Fukushima Japan Earthquake: nuclear plants Fukushima part 2

[Hiddencamper]

Consider that unit 3 underwent an automatic depressurization system (ADS) blowdown, and with this new data, we know the fuel was already damaged/melted when ADS actuated. The ADS system would have discharged a lot of fission products and noble gasses to the suppression pool.

Unit 3 did have containment venting a short while after the ADS blowdown:

http://www.cas.go.jp/jp/seisaku/icanps/eng/03IIfinal.pdf

Although depending on specifically what you read, its possible that venting may not all have gotten to the stack. Some of it may have went to unit 4, some may have gone into the reactor building. The venting was from the suppression chamber. This would have created a direct pathway for radioisotopes to migrate from the damaged fuel, out the safety relief valves to the suppression pool, and out the suppression pool to the environment.

This isn't a sure thing, just an idea looking at what we know.

 

[zapperzero]

I dunno, but the gamma signatures from the fission of generated actinides, versus that from critical U235 would be like a fingerprint.
http://www.lanl.gov/orgs/n/n1/panda/11. Nuclear Data for NDA.pdf

I am not sure the gamma detectors they had were all THAT sensitive/discriminating.
Too, one does not exclude the other.

 

[mheslep]

I am not sure the gamma detectors they had were all THAT sensitive/discriminating.
Too, one does not exclude the other.

I only know detectors that can discriminate gamma (obviously) exist. No information what was on site.

 

[etudiant]

The recent TEPCO statements do seem to provide a coherent sequence for the failure of the three reactors.
Clearly the reactor systems functioned largely as designed and postponed the meltdowns, but not long enough for the operators to regain control. This raises the question whether anything could have averted the disaster once the tsunami had struck, had the operators had better knowledge.

 

[jim hardy]

This raises the question whether anything could have averted the disaster once the tsunami had struck, had the operators had better knowledge.

With hindsight there's some things that could have been tried, for example ignoring the vessel's cooldown limits and cooling the reactor very quickly to below 100C..
Nobody knew how big the tidal wave would be. Who'd thermal shock a reactor vessel for a "maybe" ?

But without electric power they were trapped . Lots of heat to get rid of and no way to move it.

Probably they'd have been able to only postpone things a matter of hours or very few days.

just my thoughts...

old jim

 

[Hiddencamper]

I think, if they did not lose DC batter/control power at units 1/2, then maybe, they might have been able to do something.

24 hours should be more than ample time to restore power or at least implement a decay heat removal solution. But they spent so much time dealing with no reactor indications, trying to figure out the state of their cooling systems, the inboard valves for the IC at unit 1 appears to have isolated on loss of control power, and shortly after that they were dealing with core damage, high rad levels, explosions, personnel shortages.

Seriously, I think if they had control power at units 1/2, they would have kept core cooling capability of the unit 1 IC, and rather than spend time trying to figure out the status of unit 1/2, they could have devoted resources to an ultimate heat sink solution similar to the Daini site.

On a separate note, the Us industry does not assume total DC control power failure for any scenario, including the new Fukushima based scenarios or for the AP1000. I think this is a significant gap, and that there needs to be training on how to deal with this. The extensive damage mitigation guidelines do have steps for performing specific tasks without control power, like hooking batteries up to instruments to get readings, but a total cd power loss would be extremely challenging to deal with as you would be blind to the majority of your indications.

Just my thoughts.

 

[jim hardy]

The extensive damage mitigation guidelines do have steps for performing specific tasks without control power, like hooking batteries up to instruments to get readings, but a total cd power loss would be extremely challenging to deal with as you would be blind to the majority of your indications.

That's the one plant guys have nightmares about. Without DC you can't start your diesels, either.

At my plant we knew just where to connect engine driven DC welders. But you're right it wasn't in procedures . Well, more correctly it wasn't when i retired twelve years ago.

 

[jim hardy]

Hmmmm they're working on it.
http://www.gpo.gov/fdsys/pkg/FR-2012-03-20/pdf/2012-6665.pdf

golly I'm out of date ! It even mentions coronal mass ejection...

