These are inspections by IAEA Safeguards, their main goal is to track fissile material for non-proliferation treaty compliance purposes. They did not oblige the Soviets to allow the IAEA to show up in case of an accident and I'm not sure if that particular plant was supposed to have any inspectors visit at all. Here's an update from August '85 that gives you an idea of how things were going:
The agreement by the USSR to permit IAEA inspections was signed in February 1985, a month before Mr Gorbachev was appointed.
https://www.upi.com/Archives/1985/02/22/Soviets-to-allow-ins...