The emergence of thorium cycle criticism is good news, because it signals that Thorium/MSR advocates have accomplished their first goal, which is to make thorium nuclear technology widely known.
A paper titled The Thorium Fuel Cycle offers its readers
an independent review of the thorium fuel cycle by the UK National Nuclear Laboratory (NNL), highlighting the strengths and weaknesses not just in the UK context but globally.First it should be asked how did the staff of the NNL come to its conclusions. Scientists normally would begin an assessment of the potential of a technology with a literature review. In 2005 the International Energy agency published Thorium Fuel Cycle - Potential Benefits and Challenges *IAEA TECDOC-1450). That review tells us how information was collected for its composition
The information on thorium and thorium fuel cycles has been well covered in the IAEA- TECDOC-1155 (May 2000) and IAEA-TECDOC-1319 (November 2002). The objective of the present TECDOC is to make a critical review of recent knowledge on thorium fuel cycle and its potential benefits and challenges, in particular, front end, applying thorium fuel cycle options and back end of thorium fuel cycles. The review has been prepared based on three consultancy meetings held at IAEA, Vienna 1–3 July 2002, 14–16 April 2003 and 15–16 September 2003, where experts from Canada, France, India, Israel, Japan, the Russian Federation, USA and IAEA had participated and supported by information and published papers from specialists on thorium fuels and fuel cycles.
In contrast the NNL review states,
NNL has many years experience of the nuclear fuel cycle and associated science and technology, including fuels, reactors and reprocessing. We are therefore in an ideal position to be able to independently assess and advise decision makers on both current and future fuel cycles such as thorium. The statements in this note are backed up by extensive experience of nuclear R&D and the nuclear industry worldwide, including thorium assessments and programs in which the NNL was involved.
Thus the NNL was relying on its in house expertise on the thorium fuel cycle, but how competent were its researchers to make this judgement? First it would seem that NNL researchers had not participated in the Thorium fuel cycle assessment process conducted by the IAEA. We know that IAEA tells us the countries from which participants in its thorium cycle assessment process had come, and those nations did not include the UK. That
A second difference between the IAEA TECDOC-1450 and the NNL paper is the documentation of the former and the complete lack of documentation in the latter.
Other comparisons between the TECDOC-1450 and the NNL paper are also instructive. TECDOC-1450 states,
The NNL claims,
In recent years, there has been renewed and additional interest in thorium because of the intrinsic proliferation resistance of thorium fuel cycle due to the presence of 232U and its strong gamma emitting daughter products,In contrast the NNL states
Contrary to that which many proponents of thorium claim, U-233The NNL does not state the reason for its disagreement with the NAEA, nor does it state why it
should be regarded as posing a definite proliferation risk. For a thorium fuel cycle which falls short of a breeding cycle, uranium fuel would always be needed to supplement the fissile material and there will always be significant (though reduced) plutonium production.
rejects the widely heald beliefe that the thorium cycle offers more proliferation resistance than the Uranium fuel cycle.TECDOC-1450 notes
Closed’ 232Th–233U/238U denatured breeder cycle designed to maximize proliferation- resistance by minimal processing of the fuel salt and by addition of 238U to isotopically dilute and denature fissile 233U isotope. Though this lowers the breeding ratio marginally (slightly above 1.0) as compared to 232Th–233U ‘closed’ cycle, it ensures intrinsic proliferation resistance of the fuel cycle.In other words in a denatured fuel cycle, the breeding ratio would be so close to unity, that the would be weapons builder would be forced to sacrifice his reactor load of fissionable material in order to produce weapons. In addition by diluting U-233 with U-238, Weapons grade U-233 would be difficult to extract.
The NNL claims,
Attempts to lower the fissile content of uranium by adding U-238 are considered to offer only weak protection, as the U-233 could be separated in a centrifuge cascade in the same way that U-235 is separated from U-238 in the standard uranium fuel cycle.
