# How the Chernobyl reactor exploded

> A process map exported from forks.world (https://forks.world). Author: Brian. Source: https://forks.world/p/cmv221xoc0007i206t8bit053
> It describes who does what, in what order, and with which technology. Read the plain-language sections first; the JSON at the end is the exact, complete data.

## Summary

- 18 steps across 2 layers
- Persona: Plant managers, Control room operators, Soviet state, Firefighters and liquidators
- Technology / systems: Reactor 4

## Pain points

Where this process hurts, worst first:

- **Pull most control rods out to raise power again** (How the Chernobyl reactor exploded; critical): Far fewer rods in than the rules allowed
- **Graphite tips on the control rods first add power instead of removing it** (How the Chernobyl reactor exploded; critical): A design flaw that operators had not been told about
- **Silence for about two days until alarms go off in Sweden** (How the Chernobyl reactor exploded; critical): Secrecy delayed the evacuation of the nearby town

## How to read this file

- A process is made of **layers**. The main layer is the top level; any step of kind `subprocess` opens a detail layer with its own lanes and steps.
- **Lanes** are either persona (people/roles) or technology (systems). Each step belongs to one lane; `using` lists tools a person uses for that step.
- Step kinds: `start`, `task`, `decision` (its arrows carry the answer as a label), `subprocess`, `end`.

## How the Chernobyl reactor exploded

Lanes:
- Plant managers: person / role (id `plant`)
- Control room operators: person / role (id `ops`)
- Reactor 4: technology / system (id `reactor`)
- Soviet state: person / role (id `state`)
- Firefighters and liquidators: person / role (id `crew`)

Steps, in the order they run:

1. **Plans a safety test of the cooling pumps during a power cut for the night shift** [start; Plant managers; id `c1`]
   - then Test is delayed and the reactor power sinks too low
2. **Test is delayed and the reactor power sinks too low** [task; Control room operators; id `c2`]
   - then Pull most control rods out to raise power again
3. **Pull most control rods out to raise power again** [task; Control room operators; id `c3`] ⚠ PAIN POINT (critical): Far fewer rods in than the rules allowed
   - then Switch off safety systems that would stop the test
4. **Switch off safety systems that would stop the test** [task; Control room operators; id `c4`]
   - then Reactor is unstable and the coolant boils into steam bubbles
5. **Reactor is unstable and the coolant boils into steam bubbles** [subprocess; Reactor 4; id `c5`], opens the detail layer "Why the reactor ran away"
   - then Press the emergency shutdown button
6. **Press the emergency shutdown button** [task; Control room operators; id `c6`]
   - then Graphite tips on the control rods first add power instead of removing it
7. **Graphite tips on the control rods first add power instead of removing it** [task; Reactor 4; id `c7`] ⚠ PAIN POINT (critical): A design flaw that operators had not been told about
   - then Power surges and a steam explosion blows the lid off
