The nuclear meltdown at Chernobyl 20 years ago this month, even more
than my launch of perestroika, was perhaps the real cause of the
collapse of the Soviet Union five years later. Indeed, the Chernobyl
catastrophe was an historic turning point: there was the era before
the disaster, and there is the very different era that has followed.
The Chernobyl disaster, more than anything else, opened the
possibility of much greater freedom of expression, to the point that
the system as we knew it could no longer continue. It made absolutely
clear how important it was to continue the policy of glasnost, and I
must say that I started to think about time in terms of pre-Chernobyl
The price of the Chernobyl catastrophe was overwhelming, not only in
human terms, but also economically. Even today, the legacy of
Chernobyl affects the economies of Russia, Ukraine, and Belarus.
This is a quote from Gorbachev's book I obtained online here. This would suggest Gorbachev is discussing the existential costs of the accident as much as the remediation/medical costs when assessing it's weight as an input on the dissolution of the USSR. I have read elsewhere he explains that USSR was at the time being stretched fiscally and economically — not by SDI — but by the war in Afghanistan.
While an unexpected bill of $18B may not seem like much today, he asserts it pushed the USSR past a fiscal tipping point from which it could not recover. Things had to change. Certainly oil prices and exports would have played their part but for him that was not the decisive blow, Chernobyl was it. I'm not sure why Gorbachev would favor a home grow disaster born of engineering incompetence or corruption over international markets conspiring against him, although I can understand why he would want the world not to believe the KGB fell for the SDI fictions. At the time SDI proposals were openly being discredited in international science journals as completely implausible given that very effective counter measures could be deployed for a fraction of the cost amongst other reason. (A miniscule ball-bearing at velocity is enough to destroy a trillion dollar satellite mounted laser weapon system for example).