Arnie Gundersen simulating the Fuel Rods melting at Fukushima

[seanm123]

[LorenS]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

I'm not sure exactly how this relates to the inside of the plant, but the torch used was a cutting head. It runs a fairly small pilot flame, but the bulk of the torch is dedicated to streaming pure oxygen (the stream of oxygen burns the metal to produce the bulk of the heat).
On the second heating you could hear the blasts of oxygen being applied to the metal. What was interesting is that unlike a ferric metal which would have burned violently the fuel rod casing merely sparked a bit indicating that it was not burning very fast even in the presence of pure oxygen. At the very least that alloy is better than steel at resisting the action of oxygen.

I suppose if water is getting split into Hydrogen and Oxygen in the reactor core then the jet of pure oxygen is somewhat realistic. If electrolysis is happening, what is the mechanism? Is something acting as a catalyst?

[ASH]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

I suppose if water is getting split into Hydrogen and Oxygen in the reactor core then the jet of pure oxygen is somewhat realistic. If electrolysis is happening, what is the mechanism? Is something acting as a catalyst?

Zirconium is the catalyst reactant.

One disadvantage of zirconium alloys is their reactivity toward water at high temperatures leading to the formation of hydrogen gas and to the accelerated degradation of the fuel rod cladding:

Zr + 2 H₂O → ZrO₂ + 2 H₂

This exothermic reaction is very slow below 100 °C, but at temperature above 900 °C the reaction becomes rapid and is proportional to the square of mass of metal available. Most metals undergo similar reactions.

This is where the hydrogen that caused the explosions comes from. But note that the oxygen isn't generated as a free gas -- it gets tied up oxidizing the zirconium in the same process that splits the water. The blow torch with its jet of pure oxygen may be correct in spirit, if not detail. On the one hand, it takes energy to split the water molecules, even if it is net exothermic -- whereas the oxygen is already free in the blow torch. On the other hand, at those temperatures, it might be more of a detail than a difference; I'm not sure.

I do know that when I was a kid, messing around with burning magnesium, dropping a tiny bit of water onto the burning magnesium made it flare up rather than quenching it. I presume this is because oxygen is present in higher concentration in liquid water than in the atmosphere, so although it took some energy to split the water, I was essentially providing a more concentrated oxygen source to the smoldering magnesium. It might be a similar story for the fuel rods, if they get really hot.

[LorenS]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

So, basically, it's like dropping Aluminum powder into hot Iron Oxide? It's a red/ox reaction?

[ASH]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

So, basically, it's like dropping Aluminum powder into hot Iron Oxide? It's a red/ox reaction?

I think that's a correct comparison. You're breaking apart one oxide (the water or iron oxide) in order to form another oxide that is even lower energy (the zirconium oxide or aluminum oxide). Even though it takes energy to break apart the first oxide, the amount of energy released by forming the second oxide is greater, so the reaction generates net heat.

I looked up the enthalpies of formation:

zirconium dioxide = -1080 kJ / mol
water steam = -242 kJ / mol
net energy yield = ~596 kJ / mol it takes two water molecules to provide the oxygen for ZrO₂, so that's 1080 - (2*242) = 596

aluminum oxide = -1676 kJ / mol
iron (III) oxide = -826 kJ / mol
net energy yield = ~850 kJ / mol

The net energy yield for burning zirconium in steam isn't as high as thermite, but it is still pretty high.

[c1ue]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

The problem with this 'simulation' is that the blow torch produces temperatures of up to 1995 degrees C.

Well, duh, the melting point of zirconium is around 1850 degrees C.

First, let's exclude the SNFs.

Is there any indicator - anywhere - which shows the SNFs came even to half this temperature? a quarter? a tenth - they probably (almost certainly) did.

The very nature of the spent fuel rods is such that they are fissioning at fractions of 'peak' levels - under 1%.

An active reactor has hundreds of fuel rods - but let's just say there are 100.

1 reactor at Fukushima puts out about 1 GW - each fuel rod then is responsible for 10 Megawatts.

1% of 10 megawatts is then 100 kilowatts.

However, each fuel rod contain 200 fuel pellets.

So each fuel pellet puts out 1/200 of 100 kilowatts against the zirconium near it = 0.5 kilowatts.

Now maybe my math is wrong, but I don't see how 0.5 kilowatts heats up zirconium to more than 1000 degrees C.

