As the Japanese authorities deployed military pilots and firefighters to help Fukushima Daiichi personnel douse the ailing plant with water from helicopters and water cannons, in the conditions of the ever spiking levels of radiation, it was not just the reactors that so badly needed to receive cooling water to prevent them from melting down. As tpihe situation at the plant was becoming increasingly critical, reports were coming in on the receding water levels in reactor cooling ponds, specifically the one at Reactor 4, where, it was revealed earlier during the crisis, there was no longer water left in the pool, thus baring the spent fuel rods and causing them to heat up. But at least prior to the direst point in the crisis, official coverage of the situation with the cooling ponds remained meagre in Russia. And Russian nuclear authorities do not consider possible accident scenarios involving spent nuclear fuel stored at Russia’s nuclear power plants (NPPs) — thus, in effect, creating conditions that may facilitate a disaster like the one that hit Japan.
|Spent nuclear fuel rods are stored in special storage facilities for spent nuclear fuel – cooling ponds where fuel assemblies constantly remain inundated with water.|
Nuclear power plants run on nuclear fuel — and all nuclear power plants also produce an especially dangerous kind of waste: so-called spent nuclear fuel. The Russian State Nuclear Corporation Rosatom does not consider spent nuclear fuel waste — believing instead that it is a valuable resource when reprocessed — but for the purposes of this article, it matters little in which pigeonhole to file this material that threatens both nuclear and radiation hazards.
After a spent fuel assembly — a bundle of fuel rods that fire a reactor — is unloaded from a reactor core, it needs to be stored for a number of years under a sufficiently deep layer of water in a cooling pond on site. The water both protects the personnel on site from radiation exposure and cools the highly radioactive fuel rods, preventing them from heating up. It is in spent nuclear fuel assemblies, the zirconium tubes that hold the fuel rods, where all the dangerous radionuclides are found: the remaining uranium that has not fully burned in the reactor core, as well as plutonium and products of uranium fission that were generated as the fuel was burning in the reactor — radioactive isotopes of iodine, caesium, strontium, and many other radionuclides whose role in the contamination and health consequences that followed the horrible disaster at Ukraine’s Chernobyl is still making itself seen now.
Not only does this deadly cocktail of radionuclides threaten a fatal exposure dose when in the immediate vicinity of spent fuel assemblies — it also heats up independently when left without cooling. Even though a chain fission reaction of uranium nuclei does not occur in spent fuel, the energy that is produced during the alpha and beta decay processes of other radionuclides is quite sufficient, absent of stable cooling with water, to heat the surface of zirconium claddings up to several hundred degrees Celsius. This is why storage ponds are cooling ponds — water is pumped through them just like the cooling system pumps water through a reactor. But at Fukushima Daiichi, it was the cooling systems at all six reactor units that got knocked out when the earthquake and tsunami destroyed the external energy supply at the plant on March 11. As a result, water in the SNF cooling ponds has been heating up and evaporating, turning into those columns of white vapour that could be seen on news footage billowing above reactor buildings at Fukushima.
The trouble is that when zirconium claddings reach and tip over their fracture strength limit in rising temperatures, so the fuel rods inside will give and become damaged, letting all the radionuclides packed tight inside escape into the surrounding environment. This is what likely has already happened in the cooling ponds of Fukushima Daiichi.
At Fukushima, cooling ponds with SNF are situated in the reactor building of each reactor unit — just like at Russian NPPs. Under normal conditions, the layer of water to cover the top nozzles of the fuel rods must be about eight metres deep. The cooling ponds are 12 by 10 metres and 12 metres deep.
This is what the NPP operator company, the Tokyo Electric Power Company (TEPCO), and the International Atomic Energy Agency (IAEA) said as of the morning of March 19: Electricity supply is unavailable to all facilities; operating the units’ cooling systems is impossible. Storage ponds are not being cooled at all six reactor units. On March 18, white smoke was registered escaping from the reactor buildings of Units 2 and 3. It is unclear whether the smoke is coming from the reactors or the SNF ponds.
|A schematic representation of an on-site cooling pond for spent nuclear fuel at Fukushima Daiichi.|
An IAEA update released on March 19, at 4:30 UTC said, where it outlined the status of Reactor Unit 3: “Of additional concern at Unit 3 is the condition of the spent fuel pool in the building. There are indications that there is an inadequate cooling water level in the pool, and Japanese authorities have addressed the problem by dropping water from helicopters into the building and spraying water from trucks. On 18 March, Japanese Self Defence Forces used seven fire trucks to continue spraying efforts. There is no data on the temperature of the water in the pool.”
