Nuclear fuel rods removed from Japan's Fukushima plant

Man.

I'm glad germs can be fought prevent-a-tively unlike a breached nuclear reactor???
pdf brochure

An ounce of prevention?
Too many people are tripping over sense trying to accumulate dollars.

Ethics vs. law

I think the removal of rods should be televised in an unscripted reality show, but that's just me.

Continued

Originally posted by TheRedneck
reply to post by BriGuyTM90

Yes, there are. I wish all the plants were the PWR design rather than the BWR, but it does no one any good to worry about what already is.

Are you serious? You really believe that? Well one things for sure is that the NRC isn't worried about them because they are handing out 20 year license extensions on plants that were only designed to run for 40 years. Also they are granting the extensions based on information we knew in the 70s and not what we know today because it would be far to expensive to implicate current safety standards.

Originally posted by TheRedneck
As to "lower earthquake standards"... that requirement is not static. The seismic conditions used are based on the largest earthquake in the last 100 years, and the level that can be withstood is 1.0 above that recorded level. The department I worked in in the 1980s was directly involved with these seismic calculations, and the NRC reviewed EVERY SINGLE calculation. Fukushima, based on reports, shortened the historical record specifically to avoid using a massive earthquake as the basis.

Yes, the safety standards are different depending on the seismic activity of a region among other things. Lets take the North Anna incident. The plant was build to survive a M4.0 and it got a 4.0. Now you say well OK it with stood what it was designed to withstand but according to the NRC model the most that plant should have been subjected to was a M3.0 once every 100 years. Nature can over come any design basis humans build any building to and its immature to think other wise. Nature can be unprecedented any were at any time.

Originally posted by TheRedneck
There are probably abuses of power within the NRC. ... The level of abuse in the NRC, however, has a record of being some of the most minor in terms of allowing proper operation of the organization.

Sorry but when the sitting chairmen resigns because he says that the organization is not only bought out buy the industry it regulates but is also largely made up of the industry I'm going to believe him.

reply to post by BriGuyTM90

I understand that they are opposites that's why I pointed it out. You said one thing and i gave a reason for it being wrong.

I indicated that the majority of damage would be in Japan, with decreasing effects as one moves outward from the source of the radioactive contaminants. Do you disagree with this?

How about these events?

How about them?

Pilgrim does store spent fuel in a pool on-site, but that is simply because legislators keep blocking attempts to move it elsewhere. There have been no serious reported leaks. I will admit that I am a bit concerned about this plant, but so far it has remained stable.

Salem is a PWR plant. Leaks are simply water, not radioactive water. Radioactive water never exits the secondary containment in a PWR design.

Vermont Yankee has had a few leaks, but all have been repaired. There was a recent discovery of a small amount of tritium, below Federal reporting levels, but it is being investigated. In any case, tritium is an indicator that there is a minor leak, but is not itself an indication of catastrophic failure. It is a byproduct of neutron bombardment of boron (used in coolant), not a direct product of nuclear fission.

None of the plants listed in that report have any history of severe violations... only of minor maintenance issues and minor violations that have been (or are being) addressed.

This statement is not true and disingenuous sense we are only 33 years out and the full effects of genetic damage don't present them selves for up to 60 years and if damage was done sex cells effects might not show up for generations.

Actually the statement is true. After 33 years, any appreciable amount of cellular damage would have shown up.

If you only look at cancer and don't do it long enough you wont really find anything. Cancer is just one effect of radiation. Heart defects and heart disease is another major effect. But nobody takes those things into account.

Heart defects? I can only assume you are talking birth defects; the amount of radiation needed to create a heart defect in a developed human would so intense as to cause death before the heart could stop beating.

Heart disease, yes, is possible, but the diseased heart would show signs of intra-cellular damage. I know of no reports of this occurring.

Radiation causes cellular damage, period. It is not unlike placing the affected cells in a microwave oven. If the radiation dosage is low enough, it will make little to no damage; if it is higher, it can cause cellular mutations via DNA damage; if it is high enough, it will cause enough damage for radiation sickness and potentially death to occur. The latter category did not occur; the former is desirable. The only thing in question is the cellular damage over time issue, and after 33 years I believe any problem would have shown up by now. We are talking in excess of a generation, after all.

All three of the Diachi units completed SCRAM.

BLATANTLY untrue! They attempted SCRAM; completion would mean the nuclear cores were cold and inert; obviously they were not!

Are you serious? You really believe that?

Yes, I believe we have to work with what is in existence in the present. I also believe complaining about historical activity does no good. No one can change history.

