Cleaning the Augean stables : Part 3
In the final installment of our three-part special by Oscar Archer, we learn how the nuclear terrorists’ plans were always doomed to failure…
“Look, I know what I was going to do was abhorrent,” Iain Bottrell said. His hands balled into fists upon the table surface. “I know that. Even though I know it can’t be done. And I went along with it for the next four months, telling them what they wanted to know when they asked, while my warnings were completely dismissed.”
“You say it can’t be done, but we still have international safeguards in place for exactly this sort of plutonium, Doctor Bottrell,” Michelin replied.
“Yes I know. There’s every reason to believe it’s helped keep plutonium stockpiles safe for decades and contributed to the zero human cost from commercial nuclear waste management. At the same time, safeguards end up being very conservative because reactor grade plutonium is crucially different from weapons grade plutonium. I seriously believe the safeguards relating to them both helped convince the terrorists their plan made sense. That, and probably the way even the most serious authorities on non-proliferation talk about it, not to mention the questionable ones.”
“And you knew all this.”
Bottrell sighed, looking miserable. “I kept hoping some opportunity would appear, to escape without leaving tracks, even to go ahead with the operation and actually build something defective that they’d be happy enough with so I could get away. But they could still expose me no matter what. It was becoming obvious they wouldn’t hesitate to shoot and kill plant personnel. The actual theft of the fuel could go badly in so many ways, with public consequences far out of all proportion. I could only reassure myself for so long that at least building a working bomb was the least likely result no matter whatever else happened.” His quivering fingers raised to his mouth again. “I can usually find a way out of these things. I thought I’d covered my tracks the time before. Obviously not well enough. But there was no way out this time.”
The terrorists’ ultimate goal was a true nuclear explosive of a design most similar to the Mark-12, a 14 kiloton implosion device built in the US in the 50s and 60s, and notably lighter and more compact than previous designs. This choice was dictated by the illegitimate availability of blueprints, and the leaders’ unyielding intention to obtain the fissile material specifically from commercial used fuel assemblies.
The alternative source of material would have been highly enriched uranium, comprised of at least 90% uranium-235. Apart from various military stockpiles, most enriched uranium is below 20%; higher grades were once utilised in many research reactors but this is being steadily phased out globally. The only other choice would have been to purchase and operate cascades of centrifuges to secretly enrich stocks of natural uranium in the form of uranium hexafluoride, as was attempted in Iran until 2009.
Instead, the leaders were convinced by records of a weapon made from British reactor grade plutonium tested in the 60s by the US. The details about distinctly different fuel designs (military dual-use MAGNOX reactors versus conventional pressurised water reactors) and obsolete fuel grading were unheeded.
The stolen reactor grade plutonium, separated via the PUREX process and machined into the necessary pit geometry, would need to be surrounded with the remaining explosive mechanism: the reflector-tamper, and the explosive lens.
The Mark-12 design can use beryllium to efficiently reflect neutrons back at the plutonium pit, but lead may also suffice. The wedge-shaped segments of the polymer-bonded explosive lens are arranged spherically around the reflector to compress it in against the plutonium and achieve criticality upon detonation.
This would have presented the first impracticality, namely the risk of pre-initiation upon detonation due to the excessive amount of plutonium-240 in the metal, something like a quarter of the weight. This isotope undergoes spontaneous fission, effectively producing far more neutrons than is ideal for standard nuclear weapon designs. Calculations have shown this would practically always cause the detonation to “fizzle”, yielding lower than the equivalent of 100 tons of TNT.
The second serious hurdle would be the heat generated by the decay of plutonium-238, present in sufficient traces in reactor grade material to potentially thermally impact the precise geometry of the assembled device given excessive time before the terrorists decide to attempt to use the weapon, and therefore risking its operationality.
Additionally, the significantly higher proportion of plutonium-241 would produce more beta radiation, as well as americium and its radioactive daughter isotopes as time went on.
The use of weapons grade plutonium from military reactors removes these issues for nuclear armed countries, thus the research and testing to overcome them has never been carried out.
“But they just wouldn’t listen. About the radiation or heat hazard. About the herculean measures needed to seal the reprocessing facility from detection. Or the insanity of an assault on a power plant and pulling used assemblies out of the pool. And when I tried to suggest just smuggling 100 tons of trinitrotoluene to wherever they wanted it to explode, they threatened to expose me and find someone else.”
Michelin jotted a final note on her pad. “Since my colleagues collected you following your panicked phone call, the terrorists released the details of your past crimes onto the internet. I think you’re even trending right now. You might be the Klaus Fuchs of the 21st century.
“When a country commits to a weapons program the global reaction, the sanctions, are unequivocal,” she continued. “No nation is willing to be the next North Korea. And when a scientist with your knowledge exercises such poor judgement, selling military secrets you think can’t be traced, the consequences will be proportional.” Michelin stood and begun gathering her folder. “Going along with this group’s ludicrous plan for any amount of time just proves to us you’re not the kind of person who can be allowed near this field of science again.”
“I didn’t even build the bomb,” Bottrell mumbled.
“Like you say, you couldn’t have. But don’t expect credit for that.”
“Eliminating Nuclear Threats: A Practical Agenda For Global Policymakers”: Report Of The International Commission On Nuclear Non-Proliferation And Disarmament
“Production of Plutonium and Highly Enriched Uranium”: The Institute for Science and International Security
Oscar Archer holds a PhD in chemistry and has been analysing energy issues for over 15 years, focusing on nuclear technology for seven, with a background in manufacturing and QA. He helps out at Adelaide-based Bright New World as Senior Advisor (we want your support!) and writes for The Fourth Generation. Find him @OskaArcher on Twitter.