Three Mile Island Netflix Documentary

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In summary, the recently released Netflix documentary "Meltdown: Three Mile Island" focuses on the events of the Three Mile Island (TMI) accident and its aftermath. Unlike HBO's dramatized re-telling of the Chernobyl disaster, this documentary is a more factual retelling with minimal fictionalization. However, some viewers have felt that the documentary only scratches the surface of the events and does not delve into details such as the potential dangers and causes of the accident.One of the main criticisms of the documentary is its portrayal of the polar crane, which had been rebuilt before the accident. The documentary does not mention any specific details about the rebuilding process or any concerns that were raised about its capacity. This lack of information has led to
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TL;DR Summary
Discussion of the TMI accident and recent Netflix documentary about it.
Netflix recently released a documentary on the Three Mile Island accident. I'm just finishing watching it, and would like to discuss it.
https://www.netflix.com/tudum/articles/meltdown-three-mile-island-release-date-cast-news
https://www.theguardian.com/tv-and-...three-mile-island-netflix-us-nuclear-accident

TMI is different from HBO's Chernobyl show in that "Chernobyl" was completely a dramatized re-telling of the events, mostly historically accurate as a framework, but with lots of fake/composite characters and events, whereas TMI is a documentary re-telling of the events, with a few scenes of reenactment and archival footage mixed-in. There is very little that's fictional, yet I come away feeling like I learned a lot less about "TMI" than I learned about "Chernobyl". Most is short clips, just barely touching on events - dramatically - without diving in. It felt at times like a 3 hour long trailer.

There's a lot of anti-nuclear hype, and the overall tone is like The China Syndrome; whistleblower and media/grassroots protestor heroes vs the evil government and corporations. And anecdotal cancer reports. There are a lot of claims/inferences that they were very close to a much larger disaster, like 30 minutes away from a meltdown worse than Chernobyl, or if the polar crane lift failed, that would have caused a disaster worse than Chernobyl. But they don't get into the details enough to know exactly what the problems/dangers were. Even the basic causes of the accident, which I read up on and seem pretty straightforward were glossed over.

My two questions, though, are ;
  1. What, exactly, could have cause a much worse disaster in 30 minutes? I don't think they ever say.
  2. What, exactly, was wrong with the polar crane? Did they even know/was it just "we didn't check enough"?
 
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In this article:

https://pabook.libraries.psu.edu/li...e-articles/disaster-averted-three-mile-island

they mention the core was half melted and the worst case was if it completely melted and broke through containment like Fukushima did. Once they realized they needed to restore cooling they prevented this disaster.

...
Inside the control room, alarm bells rang and warning lights flashed rapidly. Instruments available to the reactor operators showed confusing and contradictory information. There was no signal that the pressure relief valve was stuck open. It was also impossible to measure the level of coolant in the core, since there was no gauge available to the operators that gave a proper reading. One of the operators, Craig Faust, later remarked, "I would have liked to have thrown away the alarm panel. It wasn't giving us any useful information." As the level of water in the main cooling system dropped rapidly, an emergency core cooling system started automatically and began pumping water into the core at a rate of one thousand gallons per minute. When the operators recognized that this was happening, they mistakenly believed the core was going to overflow with water, which would damage the reactor. This fear made the situation worse when the operators decided to shut down the emergency cooling system.

Without a proper cooling system, the nuclear fuel in the core overheated to the point that it began to melt. Although plant personnel and the authorities did not know it at the time, slightly more than half of the core melted during the accident. It was not until 9:00 a.m., more than five hours into the accident, that the cause of the problem was identified and the emergency cooling system was turned back on. This prevented any further melting of the core. In a worst case scenario, the core would have overheated to the point that it could have melted through the floors and walls of the containment building. This would have released massive amounts of deadly radiation into the surrounding environment. This worst case scenario did not occur, however, and adequate temperatures were restored to the Unit 2 core by 8:00 p.m.
...
 
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russ_watters said:
Summary: Discussion of the TMI accident and recent Netflix documentary about it.

What, exactly, was wrong with the polar crane? Did they even know/was it just "we didn't check enough"?

According to the Netlix summary, the polar crane had been rebuilt, but the summary doesn't state 'how' or 'why' it was rebuilt. Was it built with additional capacity? What was the protocol/procedure for qualifying it?

When Bechtel announced they would be lifting the lid off the Unit 2 core to repair it without testing the newly rebuilt polar crane, Parks’ concerns became dire. He knew that if the crane broke, the entirety of the East Coast of the United States would be contaminated and forced to evacuate.
Parks may have been reflecting on his naval career. The statement I bolded is nonsense.