8. **Power surges and a steam explosion blows the lid off** [task; Reactor 4; id `c8`]
   - then A second explosion and a graphite fire burn for days
9. **A second explosion and a graphite fire burn for days** [subprocess; Reactor 4; id `c9`], links to the published process "How a nuclear reactor makes electricity" (https://forks.world/p/cmv0kpxju000ojv06uvs5s547; full text at https://forks.world/api/public/cmv0kpxju000ojv06uvs5s547/export)
   - then Firefighters and liquidators fight the fire and bury the site
10. **Firefighters and liquidators fight the fire and bury the site** [task; Firefighters and liquidators; id `c10`]
   - then Is the accident announced right away?
11. **Is the accident announced right away?** [decision; Soviet state; id `c11`]
   - if "No" go to Silence for about two days until alarms go off in Sweden; if "Yes" go to Evacuation begins immediately
12. **Silence for about two days until alarms go off in Sweden** [task; Soviet state; id `c12`] ⚠ PAIN POINT (critical): Secrecy delayed the evacuation of the nearby town
   - then Build a concrete shelter and later a giant arch over it
13. **Build a concrete shelter and later a giant arch over it** [task; Firefighters and liquidators; id `c14`]
   - then Reactors of this type are changed and the world rewrites its safety rules
14. **Reactors of this type are changed and the world rewrites its safety rules** [end; Soviet state; id `c15`]
15. **Evacuation begins immediately** [task; Soviet state; id `c13`]
   - then Build a concrete shelter and later a giant arch over it

```mermaid
flowchart LR
  subgraph l_plant["Plant managers"]
    n_c1(["Plans a safety test of the cooling pumps during a power cut for the night shift"])
  end
  subgraph l_ops["Control room operators"]
    n_c2["Test is delayed and the reactor power sinks too low"]
    n_c3["Pull most control rods out to raise power again"]
    n_c4["Switch off safety systems that would stop the test"]
    n_c6["Press the emergency shutdown button"]
  end
  subgraph l_reactor["Reactor 4"]
    n_c5[["Reactor is unstable and the coolant boils into steam bubbles"]]
    n_c7["Graphite tips on the control rods first add power instead of removing it"]
    n_c8["Power surges and a steam explosion blows the lid off"]
    n_c9[["A second explosion and a graphite fire burn for days"]]
  end
  subgraph l_state["Soviet state"]
    n_c11{"Is the accident announced right away?"}
    n_c12["Silence for about two days until alarms go off in Sweden"]
    n_c13["Evacuation begins immediately"]
    n_c15(["Reactors of this type are changed and the world rewrites its safety rules"])
  end
  subgraph l_crew["Firefighters and liquidators"]
    n_c10["Firefighters and liquidators fight the fire and bury the site"]
    n_c14["Build a concrete shelter and later a giant arch over it"]
  end
  n_c1 --> n_c2
  n_c2 --> n_c3
  n_c3 --> n_c4
  n_c4 --> n_c5
  n_c5 --> n_c6
  n_c6 --> n_c7
  n_c7 --> n_c8
  n_c8 --> n_c9
  n_c9 --> n_c10
  n_c10 --> n_c11
  n_c11 -->|"No"| n_c12
  n_c11 -->|"Yes"| n_c13
  n_c12 --> n_c14
  n_c13 --> n_c14
  n_c14 --> n_c15
```

