Energoatom, operator from the Zaporizhzhia Nuclear Power Plant in the Ukrainian city of Enerhodar, announced on September 11, 2022, it turned out shutting down the last working reactor of the plant’s six reactors, reactor Simply no 6. The providers possess put the reactor within cold shutdown to minimize the chance of a radiation leak from combat in the region around the nuclear energy plant.
All of us asked Najmedin Meshkati , a professor plus nuclear safety expert at the College of Southern Ca, to explain cold shutdown, what it means for the safety of the nuclear strength plant, and the ongoing risks to the plant’s spent fuel, that is uranium that has been mostly but not completely depleted by the fission response that drives nuclear power plants.
What does it indicate to have a nuclear reactor in cold shutdown?
The fission reaction that produces heat in a nuclear power plant can be produced by positioning numerous uranium fuel supports in close proximity. Shutting down a nuclear reactor consists of inserting control supports between the fuel fishing rods to stop the fission reaction.
The reactor is then in cooldown mode as the temp decreases. According to the US Nuclear Regulatory Commission , once the temperature is certainly below 200 levels Fahrenheit (93 Celsius) and the reactor coolant system is at atmospheric pressure, the reactor is in cold shutdown.
When the reactor is operating, it requires cooling to absorb the warmth and keep the gas rods from burning together, which would head out a catastrophic chain reaction. When a reactor is in cold shutdown, it no longer needs the same level of flow.
So how exactly does being in cold shutdown improve the plant’s security?
The shutdown has removed a huge element of risk. The Zaporizhzhia Nuclear Strength Plant is a pressurized drinking water reactor . These reactors need constant cooling, and the cooling pumps are gigantic, powerful, electricity-guzzling machines.
Cold shutdown is the state by which you do not need to continuously run the primary air conditioning pumps at the same degree to circulate the cooling water within the primary cooling cycle. The International Atomic Energy Agency (IAEA) has reported that reactor No 6 is now within a cold shutdown condition like the facility’s 5 other reactors, and will require less energy for cooling.
Now, at least if the plant loses offsite power, the operators will not have to worry about cooling an operating reactor along with cranky diesel generators.
And by closing down reactor No 6, the plant workers can be relieved of a considerable amount of their workload monitoring the reactors amid the ongoing uncertainties around the web site. This substantially decreased the potential for human mistake.
The operators’ jobs are likely to be a lot less demanding and demanding now than prior to. However , they nevertheless need to constantly monitor the status of the shutdown reactors as well as the spent fuel pools.
What are the dangers from the spent fuel at the plant?
The plant still needs a reliable source of electricity to cool the six huge spent energy pools that are inside the containment structures and also to remove residual temperature from the shutdown reactors.
The cooling pumps for that spent fuel private pools need much less electrical power than the cooling pumps on the reactor’s major and secondary loops, and the spent energy cooling system could tolerate a brief electricity outage.
Yet another important factor is that the invested fuel storage racks in the spent energy pools at the Zaporizhzhia Nuclear Power Plant were compacted to increase capacity, according to a 2017 Ukrainian government are accountable to the IAEA . The greater number and much more compacted the stored spent fuel fishing rods, the more heat these people generate and so good luck is needed to cool them.
There is also a dry spent fuel storage service at the plant. Dry spent fuel storage involves packing spent fuel supports into massive cyl, or casks, which usually require no water or other coolants. The casks are made to keep the fuel fishing rods contained for at least 50 years.
However , the casks are not underneath the containment structures at the plant, and, although they were designed to withstand being crashed into by an airliner, it’s not clear regardless of whether artillery shelling and aerial bombardment, particularly repeated attacks, could crack open the casks and release radiation into the reasons of the plant.
The closest example to this scenario could be a terrorist attack that, according to the seminal study by National Research Council, could breach a dry cask and potentially result in the discharge of radioactive materials from the spent fuel. This could happen with the dispersion of gasoline particles or fragments or the dispersion of radioactive aerosols.
This would be similar to the detonation of a “dirty bomb, ” which usually, depending on wind direction and dispersion radius, could result in radioactive contamination. This in turn could cause serious problems for entry to and work in the rose.
Following steps from the IAEA and UN
The IAEA offers called on Russian federation and Ukraine in order to setup a “safety and security protection zone” around the plant . However , the IAEA is a science plus engineering inspectorate and technical assistance company. Negotiating and creating a protection area at a nuclear strength plant in a battleground is entirely unprecedented and totally different from all past IAEA efforts.
Creating a protection zone requires negotiations and approvals at the greatest political and military levels in Kiev and Moscow. It may be accomplished through backchannel, Monitor II-type diplomacy , specifically nuclear safety-focused engineering diplomacy .
In the meantime, the particular IAEA needs strong support from the Un Security Council by means of a resolution, mandate or the creation of an unique commission.