Ostensibly, the original polar crane had been used to install the upper vessel head (lid). If the 'rebuilt' polar crane had additional capacity, then it would be able to handle the upper head with additional margin. I'm sure that Bechtel was dismissive of Parks, and perhaps they minimized the risk, or they had done an analysis to indicate that the crane was sound.

Unit 2 had been commissioned at the end of 1978, and apparently that was rushed. I'd have to look back through my records, but I believe Unit 1 was in its second cycle.

When the Unit 2 reactor became operational in March 1978, it experienced a number of start-up difficulties. On March 28, the very first day of its startup, one of the reactor coolant pumps failed. A pressure release valve had opened and stayed open, causing coolant to leak out of the system. During its first year of operation, Unit 2 experienced twenty reactor "trips," immediate shutdowns of the reactor due to any malfunction. Despite these early setbacks in the testing phase of the reactor, the Nuclear Regulatory Commission deemed Unit 2's performance satisfactory for commercial operation. Unit 2 finished its testing phase and began full commercial operation on December 30, 1978.
https://pabook.libraries.psu.edu/li...e-articles/disaster-averted-three-mile-island

At the time of the accident in March 1979, Unit 2 had accumulated about 62 effective full power days (EFPD) of operation, which included startup and low power testing during 1978, so the inventory of fission products was no where near that of Chernobyl Unit 4 or the Fukushima units. The burnup on the TMI-2 fuel was probably on the order of 2 to 3 GWd/tU. Yet, there was enough decay heat such that when there was no flow in the coolant, the core essentially became adiabatic, i.e., there was no heat transfer and so the fuel heated up and began to disintegrate (rapid unstable oxidation of cladding and fuel through reaction with the hot coolant). Some of the fuel did interact with the core baffle (the plate structure that forms the outer boundary of the core) and it did fail in one location, and some core debris did spill.

On March 26, 1979, Walter Creitz, president of Met Ed, wrote in an op-ed article that the plants were being "operated in a way that places top priority on safety." The nuclear accident at Three Mile Island occurred just two days later.
Ref: Ibid.

Certainly, such a statement followed by a severe accident undermined the credibility of GPU management and the industry. There were a cascade of operational errors due to poor practice and training.

. . . An emergency cooling water system should have started automatically, but it did not. Due to a maintenance error following a test of this backup system, critical valves were left closed, in violation of NRC regulations. The closed valves prevented this emergency cooling system from engaging.

When the secondary loop stopped flowing and the backup system failed to engage, the cooling effect was lost and the primary loop began to overheat. Pressure inside this loop increased by nearly 5%, which immediately caused the reactor core to automatically shut down and halt all nuclear processes. However, the latent heat of the core continued to rise, and it soon reached a temperature high enough to cause a potential meltdown. As pressure inside the primary cooling loop continued to increase, an automatic pressure relief valve opened to release steam. This valve should have closed again automatically when pressure decreased, but it remained stuck open. When the valve failed to close, steam and cooling water poured out of the valve into a holding tank in the basement of the building. This was the same valve that had malfunctioned during initial reactor tests in March of 1978.

Inside the control room, alarm bells rang and warning lights flashed rapidly. Instruments available to the reactor operators showed confusing and contradictory information. There was no signal that the pressure relief valve was stuck open. It was also impossible to measure the level of coolant in the core, since there was no gauge available to the operators that gave a proper reading. One of the operators, Craig Faust, later remarked, "I would have liked to have thrown away the alarm panel. It wasn't giving us any useful information." As the level of water in the main cooling system dropped rapidly, an emergency core cooling system started automatically and began pumping water into the core at a rate of one thousand gallons per minute. When the operators recognized that this was happening, they mistakenly believed the core was going to overflow with water, which would damage the reactor. This fear made the situation worse when the operators decided to shut down the emergency cooling system.
Ibid.

I recall that when the core temperature indicators were off-scale, someone put a voltmeter across the leads/terminals of the temperature indicator in order to get an estimate of the temperature, and some were skeptical about the temperature indication. However, the estimate was consistent with core damage.

To be sure, there were deficiencies in the plant design, e.g., the hot legs in the primary loops (between RPV outlet nozzles and once-through steam generators (OTSGs)) were vulnerable to steam pockets which prevented natural circulation. Other steam generators designs with bottom entry of the hot leg were less susceptible.

Operating training was poor, which was endemic in the industry at the time. One result was better training and more staff in the control room, including a shift technical advisor (STA). Reactor/plant simulators became a more significant part of training.

