It is possible to produce fissionable U-233 from thorium from the same sort of reactors used to produce weapons grade plutonium, yet during the cold war, no one thought to do so. Frank von Hippel is a self-styled non-proliferation expert who has greatly influenced American, and even global non-proliferation policy. Other self-styled non=proliferation experts tend to advocates arms control policies suggested by von Hippel. Together with Jungmin Kanga and von Hippel, actually attempted to explore this seemingly rational step was not taken during and after the cold war in a paper titled U-232 and the Proliferation- Resistance of U-233 in Spent Fuel.
Uranium-233 is, like plutonium-239, a long-lived fissile isotope produced in reactors by single-neutron capture in a naturally-occurring abundant fertile isotope (see Figure 1). The fast critical mass of U-233 is almost identical to that for Pu-239 and the spontaneous fission rate is much lower, reducing to negligible levels the problem of a spontaneous fission neutron prematurely initiating the chain reaction -- even in a "gun-type" design such as used for the U-235 Hiroshima bomb (see Table 1). Why then has plutonium been used as the standard fissile material in the "pits" of modern nuclear weapons while U- 233 has not? This question is not just of historical interest, since there is increasing interest in U-233-thorium fuel cycles.Kanga and von Hippel note
One of the most important reasons why plutonium was chosen over U-233 as a weapons material is that first-generation plutonium-production reactors were fueled by natural uranium, which contains almost as large a fraction of neutron-absorbing fertile material (U-238) as is possible consistent with a reactor achieving criticality. In a natural-uranium fueled reactor, such as the Canadian heavy-water-moderated (HWR) reactor type, Pu-239 is produced by neutron absorption in U-238 at a rate of about one gram of plutonium per thermal megawatt-day (MWd) of fission energy release at low U-235 "burn ups," (see Figure 2).1 Approximately one MWd is released by the fission of one gram of fissile material. After taking into account the neutron requirements for maintaining a steady chain reaction, there is about one excess neutron available per fission and virtually all of these neutrons are absorbed by U-238. Production of U-233 requires the addition of the fertile material Th-232. If the fuel is natural uranium, only a relatively small percentage of thorium can be added before it becomes impossible to sustain a chain reaction. We"estimate that about 7 percent thorium oxide can be added to HWR fuel achievable burnup is reduced from 7000 to 1000 MWd/t (thermal megawatt- days per ton-heavy metal). Because the thermal-neutron absorption cross-section of Th-232 is almost 3 times larger than that of U-238, this concentration of thorium would yield about 0.2 grams of U-233 per MWd at burnups lower than 1000 MWd/t (see Figure 3). Thus most of the fissile material produced in the core would still be plutonium.Kanga and von Hippel also state,
For a country with uranium-enrichment capabilities, the balance between plutonium and U-233 production could be shifted almost all the way toward U-233 by fueling production reactors with highly-enriched uranium. Indeed the U.S. produced much of its weapons plutonium in the Savannah River heavy-water-moderated production reactors, using highly-enriched uranium fuel and depleted uranium targets in mixed-lattice arrangements.But Kanga and von Hippel also noted a second problem for weaponizing U-233,
But at this point it should be noted that countries with uranium enrichment capacities to the level of highly-enriched uranium already possess the capacity to produce nuclear weapons. And the process of producing U-233 using HEU-235 to in production reactors, destroys more weapons grade fissionable material than it produces. The use of U-235 at Savannah River to produce Pu-239 was motivated by the fact that Pu-239 had useful military qualities that U-235 lacked. The military qualities of U-233 are inferior too the military qualities of U-235. Thus the choice to produce Pu-239 but not U-233 at Savannah River was rational. Kanga and von Hippel acknowledge the problem,
A second problem with U-233 as a fissile material for either weapons or reactor fuel is that it contains an admixture of U-232, whose decay chain produces penetrating gamma rays. The decay chain of U-232 is shown in Figure 4. The most important gamma emitter, accounting for about 85 percent of the total dose from U-232 after 2 years, is Tl-208, which emits a 2.6-MeV gamma ray when it decays (see Appendix C). For plutonium containing a significant admixture of 14.4-year half-life Pu-241, the most important source of gamma-ray irradiation from is its 433-year half-life decay product, Am-241, which emits low-energy (< 0.1 MeV) gamma rays. These gamma rays do not represent a significant occupational hazard for weapon-grade plutonium (0.36% Pu-241) but their dose becomes more significant for "reactor-grade" plutonium, which contains on the order of 10 percent Pu-241. Thus both U- 233 contaminated with U-232 and reactor-grade plutonium are made less desirable as weapons materials by virtue of the fact that their gamma emissions bring with them the potential for significant radiation doses or shielding requirements for workers involved in nuclear weapons production and for military personnel handling nuclear weapons.How much less desirable? Kanga and von Hippel report that at a 1% U-232 contamination level a worker would begin to accumulate a cancer risk after working with U-233 for less than three minuits. But 1% U-232 is unusual to say the least. The problem is simple, U-233 poses problems for workers and military personel by exposure to radiation from a U-232 daughter product, while the same radiation poses problems for weapons electronics in storage.
