The full title is: ‘ Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency’
The declarations and reservations of the treaty is available here on the IAEA website.
Bulgaria, Hungary, Mongolia, and Poland are the only countries to have ratified the treaty and later withdrawn. 122 countries are currently signatories.
All four countries have also withdrawn from the ‘Convention on Early Notification of a Nuclear Accident’. 127 countries are currently signatories to that treaty.
Quite a few countries have recorded reservations about the wording so it does seem like an unusually controversial treaty but what makes it completely unacceptable for Bulgaria, Hungary, Mongolia, and Poland?