So to answer your question, the reactor was doomed prior to the AZ-5 button being pressed and the operators had no idea of the reaction the graphite tips would have with a core already that unhealthy. When power subsequently expanded exponentially, the AZ-5 button being pressed took the reactor that was already teetering on the edge, over the cliff. This put the reactor in a state of no return. When the test was conducted, the water coolant pumps pushed a lower volume of water through due to the turbine generating less power as it was winding down. This led to a hot spot of steam to build in the middle of the core. To increase power again, all of the manual control rods were retracted from the core. This led to excess Xenon poisoning of the reactor which in turn led to further drop in power. The safety test was supposed to be conducted at between 700-1000 MW, however Dyatlov wanted the test to be conducted at much lower (around 200, well below the operational capability of the reactor). The RBMK reactor is known to be highly unstable at low power settings. The safety test that caused the reactor to be configured in an unsafe way was performed out of regulation. However, this power spike would only be an issue in a reactor that was already so far gone that a disaster would have been imminent. So Akimov and the other operators of Reactor 4 would have had no knowledge of the power spike to come from the AZ-5 button. The KGB even attempted to have this issue rectified but it wasn't. However this information was deliberately redacted and hidden from everyone but a small circle. The control rod/power spike interaction was already noted at Ignalina in Lithuania using RBMK reactors, the same type as Chernobyl. Was it a bad idea under the circumstances? TL DR Pressing "emergency shutdown" ended badly. reward type thing, or was someone incompetent, or was all possible information about any risk kept from them by the Soviet apparatus and they just did the smart thing and reached for the shutdown button once things got out of control? We know what the outcome of that was, but was it a good or bad idea to press the button in that moment? Did the Soviet tech guy running this thing have any idea what might happen, or that there was any design flaw at all? If not, should he have known? Was it a risk vs. Things seem to get worse and worse, extremely quickly, and at some point someone presses the AZ-5 button (very unpatriotic, comrade). Let's try shutting down the turbines!) For whatever reason the position arises where the reactor is poisoned, they're taking control rods out to try to compensate (bad idea), the reactor has a power excursion and coolant starts evaporating causing power to increase in runaway fashion (bad design ideas). (Let's make sure this thing can't blow up if we lose cooling. Did the people running these things have any idea about these attributes at the time?Īnyway. I would love to better understand the process that went into this. So at this point, we know that if the power and radiation get out of control, the power and radiation will increase, AND if you try an emergency shutdown, the power and radiation will increase. Oh, and by the way, the reactor happens to be designed so that if it has a cooling problem, the power increases. However, the rods are tipped with graphite, which has the effect of increasing the reactivity and power inside the core when they're all inserted at once. This should stop the reactor in case of emergency. When you push the button, all the control rods go as far as possible into the core as fast as possible. (By the way, why was it called that? I would call it "OFF," or maybe "EMERG STOP." My guess is there were different modes, like in F1 racing where the driver might select "chassis default 01" or "engine strategy 3" - maybe "AZ" stands for shutoff in Russian and there are several available shutoff modes? But I digress.) The reactor had an emergency shutdown button labeled AZ-5 or EPS-5. This is my understanding of the relevant facts - correct me if I'm wrong. Having seen the HBO series so far and done some reading about the events, I'm wondering about this.
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