But first most would be proliferators do not possess centrifuge cascade and as Iran has discovered centrifuge technology is not easy to develop, and centrifuges are not available on the open market. Once a would be proliferator who is considering use of U-233 from a denatured thorium reactor faces a choice: Either to pull uranium out of the reactor and process it through centrifuge cascades to obtain weapons grade U-233, or to process ordinary uranium through the centrifuge cascades in order to obtain weapons grade u-235. The benefits of the two processes are the same. The cost of the U-235 path is the problems posed by obtaining the uranium. The would be proliferator may not possess a Uranium mine, or uranium bating resources. Uranium is difficult to obtain on the open market. In contrast obtaining U-233 from the reactor fuel of a unity breeder, would mean that fissionable U-233 that can only be replaced in the reactor by breeding is being withdrawn from the reactor, and will be impossible to replace by breeding. In effect in the long run the denatured U-233-thorium reactor will have to be sacrificed if U-233 is withdrawn for weapons purposes. Secondly U233 is adulterated by U-232 which decays into a extremely dangerous radioactive daughter product. This makes the handling and storage of weapons containing U-233 a far larger problem than the handling and storage of a U-235 based weapon. Centrifuges can be used to separate U-233 and u232, but this would involve more centrifuge cascade than would be required to separate U-235 and U-238, and would be more costly and time consuming. Clearly then the problems posed by attempting to weaponize denatured U-233 from a thorium cycle reactor would be greater than the problems posed by separating U-235 from U-238. Those problems are what is referred to by the term proliferation resistant.
It should be added that proliferation resistance in any reactor does not offer strong proliferation protection. Nuclear weapons proliferation is quite easy and and cheap, and nations do not need or even desire thorium reactors in order to obtain the capacity to build nuclear weapons. Proliferation resistance is about preferred paths to nuclear weapons, not prevention. Proliferation control depends on a strong international order that is capable of keeping weapons technology out of unacceptable hands. To date that international order has had mixed success at best.
A proliferation resistant technology is one which a would be proliferator would prefer to not use because it costs more, presents greater technical difficulties or poses other disadvantages. If a nation already has access to centrifuges capable of separating U-233 from U-238, it already possesses the means to separate weapons grade U-235 from U-238. The IAEA acknowledges that there are greater challenges involved in the weaponization of U-233 than in the weaponization of U-235. Thus contrary to the NNL the weaponization of U-233 produced by thorium breeding is very unlikely.
Thus it would appear that some NNL pronouncements on thorium are in significant conflict with the IAEA assessment. In addition other NNL pronouncements are unrealistically pessimistic. For example the NNL states,
In the foreseeable future (up to the next 20 years), the only realistic prospect for deploying thorium fuels on a commercial basis would be in existing and new build LWRs (e.g., AP1000 and EPR or PHWRs, [e.g. Candu reactors]. Thorium fuel concepts which require first the construction of new reactor types (such as High Temperature Reactor (HTR), fast reactors and Accelerator Driven Systems (ADS)) are regarded as viable only in the much longer term (of the order of 40+ years minimum) as this is the length of time before these reactors are expected to be designed, built and reach commercial maturity.In fact a prototype Indian commercial fast reactor is expected to be online before the end of 2012, while Indian thorium breeding fast breeders are expected to come on line in a little more than a dozen years later. By 2025 India plans to have growing fleets of Thorium Fast Breeder Reactors, and Advanced Heavy Water Reactor unity thorium converters. Thus the NNL estimate appears of the development time for thorium cycle fast breeders may be off by as much as a generation.
It would appear then that the NNL's report on thorium was prepared with less than rigorous preparation. The report includes a number of assertions which are questionable. We now have to ask why did the NNL UK publish this report? The answer can be found in Laboratory Director Paul Howath's statement of purpose at he the beginning of the report,
and advise decision makers on both current and future fuel cycles such as thorium.
It is plausible, given the content of the NNL report, that the NNL has little expertise in the thorium fuel cycle and limited resources. The leadership of the NNL prefers to focus on technology they understands, rather than technology they does not fully understand. The NNL has by now either receive enquiries about thorium cycle nuclear technology from national leaders, or has reason to believe that it will. It thus has a need to offer excuses for a lack of interest in thorium cycle research and development. No one likes to admit that we don't know how, and have our hands full with what we are doing now. The result is a bad report.