“You didn’t tell them?” Callum said, aghast. “You didn’t tell Boynak what you were sending through their disposal system?”

“Our senior management was aware,” Poi Li said.

Callum turned to her, frowning. “Our management?”

“Connexion has a share in Boynak. However, the Gylgen facility staff were not informed. There was no need.”

“So we’re helping the British government to dump their illegal plutonium?”

“The plutonium was a mistake made by a previous generation,” Major Johnston said emphatically. “We were trying to do the honorable thing and correct it.”

“Is that what you call it?”

“Actually, yes.”

“We need you, as crew chief, to be aware of what you’re actually facing in Gylgen,” Dokal said.

“Big thanks, pal.” Callum rubbed his forehead with the tips of his fingers, trying to think. “I don’t get this. Is the malfunction a terrorist group sabotage?”

“I don’t believe so,” Major Johnston said. “We have sent several batches through previously without any problem. Our canisters of plutonium are listed as medical waste from various London hospitals. The plutonium itself is broken down into small pellets, each of which is encased in a ceramic to prevent it oxidizing, then sealed in a standard canister. What I believe may have happened is plain bad luck. One canister dropped from the top of the tank landed badly. The ceramic might have cracked, or even shattered.”

“You didn’t test the ceramic for impact,” Callum said in realization.

“It’s a quiet project,” Poi Li said. “Failure to fall test that particular ceramic was an oversight.”

Callum closed his eyes, trying to remember his physics. “If you expose plutonium to moist air, it oxidizes and hydrides, then it expands by…”

“Up to seventy percent,” Johnston completed. “The canister itself may have ruptured from that expansion pressure. It is only a standard commercial plastic, printed in the Gylgen plant and shipped out to customers.”

“Never designed to contain accidental plutonium expansion,” Callum said wearily. “I’m guessing the residue trickled to the bottom of the tank and blocked the valve. Unlikely, but…”

“Our scenario is worse than that.”

“Oh, bloody hell!”

“The powder which plutonium oxidization and hydration produces has been known to flake off and ignite spontaneously.”

“Ignite?”

“Yes. If there was a fire resulting from that initial fracture, it would probably breach further canisters. And each one would multiply the problem.”

“How many plutonium canisters are in this tank?”

“Twenty-five. That’s a kilogram of plutonium in total.”

“Fuck me! Well, let’s hope I can vent the whole mess before that fire starts.”

“Cal,” Dokal said quietly. “The Gylgen facility engineers didn’t pressurize the tank.”

“But you said…Oh.”

“Yeah, there was a fire inside the tank,” Major Johnston said. “That’s what caused the pressure increase. There’s only a limited amount of oxygen in there, so that’ll be consumed by now. But we suspect that while it was burning, it turned a lot of the other canisters molten, releasing more plutonium along with all the other residue. That is probably what’s broken the valve. There are no sensors left inside; the fire took them out. We don’t know what state the waste is currently in. The canister plastic may be liquid, or it may have recongealed. If you blow a hole in the bottom of the tank, the waste might not vent.”