The Kernel
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The Kernel

Cleaning the Augean stables : Part 2

In the second part of our exciting ‘what if’ series, Oscar Archer goes full-on Bond movie as the terrorists reach their secret underground lair…

The only sound in the well-lit room was the faint air conditioner whoosh somewhere behind the ceiling vent. Agent Michelin regarded Doctor Bottrell coolly as he slouched slightly in his chair and collected his thoughts.

“What exactly were you going to do with the stolen used fuel assemblies?” she prompted.

He answered with a terse edge to his voice, “You already know what. The plan was to make a nuclear weapon for the terrorists. What you mean is ‘how?’. Well,” his fingers rose to brush his mouth, as if to drag on a non-existent cigarette. “If you thought stealing irradiated fuel from a nuclear plant sounded far out, listen to this.”

The main operation vessel would be outfitted and fuelled for the eight hundred-odd kilometre journey from the Suffolk shore to a minor uninhabited island somewhere near Orkney. The pair of stolen used fuel assemblies would be towed by braided cable in their enclosed, insulated dingy at a sufficiently safe distance. Upon arrival, the cable would be detached and reeled into a receiving dock by remotely controlled hardware, before travelling through to the hot cell accessway. Indeed, from this point forward, all manipulation would be by remote, in a facility built under the island’s rock surface to insulate the heat signatures of the radioactive materials and avoid orbital detection.

After any necessary cleaning and inspection of damage, the first assembly would be moved to the Head End process, beginning with shearing of the fuel pins into short segments by use of hydraulic ram-powered shears. This exposes the ceramic “meat” within the zircalloy to the heated nitric acid in the receiving basket, and all of the uranium, transuranics and fission products dissolve. The second assembly would then be processed in the same way.

All volatile components, including tritium, radiocarbon, radioiodine and noble gases would be captured with utmost care once they were released from the fuel material. Any leak would already risk detection by multiple national detection services that ceaselessly monitor for abnormal nuclear activity across the northern hemisphere.

The hot, radioactive nitric acid solution would transfer from the dissolver to the centrifugation, filtration and settling steps to remove any particulates, ready for solvent extraction. This requires repeated treatment of the solution with a mixture of kerosene and tributyl phosphate. By controlling the pH, the dissolved uranium and plutonium is separated from the fission products. The terrorists paid no heed to recycling of solvents, and thus the extraction of two fuel assemblies worth of material would generate copious amounts of acidic and organic waste, all highly radioactive and sealed in stainless steel tanks to avoid the risk of detection. Furthermore, the combination and quantities of chemicals would need to be obtained carefully through front companies or they may attract attention.

Source: Vanderbilt University

This also applies to the specialised reprocessing equipment, which would be constructed by machinists and engineers based on small scale designs tested at national labs like Oakridge, to avoid traceable connections to existing suppliers.

By manipulating the oxidation states of uranium and plutonium they are separated from each other, completing the extraction process. The crude dissolved plutonium nitrate is then passed through anion exchange columns to remove residual uranium, americium and fission product salts. This generates highly contaminated particulate material in considerable volumes. The purified plutonium nitrate proceeds to the precipitation step in containers of oxalic acid. This produces a solid pulp of plutonium oxalate that is transferred to a calcinator and converted to plutonium oxide at 500°C.

Source: Orano

This would technically be suitable for re-use in MOX fuel, however for a weapon it must be reduced to metallic plutonium, which is carried out by reaction with hydrofluoric acid in a stream of oxygen gas at up to 600°C, followed by reduction with lithium, calcium or barium at 1,200°C. More radioactive waste streams from these processes would have to be diverted and secured from possible leakage and consequent detection. The chemical reaction conditions are harsh and require substantial power supply.

Metallurgists would vacuum cast, hot press and machine the purified metallic plutonium into the necessary geometry for the chosen weapon design, all still in hot cells, minimising as far as humanly possible the wastage of material given the limit of what can practically be isolated from only two average used commercial fuel assemblies.

“Still in hot cells,” echoed Michelin, now rather engrossed despite herself.

“The plutonium in used fuel from power reactors is around fourteen per cent plutonium 241, a dangerous beta emitter with a relatively short half-life,” said Bottrell with pain etched into his face. “The terrorist leaders didn’t want to hear what I had to say about how badly this would complicate the next part of their plan.”

Michelin’s eyes narrowed. “You agreed to make a bomb for them.”

“I thought I had no choice,” he pleaded. “They were blackmailing me. And they made me agree before they explained anything. When I started to understand how detached from reality they really were…” Bottrell took a few deep breaths and finished with detached calm, “I suddenly understood I really didn’t have a choice. Just, in reverse. For all intents and purposes, what they wanted me to build was impossible.

Continued in Part 3…

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.



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