IEEE Spectrum did a special issue on the event. Special issue: Three Mile Island and the future of nuclear power https://ieeexplore.ieee.org/document/6368288

I remember later articles as more information became available.

As for melting, I don't believe the fuel melted as much as it oxidized from metal to ceramic oxide, which is a good indication that there was cooling water in the core, but it was boiling or mostly in steam. With respect to melting temperatures of stainless steel (~1375 - 1400°C), Zircaloy (~1850°C) and the UO2 fuel (~2840°C), well before melting, the material oxidize/corrode well below those melting temperatures, especially in steam. By the time the fuel temperature reaches about 1000°C (0.77 homologous temperature of stainless steel, and 0.60 homologous temperature of Zircaloy), the materials get very soft and flow under low stress, and they oxidize very rapidly. Fe, Cr and Ni become more readily soluble in Zr, even without the chemical oxidation reactions with H2O, which is the origin of the hydrogen of concern. In hydrogen, Zr would hydride rapidly, which then is more susceptible to oxidation.
 
  • #4
Astronuc said:
Reactor/plant simulators became a more significant part of training.
That used to be my business. Before TMI, it was a hard sell to convince utilities to spend millions on "The world's most expensive toy," a simulator. After TMI, 100% of the operators were deemed to need simulator training.

The quality of the simulators also improved. The #1 vendor, Singer Link, built simulators only valid for the planned operating regime. Planning included an enumerated set of malfunctions. A serious operator error, or an accident that took you out of that regime was not simulated correctly, if at all. I tested one by closing the feed pump suction valve during operation, and nothing happened. That valve was not simulated because no operator procedure called for that valve to be closed.

In the case of TMI, it was boiling in the primary loop of a PWR. Pre-TMI, the simulators were plain wrong and misleading if that PORV was stuck open. Post -TMI, the simulators had to be improved to handle boiling in the core and two phase flows in the primary loop.

The thing that raised my eyebrows in the Nexflix documentary was the obvious radiation burns suffered by nearby civilians. If I recall correctly, the official TMI report said that radiation releases to the public were too small to have any health effects. So if the Netflix film is correct, that exposes a major cover up and falsification of the official records.

The story of the crane concerns in the film, I found to be very speculative and not very convincing.
 
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Thanks guys.
Astronuc said:
According to the Netlix summary, the polar crane had been rebuilt, but the summary doesn't state 'how' or 'why' it was rebuilt. Was it built with additional capacity? What was the protocol/procedure for qualifying it?
The crane was exposed to the "hydrogen burn" during the accident and was damaged in some way from the heat. They did replace the cable at least, but what other repairs were done, I don't know/isn't said. And perhaps this is the answer:

anorlunda said:
The story of the crane concerns in the film, I found to be very speculative and not very convincing.
Maybe it really was just a generalized concern that they were moving too fast and not testing adequately? Ultimately the NRC did decide to delay the lift a few months for additional investigation/testing. And when the lift happened, the crane did get stuck multiple times.

In the documentary they showed/speculated that the lift could drop the reactor vessel head, causing severe damage to the lower core and leaving it open/exposed indefinitely. That didn't seem to me to be realistic. Cranes don't really fail that way (parting the cable). Getting stuck isn't good, but isn't catastrophic.
Astronuc said:
Unit 2 had been commissioned at the end of 1978, and apparently that was rushed. I'd have to look back through my records, but I believe Unit 1 was in its second cycle.
Unit 1 was down for refueling at the time of the accident.
Astronuc said:
At the time of the accident in March 1979, Unit 2 had accumulated about 62 effective full power days (EFPD) of operation, which included startup and low power testing during 1978, so the inventory of fission products was no where near that of Chernobyl Unit 4 or the Fukushima units.
So are you saying it is more the fission products that are harmful to the environment than the original fuel? A lot "dirtier"?
Astronuc said:
Operating training was poor, which was endemic in the industry at the time. One result was better training and more staff in the control room, including a shift technical advisor (STA). Reactor/plant simulators became a more significant part of training.
That's disheartening to hear. It sounds like a lot of institutional arrogance around what at the time was still a relatively young industry.