Kanga and von Hippel report that India is researching laser isotope separation of U-233 from U-232. But does this represent a proliferation challenge? First if Indian researchers can separate U-233 from U-232 using lasers, they can also separate U-235 from U-238, and U-235 from U-238 separation is one of the two classic route to nuclear weapons. U-235 based weapons are reliable enough that they do not require tests to identify their military effect. This is not the case for U-233 based weapons. The only known test of a U-233 based weapon failed to accomplish test objectives, although it did explode with a respectable if not as large as expected bang, Thus it would appear that given routs to U-233 and U-235 based weapons, given equivalent costs and technical obstacles, but without tests, military planners will prefer the U-235 based weapons.
Now it can be argued that India should not develop laser uranium enrichment technology because such technology poses proliferation risks, but Burma, a rogue state, is also developing Laser enrichment technology, although it is very unlikely that the Burmese will master it. Burma is also attempting to master centrifuge technology, and given the track records of Pakistan and Iran, that appears to more likely.
The Indian three stage nuclear Research and Development program is well known, and despite setbacks, it has made steady progress over the last 50 years. During much of that time, the global anti-proliferation community sought to punish India for its pursuit of nuclear weapons. India, which shares common borders with two nuclear armed hostile states that are allied against it, believed that a small nuclear arms program was prudent, given the likelihood that at least one of its enemies might use nuclear weapons against it. India maintained its nuclear weapons program despite a 34 year embargo on uranium and other nuclear related trade items. The embargo somewhat handicapped the development of the Indian nuclear industry, and limited the production of nuclear power in India.
It should be pointed out that in 1974, at the beginnings of the international nuclear trade sanctions against India, that nation lacked many of the characteristics of a great power. Never the less it refused to back down on its nuclear weapons program. Today, India is rapidly becoming a great power. It is conceivable that by 2050 India will have the largest economy of any nation. At worst India will have by most estimates the second or third largest economy. India, like China is developing aircraft carriers, a standard military technology for projecting power.
If in 1974, a relatively weak India refused to subordinate itself to the nuclear policies dictated by the United States, by 2050 a very powerful Indian State will certainly not place itself under American Nuclear hegemony. The 123 agreement between India and the United States offered India recognition of its great power status.
The Indian three stage Indian Nuclear development plan directly contradicts the non-proliferation policy advocated by Frank von Hippel who opposes nuclear waste reprocessing and the use of fast reactors. Von Hipple states,
Reprocessing is enormously dangerous. The amount of radioactivity in the liquid waste stored at France's plant is more than 100 times that released by the Chernobyl accident. That is why France's government set up antiaircraft missile batteries around its reprocessing plant after the 9/11 attacks.The heart of the Indian long range three stage nuclear program involves recycling spent fuel from conventional power reactors. Plutonium in that spent fuel becomes the the Fissile start charge for for fast breeder reactors, which produce plutonium and U-233 from thorium. That fuel is recycled and the the Plutonium is returned to the fast breeder while the thorium is used to power thorium fuel cycle thermal breeder reactors.
Even more dangerous, however, is the fact that reprocessing provides access to plutonium, a nuclear weapon material. That is why the U.S. turned against it after 1974, the year India used the first plutonium separated with U.S.-provided reprocessing for a nuclear explosion. President Gerald Ford and Henry Kissinger, his secretary of State, managed to intervene before France and Germany sold reprocessing plants to South Korea, Pakistan and Brazil, all of which had secret weapons programs at the time.
