Probability budget
Take a tool and strike the schematic. The goal is to carry radioactivity past the last barrier with a sequence that is no rarer than the screening threshold. Frequencies of independent events multiply: a rare event is expensive, a frequent one cheap, and one event that takes several channels at once costs its own frequency instead of the product of three. The schematic, the scenarios and the mitigations are read from the failure library.
version 2026-09-16 · library v2 · 214 scenarios · 231 incident records
status prototype — prototype: assembled, not yet checked against a reference
Scenario library · Incident library
status prototype — prototype: assembled, not yet checked against a reference
Scenario library · Incident library
How this works
Four barriers stand between the radioactivity and the outside world: the fuel matrix, the fuel rod cladding, the reactor coolant pressure boundary and the containment. A release happens when every barrier this plant actually has is breached — early designs have two or three, and that alone is half the story.
Step 1 · ModelThe plant rotates with its specs beside it. It shows what the revision rests on: a real accident, or design documentation alone.
Step 2 · SectionThe cutting plane runs to the centreline. The slider takes it further.
Step 3 · SchematicTake a tool from the palette, strike a node. The analysis on the right says what worked and what the defence held.
The threshold is a lower bound. The frequencies of independent initiating events multiply, and a sequence counts if its frequency is not below the screening threshold: what is rarer than the threshold is not taken into probabilistic analysis at all. Hence the whole arithmetic of the game — a rare destructive event falls below the threshold by itself, a frequent error spends almost none of the margin, and one event that takes several channels at once costs its own frequency instead of the product of three.
Only the initiating event carries a frequency in 1/year — where the accident begins. Everything after it enters as a conditional probability per demand. A set of conditional failures alone is not a sequence: there is nothing to start from.
Each row is one plant and its revisions run left to right: a vulnerability once closed stays closed. The colour of the left edge says what the revision rests on, and the circle is the medal taken.
Analysis
Organisational targets — not on the schematic
Barriers
Margin over the screening threshold