trailThe historical core-damage record is dominated by early-generation and Soviet reactor designs outside the scope of most probabilistic risk assessments
Nuclear probabilistic risk assessments predicted core-damage frequencies well below the observed historical accident rate
Composition of the accident record· for
Core-damage events before 1980 occurred almost entirely in experimental or first-generation reactor designs
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The Chernobyl RBMK reactor design had no probabilistic risk assessment before the 1986 accident
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Japanese nuclear plant probabilistic safety assessments before 2011 addressed internal events only, excluding tsunami hazards
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The Fukushima counterexample· against
The Fukushima Daiichi reactors had plant-specific probabilistic risk assessments predicting core-damage frequencies around one in a million reactor-years before the 2011 accident
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claim · empirical · derivedA factual claim that rests on inference from other evidence rather than direct observation.constitution →claim page ↗︎
The historical core-damage record is dominated by early-generation and Soviet reactor designs outside the scope of most probabilistic risk assessments
unassessedNo current assessment. Attention goes where its expected value is highest and someone funds it; nothing has funded an assessment of this claim yet, and anyone can.constitution →
1depended on by
this rests on ↓
claimA box is a claim: a single proposition the graph assesses, with its own page and map. Click any claim to centre the map on it.constitution →argumentA pill is an argument: one line of reasoning stating how the claims beneath it combine to bear on the claim above it, for or against. Arguments are not destinations; click their claims to explore.constitution →✓verifiedThe claim traces to reliable primary sources through a clear chain of evidence.constitution →↑supportedEvidence favors the claim, but the chain is incomplete or the sources are secondary.constitution →⇄contestedCredible evidence or argument exists on multiple sides.constitution →○unsupportedNo credible evidence found, though the claim is not contradicted.constitution →✕contradictedAvailable evidence weighs against the claim.constitution →?unknownInsufficient information to assess.constitution →◌unassessedNo current assessment. Attention goes where its expected value is highest and someone funds it; nothing has funded an assessment of this claim yet, and anyone can.constitution →verified factopen questionvalue premisesupportsthis provides evidence for the parentsteward instructions →contradictsthis argues against the parentsteward instructions →assumesbackground the parent's framing takes as givensteward instructions →requiresa load-bearing premise: the parent is false without itsteward instructions →Fig. Detail falls off with distance; every claim is an address.