0.5 kilowatts per pellet x 200 pellets/rod x 600 fuel rods over time certainly can heat up the water bath it is in, especially in aggregate, but this is a far cry from a blowtorch focused on one specific section.

Now for the reactor:

1) A major difference between the reactor and Mr. Gunderson's experiment is that the reactor has water in it. Big pools of water - which is how the heat from fission is transferring to the generators.

Did the reactors get extremely hot? Very possible even probable.

But it is unprofessional to compare a blow torch on a single fuel rod with a scrammed nuclear reactor filled with water. According to the 'demonstration' - which incidentally still didn't actually melt the zirconium, it only made it brittle - the impression left is that all the fuel rods melted down into a gigantic glowing ball.

If this had happened, then the radiation that's been reported is indeed very small.

If you're going to be irresponsible like this, you might as well compare the plutonium in the fuel rods to a gigantic H-bomb explosion given certain steps in between like refining and a weapon system.

[ASH]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

The problem with this 'simulation' is that the blow torch produces temperatures of up to 1995 degrees C.

I'd agree that spot heating by a blow torch is only going to demonstrate what happens to the material if it is heated to a certain temperature, and is not an accurate representation of the actual pattern of heating in a fuel rod. (My early comments on this thread pertain only to the chemistry.)

Now maybe my math is wrong, but I don't see how 0.5 kilowatts heats up zirconium to more than 1000 degrees C.

0.5 kilowatts per pellet x 200 pellets/rod x 600 fuel rods over time certainly can heat up the water bath it is in, especially in aggregate, but this is a far cry from a blowtorch focused on one specific section.

It's hard to work from a power like 500 W alone. Any rate of heat generation combined with perfect insulation would lead to an arbitrarily high temperature; any rate of heat generation combined with perfectly efficient transfer would lead to zero temperature rise. Obviously, the tungsten filament of a 500 W lightbulb can get hotter than 1000 C, but that example has almost zero bearing upon this discussion because such a filament is in a very different environment. The actual case depends upon the actual thermal impedance of the fuel assembly. If the rods are covered by water at atmospheric pressure, they're not going to get above 100 C. If they are dry, and can't dump energy into the water-steam phase transition, then you have to start wondering about the temperature of whatever is acting as the external heat sink, the geometry of the problem, and the thermal conductivity, emissivity, and heat transfer coefficients that apply to the conductive, radiative, and convective paths for removing heat. My guess is that the thermal problem is closer to a large mass trying to dissipate 500 W x 200 pellets/rod x 600 fuel rods through a limited surface area, than a small mass trying to dissipate 500 W, or it wouldn't be necessary to store spent fuel rods under water for the first several years after unloading (or to cool a reactor core after shutdown).

But it is unprofessional to compare a blow torch on a single fuel rod with a scrammed nuclear reactor filled with water. According to the 'demonstration' - which incidentally still didn't actually melt the zirconium, it only made it brittle - the impression left is that all the fuel rods melted down into a gigantic glowing ball.

I haven't watched the video, and was only commenting on the chemistry, but I agree that a blowtorch on a section of one fuel rods doesn't have any bearing on the conditions of a submerged fuel rod in a scrammed reactor. I would think the demonstration applies to what happens to an uncovered fuel rod if it overheats, in a rather narrow 'material properties' sense. Did Gundersen actually claim he was simulating conditions of a submerged rod in a scrammed reactor, or merely "this is what happens when fuel rods get too hot"?

[c1ue]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

It's hard to work from a power like 500 W alone.

Quite true. Let me put more dimensions on the situation:

1) We know the SNFs were fine on the day of the quake (March 11) and the pools were filled at that time
2) We know the fuel rods aren't stacked up like cordwood - the pics from the other Fukushima thread show a circular setup
3) We know the SNFs had water pumped into them no later than day 4

Thus the total heat release (and note also: 1% is likely the upper limit for fission state of fuel rods in the SNFs, also 0.3% is probably a lower limit. Also the fission energy generated vs. thermal energy is not 1 to 1) cannot be more than 0.5 Kwh x 48 hours = 24 Kwh per pellet. Multiplied out by the rough numbers of pellets/rod and fuel rods/pool = 2.88 Mwh. The actual number is probably somewhere below 2.88 Mwh and above 1 Mwh.

We know the SNF dimensions - roughly 40 feet deep by 40 foot diameter. We don't know the thermal conductance between the SNF water pool and the sides of the SNF nor air.

