Here is a study of future scenarios where there is a lot of nuclear power.
Can Future Nuclear Power Be Made Proliferation Resistant ?" by the
Center for International and Security Studies at Maryland.
From that study it seems clear the problems are manageable, especially with proper reactor design selection and looking at processing, reprocessing and the entire chain of material flows.
Nuclear Facilities, Materials and Terrorism
It appears prudent to assume that a sophisticated terrorist group could construct a nuclear device if it obtained the requisite amounts of weapons-grade uranium or plutonium – all the more so, if we imagine the situation 50 years or more in the future. With respect to plutonium, although the task would be made more difficult, we must also assume that the isotopic composition of the plutonium, including the possibility of high amounts of plutonium-238, will not be an insuperable barrier. Nor would the admixture of transuranics with the plutonium be a deterrent. As we noted earlier, such admixture would increase the critical mass by no more than a factor of two or so, and would not be self-protecting in the way in which spent fuel is, and it would not raise insuperable problems of pre-initiation or heat management.
Given the formidable difficulties of a terrorist group generating their own nuclear material, it is critical to block all other ways for them to obtain such material. At present, probably the greatest vulnerabilities are fissile materials generated by the nuclear weapon states for use in weapons. This is not an issue of the civilian fuel cycle; we assume that in our nuclear future all such material will have been destroyed or secured.
Clearly, if nuclear power is to grow substantially, nuclear facilities – especially reactors that will be many and spread widely – must be made extremely safe from incidents that could release massive quantities of radioactivity to the public.
• There should be no use of HEU (Highly Enriched Uranium) in the nuclear fuel cycle, including in research and isotope-production reactors, and in naval reactors.
• Separated fissile material should not be located anywhere in the fuel cycle where terrorists could plausibly appropriate it. Possibly such separated materials could be tolerated in a center controlled by an international authority or embedded in a sealed fuel assembly such as envisioned for the nuclear battery. But separated weapons usable materials should not be used in fuel elements that would routinely be sent to hundreds of nuclear reactors, as would be the case in some of the scenarios described.
• An international norm needs to be established that requires states to take strong action against individuals and entities engaged in nuclear terrorist activities.
• Reactors with features of intrinsic safety should be given extra weight in consideration of future nuclear power.
In addition, reactor and system designs that achieve deep burn (99+% burning of uranium, thorium and plutonium) should be the preferred path not just for non-proliferation but also for better use of the resources.
Thoriumenergy blog looks at burning all nuclear waste with advanced reactors.
Jorgensen, drawing on work by French nuclear scientists, H. Nifenecker, D. Heuer, J.M. Loiseaux, O. Meplan, A. Nuttin, S. David, and J.M. Martin, offers plans to simultaneously reduce the current TRU wastes 15-fold (with onsite recycling) to 15,000 fold reduction (with the best offsite recycling), while also supplying 9000 GWe electricity for an energy-hungry world.
A discussion of plutonium from reactors to get sub-par military grade material with explosions in the 100 ton to 20 kt range.
Chloride Molten Salt Reactors can burn depleted uranium as fuel. There is over a million tons of depleted uranium now. Transmutation into weapons grade material is possible, but the transmutation processes can be used to make depleted uranium into fuel.
With respect to country proliferation:
• Any country with nuclear power and a nuclear power infrastructure could get fissile material if it wished – within months or a year – barring international action to prevent this. If it had a commercial reactor, it could build a reprocessing plant to separate out plutonium; or it could build a dedicated reactor and reprocessing plant in a somewhat longer period. It could also enrich uranium over time, but as long as the country did not have any enrichment facilities to begin with, such a route would take longer than would a plutonium path.
• However, in the scenarios considered, it should be possible to have a safeguards regime such that any diversion of facilities and materials would be quickly detected, giving time for an international response (see the following bullet). In this respect, the once-through fuel cycle, the hub-spoke arrangements with sealed reactors, and possibly certain thorium cycles appear particularly attractive in making immediately visible an attempted diversion and lengthening the time for a diversion to be consummated.