It struck me while watching that unlike Chernobyl which had somewhat complex nuclear problems contributing to the accident, TMI was an almost completely mundane mechanical engineering set of problems. A stuck relief valve. Blocking valves that were left closed after maintenance. Insufficient instrumentation. Pumps; on or off? At TMI, the role of the reactor in the accident was just that of a generic boiler in a lot of ways. The level of understanding of the non-nuclear functioning of the reactor and ability to deal with fairly small and straightforward problems was pretty shockingly low. I'll grant that the lack of instrumentation caused a lot of the problems, but one of the key problems (the stuck relief valve) was noticed and corrected almost immediately by a technician just arriving for his shift 2 hours after the accident started. How? There's a temperature sensor in the outlet pipe, and high temperature means there's steam flowing through it.

anorlunda said:
The thing that raised my eyebrows in the Nexflix documentary was the obvious radiation burns suffered by nearby civilians. If I recall correctly, the official TMI report said that radiation releases to the public were too small to have any health effects. So if the Netflix film is correct, that exposes a major cover up and falsification of the official records.
I can't remember if they were archival photos/footage or dramatized. I find it hard to believe that members of the public could have had such acute radiation effects when nobody at the plant did. My first thought at seeing the girl with the burns was; did she apply sunscreen that day?

Even with Chernobyl as far as I know nobody outside the plant had severe burns/radiation sickness, and Chernobyl lobbed chunks of core material out of the plant and into the surrounding area. My understanding was that everything the public was exposed to from TMI was in vented gases, which couldn't be dense enough a mile downwind to cause burns.
 
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russ_watters said:
The crane was exposed to the "hydrogen burn" during the accident and was damaged in some way from the heat. They did replace the cable at least, but what other repairs were done, I don't know/isn't said. And perhaps this is the answer:
I would agree with anorlunda.

About 10 hours after the March 28, 1979 Loss-of-Coolant Accident began at Three Mile Island Unit 2, a hydrogen deflagration of undetermined extent occurred inside the reactor building. Examinations of photographic evidence, available from the first fifteen entries into the reactor building, yielded preliminary data on the possible extent and range of hydrogen burn damage. These data, although sparse, contributed to development of a possible damage path and to an estimate of the extent of damage to susceptible reactor building items.
Ref: https://www.osti.gov/biblio/5330864...amage-three-mile-island-unit-reactor-building

I'd have to look more into how that was done. Hydrogen gas is very light, so I would expect it to migrate to the top of containment. The only place where there could be deflagration would be the interface between the hydrogen gas and the air, and perhaps some air that got mixed into the hydrogen. Pure hydrogen would not burn, because it requires presence of, or contact with, air/oxygen, or oxygenated compounds. See more discussion below.

russ_watters said:
So are you saying it is more the fission products that are harmful to the environment than the original fuel? A lot "dirtier"?
Yes. Fission products of concern include various radionuclides of Xe, Kr, and I, Cs, Br, Sr, Co (Co from transmutation of Ni and activated Co, an impurity found in Ni alloys) and others that could be inhaled or absorbed into living organisms. As for original fuel, consider that the 'fresh' fuel is fairly 'clean', mostly stoichiometric UO2, as opposed to the unprocessed ore, which would contain various heavy elements from radioactive decay. I've handled fresh fuel pellets in my hand (wearing protective gloves) in several manufacturing plants, and I know several people who have handled pits of Pu, which have been described as warm to the touch.

russ_watters said:
That's disheartening to hear. It sounds like a lot of institutional arrogance around what at the time was still a relatively young industry.
There was still a lot of that when I joined industry. It's not limited to the nuclear industry, or power industry. I tend to be cautious.

russ_watters said:
I find it hard to believe that members of the public could have had such acute radiation effects when nobody at the plant did. My first thought at seeing the girl with the burns was; did she apply sunscreen that day?
I don't recall people getting radiation burns from fission products from TMI. More likely, there were a lot of spectators standing around in the sun gawking at the fiasco, so I would expect sunburn of solar UV.

russ_watters said:
Even with Chernobyl as far as I know nobody outside the plant had severe burns/radiation sickness, and Chernobyl lobbed chunks of core material out of the plant and into the surrounding area. My understanding was that everything the public was exposed to from TMI was in vented gases, which couldn't be dense enough a mile downwind to cause burns.
I don't think we know how many people received significant radiation exposure from Chernobyl, since the area (e.g., Pripyat) was evacuated, and I doubt they did monitoring. More recent, Russian soldiers, who apparently dug foxholes or trenches in the ground near Chernobyl did get some unknown (or as-yet unquantified) radiation exposure.