In another thread - it was estimated that 0.722 Kwh is needed to vaporize 1 liter of water. The SNF should contain 1423359 liters of water (20 * 20 * pi * 40 * 28.31 liter/cubic foot). Were all of the SNF energy focused without loss on water vaporization, then only 1 Mwh would be necessary to vaporize all the water. But of course in the real world it requires far more.

My point is that while the absolute numbers for thermal energy generated are high - even without doing the full exercises, it seems highly improbable that enough was accumulated in 2 days to melt any fuel rods in the SNFs barring an actual physical leak in the SNFs.

Did Gundersen actually claim he was simulating conditions of a submerged rod in a scrammed reactor, or merely "this is what happens when fuel rods get too hot"?

Yes, at the end of the video he specifically said this is what happened inside the Fukushima reactor after the tsunami. All the fuel rods melted into a big glowing ball in so many words.

[thriftyandboringinohio]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

The Japanese nuclear authorities have just declared that, on the official scale of 1 to 7, the Fukushima event is now a 7.
They skipped over 6, going from 5 to 7.
The only other event of that rating was Chernobyl.

[mesyn191]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

FYI that doesn't actually mean very much, and they've also stated that it was a provisional change much like that level 5 status was. Put plainly they can change it back to 5 or even 4 or 3 any time they like, they're just being cautious, which is good IMO. They won't really know what level of disaster it truly is until its finally properly contained and the site properly surveyed, which is something that they've also said too.

So far though this isn't any worse than TMI really, which is amazing considering the beating that site took.

[c1ue]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

Fukushima is clearly worse than TMI - the radiation released is far greater.

However, it is still 1 order of magnitude smaller than Chernobyl, and furthermore the releases are in a much smaller area.

The amusing part is how many still think the Japanese government is hiding facts.

The reality is that the reactors have been stable for a long time, radiation releases are falling daily, and what is going on is cleanup and decontamination.

However, despite a clearly improving situation, the NISA has the integrity to acknowledge what is fact - if perhaps not the sense to manage the situation.

The latest IAEA report:

Overall, the situation at the Fukushima Daiichi plant remains very serious but there are early signs of recovery in some functions such as electrical power and instrumentation.

In Units 1, 2 and 3, 60 000 T of contaminated water need to be removed from the turbine buildings and trenches. This water will be transferred to the condensers of each unit and the Radioactive Waste Treatment facility. In addition, temporary storage tanks have been ordered to provide additional capacity for the water and will be located adjacent to the Radioactive Waste Treatment facility. At Unit 1 and 2 water transfer from the condenser to the condensate storage tank was completed on 10 April.

In order to make room for higher contaminated water from the turbine buildings and trenches, 1 343 T of low level contaminated water from Units 5 and 6 sub-drain pit were released to the sea from 4 to 9 April. In addition, 9 070 T of low-level contaminated water was discharged from the Central Radioactive Waste Disposal Facility to the south discharge point.

Nitrogen gas is being injected into the Unit 1 containment vessel to reduce the possibility of hydrogen combustion within the containment vessel. The pressure in this containment vessel is increasing due to the addition of nitrogen.

Since 6 April, TEPCO has been moving debris from Units 1 to 4 to a common storage area on-site using remote controlled heavy equipment.

On 10 April additional anti-scattering agent was sprayed in an area of about 550 m2 on the mountain-side of the Common Spent Fuel Pool to prevent the radioactive materials on the ground from being scattered.

In Unit 1 fresh water is being continuously injected into the RPV through the feed-water line at an indicated flow rate of 6 m3/h using a temporary electric pump with off-site power. In Units 2 and 3 fresh water is being continuously injected through the fire extinguisher lines at an indicated rate of 7 m3/h using temporary electric pumps with off-site power.

In Unit 1 the pressure in the RPV is increasing, as indicated on both channels of instrumentation. In Units 2 and 3 Reactor Pressure Vessel and Drywell pressures remain at atmospheric pressure.

RPV temperatures remain above cold shutdown conditions in all Units, (typically less than 95 °C). In Unit 1 temperature at the feed water nozzle of the RPV is 228 °C and at the bottom of the RPV is 121 °C. In Unit 2 the temperature at the feed water nozzle of the RPV is 149 °C. The temperature at the bottom of the RPV was not reported. In Unit 3 the temperature at the feed water nozzle of the RPV is 92 °C and at the bottom of the RPV is 111 °C.