Now if you want to propose an operable plan for replacing all the BWR reactors with PWR designs, count me in.

Nature can over come any design basis humans build any building to and its immature to think other wise.

A volcano can erupt beneath my feet at any time. Sure. What do I gain by worrying about it? Should I move somewhere else? Should I fireproof my shoes?

Sorry but when the sitting chairmen resigns because he says that the organization is not only bought out buy the industry it regulates but is also largely made up of the industry I'm going to believe him.

Of course you are! It's not as if he could have sour grapes over something else, is it?



TheRedneck

reply to post by TheRedneck

I indicated that the majority of damage would be in Japan, with decreasing effects as one moves outward from the source of the radioactive contaminants. Do you disagree with this?

Anyone who disagrees with this is a clueless idiot.

Pilgrim does store spent fuel in a pool on-site, but that is simply because legislators keep blocking attempts to move it elsewhere. There have been no serious reported leaks. I will admit that I am a bit concerned about this plant, but so far it has remained stable.

Spent fuel is extremely hot in the instant of time it is removed from the reactor, as it is emitting large amounts of radiation and is still generating quiet a bit of heat. It must be kept under water for a period of time after it is removed, eventually it will be able to be offloaded to dry-storage. Even if there were another place to store the fuel, it would likely stay on site to cool for a period of time, but wouldn't accumulate over time in this pool.

Salem is a PWR plant. Leaks are simply water, not radioactive water. Radioactive water never exits the secondary containment in a PWR design.

In PWR plants the primary loop never exits the primary containment. However, the secondary loop does. For engineering reasons, the main condenser is not powered by the emergency DC power, hence cooling the reactor to cold shutdown without off-site power involves venting steam directly into the atmosphere. If there were a leak in the steam generators this would involve venting a tiny amount of radioactivity into the environment. There are also likely other pathways.

Vermont Yankee has had a few leaks, but all have been repaired. There was a recent discovery of a small amount of tritium, below Federal reporting levels, but it is being investigated. In any case, tritium is an indicator that there is a minor leak, but is not itself an indication of catastrophic failure.

It is a byproduct of neutron bombardment of boron (used in coolant), not a direct product of nuclear fission.

It is a direct product of nuclear fission. Also boron isn't used in the coolant of BWRs, but it can be used in the control rods.

None of the plants listed in that report have any history of severe violations... only of minor maintenance issues and minor violations that have been (or are being) addressed.

Correct.

The latter category did not occur; the former is desirable. The only thing in question is the cellular damage over time issue, and after 33 years I believe any problem would have shown up by now. We are talking in excess of a generation, after all.

Correct.

BLATANTLY untrue! They attempted SCRAM; completion would mean the nuclear cores were cold and inert; obviously they were not!

Scramming a reactor only shuts down the self-sustaining fission reaction, but it does not imply that the reactor will be cool or will not be generating massive amounts of decay heat.

In BWRs scramming only takes several seconds. The control rods are inserted into the reactor from the bottom via hydraulic accumulators. In PWRs gravity does the work. It is likely the reactors shut down only several seconds after the earthquake started, when computer systems detected the shaking. The will fuel still generate a significant amount of heat immediately afterwards, about 8% of the initial output. Assuming a 3500 megawatt (thermal) reactor, that's 280 MW. After 15 minutes that has dropped to about 2% of the initial output (70 MW).

If that heat isn't taken away, the pressure will rise to the point where steam needs to be vented. If the fuel is uncovered, the fuel will quickly get too hot then the zirconium fuel cladding reacts with water, creating hydrogen gas. Most interesting with Fukushima, is why a hydrogen explosion occurred, I was under the impression reactors today had been retrofitted with passive hydrogen recombiners and proper venting to prevent an explosion. Either the reactors were not fitted with them or something unexpected happened. Also the mark 1 containment is known to be rather weak.

If you want to find an avenue to show most reactors are safe, then I highly suggest you look into that. I'm afraid I no longer have the time.

Now if you want to propose an operable plan for replacing all the BWR reactors with PWR designs, count me in.

In general; the BWR is not any less safe than the PWR. The core damage frequency is lower than that of PWRs actaully, but the containment in the early ones is weaker which leads to a similar calculated large release frequency. The late BWRs with stronger containments are probably the safest reactors operating.


I'm afraid I'm done for the night. I replied to you first because I am more interested in having a discussion with people who I broadly agree with. I'll reply to BriGuyTM90 on the train ride home tomorrow. I have actual engineering to do.

reply to post by C0bzz

Spent fuel is extremely hot in the instant of time it is removed from the reactor, as it is emitting large amounts of radiation and is still generating quiet a bit of heat. It must be kept under water for a period of time after it is removed, eventually it will be able to be offloaded to dry-storage. Even if there were another place to store the fuel, it would likely stay on site to cool for a period of time, but wouldn't accumulate over time in this pool.