Update/edit: Analysis of the Three Mile Island (TMI-2) hydrogen burn
https://inis.iaea.org/search/search.aspx?orig_q=RN:14750113 (1982)
A study of recorded temperatures and pressures was made. Hydrogen concentrations were calculated. Postburn average ambient temperatures versus time were calculated. Average temperatures were calculated for the region above elevation 347, below elevation 347, and within the D-shield compartments. Results were: Prior to the burn, the hydrogen was well mixed with the containment air. Average hydrogen concentration was 7.9%, wet basis. The hydrogen burn occurred at all three levels in the containment. The burn was initiated somewhere in the lowest level, probably on the west side. The burn time was about 12 s. About 3570 m3 or 126,000 ft3, 160 kg moles or 319 kg of hydrogen burned. Containment gas temperatures in the flame front were 760°C (1400°F). Average containment gas temperature at end was 660°C (1220°F). The gas temperatures decreased much faster below elevation 347 than above elevation 347. The average temperature rise was only about 1.2°C (2.2°F) as a result of the hydrogen burn. Considerably more energy came from the hot water and steam vented. The burn damage observed was predominantly at the upper elevations and on the north, east, and south quadrants. 1.1% hydrogen remained in the containment after the burn. Venting of the reactor cooling system during the hour following the burn added an additional 0.6%. Hydrogen concentrations increased from this 1.7% to about 2.2% between March 30 and April 2. One of two Rockwell hydrogen recombiners removed 112 kg of hydrogen. A total of 459 kg of hydrogen gas were accounted for. Assuming that 432 kg were generated by the zirconium-steam reaction, 9850 kg Zr would have been oxidized . . .
Report here: https://inldigitallibrary.inl.gov/TMI/GEND-INF-023-VOL-4.pdf

Time at temperature, total energy and mass are important parameters in annealing of metals. Twelve (12) seconds is a very short time at 660°C, or even 760°C, but those temperatures would be a concern for carbon steels over longer periods of time.

Investigation of hydrogen-burn damage in the Three Mile Island Unit 2 reactor building
https://inis.iaea.org/search/search.aspx?orig_q=RN:14724054 (1982)

I would expect the staff to do a quick lift test and monitor the crane before committing a full load of the vessel head.
 
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Astronuc said:
I've handled fresh fuel pellets in my hand (wearing protective gloves) in several manufacturing plants
The ASEA ATOM fuel factory in Sweden, they held an open house every year. Members of the public were allowed to handle fresh fuel pellets without gloves. However, those pellets were kept for show and never used because they would be contaminated with skin oils.

One of the most stupid project mistakes ever happened at the ill fated Shoreham Nuclear Power Plant on Long Island. It was built, but opposition never allowed it to operate, and it was abandoned. The project manager was angry and ordered the operators to make it go critical. It achieved it's first criticality for about 60 seconds. In that one minute, he transformed an asset worth about $1.5 billion (fresh fuel which could be handled without special precautions, and reformable for use in another plant) into nuclear waste liability worth perhaps -$3 billion. Wasting $4.5 billion in one minute as an angry gesture is a record I don't believe will ever be broken.

Incredibly, he was promoted. 30 years later, he became CEO where I worked and retired a rich man. I would say he really earned the label arrogant.
 
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anorlunda said:
In that one minute, he transformed an asset worth about $1.5 billion (fresh fuel which could be handled without special precautions, and reformable for use in another plant) into nuclear waste liability worth perhaps -$3 billion. Wasting $4.5 billion in one minute as an angry gesture is a record I don't believe will ever be broken.
It wasn't entirely wasted. PECO bought the fuel and had it shipped by barge and perhaps by truck or rail to Limerick, where it was used. It took a lot of effort to make that happen.

The cumulative number of discharged assemblies classified as temporarily discharged increased from 610 assemblies at the end of 1993 to 798 assemblies at the end of 1994 (Table 3). Of these temporarily discharged assemblies, 504 are assemblies from the Long Island Power Authority's Shoreham plant. In 1988, these assemblies were classified as permanently discharged when the Shoreham plant shut down. As a result of the transfer of ownership of the Shoreham fuel to PECO Energy Company, 306 assemblies in 1993 and 254 assemblies in 1994 were reclassified as temporarily discharged. Of these assemblies, 56 were reinserted into PECO's Limerick plant in 1994.
https://inis.iaea.org/collection/NCLCollectionStore/_Public/27/053/27053822.pdf (see page 15/270, and Appendix E starting on page 253 of pdf)

A total of 118 U.S. commercial LWR's have discharged spent nuclear fuel as of December 31, 1994. This includes Comanche Peak 2 which discharged spent fuel for the first time in 1994. Of the 118 reactors, 9 reactors are permanently shutdown or retired, 109 reactors are currently in operation. A total of 58 reactors discharged 6,702 spent nuclear fuel assemblies in 1994 (Table 1).
When I joined industry, there were 110 operating reactors. Yankee Rowe, San Onofre 1 and Trojan shutdown in 1992. Maine Yankee and Connecticut Yankee (Haddam Neck) were soon to follow. Comanche Peak 2 came online (1993), and Watts Bar units were under construction, but unit 2 was deferred as were the Bellefonte units.

https://en.wikipedia.org/wiki/Nuclear_power_in_the_United_States (some information is not up-to-date).
 
