“Recently, the situation at the Zaporizhzhya NPP (ZEP) has aggravated to a critical point. President of Ukraine Volodymyr Zelensky openly states the threat of a radiation accident, and leading Western media, such as The Guardian, write about critical instability at the facility. Similar estimates also operates with the IAEA. The station was completely disconnected from the last active line of external power supply that is vital to ensure”, – WRITE ON: ua.news
Recently, the situation at the Zaporizhzhya NPP (ZEP) has aggravated to a critical point. President of Ukraine Volodymyr Zelensky openly states the threat of a radiation accident, and leading Western media, such as The Guardian, write about critical instability at the facility. Similar grades Operates And the IAEA.
The station was completely disconnected from the last external power supply line, which is vital to ensure the safety of nuclear fuel. This loss caused by combat operations forced the ZPP to move on to offline. For the eighth day in a row, the station operates exclusively on emergency diesel generators (DG). Such a long period of work on reserve systems is much exceeding prose and operational standards.
The continuation of this regime within eight days creates a cumulative effect that causes a freelance and potentially emergency condition. However, the risks of a radiation disaster, although undoubtedly real, are still seriously exaggerated, which can indicate misunderstanding of what is now The situation on the ZPP .
What happens at the nuclear power plant and is there a threat of a “second Chernobyl”? UA.News was understood in the question.
What and why is the ZPP
The fundamental principle of nuclear safety is based on the need for a constant and reliable external source of electricity. Energy is required to operate pumps and security systems even when the reactors do not work. Its primary task is to ensure forced cooling of nuclear fuel, which remains in the active area, as well as the exhaust fuel stored in special endurance pools. This dependence on the external network is the greatest vulnerability of any nuclear power plant in the face of armed conflict.
The current critical state is caused by the loss of the last line of power transmission, which connected the NPP with the Ukrainian energy system. Repair crews cannot promptly restore damaged infrastructure. Because of this, the invaders were forced to transfer the station to diesel generators. Their functional purpose is to provide fuel cooling during a short transition until the main power is restored. Emergency systems are usually not projected for continuous operation for many days, as this significantly increases the risks of mechanical wear and tear.
The fact that the ZPP works on the generators for the eighth day indicates a serious violation of operational standards and creates cumulative risk. Although the IAEA confirmed that the DG is currently functioning and fuel reserves are sufficient for them, the main threat is not to exhaust fuel. It is the increase in the probability of mechanical failure not too new, to put it mildly, generators. That is, the longer the DGs work outside the regulation, the higher the risk of their simultaneous cascading failure.
Are there any risks of “second Chernobyl”?
Due to insufficient awareness in technical matters, the information space is often filled with panic statements that the ZPP may “explode” as this happened at the Chernobyl NPP. This fear is clear, but it is based on the wrong sense of engineering differences between reactor technologies. The repetition of the Chornobyl scenario to the ZPP is physically impossible, and this risk can be guaranteed.
The 1986 Chernobyl disaster was caused by the disadvantages of the RBMC reactors, which included the presence of graphite retardant and the positive reactivity ratio at low power. This has led to uncontrolled dispersal of power and a subsequent devastating steam explosion.
Unlike RBMK, the VVER-1000 reactors (water-water-water reactors) were installed at the ZPP. These reactors belong to the class of lightweight reactors under pressure that do not contain graphite and have a negative reactivity factor. Which, in turn, makes it impossible for uncontrollable power acceleration and, as a consequence, the Chernobyl steam explosion. Even if the station worked at full capacity, such a scenario would be considered engineering.
In addition to engineering differences, a critical factor that reduces the danger is the current mode of operation of the station. All six power units have been in a cold stop mode or a “cold reserve” for a long time. Although the fuel still requires constant cooling, reducing heat dissipation provides a significant time, compared to the scenario when the reactor stops only a few hours before the power loss. In this state, the fuel releases much less heat, which slows the boiling process and evaporation of cooling water, giving the operators much more time to restore energy supply.
However, despite the exclusion of a catastrophic scenario such as Chernobyl and the benefits of a long cold stop, the risk of a radiation accident really exists and, unfortunately, is real. This risk is linked solely with the inability to discharge residual heat for a long time, which is provided by forced cooling systems.
