Brittle Power- PARTS 1-3 (+Notes) - Natural Capitalism Solutions

Chapter Thirteen: Designing for Resilience 197missile guidance system may use inertial guidance, fluidic, and electronic subsystemsso that damage to one of them—for example, by the intense radiationfield from a warhead exploding nearby—will not cause total failure. 66 Likewise,nuclear bombs generally have functionally redundant proximity and barometricfuses, backed up by a simple salvage fuse to ensure detonation (or atleast destruction to prevent recovery) on hitting the ground.Diversity need not be purely technological. To enter a Minuteman missilesilo, for example, requires two different lock combinations, held respectivelyby the separate security and maintenance staffs. Many of the former areOriental in order to make apparent any association with the latter, who aremostly Caucasian. This makes conspiracies for unauthorized entry more difficultand conspicuous to arrange.Functional redundancy introduces problems of its own. Batteries whichback up a diesel generator can eliminate (temporarily) the need to be able tofix a failed diesel, but they also mean that not only diesel spares but also batteryparts, distilled water, and so forth must be kept in stock. Thus greatertechnical diversity can make support logistics more complex.A functionally redundant back-up system is also one more thing to gowrong, and when it goes wrong, it does so in different ways than the systemit backs up. That is the point of diversity, but it can also be a nuisance. Ingraphite-moderated reactors, for example, some types of accidents might distortthe core so that control rods can no longer be fully inserted to stop thechain reaction. The newer British reactors therefore have a last-ditch emergencyshutdown device known as the “O Jesus” system, whereby pneumatichoses can be coupled up by hand to blow neutron-absorbing boron dust intothe core. Because this would mean writing off the reactor, the system is welldesigned to take quite a while to couple up, so that it cannot be used accidentallyor thoughtlessly. However, the Fort St.Vrain gas-cooled reactor inColorado uses hoppers of boronated steel balls which fall down into holes inthe graphite moderator block if the current to magnetic latches is interrupted.An accidental activation of this system reportedly left the operators spendingthe best part of a year vacuuming the balls out again.The apparent diversity of supposedly independent systems can also be compromisedby poorly designed links between them. Westinghouse reactors, forexample, commonly activate back-up (safety) systems with the same electricalsignals which control normal operation. Interactions via this link have on occasiondisabled both systems at once—leading a senior Nuclear RegulatoryCommission safety advisor, Dr. Stephen Hanauer, to note that Westinghouse“thinks this [interconnection] is great [because it is cheaper]. I think it is unsafe.This feud has been going on for years.” Nor does functional redundancy mean