Correct. The issue is, as I understand the discussion, not about holding spent fuel until it can be safely moved, but more about storing it for extended periods after it has cooled. Fukushima was storing spent fuel indefinitely: an extremely bad idea. Pilgrim is storing fuel as well past the point it could safely be moved, but this is not for lack of desire to move it; it is for lack of anywhere to move it to.

NIMBY strikes again.

In PWR plants the primary loop never exits the primary containment. However, the secondary loop does. For engineering reasons, the main condenser is not powered by the emergency DC power, hence cooling the reactor to cold shutdown without off-site power involves venting steam directly into the atmosphere. If there were a leak in the steam generators this would involve venting a tiny amount of radioactivity into the environment. There are also likely other pathways.

The heat exchanger in the Bellefonte Alabama plant is located between the primary and secondary containment walls. Thus the primary coolant never exits the reactor building itself, and the secondary (main) lines never enter the primary containment (reactor room).

There is an emergency water inlet into the primary loop; otherwise there would be no way for water to be introduced in the first place. That inlet valve is a last-chance method for cooling the core if all else fails (which, incidentally, has never happened in a PWR reactor). Of course, water introduced has to go somewhere, and you are correct that that somewhere is in the form of a steam venting. Such venting can indeed be radioactive, and is the worst thing that can happen to a PWR reactor short of a meltdown itself. TMI, if memory serves, released steam from the core (despite the fact the readings indicating that operation were faulty).

Any radiation in the main steam lines is from radiation that manages to cross the barriers in the heat exchanger. It is minuscule compared with the radiation levels inside the primary containment.

During a SCRAM, the control rods are inserted into the core, separating critical mass and slowing the fission reaction below criticality; the primary loop pumps continue to operate, and the secondary loop pumps continue to operate as well. The generators are bypassed and water is shunted straight to the cooling towers for maximum effect. Should power be lost during a SCRAM, the control rods alone (gravitationally inserted automatically should power be lost) would be the only thing that would operate and the heat would damage them (although theoretically they would still prevent a total meltdown). That's why diesel generators are on-site and constantly tested; they automatically crank up during a SCRAM. There are also batteries that are maintained as an additional backup, although usage of the batteries means GET A GENERATOR HERE NOW! That was one problem with Fukushima; after the diesel generators failed, it took too long to restore power and the batteries failed before the cores could cool due to the time needed being extended from the plant damage.

Had the diesel generators not failed, or had additional generators been brought in before the batteries failed, we would still have seen a radiation release, but it would have been for a limited time. As it turns out, there are still pools of molten uranium reacting away below the reactor buildings spewing radiation.

I should also mention that there are backups for every main pump in a US facility.

It is a direct product of nuclear fission. Also boron isn't used in the coolant of BWRs, but it can be used in the control rods.

Pray tell, what is the direct fission sequence that produces tritium from uranium?

Tritium in a reactor is typically a byproduct of neutron absorption of boron, which can decay into 2 lithium atoms and one atom of tritium. It can also be produced through neutron absorption of deuterium. These are indirect sources.

Also, while you are correct that boron is only used in coolant for PWR reactors, it is commonly used in the control rods for BWR reactors.

~continued~

~continued~

Scramming a reactor only shuts down the self-sustaining fission reaction, but it does not imply that the reactor will be cool or will not be generating massive amounts of decay heat.

SCRAM also implies the continued cooling to safe levels. Insertion of the control rods is only the first stage. Heat is still produced until the free neutrons are either absorbed or release their energy. Thus the need for power backups to operate coolant systems until excess heat is removed from the core.

Incidentally, PWR reactors do not rely on gravity to insert them; they can operate solely on gravity as a safety measure, but under powered conditions are inserted electrically to decrease the time needed for insertion.

It is likely the reactors shut down only several seconds after the earthquake started, when computer systems detected the shaking. The will fuel still generate a significant amount of heat immediately afterwards, about 8% of the initial output. Assuming a 3500 megawatt (thermal) reactor, that's 280 MW. After 15 minutes that has dropped to about 2% of the initial output (70 MW).