The problem with Reactor Unit 3 is that its reactor was using a mixed plutonium and uranium oxide (MOX) fuel, and an accident involving a storage pool with spent fuel of that kind — as well as a melting reactor core loaded with such fuel — threatens contamination with plutonium-239, whose half-life period is about 24,000 years.
|A cross-section sketch of a typical boiling water reactor containment as used in Units 1 to 5 at the Fukushima Plant, with the spent fuel storage area (5) and the actual used fuel rods in storage (27).|
Another problem is that a lack of reliable information on the temperature of the spent fuel rods that become exposed as water recedes from the pool makes it difficult to make the right decisions on what measures to take to stop the accident from aggravating further.
The New York Times, in an animated illustration of a possible accident scenario involving a spent nuclear fuel storage pond, specifically where it concerns the ongoing crisis at Fukushima, says: “If cooling systems fail, or if the water level drops and is not restored, evaporation accelerates and water can eventually boil away at an estimated two feet [61 centimetres] per day, exposing the fuel rods.”
The paper speculates that if the earthquake damaged the pools at Fukushima, the water in the pools may have leaked, baring the spent fuel rods, and warns of what may happen then: “The loss of water allows radiation from fuel to escape. The increased heat […] could cause a zirconium fire that would further spread radiation.”
If the zirconium tubes heat up to over 100 degrees Celsius, attempts to douse them with water to prevent overheating may in fact make the situation worse as cold water may cause them to brittle — leading to further releases of radiation. “[But] because of the extreme dangers caused by a partly or fully drained pool,” the New York Times says, “there is little choice but to [pour water] and accept the consequences.”
On March 15, a fire erupted at Reactor Unit 4 — where the reactor was in fact in shutdown when the dual disaster hit four days earlier. Furthermore, as the Los Angeles Times reported, the reactor was not loaded with fuel at the time as it was undergoing planned maintenance. Fuel was unloaded and transferred to the reactor cooling pool sometime after December, the paper said. The cooling pond was actually filled with spent fuel assemblies. This is where the March 15 fire broke out.
It is possible that water in the pool may have boiled away, evaporated, or leaked, as a result of damaged sustained by the building following a March 14 hydrogen explosion at the neighbouring Reactor Unit 3. Water loss was gradual, and vapour, coming into contact with the hot zirconium claddings of the spent fuel assemblies broke into hydrogen and oxygen, and the hydrogen may well have caught a spark and fired up. The IAEA said the smoke above the building of Reactor 4 was still visible on March 18.
At Reactor Units 5 and 6, where the reactors were also in shutdown during the quake, the cooling ponds, too, remain the most worrisome problem. Not all the equipment there became inoperative. But in its March 19 update, the IAEA said: “Instrumentation from both spent fuel pools, however, has shown gradually increasing temperatures. Officials have configured two diesel generators at Unit 6 to power water circulation in the spent fuel pools and cores of Units 5 and 6.
Workers have opened holes in the roofs of both buildings to prevent the possible accumulation of hydrogen, which is suspected of causing explosions at other units.”
The IAEA has been traditionally conservative in its estimations — it was several days into the accident when its head, Yukiya Amano, called the situation at the plant “very serious,” and only after the French nuclear safety authorities raised their rating of the Fukushima crisis to Level 6 out of 7 on the International Nuclear Event Scale that the agency raised its own to Level 5 from the previous 4 – and it may well be that the IAEA refrains from spelling out what is really happening in the cooling ponds of Units 5 and 6: Water is boiling absent of stable cooling; hydrogen is being produced as the exposed fuel rods come into contact with vapour. This is the only explanation for where hydrogen can “accumulate” from: Just like in the case of Reactor 4, the reactor cores of Units 5 and 6 had no fuel in them.
