In the 1950s, when the RBMK design was developed and approved, Soviet industry had not yet mastered the technology necessary to manufacture steel pressure vessels capacious enough to surround such large reactor cores. For that reason, among others, scientists engineers, and managers in the Soviet nuclear-power industry had pretended for years that a loss-of-coolant accident was unlikely to the point of impossibility in an RBMK. They knew better. The industry had been plagued with disasters and near-disasters since its earliest days. All of them had been covered up, treated as state secrets; information about them was denied not only to the Soviet public but even to the industry’s managers and operators. Engineering is based on experience, including operating experience; treating design flaws and accidents as state secrets meant that every other similar nuclear-power station remained vulnerable and unprepared.
Unknown to the Soviet public and the world, at least thirteen serious power-reactor accidents had occurred in the Soviet Union before the one at Chernobyl. Between 1964 and 1979, for example, repeated fuel-assembly fires plagued Reactor Number One at the Beloyarsk nuclear-power plant east of the Urals near Novosibirsk. In 1975, the core of an RBMK reactor at the Leningrad plant partly melted down; cooling the core by flooding it with liquid nitrogen led to a discharge of radiation into the environment equivalent to about one-twentieth the amount that was released at Chernobyl in 1986. In 1982, a rupture of the central fuel assembly of Chernobyl Reactor Number One released radioactivity over the nearby bedroom community of Pripyat, now in 1986 once again exposed and at risk. In 1985, a steam relief valve burst during a shaky startup of Reactor Number One at the Balakavo nuclear-power plant, on the Volga River about 150 miles southwest of Samara, jetting 500-degree steam that scalded to death fourteen members of the start-up staff; despite the accident, the responsible official, Balakavo’s plant director, Viktor Bryukhanov, was promoted to supervise construction at Chernobyl and direct its operation.
Rhodes, Richard. Arsenals of Folly: The Making of the Nuclear Arms Race. Vintage Books, 2007. p. 6–7