Japanese nuclear reactor problems??

[Blahah]

Read more: http://www.dailymail...l#ixzz1GytLRBVX

 

A reliable source? I've been watching every single live press conference from TEPCO and Edano - nobody has said there is deadly radiation or that they should have been telling people sooner.

Edited March 18, 2011 by Blahah

[swansont]

It's the Daily Mail, so consider the source, and it looks like they are not actually quoting anyone — they are going from the definition of a level 5 accident, which includes the possibility of a small number of deaths. But the definition also includes a certain level of core damage and amount of material released. The two are not necessarily equivalent, so you can't turn it around and conclude that level 5 implies that there were deaths.

 

I've read several reports/stories where the Japanese government talked about release of radioactive material. This looks to be sensationalism.

 

http://en.wikipedia.org/wiki/International_Nuclear_Event_Scale#Level_5:_Accident_with_wider_consequences

 

edit: TMI was level 5 with no deaths

Edited March 19, 2011 by swansont
add TMI

[michel123456]

You may notice that in all early litterature, although it has been ranged as level 4 for days, it is mentioned as an "incident".

It is not an incident, it is an accident. Even level 4 is characterized "accident".

 

Wikipedia should be corrected. Oops, it has been corrected already...

Edited March 18, 2011 by michel123456

[louis wu]

The main coolant pump for the AP1000 system (warning: pdf. it's what I could find, so not necessarily the one in use but should be representative) is rated at 7000 HP, which is a little over 5MW. That's just one pump; the BWR drawings show three feedwater pumps, though I imagine only one would need to be running in shutdown, and not at full speed. This doesn't count other systems that would need to run.

 

So we're talking about MW-capacity generators. And a system designed to run in a specific voltage range.

 

A problem, as has been explained a few times, is where you hook them up. If the switchgear was destroyed or submerged, this is a problem. You don't just plug in a ~10 kV line carrying ~100 Amps with an extension cord.

Well Swansont

 

Without wishing to be too argumentative I think you are wrong. The information you have posted is for the main circulation system on the AP1000. This system would be powered from the grid in a reactor SCRAM. BWR emergency systems based on diesel generators do not run the main circulation pump, They are on totally different lines. See this diagram.

 

 

The main circulation pump is not needed in a SCRAM because in the same second that the rods go in; the heat output from the fuel is reduced to 10% and drops quickly thereafter. The diesel generators will be hefty beasts, and sized so that a single one of them can cope with the job; however I think that they will be commercially available items rather than specials.

 

I entirely agree with you emphasising the flooded switchroom. I believe that this was the single most important factor in changing the situation from an entirely controlled shut-down into a disaster. If 1 replacement diesel had been plumbed in during the 12 hours of battery power TEPCO would be telling us all about a vindication of the defence in depth strategy.

[swansont]

Well Swansont

 

Without wishing to be too argumentative I think you are wrong. The information you have posted is for the main circulation system on the AP1000. This system would be powered from the grid in a reactor SCRAM. BWR emergency systems based on diesel generators do not run the main circulation pump, They are on totally different lines. See this diagram.

 

 

On the contrary, I'm happy to be corrected about the details. As I said, I wasn't able to find specs for the BWR-3 system.

 

 

The main circulation pump is not needed in a SCRAM because in the same second that the rods go in; the heat output from the fuel is reduced to 10% and drops quickly thereafter. The diesel generators will be hefty beasts, and sized so that a single one of them can cope with the job; however I think that they will be commercially available items rather than specials.

 

The issue though is the power draw, and even though you are using a different set of pumps, it needs the capacity to move the water around at some rate, and this will be at some fraction of the main coolant system. So yes, we're still talking about some hefty generators.

[Iggy]

If the heat of vaporization of water is 40,650 J/mol and the specific heat of liquid water is 75.3 J/K/mol and it takes roughly 5 days to heat the spent fuel pool from roughly 25 C to 100 C then would the pool be expected to completely boil off in roughly 36 days--36 days after it started boiling that is?

 

This assumes, of course, that the pool isn't ruptured by the melted fuel.

 

Thanks in advance.

Edited March 18, 2011 by Iggy

[FX]

Or a hydrogen gas explosion that rips the building to shreds.

[Iggy]

I agree. I certainly don't mean to argue that everything will be fine with the pools for some time to come. The New York Times reported that imaging from a Global Hawk drone indicated that there was a major rupture and I'm sure there are other scenarios (like maybe a return to criticality from a conglomerate of melted fuel) that would result in a dry pool at this point.

 

I'm just wondering if we can find an estimate for when the pool would be dry given what we know about the rate that the pool heated up and assuming no other complications.

[dragonstar57]

I agree. I certainly don't mean to argue that everything will be fine with the pools for some time to come. The New York Times reported that imaging from a Global Hawk drone indicated that there was a major rupture and I'm sure there are other scenarios (like maybe a return to criticality from a conglomerate of melted fuel) that would result in a dry pool at this point.

