To be fair, the show over dramatized the KGB angle. But yes, the Soviets knew RBMKs were not the safest design, reactor 4 was built violating safety standards, operators for the test were not properly trained and then safety procedures were ignored during the test. The official incident report is a fascinating read, and should be mandatory reading for everyone studying with goal of having the word engineer in his future job title.
What with regards to the effect of graphite tipped control rods was, IMHO, as bad as having a dramatic KGB effort to keep it secret: it was forgotten. In 1983, there was an incident in an other RBMK reactor, the HBO series claims the KGB kept it secret, in reality this happened (from the INSAG-7 report and the cited USSR investigative reports):
>> The SCSSINP Commission (Annex I, Section 1-3.8) reports that, after discov-
ery of the positive scram effect at Ignalina in 1983, the chief engineering organiza-
tion informed other organizations and all nuclear power plants with RBMK reactors
that it intended to impose restrictions on the complete withdrawal of control and
safety rods from the core. Such restrictions were never imposed and apparently the
matter was forgotten.
That means in the fact it coupd explode was known, but ignored. Ignored by everyone in the Soviet scientific establishment and nuclear authorities. I don't what's worse, a secret police intervention or a whole science and industry community ignoring safety concerns until it is too late.
> Ignored by everyone in the Soviet scientific establishment and nuclear authorities. I don't know what's worse, a secret police intervention or a whole science and industry community ignoring safety concerns until it is too late.
“Whole .. community” is a stretch here.
Keep in mind that information spread is different in ussr. Kgb had people recruited from all over the place (from factory workers to politicians; 0.1% of population were in kgb). Also, lot of institutions had party representative present (officially, not hidden).
Press did not report accidents or significantly under-report casualties, and of course various good metrics were inflated a lot, even to comical levels.
In this environment, somebody using his influence in kgb or party to stop certain restrictions (because they would point to design flaw and would delay stuff) is very believable, and probably common.
Well, that the whole community of nuclear scientists, engineers and operators ignored the design flaws of RBMK reactors was an indirect conclusion of the two late 80s investigation boards the USSR (!) put in place. Read the annexes to INSAG-7, you can even find the design bureaus and directors named in there.
The KGB blocking the refit of the RBMK fleet is a myth from HBOs Chernobyl series. Truth is rather different, Legasov was seen by the younger generation as part of the establishment that held back modifications, while he simultaniously managed to piss off said establishment. And without support from the rank and file, and some enemies with the higher ups, his career was shot. Compounded by serious health issues following the Chernobyl clean up. Less dramatic than a KBG conspiracy for sure, but still bad enough.
If the HBO show had the science somwhat correct, then the operators did everything they could to make it go boom. In failure modes already defined and warned about.
That, and the fact that it wasn't was not communicated. The necessary assessments have not been done during Chernobyl No. 4s commissioning, hence not counter measures have beem defined and put in the procedures. The RBMK chief engineering org wanted to adress the incident in Lithuania, and informed operators and authorities about that intention. Chief engineering didn't follow up so, and nobody bothered asking where the announced measures and procedures were.
In the end the operators of Chernobyl No. 4 were the fucked ones, their procedures were incomplete, sometimes dangerously wrong. Leadership, incl. Dyatlov, failed to put a safety culture in place. The reactor design was not well understood, operating characteristics at below 50% capacity were never even analyzed or modelled, and inheretly unsafe (missing sensors, bad control rod design and operating procedures...). And the night shift wasn't even briefed on the test to be conducted.
One of the conclusions of INSAG-7 was, that the accident could even have happened with properly designed control rods, coolant failure could have led to the same accident. If your equipment is so inherently unstable and fragile, operating procedure, training and operators have to compensate. None of those measures was taken.
Heck, in some circunstances RBMK operators had to conduct up to 1,000 manual operations per hour (!) to keep the reactor stable. And by the way, the RBMK design didn't even meet Soviet design and safety requirements applicable in 70s when those reactors were designed.
A complete clusterfuck. The circumstances allowing said clusterfuck still exist everywhere, in all countries, industries and organisations to this day.