Investigation ran on two tracks: a Soviet criminal and party file, and an IAEA scientific file.
English readers meet the second track first; the first track produced the 1987 sentences.
Agencies
- Soviet government commission — Immediate technical and political inquiry, with Legasov among the scientific leads.
- IAEA / INSAG — International cause reports in 1986 and 1992 that became the English reference narrative.
- UNSCEAR and WHO — Dose reconstruction and health-effect annexes, notably the 2008 report.
- Ukrainian and Russian successor archives — Post-1991 releases of plant logs, maps and party correspondence that filled gaps in INSAG-1.
What followed
- Stabilise the ruin
Helicopter drops, tunnel work and the first sarcophagus were emergency engineering, not a forensic pause.
- Brief Vienna
August 1986 Post-Accident Review Meeting produced INSAG-1 from a still-partial Soviet account.
- Try the managers
The 1987 court located blame in plant leadership while the design remained a state secret in public.
- Open the design
After 1989–91, RBMK details allowed INSAG-7 to re-rank causes.
- Register doses
UN and national registries tracked liquidators, evacuees and thyroid cases rather than a single death list.
- Fund a second shelter
The Shelter Fund and Novarka contract turned the ruin into an international construction case.
Turning points
- Forsmark, 28 April 1986 — Foreign detection ended the chance of a purely domestic file.
- INSAG-7, 1992 — The cause statement English regulators still teach.
- NSC move, 2016 — A visible end to the 1986 sarcophagus as the only lid on unit 4.
The investigation succeeded as engineering history. It did not produce a single uncontested lifetime casualty number.
Public-record encyclopedia. Not legal advice. Not a how-to. Graphic detail is withheld. Wars belong in a separate atlas.