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Zaporizhzhia Nuclear Power Plant: Attempt at Risk Analysis [1]
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Date: 2022-09-12
IAEA Director General’s Statement on Serious Situation at Ukraine’s Zaporizhzhya Nuclear Power Plant, Rafael Mariano Grossi, September 9, 2022
Today, I have learned from IAEA staff on the site of the serious situation that developed last night at Zaporizhzhya Nuclear Power Plant (ZNPP).
The power infrastructure feeding the city of Enerhodar, home to the NPP’s operators and their families, has been destroyed by shelling of the switchyard at the city’s thermal power plant, leading to a complete power black-out in Enerhodar: no running water, no power, no sewage.
Given the increased and continued shelling, there is little likelihood of re-establishing reliable offsite power to the ZNPP, especially as the shelling continually and repeatedly damages the power infrastructure.
As a result, the IAEA understands that the operator, having no longer confidence in the restoration of offsite power, is considering shutting down the only remaining operating reactor. The entire power plant would then be fully reliant on emergency diesel generators for ensuring vital nuclear safety and security functions. And as a consequence, the operator would not be able to re-start the reactors unless offsite power was reliably re-established.
Furthermore, there are indications that, with the increasingly dire circumstances that the people of Energodar are facing, there is the significant risk of an impact on the availability of essential staff on site to continue to safely and securely operate ZNPP.
This is an unsustainable situation and is becoming increasingly precarious. Enerhodar has gone dark. The power plant has no offsite power. And we have seen that once infrastructure is repaired, it is damaged once again.
This is completely unacceptable. It cannot stand.
I therefore urgently call for the immediate cessation of all shelling in the entire area. Only this will ensure the safety and security of operating staff and allow the durable restoration of power to Enerhodar and to the power plant.
This dramatic development demonstrates the absolute imperative to establish a nuclear safety and security protection zone now.
This is the only way to ensure that we do not face a nuclear accident.
Preliminary note: I am neither a physicist nor a nuclear engineer, but I have a family background on this subject: my father worked as an engineer on nuclear power plants, and I was a lifelong opponent of nuclear power. He knew not only Western, but also Eastern European and Chinese nuclear power plants from his own experience. At family celebrations it was always agreed not to bring up the subject…
Zaporizhzhya Nuclear Power Plant (ZNPP) is located near the city of Enerhodar on the southern bank of the Kakhovka Reservoir on the Dnieper River. At the lower end of the Kakhovka reservoir is the Nova Kakhovka dam, at the upper end the Dneprostroi Dam near the city of Zaporizhzhia. The six reactors were connected to the grid between 1984 and 1995. In the immediate vicinity of ZNPP is the Enerhodar thermal power station, a coal-fired power plant: both draw their cooling water from the Kakhovka Reservoir. Let's take a closer look at the risks posed by the location of this power plant complex between two large dams:
Nova Kakhovka dam, Kakhovka Hydroelectric Power Plant
The distance between the ZNPP and the Nova Kakhovka dam in the southwest is 181 km (112 miles).
Type of dam: partly a bulk material dam, partly a gravity dam.
Height: 30 m (98 ft), length: 3,273 m (2.03 miles).
The Kakhovka reservoir stretches 240 km (149 miles) upstream to the Dneprostroi Dam and is up to 23 km (14 miles) wide. The total water volume is 18.2 km³, about half of Lake Mead with 34.9 km3. Upstream of the dam begins the North Crimean Canal, which supplies water to the whole Crimea to Kerch.
Dneprostroi Dam, Dnieper Hydroelectric Station
The distance between the ZNPP and the Dneprostroi Dam in the northeast is 59 km (37 miles).
Type of dam: arch-gravity dam from reinforced concrete.
Height: 60 m (197 ft), length, 760 m (0.47 miles).
The Dnieper Reservoir stretches 129 km upstream to near Dnipro city and is up to 7 km (4.35 miles) wide. The total water volume is 3.3 km³.
During World War II, the Dneprostroi Dam was blown up by retreating Red Army troops in 1941 after the German invasion of the Soviet Union. The tidal wave killed tens of thousands of unsuspecting Ukrainian civilians. In 1943, the dam was blown up again by retreating German troops.