If that heat isn't taken away, the pressure will rise to the point where steam needs to be vented. If the fuel is uncovered, the fuel will quickly get too hot then the zirconium fuel cladding reacts with water, creating hydrogen gas. Most interesting with Fukushima, is why a hydrogen explosion occurred, I was under the impression reactors today had been retrofitted with passive hydrogen recombiners and proper venting to prevent an explosion. Either the reactors were not fitted with them or something unexpected happened. Also the mark 1 containment is known to be rather weak.

As I understand the events, your description was precisely what happened. I believe the retrofitting had not occurred; the actions (or should I say inactions) of TEPCO during this disaster have shown them to be extremely irresponsible. The earthquake probably damaged the reactor core as well as the primary pumps. There was a short period of time between the diesel generator failure and the switch to battery power that probably caused the pumps to stop. Damage to the system then caused the pumps to fail upon restart, and of course there was an even longer outage between battery exhaustion and generator installation.

In general; the BWR is not any less safe than the PWR.

I disagree, based in large part on the dual-loop cooling system used in the PWR design. There is nothing 'safe' about routing highly-radioactive water/steam through an entire plant complex. Every foot of pipe is a foot of pipe that can leak; every component (pump, flange, valve, turbine, etc.) is another piece of the system that can fail. KISS (Keep It Simple, Stupid) applies here especially.

TheRedneck

Originally posted by TheRedneck
~continued~

Scramming a reactor only shuts down the self-sustaining fission reaction, but it does not imply that the reactor will be cool or will not be generating massive amounts of decay heat.

SCRAM also implies the continued cooling to safe levels. Insertion of the control rods is only the first stage. Heat is still produced until the free neutrons are either absorbed or release their energy. Thus the need for power backups to operate coolant systems until excess heat is removed from the core.

SCRAM is the process of inserting the control rods. It usually only takes seconds, Cold Shutdown is the state achieved when the water reaches 95C and the pressure inside the PRV is at ~100 kPa.

Originally posted by TheRedneck
Pilgrim is storing fuel as well past the point it could safely be moved, but this is not for lack of desire to move it; it is for lack of anywhere to move it to.

Correct but what they could do but are not because they don't want to spend the money on it is move the fuel into dry cast storage. Instead they have kept the spent fuel form the reactors entire life time in the spent fuel pool. One thing Positive thing about Fukushima is that all the dry-casts survived the earthquake and tsunami, its a very expensive process but is much safe than spent fuel pools.

Installing dry-cask storage infrastructure at a plant with two reactors would cost between $20 million and $30 million, and annual costs for buying casks, loading them and running a dry-cask storage facility are $7 million to $10 million, according to Exelon.

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Originally posted by COBzz
Most interesting with Fukushima, is why a hydrogen explosion occurred, I was under the impression reactors today had been retrofitted with passive hydrogen recombiners and proper venting to prevent an explosion. Either the reactors were not fitted with them or something unexpected happened. Also the mark 1 containment is known to be rather weak.

Nope the only gas treatment system they had needed electricity to operate.
page 15
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reply to post by BriGuyTM90

SCRAM is the process of inserting the control rods. It usually only takes seconds, Cold Shutdown is the state achieved when the water reaches 95C and the pressure inside the PRV is at ~100 kPa.

It appears we are discussing two different definitions of the same word. When I worked at Bellefonte, SCRAM was defined (in continuing education nuclear safety classes approved by both TVA and the NRC) as the process of moving the plant from power production status to a state of shutdown in an emergency situation. It begins with the decision to insert the control rods and ends when the plant exhibits expected cool-down activity to the extent all immediate danger has passed.

If SCRAM is defined as emergency insertion of the control rods, yes, it takes seconds.

If SCRAM is defined as the operations happening from recognition of an emergency to resolution of that emergency, it can take much longer... technically one could say that the SCRAM at Fukushima is still ongoing, since the emergency situation is still extant. I would characterize the situation after power was restored as a catastrophe from a failed SCRAM, but then again, that is semantics. The bottom line is that the plants have never returned to a safe condition.

...and never will in our lifetimes...

Correct but what they could do but are not because they don't want to spend the money on it is move the fuel into dry cast storage.

Correct as well. I am a bit surprised Pilgrim has not been forced to do so.

I have stated numerous times that the biggest problem with nuclear power is proper waste disposal. A large part of this problem is political: no one dares to support nuclear research because too many people consider anything to do with nuclear power to be devastatingly hazardous. Research is the only way to overcome the problems we have encountered, and as long as people in general see anything nuclear as a big bad boogeyman who wants to create three-eyed fish and melt the flesh off humans, they will continue to do so and the problems will never have a solution.

TheRedneck

I'm afraid I am busy for the rest of the week, so I won't be able to continue this discussion for several days.

Cheers.