 

I'm just wondering if we can find an estimate for when the pool would be dry given what we know about the rate that the pool heated up and assuming no other complications.

assuming no complications seems to be a bad idea when it comes to nuclear plants that are having problems

[alohahawaii]

to temporary cooling of the rods until they get full control of their power again couldnt they, since they are right next to the ocean, couldnt they make a trench from the ocean that pores directly into where the rods are?

[Iggy]

assuming no complications seems to be a bad idea when it comes to nuclear plants that are having problems

 

Having no complications at a plant that is having problems is not only a bad idea, it is impossible by definition.

 

to temporary cooling of the rods until they get full control of their power again couldnt they, since they are right next to the ocean, couldnt they make a trench from the ocean that pores directly into where the rods are?

 

The pool is uphill from the ocean.

[swansont]

If the heat of vaporization of water is 40,650 J/mol and the specific heat of liquid water is 75.3 J/K/mol and it takes roughly 5 days to heat the spent fuel pool from roughly 25 C to 100 C then would the pool be expected to completely boil off in roughly 36 days--36 days after it started boiling that is?

 

This assumes, of course, that the pool isn't ruptured by the melted fuel.

 

Thanks in advance.

 

You're ignoring evaporation. There will be less water to boil away than was heating up, and the heatup took more energy than 75.3 J/mol-K because of it.

 

edit: this also assumes there is no leak of any size caused by the earthquake.

Edited March 19, 2011 by swansont

[Iggy]

You're ignoring evaporation.

 

Good point. I had considered evaporation but figured it would be a second order effect of a first order approximation especially if the room containing the pool was sturdy-enough and airtight-enough to act as a vapor pressure cap on the pool at least until the room exploded.

 

edit: this also assumes there is no leak of any size caused by the earthquake.

 

Right. I should have explained better.

 

I was reading an article saying there was some disagreement between the NRC and TEPCO about whether there was water in reactor 4's pool. I thought "even if there was water at the time of the explosion at reactor 4, it would surely be well on its way to boiling off by now" which led me to wonder "is it possible to estimate how long the pool could contain water given only the info that has been published?"

 

Now that I’ve searched for it I have better info,

 

However, the temperature in the storage pool reached 84 C on March 14. There was a fire the following day, possibly caused by a hydrogen explosion at the pool.

 

http://www.voanews.com/english/news/Confusion-anxiety-abound-near-Fukushima-118285529.html

 

So the temp rose roughly 60 C in 3 days making the pool dry at roughly 13 days after the quake assuming no other complications such as damage to the pool or a return to criticality of the fuel.

 

That said, I don’t believe there is any steam rising from reactor 4 which is consistent with the NRC’s claim that the pool is dry. Since the core’s current un-spent fuel is in the pool, this seems like a rather large problem to me.

[dragonstar57]

Good point. I had considered evaporation but figured it would be a second order effect of a first order approximation especially if the room containing the pool was sturdy-enough and airtight-enough to act as a vapor pressure cap on the pool at least until the room exploded.

 

 

 

Right. I should have explained better.

 

I was reading an article saying there was some disagreement between the NRC and TEPCO about whether there was water in reactor 4's pool. I thought "even if there was water at the time of the explosion at reactor 4, it would surely be well on its way to boiling off by now" which led me to wonder "is it possible to estimate how long the pool could contain water given only the info that has been published?"

 

Now that I’ve searched for it I have better info,

 

 

 

So the temp rose roughly 60 C in 3 days making the pool dry at roughly 13 days after the quake assuming no other complications such as damage to the pool or a return to criticality of the fuel.

 

That said, I don’t believe there is any steam rising from reactor 4 which is consistent with the NRC’s claim that the pool is dry. Since the core’s current un-spent fuel is in the pool, this seems like a rather large problem to me.

the spent fuel probably can't maintain a chair reaction if it could it would probably still be in the reactor....

[Iggy]

The active fuel from the core is currently being held in the spent fuel pool.

 

-- Reactor No. 4 - This is the second most serious situation, at present. The reactor was under maintenance when the quake struck and its fresh fuel rods (much more dangerous than the spent rods in other reactor buildings) were all safely submerged at the time to keep them cool. However, the temperature in the storage pool reached 84 C on March 14. There was a fire the following day, possibly caused by a hydrogen explosion at the pool. A fire was observed Wednesday at the building housing the reactor. A renewed nuclear chain reaction was feared after the pool water level dropped.

 

http://www.voanews.com/english/news/Confusion-anxiety-abound-near-Fukushima-118285529.html

 

Japans Kyodo News reports that "Tokyo Electric Power Co. said Wednesday it is considering spraying boric acid by helicopter to prevent spent nuclear fuel rods from reaching criticality again, restarting a chain reaction, at the troubled No. 4 reactor of its quake-hit Fukushima No. 1 nuclear power plant.

 

http://www.dailygalaxy.com/my_weblog/2011/03/japan-crisis-update-spent-fuel-rods-could-go-critical.html

Edited March 20, 2011 by Iggy

[michel123456]

Why don't they transport the fresh fuel rods?

