Secret First Deputy Minister of Energy and Electrification of the USSR 04 26 86 About the accident At Energy Block No 4 of Chernobyl NPS Urgent Report On 04 26 86 at 1 21 AM during the decommissioning of energy block No 4 of the Chernobyl NPS during planned maintenance after the reactor had been stopped there was an explosion in the upper part of the reactor compartment According to the director of Chernobyl NPS the explosion caused the collapse of roofs and parts of the wall paneling of the reactor compartment several panels of the roof in the machine hall and a unit of the auxiliary systems of the reactor compartment and also a roof fire At 3 30 AM the fire was extinguished Measures are being taken by the staff to cool down the active zone of the reactor In the opinion of the three main administrators under the USSR Ministry of Health the adoption of special measures including evacuating the population from the city is unnecessary Nine operational personnel and 25 paramilitary fire protection personnel were hospitalized Measures are being taken to eliminate the consequences and investigate the incident A N Makukhin Translated by Brooke Lennox for the National Security Archive This document is from the holdings of The National Security Archive Suite 701 Gelman Library The George Washington University 2130 H Street NW Washington D C 20037 Phone 202 994-7000 Fax 202 994-7005 nsarchiv@gwu edu