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Astronuc said:
t wasn't entirely wasted. PECO bought the fuel and had it shipped by barge and perhaps by truck or rail to Limerick, where it was used. It took a lot of effort to make that happen.
Thanks, I hadn't heard about that. Imagine the radiological safeguards they must have provided to allow that to happen.
 
  • #10
anorlunda said:
Thanks, I hadn't heard about that. Imagine the radiological safeguards they must have provided to allow that to happen.
As I recall, they used spent fuel transportation casks, maybe those from NAC.

At the time this happened, I'd been evaluating PCI in barrier fuel and the degradation of failed BWR fuel (some with long axial splits and high off-gas), starting in 1991 through lasting 1994 (in 1995, my colleagues and I did a similar study of grid-to-rod fretting in PWR fuel). PECO was one of the sponsors, as well as a contributor of information/data.
 
  • #11
Astronuc said:
I don't recall people getting radiation burns from fission products from TMI. More likely, there were a lot of spectators standing around in the sun gawking at the fiasco, so I would expect sunburn of solar UV.
There was an interview in the documentary of a tech who went into the reactor building during the accident to get a boron sample. He said his badge registered an exposure of 2.8 rem. Evidently he got the highest dose of anyone. Fortunately no short or long term health impact as of today.
 
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russ_watters said:
Cranes don't really fail that way (parting the cable).

I think they can. . .



.
 
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anorlunda said:
The ASEA ATOM fuel factory in Sweden, they held an open house every year. Members of the public were allowed to handle fresh fuel pellets without gloves. However, those pellets were kept for show and never used because they would be contaminated with skin oils.

One of the most stupid project mistakes ever happened at the ill fated Shoreham Nuclear Power Plant on Long Island. It was built, but opposition never allowed it to operate, and it was abandoned. The project manager was angry and ordered the operators to make it go critical. It achieved it's first criticality for about 60 seconds. In that one minute, he transformed an asset worth about $1.5 billion (fresh fuel which could be handled without special precautions, and reformable for use in another plant) into nuclear waste liability worth perhaps -$3 billion. Wasting $4.5 billion in one minute as an angry gesture is a record I don't believe will ever be broken.

Incredibly, he was promoted. 30 years later, he became CEO where I worked and retired a rich man. I would say he really earned the label arrogant.
Wow that is an interesting story , but I'll admit at first I found it hard to believe (before @Astronuc replied) I did try to google it but came up with nothing.As for handling used fuel (or slightly used as in this case) it shouldn't be a problem, after all spent fuel gets handled all the time from reactors after the fuel life end.

In fact in my neighboring Lithuania which at one point had the worlds most powerful nuclear reactor - the RBMK 1500 (two units at Ignalina) they did just that.
At the shutdown of Unit 1 of Ignalina NPP they took the used fuel from it and transported to the Unit 2 to use it fully while Unit 1 was already put into decommissioning.
Both units are connected by rails so a train can move between them. RBMK's are built such that train rails come right into the station and into the reactor building side. Inside the building is an unloading place where fresh fuel is unloaded from a train and lifted up directly into reactor hall.
There it is mounted inside the fuel loading machine and then into core.

The same process happens backwards. Old spent fuel can be taken out of core and placed inside the spent fuel pool and then lifted out of it and down onto a fuel container on a special rail car.

The only part that I don't understand in all of this is how they took the half spent fuel from reactor 1 and directly put it into reactor 2, while the fuel is inside the refueling machine of the RBMK it is cooled but it had to be taken out of the machine and lifted down into the rail car container and that as far as I know doesn't have active cooling.

Here is a paper from Ignalina describing in short the fuel unloading process, has few pictures
https://www.witpress.com/Secure/elibrary/papers/WM08/WM08009FU1.pdf

Maybe @Astronuc knows how the fuel is/was cooled while transported outside of reactor hall/fuel machine.
 