There is one more logical conclusion that, given the impossibility to take any direct and precise measurements because of the very high radiation levels and deadly risks of exposure, the Japanese authorities and the IAEA are making no mention of: If the storage ponds with SNF at all reactor units are losing water, if the cooling water in the pools is boiling out, if the exposed fuel rods are causing the generation of hydrogen — which fires up, as it happened at Reactor Unit 4 — then it stands to reason that the fuel rods themselves have already been damaged and are emitting massive amounts of radiation. It is evident that the iodine-131 and caesium-137 which have just been reported to have contaminated milk and spinach from the Fukushima and Ibaraki prefectures, as well as drinking water supplies of Tokyo, 240 kilometres south of the plant, and other areas, must have come both from Fukushima’s reactors and its spent nuclear fuel stored on site.
It is, then, the SNF cooling ponds that are apparently posing the biggest radiation risk at the moment.
The Russian nuclear industry, meanwhile, seems to pretend as if no problem of spent nuclear fuel exists in Russia at all — and the world is yet to come up with an efficient solution for safe storage of this waste, which remains radioactive for hundreds of thousands of years, to begin with — or as if no Russian nuclear power plants store their nuclear waste on site.
No data on the condition of the Russian on-site SNF cooling ponds or the amounts of fuel stored in them are ever published. The lack of information is so pronounced that in certain cases, no SNF storage ponds are even shown on NPP site diagrams. And if a cooling crisis occurs at one of Russian nuclear power plants — and such a disaster does not have to result from devastation as unprecedented as a 10-metre tsunami wave following in the footsteps of a 8.9-magnitude earthquake — the same problems may evolve with its spent nuclear fuel storage pond.
For instance, the on-site cooling ponds containing spent nuclear fuel of reactors of the Soviet-designed RBMK series, of Chernobyl infamy — these are at Leningrad (near St. Petersburg) and Kursk and Smolensk NPPs (in Western European Russia) — are, just like at Fukushima, arranged near the reactors and have no containment vessel to keep radiation inside should an accident strike. A similar arrangement is in place at Kola NPP on the far northern Kola Peninsula, which does not run RBMK reactors. If the cooling systems servicing these stations fail for one reason or another, a repeat of Fukushima may be quite possible at the site — complete with hydrogen explosions, destruction of the reactor buildings, baring and cracking of spent fuel assemblies, and a massive release of radionuclides into the surrounding atmosphere.
In fact, a blood-curdling preview of the Fukushima disaster already occurred once at Kola NPP: In February 1993, ice accumulation knocked out power lines feeding power to the station, where the reactors were immediately shut down, but two out of four diesel-powered generators turned out to be faulty and could not be activated. Reactor cooling was maintained for some time via natural circulation. Fortunately, a severe accident was avoided that could have ended up in a large-scale release of radiation.
Adverse weather conditions such as in 1993 — or thunderstorms that caused breakdowns in power transmission lines and emergency reactor shutdowns at the same Kola NPP last July, or the devastating fires that swept through European Russia in the summer of 2010 and threatened external power supply failures at a number of Russian nuclear power plants — are not infrequent.
But Russia is not the European Union, which, in the wake of the crisis that erupted in Fukushima, moved on March 15 to subject its 143 nuclear power plants to stress-testing to see how they would behave during an earthquake or other serious emergencies. Russia is not Germany, either, where seven out of the country’s 17 nuclear plants have been shut down for three months for safety checks. The Russian government, though having heard an order from its prime minister, Vladimir Putin, to examine the state of the nuclear energy generation industry and report back within a month, is yet to announce any decision to stress-test Russian NPPs — both long-completed or developing projects – or to temporarily shut down its oldest sites, much less to consider the option of gradually phasing nuclear generation out completely.
For some years now, Russia has been developing a new, Generation-3 reactor series under a project dubbed AES-2006 (for Russian NPP-2006). According to information available on the website of the Russian NPP operator company, Concern Rosenergoatom, at the core of this “evolutionary step in the history of Russia’s nuclear industry […] [combining] active and passive safety systems based on innovative technologies […] is WWER-1000 (water-water energy reactor, pressurized water reactor, 1,000 [megawatts]), which has been successfully operated for two decades in Russia, Ukraine, and some other countries. The new [design] solutions applied under this project are supposed to enhance the efficiency and capacity of the reactor. The electric capacity of this reactor is 1,150 [megawatts], which means that it will be able to produce 15 percent more energy than WWER-1000; the service life is 50 years. The new reactors will be built at Novovoronezh NPP-2 and Leningrad NPP-2. The first NPP-2006 reactor is to be launched in 2012.”