An additional 60 T of fresh water was injected via the Spent Fuel Cooling System line to the spent fuel pool in Unit 2 by a temporary pump on 10 April.

There has been no change in status in Units 4, 5 and 6.

2. Radiation Monitoring

On 10 April, deposition of both iodine-131 and cesium-137 was detected in 7 and 6 prefectures respectively. The values reported for iodine-131 ranged from 6.3 to 920 Bq/m2 and for cesium-137 from 7.9 to 800 Bq/m2. The highest deposition was reported for both, iodine-131 and cesium-137, in the prefecture of Ibaraki. /p>

Gamma dose rates are measured daily in all 47 prefectures, the values tend to decrease. For Fukushima, on 10 April a dose rate of 2.2 µSv/h, for the Ibaraki prefecture a gamma dose rate of 0.15 µSv/h was reported. The gamma dose rates in all other prefectures were below 0.1 µSv/h.
Dose rates are also reported specifically for the Eastern part of the Fukushima prefecture, for distances of more than 30 km to Fukushima-Daiichi. On 10 April, the values in this area ranged from 0.2 to 25 µSv/h.

MEXT has set up an additional monitoring programme, in cooperation with local universities, measurements are made in 26 cities in 13 prefectures. As of 10 April, in 19 cities, the gamma dose rates were below 0.1 µSv/h. In 6 cities, gamma dose rates ranged from 0.13 to 0.17 µSv/h. In Fukushima City, a value of 0.42 µSv/h was observed. Typical normal background levels are in the range of 0.05 to 0.10 µSv/h.

Only in a few prefectures, iodine-131 or cesium-137 is detectable in drinking water at very low levels. As of 10 April, a restriction for infants related to iodine-131 (100 Bq/l) is in place as a precautionary measure in only one village of the Fukushima prefecture.

On 10 April, the IAEA Team made measurements at 7 different locations in the Fukushima area at distances of 23 to 39 km, South and Southwest from the Fukushima nuclear power plant. At these locations, the dose rates ranged from 0.4 to 1.6 µSv/h. At the same locations, results of beta-gamma contamination measurements ranged from 0.01 to 0.18 Megabecquerel/m2. The highest beta-gamma contaminations have been determined at distances of less than 30 km from Fukushima-Daiichi.

Analytical results related to food contamination, reported by the Japanese Ministry of Health, Labour and Welfare from 8 to 10 April covered a total of 157 samples taken from 6 to 10 April. Analytical results for 153 of the 157 samples for various vegetables, spinach and other leafy vegetables, shitake mushrooms, fruit (strawberries), pork, seafood and unprocessed raw milk in eight prefectures (Chiba, Fukushima, Gunma, Ibaraki, Kanagawa, Nagano, Niigata and Saitama), indicated that I-131, Cs-134 and/or Cs-137 were either not detected or were below the regulation values set by the Japanese authorities. In Fukushima prefecture, one sample of seafood (sand lance) taken on 7 April was above the regulation values set by the Japanese authorities for I-131 and three samples of shiitake mushrooms taken on 8 April were above the regulation values set by the Japanese authorities for I-131 and/or Cs-134 and Cs-137

3. Marine Monitoring

TEPCO Monitoring Programme

As reported in the brief of 8 April TEPCO is conducting a programme for seawater (surface sampling) at a number of near-shore and off-shore monitoring locations as illustrated in Map 1.

Map 1: TEPCO Seawater Sampling Locations:
Until 3 April a general decreasing trend was observed at the sampling points TEPCO1 to TEPCO4. After the discharge of contaminated water on 4 April, a temporary increase has been reported.

On 11 April new data (8 April sampling day) for TEPCO 1 - 4 sampling points have been reported. At the near-shore sampling point TEPCO 1 an increase from 2,2 kBq/l (7 April) to 19 kBq/l for I-131 and from 1.7 kBq/l (7 April) to 12 kBq/l for Cs-137 has been reported. As for TEPCO 3 and TEPCO 4 a further decrease as respect to the results for the sampling day, 7 April, in the concentration of I-131 and Cs-137 has been reported. At the sampling point TEPCO 2 a decrease in the concentration of I-131 to about 50 kBq/l) and Cs-137 to about 34 kBq/l as respect to the results obtained on 7 April was observed.

For the six sampling points TEPCO 5 to TEPCO 10 since 7 April no new data have been reported. The data since 7 April have been summarized in the previous brief of 10 April.