  • #15
artis said:
As for handling used fuel (or slightly used as in this case) it shouldn't be a problem, after all spent fuel gets handled all the time from reactors after the fuel life end.
Wow. Maybe not the best choice of words for that sentence. Handling spent fuel with bare hands is very lethal. But using proper precautions, such as robotic handlers and shipping casks, it can be done safely. As you say, it is done every day, but only with proper precautions.
 
  • #16
anorlunda said:
Wow. Maybe not the best choice of words for that sentence. Handling spent fuel with bare hands is very lethal. But using proper precautions, such as robotic handlers and shipping casks, it can be done safely. As you say, it is done every day, but only with proper precautions.
Yes true. But either way a reactor is not loaded by hand , so given they use crane and the full procedure the only difference between fresh fuel and spent (in PWR, BWR IIRC) would be the need to flood the reactor compartment to provide a biological shield and then load the fuel assemblies into a container for transport.

Again @Astronuc please comment but is it not the case that fuel is transported in the same safety containers whether fresh or spent? Or is fresh fuel transported to the plant in some lesser security fashion?

PS. @anorlunda is there an article online where I can read about your mentioned incident?
Was it big news at the time?
 
  • #17
artis said:
is fresh fuel transported to the plant in some lesser security fashion
Typically, fresh fuel is delivered to the power plant site in regular trucks. The fuel assemblies are in special boxes to protect them from shipping damage (because they are very expensive!). There is no appreciable radiation dose from fresh fuel.
is there an article online where I can read about your mentioned incident?
Was it big news at the time?

here's a good start:
https://en.wikipedia.org/wiki/Shoreham_Nuclear_Power_Plant
 
  • #18
artis said:
Here is a paper from Ignalina describing in short the fuel unloading process, has few pictures
https://www.witpress.com/Secure/elibrary/papers/WM08/WM08009FU1.pdf
I'm not familiar with that method of spent fuel transportation, but it is unique to that facility, and possibly other RBMKs. The documents mentions 6 SFAs (spent fuel assemblies), perhaps in a string. The set of fuel assemblies is transported in a special "steel thick-walled cylindrical vessel". The article does not mention the atmosphere within the sealed container. However, cooling would be accomplished by a combination of conduction and convection of the gas/atmosphere in the container.

In LWR systems, spent fuel is stored in the spent fuel pool, with the top of the fuel at least 8 m (~25 feet) of water covering the top of the fuel. The oldest fuel from the initial core will usually have low burnup (perhaps 5 to 15 GWd/tU), while later discharged fuel would have increased burnup. In the 1970s, it was expected to discharge fuel with burnups of about 33-38 GWd/tU, but in the absence of reprocessing and lack of a final repository in the US, discharge burnup were increased to about 60-65 GWd/tU, and batch sizes were reduced, but then increased due to plant uprates and increased cycle lengths. In any event, spent fuel is moved into 'dry' storage cask, which are kept onsite pending transfer to some final location.

https://nap.nationalacademies.org/c...-commercial-spent-nuclear-fuel-storage-public
https://www.nrc.gov/waste/spent-fuel-storage/pools.html

The amount of time spent fuel spends in the storage pool depends on its burnup. The higher the burnup, the longer the time in the spent fuel pool. Utilities may mix fuel or different burnups to place hotter (high burnup) spent fuel mixed in with cooler (low burnup) spent fuel.

Storage casks are loaded underwater in the spent fuel pool, usually in an are to one side/end of the pool (so-called cask loading area). In the casks, the environment is back-filled with helium (He) gas, which serves to conduct decay heat to the boundary walls of the storage container, and heat is conducted through the walls into the ambient environment. There are different designs from different manufacturers, and some designs have an inner container (or basket) and outer container.

Temperatures on the surface of the inner containers can be above 300°F. There are cooling channels between the inner container and outer container. The inner and outer container walls provide shielding from the radiation. Some containers may be placed in ventilated storage vaults.

Shipping containers for spent fuel are different from storage containers, since they have to be mobile, and there are some designs that are dual purpose, both storage and transportation. Transportation casks may be fitted with overpacks and end protection systems.

Fresh (as-manufactured, or unirradiated) fuel has very little decay heat, and the fuel assemblies are placed in strong-back steel containers, which are then placed in shipping boxes. PWR assemblies are usually placed one to an inner container, while two BWR fuel assemblies are placed into one special container. In either case, the inner container is placed in an outer container (shipping box). Shielding, like that for spent fuel, is not required. Some fuel types, such as fuel using recycled uranium or MOX fuel has more shielding than fresh fuel fabricated from virgin UO2.
 