### Why the reactor ran away (detail of step "Reactor is unstable and the coolant boils into steam bubbles")

Lanes:
- Reactor 4: technology / system (id `reactor`)

Steps, in the order they run:

1. **This design gets MORE reactive when the water boils** [start; Reactor 4; id `p1`]
   - then More steam means more power, which means more steam
2. **More steam means more power, which means more steam** [task; Reactor 4; id `p2`]
   - then Power rises faster than anyone can respond
3. **Power rises faster than anyone can respond** [end; Reactor 4; id `p3`]

```mermaid
flowchart LR
  subgraph l_reactor["Reactor 4"]
    n_p1(["This design gets MORE reactive when the water boils"])
    n_p2["More steam means more power, which means more steam"]
    n_p3(["Power rises faster than anyone can respond"])
  end
  n_p1 --> n_p2
  n_p2 --> n_p3
```

## Full data (JSON)

```json
{
  "title": "How the Chernobyl reactor exploded",
  "maps": {
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      "id": "m_root",
      "lanes": [
        {
          "id": "plant",
          "name": "Plant managers",
          "type": "person"
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          "type": "person"
        },
        {
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          "name": "Reactor 4",
          "type": "system"
        },
        {
          "id": "state",
          "name": "Soviet state",
          "type": "person"
        },
        {
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          "name": "Firefighters and liquidators",
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        }
      ],
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            }
          ],
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          "label": "Plans a safety test of the cooling pumps during a power cut for the night shift"
        },
        {
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          "kind": "task",
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          "next": [
            {
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            }
          ],
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        },
        {
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          "kind": "task",
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            {
              "to": "c4"
            }
          ],
          "pain": {
            "note": "Far fewer rods in than the rules allowed",
            "level": 3
          },
          "uses": [],
          "label": "Pull most control rods out to raise power again"
        },
        {
          "id": "c4",
          "kind": "task",
          "lane": "ops",
          "next": [
            {
              "to": "c5"
            }
          ],
          "uses": [],
          "label": "Switch off safety systems that would stop the test"
        },
        {
          "id": "c5",
          "kind": "subprocess",
          "lane": "reactor",
          "next": [
            {
              "to": "c6"
            }
          ],
          "uses": [],
          "child": "m_physics",
          "label": "Reactor is unstable and the coolant boils into steam bubbles"
        },
        {
          "id": "c6",
          "kind": "task",
          "lane": "ops",
          "next": [
            {
              "to": "c7"
            }
          ],
          "uses": [],
          "label": "Press the emergency shutdown button"
        },
        {
          "id": "c7",
          "kind": "task",
          "lane": "reactor",
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            {
              "to": "c8"
            }
          ],
          "pain": {
            "note": "A design flaw that operators had not been told about",
            "level": 3
          },
          "uses": [],
          "label": "Graphite tips on the control rods first add power instead of removing it"
        },
        {
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          "lane": "reactor",
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              "to": "c9"
            }
          ],
          "uses": [],
          "label": "Power surges and a steam explosion blows the lid off"
        },
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          "kind": "subprocess",
          "lane": "reactor",
          "link": {
            "id": "cmv0kpxju000ojv06uvs5s547",
            "scope": "public",
            "title": "How a nuclear reactor makes electricity"
          },
          "next": [
            {
              "to": "c10"
            }
          ],
          "uses": [],
          "label": "A second explosion and a graphite fire burn for days"
        },
        {
          "id": "c10",
          "kind": "task",
          "lane": "crew",
          "next": [
            {
              "to": "c11"
            }
          ],
          "uses": [],
          "label": "Firefighters and liquidators fight the fire and bury the site"
        },
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          "id": "c11",
          "kind": "decision",
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          "next": [
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              "to": "c12",
              "label": "No"
            },
            {
              "to": "c13",
              "label": "Yes"
            }
          ],
          "uses": [],
          "label": "Is the accident announced right away?"
        },
        {
          "id": "c12",
          "kind": "task",
          "lane": "state",
          "next": [
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              "to": "c14"
            }
          ],
          "pain": {
            "note": "Secrecy delayed the evacuation of the nearby town",
            "level": 3
          },
          "uses": [],
          "label": "Silence for about two days until alarms go off in Sweden"
        },
        {
          "id": "c13",
          "kind": "task",
          "lane": "state",
          "next": [
            {
              "to": "c14"
            }
          ],
          "uses": [],
          "label": "Evacuation begins immediately"
        },
        {
          "id": "c14",
          "kind": "task",
          "lane": "crew",
          "next": [
            {
              "to": "c15"
            }
          ],
          "uses": [],
          "label": "Build a concrete shelter and later a giant arch over it"
        },
        {
          "id": "c15",
          "kind": "end",
          "lane": "state",
          "next": [],
          "uses": [],
          "label": "Reactors of this type are changed and the world rewrites its safety rules"
        }
      ],
      "title": "How the Chernobyl reactor exploded",
      "parent": null
    },
    "m_physics": {
      "id": "m_physics",
      "lanes": [
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          "id": "reactor",
          "name": "Reactor 4",
          "type": "system"
        }
      ],
      "steps": [
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          "kind": "start",
          "lane": "reactor",
          "next": [
            {
              "to": "p2"
            }
          ],
          "uses": [],
          "label": "This design gets MORE reactive when the water boils"
        },
        {
          "id": "p2",
          "kind": "task",
          "lane": "reactor",
          "next": [
            {
              "to": "p3"
            }
          ],
          "uses": [],
          "label": "More steam means more power, which means more steam"
        },
        {
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          "kind": "end",
          "lane": "reactor",
          "next": [],
          "uses": [],
          "label": "Power rises faster than anyone can respond"
        }
      ],
      "title": "Why the reactor ran away",
      "parent": {
        "map": "m_root",
        "step": "c5"
      }
    }
  }
}
```