MEXT Off-shore Monitoring Programme

As reported in the brief of 8 April MEXT initiated the off-shore monitoring program on 23 March and subsequently points 9 and 10 were added to the off-shore sampling scheme. On 4 April, MEXT added two sampling points to the north and west of sampling point 1. These are referred to as points A and B on the map below.

Map 2: MEXT Seawater Sampling Locations:


0n 11 April new data have been reported for MEXT 1, 3, 5, 7 and 9 for 9 April sampling day.

At MEXT 1 both I-131 and Cs-137 were no longer detectable. At MEXT 3 an increase of the level of both I-131 and Cs-137 was recorded. At MEXT 5 the level of I-131 decreased and Cs-137 was not detected. At MEXT 7 and MEXT 9 an increase for I-131 was recorded and Cs-137 was no longer detectable.

No new data for the other sampling points have been reported at the date of 11 April 2011.

[ASH]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

Yes, at the end of the video he specifically said this is what happened inside the Fukushima reactor after the tsunami. All the fuel rods melted into a big glowing ball in so many words.

Yeah -- I finally watched the video last night after work. The first part of what Gundersen said seems consistent with other reporting -- that the cores melted at least partially when the water level dropped. It also sounds like the NRC still believes there was "significant fuel damage" in the spent fuel pools, so they must think the pools lost water through leaks in addition to evaporation. But at the end of the video Gundersen seems to imply that core material could still be molten inside the reactors, even after the reactors were flooded. I wonder under what circumstance that could be the case. You'd think the melted core material would have to return to criticality to generate enough heat to stay molten under water. Since the control rods went in, and the melt would tend to spread the core material out into a less compact mass, that seems unlikely. But then again, Gundersen has some professional background in this area, and I do not.

[c1ue]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

It also sounds like the NRC still believes there was "significant fuel damage" in the spent fuel pools, so they must think the pools lost water through leaks in addition to evaporation.

It would be nice if the NRC would actually release data backing this belief, as opposed to making general statements. You'd think that a public safety entity would want to make transparent any real dangers that exist from Fukushima - as opposed to fan the media flames. Or did I reverse the order of their mission statement?

You'd think the melted core material would have to return to criticality to generate enough heat to stay molten under water. Since the control rods went in, and the melt would tend to spread the core material out into a less compact mass, that seems unlikely. But then again, Gundersen has some professional background in this area, and I do not.

I'd note that the IAEA and TEPco have been reporting temperatures at the reactors daily - none of them are going up and all are under 250 degrees C.

As for Gundersen's background - it is unclear just what technical background he has, if any.

Certainly his facts seem to be few and far between.

[ASH]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

Here is what is supposedly a Reactor Safety Team (RST) assessment of the plant from March 26th.

From page 13, concerning the spent fuel pond at #4:

Given the amount of decay heat in the fuel in the pool, it is likely that in the days immediately following the accident, the fuel was partially uncovered. The lack of cooling resulted in a zirc water reaction and a release of hydrogen. The hydrogen exploded and damaged secondary containment. The zirc water reaction could have continued, resulting in a major source term release.

Fuel particulates may have been ejected from the pool (based on information of neutron emitters found up to 1 mile from the units, and very high dose rate material that had to be bulldozed over between Units 3 and 4. It is also possible the material could have come from Unit 3).

[mesyn191]

Re: Arnie Gundersen simulating the Fuel Rods melting at Fukushima

Fukushima is clearly worse than TMI - the radiation released is far greater.

In terms of effects? Nah. The damage to core and cooling ponds is catastrophic but the actual radiation released is trivial. TMI supposedly released the equivalent to 2 or 3 chest x-rays if you lived close to the reactor when it underwent partial melt down. Fukushima appears to be more than that but no one is going to die or even get statistically elevated chance of cancer from this. Worst I've heard is somewhere around effectively 1/5th of what a nuclear plant operator gets in a year. "Another TMI" is pretty much spot on.

http://bmartinmd.com/2011/03/fukushi...on-levels.html

Mean while we've got people freaking the fuck out all the way over here on the West coast in CA and even some up in Canada, thinking they're gonna get irradiated. This disaster could've been much worse, maybe even as bad as some feared, but it was clear IMO it wasn't going to be at least days ago.

If you want to freak out about something these places are sooo much worse its mind boggling you don't hardly ever hear anything about them, and they've been around for decades.

http://www.redorbit.com/news/science...ts_just_130km/
http://www.logtv.com/films/chelyabinsk/