This is also the reactor design that Russia touts to its prospective customers — like Belarus, with which the Russian government signed a highly controversial reactor construction agreement at the height of the nuclear crisis at Fukushima Daiichi. The problem is that the official reports on the Environmental Impact Assessment of Russian NPP-2006 nuclear reactor projects hold insufficient data on the on-site storage facilities for spent nuclear fuel. Furthermore, the reports contain no analysis at all of potential accident scenarios involving the cooling pools of such plants. This leads one to believe that no one at Rosatom is even considering such contingencies, leaving new Russian NPPs — or those the nuclear corporation hopes to build abroad — to face, unprepared, the same dangers that Fukushima Daiichi is fighting a desperate battle to overcome now.
This is, for instance, a fragment from Rosatom’s Environmental Impact Assessment study done on the Baltic Nuclear Power Plant, a project Rosatom is building in Neman in Russia’s westernmost enclave of Kaliningrad, near the European Union border. Construction there started on February 25, 2010. The chapter entitled “Management of Spent Fuel” consists of two paragraphs:
“Storage (cooling) of spent nuclear fuel in the reactor building is done in the cooling pond. In the pond, residual heat is removed from [spent fuel assemblies]. The capacity of the cooling pond provides for densified storage of spent fuel in racks for a period of 10 years.” (Environmental Impact Study of Baltic Nuclear Power Plant, page 145). The study simply goes on to say that after the cooling period, the SNF is removed from the plant. And that’s it.
|A cross-section model of Rosatom’s NPP-2006 project; the cooling pond with SNF is not provided in the model.|
At least, this Environmental Impact Assessment report acknowledges the Baltic NPP project will have an SNF storage pond at all, and that it will be situated in the reactor building. But there is no other information about it. There are no data on the size of the pool, nor on its cooling system — and, of course, nothing is said about any possible accident risks involving a failure of the cooling system (following a loss of external power supply, an earthquake, or a plane crash) that would entail loss of cooling, rising temperatures in the pool, boiling water, cracking fuel rod claddings, release of radiation, and hydrogen explosions… In other words, the Russian nuclear authority either didn’t think of such a scenario that came true at Fukushima or they did — but made no known provisions for it.
At a public hearing that was organised to present the project to the Kaliningrad population, the Russian environmental group Ecodefense! openly pointed out this glaring lack of information on the future plant’s SNF cooling pond: “The properties of the cooling pond are not provided [in the report], such as the number of [spent fuel assemblies stored], the amount of water in cubic metres. Possible accident scenarios associated with SNF transfer operations or leaks from the cooling pond have not been examined. Such accidents have taken place at other NPPs and they cannot be ruled out at the Baltic NPP, either.”
The environmentalists’ criticism was left unanswered. Construction started as planned at the Kaliningrad site — and now, as the unfolding disaster at Fukushima demonstrates, the ecologists were right: Radiation accidents in spent fuel storage pools are a reality, not a bunch of empty conjectures.
If one were to be smart about it, when the reality of all that is going on with Fukushima’s on-site SNF storage ponds sinks in, all activities involved in building new reactors to the NPP-2006 design should be halted. These are currently the projects of second lines of construction at Novovoronezh NPP (Western European Russia) and Leningrad NPP, as well as the Baltic NPP in Kaliningrad Region. The Russian federal industrial, atomic, and environmental safety watchdog, Rostekhnadzor, should revoke the construction licenses issued for these sites at least on the merit of “newly discovered facts in evidence.” Other new projects, currently at the stage of inception, should be halted as well and their project documentation examined closely: Russia’s future NPP projects in Nizhny Novgorod, Tver, and Kostroma (all in Central or Western European Russia), and the one Russia and Belarus have agreed to build in the Belarusian town of Ostrovets.
A detailed analysis must be done of various accident and emergency event scenarios that may be possible at reactor cooling ponds with spent nuclear fuel in storage, complete with assessments of environmental impact and impact on population health.
Alas, the Russian safety and supervision authorities are unlikely to mount such a campaign of close scrutiny against the powerful Rosatom and its nuclear power plant projects — however obvious such a step, in light of the still ongoing tragedy at Fukushima, may be.