powered future.
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Suggesting that more elaborate precautions will reduce people's concerns about nuclear power is a fundamental failure to observe the psychology of "nuclear fear".
Precautions are equated with danger. Extreme precautions - and putting reactors 100m underground is extreme - are regarded as meaning extreme danger. In fact I can almost hear the protests about water table contamination, stealth nuclear plants and hidden contamination now.
Joffan the rational for underground placement is lower nuclear cost, not safety. Safety is a secondary benefit. As for water tables, we can simpky point out that the reactor is geing placed in dry rocks, that have remained dry for millions of years.
Charles Barton: As for water tables, we can simpky point out that the reactor is geing placed in dry rocks, that have remained dry for millions of years.
An argument which applies just as well to the final storage site of nuclear waste once we've extracted all the energy from the Uranium or Thorium.
Doesn't stop the anti-nuclear movement from using it though.
Still, phone companies have responded to the baseless claims that phone towers cause cancer and the non-existent condition of electrosensitivity by making the towers look like trees and amazingly enough it actually seems to work (almost as if the complaints were really about what they do the view but the complainer didn't think they'd get as much sympathy with "but it'll ruin my view of the ocean/trees/carpark/whatever" as with "but it'll kill the children"). OK, they still get the real kooks, but those people haven't been able to make the same kind of fuss about fake trees.
Much of the opposition to new nuclear plants won't be motivated by the baseless concerns the people opposing it claim to have, but by the likelihood that their property values will drop if their view out the window has a big cooling tower in it.
I'm sorry Charles, I cannot believe that putting a reactor 100-300m underground is cheaper than putting it 10m underground. Your cost argument appears to be an implicit risk aversion argument.
As for "simply pointing out" anything technical, you should have enough experience of anti-nuclear feeling to realise that will not work. Yucca Mountain springs to mind in that regard.
Perhaps you do not agree with my point about precautions and perceptions. But I have seen it played out on the web -
"why do they do X if it's so safe?"
Can I also object to the phrase "dramatically increasing nuclear safety"?
It is completely impossible to dramatically increase nuclear safety. Even reducing future incidents by a factor of 100 makes basically no difference. Current plants are already safe.
I don't agree at all that the general public would not 'feel' that underground nuclear is safer. I think just the opposite is the case.
From the multireactor parks reference I'm assuming this is not just for SMR's but for full-size reactors as well. I have read that tunnel-boring machines have greatly reduced the cost of underground excavation and these numbers seem to bear that out.
I've suspected that a lot of environmentalists are actually motivated by aesthetics. I.e, they really object to industry because its "ugly", make it pretty, or better yet invisible, and their objections evaporate.
If the Russian and Japanese plants that released radiation were sited underground, radiation from the blasts would not have escaped into the air and widely dispersed.
And the Japanese reactor failure might have been totally avoided.
Best regards and health
Axil
Locating the nuclear power plants underground will be useful for containing the radioactivity but what about heat? Some 65-70% 0f heat has to be rejected for converting the rest into electricity. Also the reactor has to be kept at a limited maximum temperature for functioning. Dissipation of extra heat will be more difficult underground.
Jagdish, I have several times proposed a passive heat disposal system that uses a chimney to draw heated air out of the underground MSR chamber, as the heated air rises, fresh air is drawn into the reactor chamber. This system will also take care of emergency cooling for the reactor dump tank.
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