Earthquake and Tsunami Safe Nuclear Power Plants and Waste Disposal
By Ernst G. Frankel, Professor Emeritus, MIT
Many of our existing and planned nuclear power plants are in earthquake prone locations which may in some cases also be exposed to potential tsunamis as shown by the recent Japanese disaster. While nuclear power is environmentally and in many cases economically attractive, we must develop approaches which permit the exploration or use of this important source of energy generation while greatly reducing exposure to damage or destruction which affect population centers and economic assets. As many of the most desirable locations are along coasts such as the U.S. West Coast states and Western Europe, it may be desirable and attractive to locate nuclear power plants on large floating platforms or ships which can be positioned with flexible tension anchors places in the ocean bottom by explosive anchor placements.
Such platforms and/or nuclear power plant ship platforms would have limited propulsion and positioning power and be big enough to sustain high waves, including tsunami waves. The platform would be completely self-contained and include all services as well as helicopter platforms and ship/boat docking facilities to assure availability of efficient ship to platform/ship base communications and supply links. The advantages of floating nuclear plants are:
1. Earthquake proof.
2. Infinite amount of cooling water.
3. Relocatable to safer locations and/or in response to changing needs.
4. Can be designed to facilitate easy and safe disposal of spent fuel rods.
5. Capable of riding out high waves and tsunamis.
6. Based on long term experience with floating nuclear reactors used on nearly all large U.S. aircraft carriers, large submarines, and more.
7. Easy maintenance and refueling as facility can be brought to well equipped ship/maintenance yards with heavy equipment, effective safety facilities, and more.
8. In case of equipment failure, float-supported relief equipment can readily be positioned and connected.
9. In case of accident, whole floating plants can be repositioned for repair, resupply to major facilities, such as large shipyards.
10. Workers only spend limited and intermittent time at or near the reactors and would live elsewhere. Similarly, plants would be remote from population centers.
Disposal of spent fuel would be in temporary, always flooded fuel ponds with long term or permanent disposal in abandoned, deep, deep sea oil or gas wells which penetrate the outer crust of the earth and go into the still hot molten lava crust of the earth which suffers persistent natural radioactivity. There are abandoned, deep ocean, deep wells which penetrate the sea bottom earth crust and often extend to hot lava fields as do many submarine volcanic craters. It is suggested to deposit (drop) spent fuel rods into this inner crust domain which is naturally radioactive. Such an approach could become a safe way to deposit radioactive material and other major pollutants.
Considering floating or floatable platforms for nuclear power plants, we should first remember that we have nearly as many seaborne reactors as land based reactors now. There are the Russian ice breakers, starting with the Lenin, all U.S. large aircraft carriers, and about 100 U.S., U.K., Russian, etc. nuclear submarines. We also had a number of commercial nuclear-powered vessels, starting with the U.S. NSS Savannah, a German, and some other commercial nuclear ship ventures which all disappeared for commercial and political reasons. However, overall our experience with seaborne nuclear power plants is nearly as extensive as with land-based power reactors. At the same time, we have extensive experience with ocean-borne platforms which serve oil and gas drilling, storage, and production as well as various other activities. We have floating or floatable port facilities.
All of these have an excellent safety record. Some are simple displacement hulls such as large ships, while others as semi-submersible catamarans, self-elevating and/or tension leg platforms and more (Figure 1). Most are easily relocatable and some can be equipped with their own propulsion system. Very large platforms or ships such as VLCCs can easily sustain large waves and swells, including even large tsunami-type ocean elevations. The choice of nuclear power plant platform depends on:
1. Location and local environmental conditions.
2. Size of nuclear power plant.
3. Available support facilities such as work boats, supply boats, tug boats, shore transformer/switching, etc. facilities.
4. Seabed conditions and materials (sand, rock, etc.).
5. Methods of power transmission and supply (people, materials, services, etc.) delivery.
From an economic point of view, floating/floatable nuclear power plants are expected to be very attractive. Not only is the cost of a platform less than the cost of a land-based site, including safety zones, but the costs of the plant, particularly cooling, etc. systems and various safety arrangements are expected to be much lower. Most importantly is the fact that such plants can be relocate or even scuttled if necessary and that they have infinite amounts of cooling water at their disposal at all times.
Floating, relocatable nuclear power reactors appear to offer major economic, environmental, strategic, and safety advantages, and should be seriously considered not only for new plants but also replacement by repositioning of existing plants in earthquake prone areas. We should also recognize that the proliferation of large offshore wind energy forms has resulted in the development of very effective ocean cable laying for large power transmissions.
There has been a flurry of expansion of cable laying vessels to meet this new demand and new trenching, laying, and position control technology assures more accurate and cost effective transmission cable connections and ultimately lower transmission costs. The large increase in large offshore wind turbines has a great impact on offshore electric power developments, including establishment of large fleets of service, crew, and supply boats. In fact, we expect that more and more electric power will be generated offshore. Some nations like Denmark, the U.K. and others are now generating significant percentages of their electric power needs offshore. It would be appropriate for the U.S. to consider offshore sites not just for wind power but also nuclear power to prevent the types of problems experiences by Japan and to assure more economic and safer development and use of nuclear power.
Though America has been fortunate not to have suffered nuclear accidents since the Three Mile Island accident, it does have a large problem with the disposal of nuclear waste, not just from and at the comparatively old nuclear power plants but also of nuclear enrichment facilities such as Hunford in Washington State which is looking for a safe and permanent way to store or dispose of nuclear waste from weapons-grade, plutonium-grade production. Currently over 200m liters of highly toxic waste are stored in leaky underground tanks. Developments are underway to establish a vitrification process to transform the liquid radioactive waste into solid radioactive waste which can be stored more effectively. But even then, there remains the problem of long-term storage in a safe manner. Again, abandoned, deep water offshore wells may provide a safe and rational opportunity for safe, long term disposal or storage.
I most seriously suggest a detailed evaluation of the use of offshore locations for nuclear power development and use. In this regard, formal discussions with the IMO and the U.N. seabed authority (located in Jamaica) may be appropriate.
About the Author:
Ernst G. Frankel
Professor Emeritus of Ocean/Mechanical Engineering and Management at MIT; Director of AET Tankers and Offshore; member, Advisory Board of the Panama Canal; worked on nuclear ship propulsion for 40 years; served as Chief engineer of major shipping companies and shipbuilders. Was head of the World Bank Shipping, Ports, Aviation, and Shipbuilding Projects; Advisor to IMO; President of the International Association of Maritime Economists; and Chairman of American President Lines.