The location of the power plant complex – nuclear and thermal – between two large dams presents a first set of risks: If the Dneprostroi Dam failed, the power plant complex would be flooded; what effect this would have on the Nova Kakhovka dam is difficult to estimate, whether the tidal wave would spill over it or whether it would burst; if the Nova Kakhovka dam fails, the cooling water supply would be expected to fail. In both cases, this could lead to a catastrophe comparable to Fukushima. Risks caused by flooding of the Dnieper River in general are addressed in a Greenpeace briefing "The vulnerability of nuclear plants during military conflict”, March 2, 2022. During an armed conflict, due to the massive impact of possible destruction on the civilian population and the environment, a dam is to be considered as an "installation containing dangerous forces" according to international humanitarian law. Well-known other cases of military attacks on dams in the past are the bombings of Edersee Dam 1943 in World War II and of the Sui-ho Dam 1952 in the Korean War.
International Law Association, “Resolution on the Protection of Water Resources and Water Installations in Times of Armed Conflict” (1976) Article 56 - Protection of works and installations containing dangerous forces 1. Works or installations containing dangerous forces, namely dams, dykes and nuclear electrical generating stations, shall not be made the object of attack, even where these objects are military objectives, if such attack may cause the release of dangerous forces and consequent severe losses among the civilian population. Other military objectives located at or in the vicinity of these works or installations shall not be made the object of attack if such attack may cause the release of dangerous forces from the works or installations and consequent severe losses among the civilian population. An attack on either dam, comparable to the use of weapons of mass destruction, would not only be a blatant violation of international humanitarian law but, moreover, an escalation of hostilities that would likely fall just short of the use of a tactical nuclear weapon and would draw appropriate international reactions. The ZNPP has been occupied by Russian forces since 3 March 2022. During the 2022 Russian invasion of Ukraine, it has become the center of an ongoing nuclear safety crisis, described by Ukraine as an act of nuclear terrorism by Russia. On September 5 2022, the IAEA published the "2nd Summary Report by the Director General, 28 April – 5 September 2022 on Nuclear Safety, Security and Safeguards in Ukraine”, key takeaways: The IAEA has been regularly assessing the situation against these Seven Pillars, which are the following: 1. The physical integrity of the facilities – whether it is the reactors, fuel ponds or radioactive waste stores – must be maintained;
2. All safety and security systems and equipment must be fully functional at all times;
3. The operating staff must be able to fulfil their safety and security duties and have the capacity to make decisions free of undue pressure;
4. There must be secure off-site power supply from the grid for all nuclear sites;
5. There must be uninterrupted logistical supply chains and transportation to and from the sites;
6. There must be effective on-site and off-site radiation monitoring systems and emergency preparedness and response measures; and
7. There must be reliable communications with the regulator and others. The IAEA Director General has regularly expressed grave concern when these Seven Pillars were compromised at the sites of nuclear facilities in Ukraine. The Director General has continuously stressed the IAEA’s readiness to help ensure that the Seven Pillars are maintained in Ukraine. The report’s main conclusion was that the occupation of the power plant by Russian armed forces violates all seven pillars of nuclear safety. In his statement of September 9 2022, IAEA’s Rafael Mariano Grossi addressed two specific problems caused by the ongoing shelling of the area: the unsustainable living and working conditions of the operators of the power plant complex and the impossibility of ensuring a reliable power supply to the facilities. There is hardly a more serious incident in a nuclear power plant in which human error had not played an immediate role: Chernobyl is the most extreme example of this, Three Mile Island another. Optimal working conditions are a basic requirement for safe operation of such a plant, but here the operators live in a shelled city without electricity and water, and they work under military occupation and interference by Russian Rosatom officials on a shelled workplace. Whether the entire original staff is still on site, I dare to doubt.
