It took years to find that out though.
The containment vessel held, and most of the radiation released was in the form of xenon and krypton gas vented from the reactor.
“ It was later found that about half the core had melted, and the cladding around 90% of the fuel rods had failed,[21][76] with 5 ft (1.5 m) of the core gone, and around 20 short tons (18 t) of uranium flowing to the bottom head of the pressure vessel, forming a mass of corium.[77] The reactor vessel—the second level of containment after the cladding—maintained integrity and contained the damaged fuel with nearly all of the radioactive isotopes in the core.”
Definitely not Chernobyl, but it was a significant amount of damage to the reactor. It was totaled.
Many of the "small modular reactor" schemes say they don't need a big, strong, expensive containment vessel because, reasons. You can read those arguments for NuScale in NRC documents. The prototype was going to be built at the Idaho National Laboratory, formerly the National Reactor Testing Station, which is in outer nowhere, just in case.
[https://www.newequipment.com/plant-operations/article/219218...]
While the precise mechanism by which the #4 reactor in Chernobyl was destroyed in 1986 was rooted in the flawed design combined with unsafe operation, this does not mean that other reactor designs cannot fail catastrophically with loss of containment and release of radioactive material. Particularly when operated outside of their specification through operator error, accidents or a combination thereof.
Any reactor can fail and any can be operated safely. The reactivity coefficients of RBMK made it harder to control, perhaps, than a PWR. Modifications made after the Chernobyl accident have improved this.
The main issue with Chernobyl 4 was its lack of a containment building. Even so, the response was an over-reaction that made the situation worse.
Not sure which response to the accident was an over-reaction in your opinion so.
No, sadly.
PWR's sure can explode (due to hydrogen, vapor...).
The root causes will not be identical to Chernobyl's causes, and the containment will probably limit leaks for a while (theoretically at least a few days), but they sure can explode.
It also happened at Fukushima.
Some protective measures are PACs and containment, however nothing can guarantee that an explosion won't happen, nor that dangerous radionuclides won't leak outside the plant.
PAC: https://en.wikipedia.org/wiki/Passive_autocatalytic_recombin...
Containment: https://en.wikipedia.org/wiki/Containment_building
Edit: That should be the one https://www-pub.iaea.org/MTCD/publications/PDF/Pub913e_web.p...
You also have this one: https://www.nrc.gov/docs/ML0716/ML071690245.pdf
Edit 2:
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.
“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.
Conspiracy in ussr != conspiracy in us.
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.
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.