  • #19
gmax137 said:
Typically, fresh fuel is delivered to the power plant site in regular trucks. The fuel assemblies are in special boxes to protect them from shipping damage (because they are very expensive!). There is no appreciable radiation dose from fresh fuel.here's a good start:
https://en.wikipedia.org/wiki/Shoreham_Nuclear_Power_Plant
I know that, I was looking to find the mentioned man who against the decision of authorities decided to make the reactor critical.

@Astronuc given they load those containers for irradiated fuel (whether transport or storage) underwater, I would assume then that they have water within them as they are transported?PS. Thanks @russ_watters for making this thread I did not know there was a new documentary out, already downloaded it will give it a try see how it turns out
 
  • #20
artis said:
@Astronuc given they load those containers for irradiated fuel (whether transport or storage) underwater, I would assume then that they have water within them as they are transported?
No. The inner container are filled helium, probably to about 5 bar, so that heat is conducted from the fuel to the container wall from which the heat is conducted to the atmosphere. The containers have inlet and outlet valves. There is a drying procedure to remove water, and then backfill with He. Any moisture in the environment would react with the Zr-alloy cladding (in addition to the radiolysis from gamma and beta radiation), which would then lead to a build up of hydrogen in the container.
 
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Likes hutchphd
  • #21
Astronuc said:
No. The inner container are filled helium, probably to about 5 bar, so that heat is conducted from the fuel to the container wall from which the heat is conducted to the atmosphere. The containers have inlet and outlet valves. There is a drying procedure to remove water, and then backfill with He. Any moisture in the environment would react with the Zr-alloy cladding (in addition to the radiolysis from gamma and beta radiation), which would then lead to a build up of hydrogen in the container.
That must be a complicated procedure or the container inner structure must be well made with this in mind because I assume one cannot just take the loaded container outside of water with it's lid still open and just let it dry out in the sun. Do you happen to have some materials on how the drying is done?
 
  • #22
Here is a general overview of the process. However, it specific to NAC's MPC dual use cask system. The video simply states that the inner container is vacuum dried (to remove moisture) and filled with helium through special ports that are then sealed. A lid is welded (underwater) in place, and the canister is placed into an transfer container. Ultimately, in this system, the inner canister is transferred from the transfer container to a storage container. It is somewhat complicated.

From Yankee Rowe (PWR) -


From Energy Northwest - Columbia Generating Station (BWR)


PGE - Diablo Canyon Plant (PWR) - note that the welding is done in air (but probably inert cover gas). Video shows the drying and helium filling system, but does not show the details of the ports.

 
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  • #23
I watched it yesterday, all of it.

1) What caught my attention is that , in episode 2 IIRC Michio Kaku is shown saying that the hydrogen bubble that did arise in the PWR and containment after the TMI accident is the same reason Chernobyl blew up. That I think is wrong. Chernobyl never had time to build up any hydrogen, the reactor was intact and few seconds after it exploded within a massive steam explosion.
The blast was a result of very sudden extreme heating within the core caused by a sudden but also extreme jump in thermal power due to the core experiencing a transient. The core was idling at 200MW thermal and then jumped in few seconds to Gigawatts of power. From what I understand hydrogen takes time to form from the Zr cladding due to heat in the presence of water.

2) What I found interesting is that one of the former residents that lived across the river from the plant spoke about how she saw dead fish in the days after the accident washed up by the shore, what I disliked is that in the video while she was talking you could clearly see the original videos showing the river and then the scene cut to a much higher quality video showing just some water and dead fish, as if that was from 1979 but I'm sure it wasn't , it was a montage of a different video from another place. 3) At the end of episode 2 they show the original video of lowering a camera into the core. Then Michio Kaku and others start talking about how they saw the core damage and for whatever reason Michio Kaku talks about how the massive core damage was just roughly 30 minutes away from a steam explosion.
What is the basis for such claims? Steam can only explode if confined in a sealed volume against which it can expand eventually violently breaching the volume, like the fuel channels in Chernobyl.
The overpressure had already been vented off during the hours before from the PWR vessel why would further melting of the fuel rise the potential for some sort of vessel overpressure?4) This final one interests me, @Astronuc please comment on this, one of the characters in that movie, Richard Parks who was the whistleblower focused on how he thought they cannot use the crane that exists with the PWR containment structures that moves heavy stuff around inside namely the vessel head during refueling etc.
Given there were no large fires etc , could the hydrogen gas and other fission products realistically compromised the metal structure of the crane during the years they had been present within the containment structure to varying levels?
 

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