On the risk of operator shortages: VVER-1000/320 type reactors are well known in their operation and are running not only in Ukraine but also in other countries, in Ukraine at Rivne, Khmelnytskyi and South Ukraine (near Yuzhnoukrainsk), in Bulgaria at Kozloduy and in Czech Republic at Temelin, seven plants in total. The IAEA even has software to simulate the operation of a reactor of this type for educational purposes. Lack of available operators experienced for this type of reactor should thus not be a insoluble problem. When the connection to the external power supply fails, a nuclear power plant can no longer supply its generated electrical power to the grid. The nuclear power plant then drastically has to reduce its output to a value that corresponds to its own demand for electrical power. In this way, the nuclear power plant can supply itself with electricity in isolated operation, isolated from the rest of the power grid. This process is called "load shedding to own demand." If load shedding on own demand fails, the nuclear power plant is automatically shut down and has to cover its demand for electrical power in stages via emergency diesel generators. ZNPP has twenty emergency power diesels that can supply all systems required for safety: cooling water pumps, instrumentation and control. The ZNPP diesel generators should have been upgraded under the Complex Consolidated Safety Upgrade Programme (CCSUP) of Energoatom, financed by a Euratom (EIB) and European Bank for Reconstruction and Development (EBRD) loan of 600 Million EUR. The EBRD is the lead in this programme. In this programme, the diesels should have received modern electronic controls. The final date of completion of the CCSUP has been put back from 2017 to 2023. Regarding the general safety of the ZNPP, there is a document from the Environment Agency Austria from 2021 in connection with clarifications on the lifetime extension, which sees a need to catch up in various points. Press release as of September 11, 2022, Ukrainian Energoatom on Telegram:
The operator of the embattled Zaporizhzhya nuclear power plant has stopped the operation of Europe's largest nuclear power plant. This was announced by the company Energoatom on Telegram. "Today, on September 11, 2022, at night at 03:41, unit 6 of the Zaporizhzhya nuclear power plant was disconnected from the power grid”, it said. "Preparations for cooling down and transfer to cold state are underway”. Unit 6 was the last reactor still operating at the ZNPP and had been supplying power to the NPP itself. On Saturday evening, a power line was restored to operation, according to Energoatom. The ZNPP was now being supplied with electricity from the Ukrainian power grid, it said. "Therefore, it was decided to shut down the No. 6 power unit and put it in the safest condition”.
Latest news as of September 11, 2022: IAEA Director General Statement on Situation in Ukraine
A back-up power line to Ukraine’s Zaporizhzhya Nuclear Power Plant (ZNPP) has been restored, providing the plant with the external electricity it needs for reactor cooling and other essential safety functions, the International Atomic Energy Agency (IAEA) learnt at the site today. Yesterday evening’s restoration of a 330 kilovolt (kV) reserve line – which connects Europe’s largest nuclear power plant to the Ukrainian network through the switchyard of a thermal power station in the nearby city of Enerhodar – enabled the ZNPP to shut down its last operating reactor early this morning. This reactor had over the past week provided the ZNPP with power after the facility was disconnected from the grid. With the line restoration, electricity needed for nuclear safety at the ZNPP once again comes from the external grid. [...] The ZNPP also has 20 emergency diesel generators available if needed, with supplies for at least 10 days of operation. There was no need to operate the generators during this operational change. Although the Enerhodar thermal power station remains down, the now restored power line provides the ZNPP with power from the Ukrainian grid transported through the station’s switchyard. As is the case for the five other reactor units, ZNPP operating staff plan to bring unit 6 to a cold shutdown state, which can take about 30 hours. The ZNPP will still need electricity for safety-related functions. However, in this state only power from one diesel generator per reactor is needed to maintain safety. [...]
Cold shutdown: The six units of the ZNPP are pressurized water reactors of the VVER-1000/320 type: the boiling point of water is pressure-dependent, and the pressure in the primary circuit is so high that the water does not boil. In an VVER-1000 in operation, at the inlet to the primary circuit the water has a temperature of 289°C (552°F) and at the outlet 324°C (615°F) at a pressure of 160 bar (16 megapascals). After a cold shutdown, after the decay heat has been dissipated, “which can take about 30 hours”, the water temperature is less than 95°C (203°F) at normal atmospheric pressure.
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