It left a total of 48 members of the Soviet Missile Troop dead.
Russian NTV International said the accident occurred during the launch of a Vostok rocket on 18 March, 1980.
It left a total of 48 members of the Soviet Missile Troop dead.
The rocket had been carrying a military spy satellite, Ikar.
The TV programme said the Soviet Communist Party newspaper, Pravda, reported at the time that the launch had been a success.
The explosion of 300 tonnes of fuel completely incinerated the launch pad and its surroundings at the Plesetsk cosmodrome in north-west Russia.
Doctors from a nearby hospital said injured personnel had arrived with acute burns, in particular to their lungs.
A state commission which investigated the tragedy at the time concluded that operator error was to blame for the accident. It said the blast had been caused by the escape of liquid oxygen.
But the TV programme, called Independent Investigation, said it had established that the explosion on the launch pad had in fact resulted from a leakage of oxygen peroxide caused by the poor quality of the rocket's fuel filters.
TV finds little change
The programme said pre-launch procedures at the Plesetsk cosmodrome have remained unaltered since the blast.
"The launch pad has never been modernised, ever since it was first built.
"The design centre drafted the blueprints for the facility during the Cold War and the safety of personnel was the least of its worries," the programme said.
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