 

I found http://en.wikipedia.org/wiki/Nuclear_fuel_cycle#Transport_of_radioactive_materials

Transport of radioactive materials

Transport is an integral part of the nuclear fuel cycle. There are nuclear power reactors in operation in several countries but uranium mining is viable in only a few areas. Also, in the course of over forty years of operation by the nuclear industry, a number of specialized facilities have been developed in various locations around the world to provide fuel cycle services and there is a need to transport nuclear materials to and from these facilities. Most transports of nuclear fuel material occur between different stages of the cycle, but occasionally a material may be transported between similar facilities. With some exceptions, nuclear fuel cycle materials are transported in solid form, the exception being uranium hexafluoride (UF6) which is considered a gas. Most of the material used in nuclear fuel is transported several times during the cycle. Transports are frequently international, and are often over large distances. Nuclear materials are generally transported by specialized transport companies.

 

Since nuclear materials are radioactive, it is important to ensure that radiation exposure of both those involved in the transport of such materials and the general public along transport routes is limited. Packaging for nuclear materials includes, where appropriate, shielding to reduce potential radiation exposures. In the case of some materials, such as fresh uranium fuel assemblies, the radiation levels are negligible and no shielding is required. Other materials, such as spent fuel and high-level waste, are highly radioactive and require special handling. To limit the risk in transporting highly radioactive materials, containers known as spent nuclear fuel shipping casks are used which are designed to maintain integrity under normal transportation conditions and during hypothetical accident conditions.

(wikipedia)

 

 

 

and this about spent nuclear fuel shipping casks

[CharonY]

Just a little update: http://www.world-nuclear-news.org/RS_Stabilisation_at_Fukushima_Daiichi_2003111.html

[swansont]

The worry of the rods is that the fuel elements could melt, and that would change the geometry and one might achieve criticality. That's why you dump boron on them — it's a good neutron absorber. I think the mention of "fresh fuel rods" just means they were generating a large amount of decay heat. I don't think it means they would have been put back in the core, but commercial plant refueling is different from the navy strategy.

[Blahah]

Another interesting link is this guy who has used the CBTBO radionuclide monitoring network data to model the atmospheric dispersion of the radionuclides...

 

Quote from the current article about it in Science:

Based on the radionuclide data he has received so far, he believes none of the Fukushima reactors has experienced a full meltdown. Most of what has been detected have been volatile isotopes, including iodine, cesium, and xenon. A meltdown would have added less volatile elements to the mix, such as zirconium and barium, and these haven't been detected in large quantities.

[badmood]

I'm wondering why Michio Kaku today stated on Good Morning America that there is a chance that this reactor could create a Chernobyl-like incident. When asked point blank if the scientists that were saying that the reactor wasn't going to blow up or anything, he said that they were wrong. Has anything changed or is he speaking of some "danger" that I'm currently unaware of.

 

I tried to find a link to it, but I couldn't.

[swansont]

I'm wondering why Michio Kaku today stated on Good Morning America that there is a chance that this reactor could create a Chernobyl-like incident. When asked point blank if the scientists that were saying that the reactor wasn't going to blow up or anything, he said that they were wrong. Has anything changed or is he speaking of some "danger" that I'm currently unaware of.

 

I tried to find a link to it, but I couldn't.

 

Kaku appears to like the camera to the exclusion of limiting himself to topic he knows about. The networks have to stop turning to him for commentary on topics outside of his slice of physics. It's irresponsible.

[louis wu]

I'm wondering why Michio Kaku today stated on Good Morning America that there is a chance that this reactor could create a Chernobyl-like incident. When asked point blank if the scientists that were saying that the reactor wasn't going to blow up or anything, he said that they were wrong. Has anything changed or is he speaking of some "danger" that I'm currently unaware of.

 

I tried to find a link to it, but I couldn't.

Kaku is an opponent of nuclear fission power. He has been doing some scaremongering because if you dislike nuclear power then this is a great time to give the nuclear industry a kicking. This article for example is blatant scaremongering.

http://bigthink.com/ideas/31595

I think he has a new book out as well, so he needs to increase his public profile by any means possible.

[imatfaal]

Could someone explain where the Hydrogen that exploded comes from? I guess something is splitting the water - but what? Is something oxidising and freeing up Hydrogen from water? The fuel is already an oxide so it's not that - and I cannot see that it could be electrolysis

[louis wu]

Could someone explain where the Hydrogen that exploded comes from? I guess something is splitting the water - but what? Is something oxidising and freeing up Hydrogen from water? The fuel is already an oxide so it's not that - and I cannot see that it could be electrolysis

Zircaloy will steam oxidise if it becomes hot enough, producing hydrogen.

[imatfaal]

Zircaloy will steam oxidise if it becomes hot enough, producing hydrogen.

 

And that's the Zirconium Alloy cladding the fuel pellets - thanks Louis.

Edited March 22, 2011 by imatfaal