Observer: Building B30 is a large, stained, concrete edifice that stands at the centre of Sellafield, Britain’s sprawling nuclear processing plant in Cumbria. Surrounded by a three-metre-high fence that is topped with razor wire, encased in scaffolding and riddled with a maze of sagging pipes and cabling, it would never be a contender to win an architectural prize. Yet B30 has a powerful claim to fame, albeit a disturbing one. “It is the most hazardous industrial building in western Europe,” …