The true threat is the long and complete loss of diesel generators, which will stop all pumps of the residual heat discharge system. If the forced supply of cooling water stops, it will evaporate. This will lead to the exposure of fuel elements in the active area. Their uncontrolled heating will cause the zirconium membranes and then the nuclear fuel itself. This process leads to the formation of a high -storage molten mass of fuel and structural materials called Corium .
If the process cannot be stopped, the corium will start to melt the structures, including the reactor housing. This is already considered a heavy accident, which leads to the exit of molten masses and radioactive materials into the room under a sealed protective shell.
A similar scenario, if it happens, is an accident typologically similar to the one that took place at the Japanese NPP Fukushima In 2011, not Chornobyl. However, even such a comparison is conditional and requires caution. Fukushima was a stable working station. In Zesc, thanks to the long-standing “cold stop”, it contains much less short-lived and most dangerous isotopes, including iodine-131, compared to actively working reaches Toro. This is significant Reduces the risks And, in particular, it removes the need for mass use of potassium iodide in the event of an accident.
In addition, VVER-1000 reactors are equipped with a strong, sealed protective sheath, which is designed to contain radiation emissions even in the case of melting the active area. Even in the worst case, melting radiation emission, most likely, will not have a catastrophic scale like Chernobyl. However, such an incident will cause serious local pollution, which will require evacuation and have long -term consequences for the environment and the population in the immediate vicinity of the station.
What do the invaders think?
Since the Zaporizhzhia NPP is under occupation The Russian Federation, it is fully responsible for ensuring the technical condition, proper maintenance, as well as for the restoration of all the necessary safety conditions, including the uninterrupted regular energy supply of the station. Today’s crisis is a direct consequence of military aggression and negligence of the occupation administration.
The question of the motives of the invaders is key. Do they try to deliberately cause a nuclear accident? Most likely, no. The Russians are anyone but not suicide, in such a strange way. The deliberate accident threatens their military forces, which are located directly at and near the station, as well as part of the occupied territories and, in adverse weather conditions, even the border regions of Russia.
The key strategic goal of the invaders is to integrate the Zaporozhye NPP into the Russian power system. Creating and maintaining a critical situation can be used as a political pressure on Ukraine and the international community, forcing them to agree to the conditions of “stabilization”, which include the actual legitimation of Russian control over the station.
The expert’s opinion
UA.news appealed to Sergei T., a senior engineer who worked for a long time before the full -scale war and occupation. According to the expert, the key goal of the Russians is to connect the station to their own energy system.
“The station has not been working for over three years. The blocks are in the so -called “cold reserve”. That is, no reactions are there, the blocks are muted. But they need to be cooled constantly, and there is a cooling system that works from the power line that goes from the territory of Ukraine. All these years, they (invaders – ed.) Were constantly destroyed, and ours were restored. Now what day the line is again destroyed and is not allowed to repair. Instead, reserve diesel generators work. They should not work for more than three days by standards. Here ours raised Bucha, and the Russians say that they have everything under control, and that everything will be fine, so we just need to switch the station to their power system. Ours are against. This is the main thread of the situation … There were no such reactors. This is a freelance situation. Diesel generators are a extreme case. Tomorrow they will fail – and what will the Russians do? This is generally a situation that cannot be allowed, but it has been admitted. Ukraine has never allowed this… some explosion, most likely, will not be a melt if the fuel in the reactor is very warming ”, Said Sergei.
Summarizing, the situation at the Zaporozhye NPP really remains very dangerous. However, the “second Chernobyl” scenarios are unjustified due to the engineering features of the VVER reactors and their long -standing cold stop, which guarantees the absence of a steam explosion. In addition, the low level of residual heat dissipation significantly reduces the speed of development of the emergency process.
However, the danger of a serious radiation accident caused by the refusal of cooling systems is quite real. Exercise on emergency diesel generators within eight days is much higher than the performance and creates a high risk of cascade technical failure. The complete refusal of all DG can lead to the melting of the active zone and radiation emission of a local scale, similar to a crash at Fukushima, although with a much lower content of radioisotopes.
The whole responsibility for the technical condition and critical situation at the NPP lies completely on the Russian aggressor. Negligence, military activity and use of the object as a political lever pose an unacceptable threat. Although the occupiers are unlikely to seek nuclear suicide, they consciously operate technical risks as a strategic tool to achieve their ultimate goal – integration of the NPP into their own energy system.