Von Hippel apparently has not produced a comprehensive case study of nuclear disarmament issues from the Indian perspective, but he thinks he knows what the Indians should be doing. In 2006 he co-authored a paper which offered prescriptions for demands which the United States should seek to include in any nuclear trade agreement with India. In particular von Hippel demanded that any nuclear trade agreement with India should require that before trade can begin
that India has stopped the production of fissile material (plutonium and highly enriched uranium) for weapons or else joined a multilateral fissile production cutoff agreement;Von Hippel also called for
A determination and annual certification that U.S. civil nuclear trade does not in any way assist or encourage India's nuclear weapons program.The Conditions which von Hippel sought to impose on India might be described as humiliating for a great power, even a great power which was content to hold a small number of nuclear weapons. India faces a possible military alliance between China and Pakistan which together hold far more nuclear weapons than India does. Thus India's nuclear arsenal may not offer India sufficient for conceivable national defense needs.
In addition von Hippel has taken a stance that nuclear fuel reprocessing is conducive to weapons use of fissile materials. Von Hippel also objects to fast reactors because a fast reactor fleet will inevitably be dependent on fuel reprocessing, and theoretically fast reactors could produce fissionable materials that could be used in nuclear weapons. Later in this essay, I will examine problems with von Hippel's belief that reprocessing and fast reactors increase the likelihood of nuclear proliferation. In Fast Breeder Reactor Programs: History and Status, a study coauthored by von Hippel, he remarks
India’s Prototype Fast Breeder Reactor (PFBR), expected to be completed in 2010, will have the capacity to make 90 kg of weapon-grade plutonium per year, if only the radial blanket is reprocessed separately and 140 kg per year if both radial and axial blankets are reprocessed.15 The Nagasaki bomb contained 6 kg of weapon-grade plutonium and modern weapons designs contain less. At 5 kg per warhead, the PFBR would produce enough weapon-grade plutonium for 20–30 nuclear weapons a year, a huge increase in production capacity in the context of the South Asian nuclear arms race. were left mixed with the plutonium, however — a project that the U.S. Department of Energy abandoned when it learned that the technology was not in hand — the gamma radiation field surrounding the mix would still be less than one-hundredth the level the IAEA considers self-protecting against theft and thousands of times less than the radiation field surrounding plutonium when it is in spent fuel (figure 1.4).It is doubtful that von Hippel favors Indian reprocessing of Thorium cycle nuclear fuel. Thus to the extent that American nonproliferation policy is influenced by von Hippel and his followers, American nonproliferation policy, it is likely to conflict with Indian nuclear policy. The Indian nuclear policy had from its inception of using nuclear power to turn India into a rich and powerful nation. Not just militarily and politically powerful, but economically powerful as well. It is unlikely that the Indian political leadership will abandone their goal of achieving great power political and economic status for India, and the prevailing view that nuclear power will play a key roal in accomplishing that goal. To understand Indian national goals is to begin to understand the realpolitik of Indian objections to American nonproliferation as interpreted by Frank von Hippel.
Much 20th century thinking about nuclear nonproliferation, sprang from ethical goals. Nuclear war, is a moral wrong, and the use of nuclear weapons is evil. These assumptions cannot be dispited. But nuclear weapons and their use exist in a morally imperfect world, where people believe that they are sometimes are forced to commit acts that are morally wrong, and even to do things which in absolute moral terms are evil. It is not necessicary to justify such behavior in order to acknowledge that it exists, and to regard the necessity of responding to the real acts of people, as imposing on us constraints on the moral aspects of our life and thought. It is desirable to bring together the real world of human thought and action, with the more lofty goals offered by moral thought. Such is the case if we wish to control the production and use of nuclear weapons.
Thus future American policy towards India nuclear developments ought to focuse on a conversion of the ethical with the realpolitik goals. American policy has no choice but to accept that India has chosen a path that will lead to a thorium based economy. as well as the Indian need for a limited stock of nuclear weapons, at least in the short run.. Once Indian goals accepted, India will willingly participate in the creation on an international order directed towards arms control.