How much water is needed to keep a nuclear power plant operating? The question, which until recently seemed purely technical, now has a direct bearing on Bulgaria's energy security. The sharp drop in the Danube level forced the Kozloduy NPP to reduce the power of Unit 5, and with a continuing drought, the possibility of the plant's normal operation will become increasingly limited. At the same time, the heat increases electricity consumption and reduces the efficiency of some of the energy capacities. What else awaits us… Dr. Borislav Kolev speaks on the topic to FACT – an expert with many years of experience in energy and a participant in the development of modern energy policies.
- Mr. Kolev, the low levels of the Danube have already forced the Paks NPP in Hungary and the Cherna Voda NPP in Romania to limit their production. How close is the Kozloduy NPP to a situation where it will also have to reduce its capacity?
- On August 20, our plant announced a reduction in the capacity of Unit 5 by 120 MW. From the real-time data, we see that Unit 6 is not operating at maximum capacity either. Currently, the load is about 80% on one unit and about 90% on the other. But once the real restrictions have begun, it means that the buffer in front of us is extremely thin and if the level continues to fall**, from now on** more serious measures will follow, including stopping electricity production.
- At what drop in the Danube level does the operation of the “Kozloduy“ NPP start to become a real problem and what would this mean for electricity production in Bulgaria?
- For normal operation, a 3-meter water column is needed. Currently, the level is 20-30 centimeters lower than that. There is already a risk of cavitation and dangerous vibrations of the pumps. If this starts to occur, it will probably affect all pumps and further normal operation of the plant would not be possible. In such a scenario of the plant shutdown, about 37-38% of the daily electricity production in Bulgaria will be lost.
- Which is the bigger challenge for the Kozloduy NPP - the extremely low river level or the high water and air temperature?
- The river level is currently the immediate threat. However, high temperatures have an additional negative impact, reducing the efficiency of heat exchange in the condensers and complicating compliance with environmental standards for discharge back into the river. The plant has not operated under such conditions before, and it is not yet clear where the practical limits of normal and safe operation lie.
- If a prolonged drought combined with heat leads to a temporary shutdown of the Kozloduy NPP, how would the missing capacity be compensated?
- In the last week or two, we have been a net exporter, and in addition, there are still reserve coal and natural gas capacities in the region that are not operating because the price is too low for them. This means that we will certainly not reach a situation of shortage and power supply mode. But at certain times, prices will increase dramatically, which is good news for owners of storage capacities.
- Is climate change already changing the way we should plan energy infrastructure?
- Yes. Climate change has become a daily engineering challenge. Warming leads to a more extreme water cycle - longer droughts and more intense precipitation. Traditional hydrological and temperature statistics from the last century are no longer a reliable basis for design, as extreme climate anomalies are occurring more frequently and on a larger scale.
- Should new power plants, power lines and facilities be designed for a climate we have not yet seen?
- More vulnerable technologies should include greater safety factors and adaptability to temperature amplitudes and water deficits. Design should calculate potential extremes that go beyond our current experience.
- The problem does not only affect nuclear power plants. Which energy capacities are most vulnerable to extreme heat - nuclear power plants, thermal power plants, hydroelectric power plants, photovoltaics, wind farms or batteries?
- The most vulnerable to the low level of water sources are naturally hydroelectric power plants. But thermal power plants and nuclear power plants, which draw water for cooling from a river or water basin, are also highly dependent on its level. The heat negatively affects the efficiency of all technologies, because most of them rely on cooling from the environment. Low air density and frequent calm during the summer months lead to poor performance of wind generators. Photovoltaics and all conductors have higher internal losses when the ambient temperature is high. Batteries rely on additional cooling, which is usually sufficient. This makes photovoltaics, batteries and good network connectivity among the most reliable sources in extreme weather - especially since they are decentralized sources and when individual sites fail, this does not lead to a major shock to the system.
- Is it possible for Bulgaria to fall into a situation where, precisely on the hottest days, electricity production drops and consumption reaches record levels? Is there such a scenario in our energy estimates?
- We observe that more and more often people rely on active cooling with heat pump systems and the consumption levels that we register during the summer months are increasingly approaching the typical values in winter. If for some reason we stop investing in new capacities and the old ones fall off naturally, it is a completely realistic scenario of chronic shortages during heat waves. That is why it is important to continue to renew and upgrade our energy system.
- How much will it cost Bulgaria to adapt its energy infrastructure to more frequent droughts, heat waves and floods, and can we afford to postpone these investments?
- The cost of postponement is always higher, since a large-scale energy crisis or accident would cost the economy many times more. Unfortunately, we often observe this phenomenon - we postpone prevention for years and subsequently the state invests much more funds to deal with the disaster that has occurred. I cannot say how much it will cost, because this requires a large-scale analysis and data that probably only the system operator has. But the most important thing is to invest in a stable network that is ready to connect new capacities and absorb peak loads in winter and summer.
- The Danube is a cross-border system. Is a common plan between Bulgaria, Romania, Serbia, Hungary and the other Danube countries for water management and protection of energy security in extreme droughts already necessary?
- In Hungary, there is now talk of building a dam that would locally raise the river level to enable their nuclear power plant - the Paks NPP - to operate. But it is not known whether this will not lead to a further decrease in the level further downstream and the impossibility of the Kozloduy NPP operating. Given that the electricity systems are connected, this will not really alleviate the situation in the region. Such uncoordinated and individual measures, besides being a serious intervention in natural systems, will not lead to a general positive effect, because the negatives almost always seriously outweigh the positives. The only way to deal with crises more easily is if we work together for common solutions and greater connectivity. So even if there are extreme events in a region, everyone else can join in solving them. So instead of investing huge funds to stock up locally, we can distribute the burden among everyone and direct collective efforts to solving local crises.
- What lessons should we learn this year to be prepared for the heat and drought in the Danube next year? What should we do preventively?
- Measures will probably be taken with the canals and pumping stations of the power plants along the Danube, but next year there may be another crisis that “surprises” us. The most optimal solution is to have good enough connectivity and flexibility so that we do not rely entirely on individual unit capacities. The larger the set of solutions you have for the same problem, the less vulnerable you are. Production and storage should come from increasingly smaller, decentralized and flexible systems that are close to the consumer, and therefore state aid and measures should be directed at household and small consumers, not at large companies, which already have enough funds to invest on their own. And why shouldn't district heating companies in our country, in addition to heating, also start offering cooling services to their consumers. This is something that has existed around the world for decades.