• Since technically most countries will be able to get nuclear weapons, enforcement and compliance provisions of any international control regime are crucial.
The Five Nuclear Future Scenarios
Five nominal scenarios based predominantly on specific reactor types:
• Advanced light water reactors (LWRs) and/or gas-cooled thermal reactors on a once through fuel cycle In this scenario, LWRs and gas-cooled reactors such as the pebble bed reactors operate on a once-through fuel cycle through 2050 (as described in the MIT study) and also to the end of the century. The reactors will be fueled by low-enriched uranium. Spent fuel will be put directly into geological repositories.
• Actinide burning based on fast reactors
This is the vision of the Global Nuclear Energy Partnership (GNEP). Spent fuel from
LWRs and from a fleet of fast reactors will be reprocessed to separate plutonium and
other transuranics (TRU – americium, curium, and neptunium). These will be
fabricated into fuel for fast reactors and will be fissioned in the fast reactors in several cycles, such that the plutonium and other TRU are eventually mostly burned away. The fission products will be put into geological repositories.
• Fast breeder reactors in a closed fuel cycle
We imagine, in equilibrium, a division of LWRs and fast breeders in roughly a 55-45 ratio, similar to that described in the MIT study. Spent fuel from both types of reactors will be reprocessed and the separated plutonium used to start-up and re-fuel the breeder reactors.
• Thorium fuel cycles
Several different thorium cycles are considered. In particular, we note the possibility of breakeven breeding in a molten salt reactor. While such a reactor requires enriched uranium (typically 20 % U-235) for startup, relatively little further supplies of enriched fuel are required during subsequent operation. The U-233 produced by neutron absorption in Th-232 is never separated from the fuel, and it is also denatured by the addition of U-238 which means that isotope separation would be required to obtain weapons-grade U-233. In addition, the isotope U-232, which has a high gamma-emitting daughter, is produced during reactor operation, thus further
complicating attempts to obtain weapons-usable U-233 from this cycle.
• Nuclear batteries in a hub-spoke configuration
At a central facility, reactors nominally in the range of 20-100 MWe would be fueled either with 20% uranium or plutonium, sealed, and then transported to countries deploying the reactors. The reactors would not need to be refueled during their core life, nominally 20 to 30 years, at the end of which time they would be sent back to the central facility, where the plutonium would be separated and re-fabricated into cores for the replacement reactors.
Civil Defense Enhancement Against Nuclear Bombs
To address possibility of limited numbers of weak bombs - then follow my revised civil defense approach and more here
As the technology becomes available and affordable continue to increase to higher levels of robustness.
Level 1: Hurriquake nails and other cheap adjustments that are widely available now and in use for some new construction. Expect to get to 2-5 PSI and up to 10-15 resistant houses. Also need treatments for improved fire resistance. 50-70% casualty reduction.
Level 2: Use cellustic fiber that is almost up to the strength of steel (nanopaper made from wood), more steel framed construction, better concrete or carbon fiber, or graphene reinforcement. Stronger windows, doors OR monolithic domes for some new construction. Resistant PSI 10-25+. 60-85% casualty reduction. Add anti-radiation
damage drugs (new carbon nanotube based drugs that are 5000 times more effective.) Total 85-92% casualty reduction.
Level 3: Better materials (more advanced carbon nanotube, graphene reinforcement with hydrogen impregnated for radiation shielding) and designs. PSI 25-100+. 85-98% casualty reduction. Need anti-radiation gene therapy and anti-radiation drugs as the radiation casualties would be dominant.
Level 4: Molecular nanotechnology. PSI 1000+.
Integration of radiation to electricity systems Integrate room temperature superconductors for strong magnetic shielding. Rapid evacuation from utility fog systems. Metamaterials that guide earthquakes shocks and other waves around buildings. 99.9%+ casualty reduction.
Mostly technical discussion of the study and this article at the Energy from Thorium forum.