 

[Hiddencamper]

We can start our DGs once without control power. I actually simulated the emergency start procedure today for one of my license qualifications. But we are just one plant. Manually open the air start solenoids, while you have a guy standing by the generator breaker and service water breaker to close them in and at least pick up the bus. Let the mechanical governor hold the engine rpm until you can bring the battery charger on service.

Obviously it's a very complicated procedure. If 9/11 and Fukushima brought anything good, it's the fact that we actually have this procedure and others like it, and we train on it.

 

[jim hardy]

Manually open the air start solenoids,

Now THAT's interesting.

I wonder if they've added such a bypass at my prior plant.

Our diesels were air cooled by huge radiators and the fans driven mechanically by engine shaft so they needed no service water
had hours of fuel available by gravity feed day tank
the air start reservoirs were sized for five start attempts
the starting air electric compressors could run from either bus
and we had a small one cylinder diesel compressor to recharge the start reservoirs if things ever got that bad...
...but we needed battery.

How'd you flash your field? Pilot exciter?

 

[Hiddencamper]

Engineering evaluated it and then we later did a test on a generator to show it works. There is enough residual magnetic field for one flash. It's not pretty but it can be done.

 

[nikkkom]

On a separate note, the Us industry does not assume total DC control power failure for any scenario, including the new Fukushima based scenarios or for the AP1000. I think this is a significant gap

I suppose I should feel happy. Only 3 years past Fukushima and some in US nuclear industry start to think they need to be prepared for SBO.

I guess only short 20 years to wait more and US plants will actually have procedures in place to survive SBO. Just about time when most of them will be closing down.

(angry unproductive rant mode off)

 

[jim hardy]

Is effort better spent on preventing it?

Either way, one is preparing for "what if's".
Those "what if's" are assigned likelihoods by something called "Probabilistic Risk Assessment" (PRA) and dealt with in their order of probability. Those below some threshold are ignored.

So the key is a good and honest set of PRA "What If" risk assessments.
When those 900 year ago tidal waves in the region were discovered the PRA didn't get adjusted for them.
Those basements housing diesels and switchgear should have got wrapped in something like a submarine hull, or moved up the hill.
But they didn't.

If you want to make something a certainty just publicly declare it an impossibility.
I guess that's a strength of PRA, nothing is considered impossible .

When PRA was first getting started some wag at our plant wrote a procedure for "loss of gravity" and submitted an engineering request for springs to push the rods into the core, and seatbelts for operators. We all enjoyed a good laugh...
He was an ex -submariner. Submarines can turn upside down... so their "loss of gravity" weighting in PRA reflects that fact.

Point being - with the plants we have that are designed around the concept of emergency power being available, i'll choose even a pound of prevention over the unforseen consequences of a necessarily piecemeal redesign.
After all - we only need twenty more years out of them.

old jim

 

[jim hardy]

A step forward in passive system thinking..
especially the middle video

http://nuclearstreet.com/nuclear_po...n-the-ap1000-reactor-081302.aspx#.U-uaFWdASih

 

[etudiant]

DC power was also an imperative for the Bell phone system, so they used large, custom designed round lead acid batteries. These gave very long and very reliable service. I'm surprised the Bell know how has not diffused into the nuclear industry.

 

[Rive]

DC power was also an imperative for the Bell phone system, so they used large, custom designed round lead acid batteries. These gave very long and very reliable service. I'm surprised the Bell know how has not diffused into the nuclear industry.

It's not about the knowledge needed for building such batteries but about the knowledge that those batteries should be built.

 

[jim hardy]

We had four of them each somewhat larger than this:

larger image here:
http://assets.safetyfirst.nei.org.s3.amazonaws.com/wordpress/wp-content/uploads/2011/11/IndianPointBatteryPower.jpg

 

[mheslep]

We had four of them each somewhat larger than this:

larger image here:
http://assets.safetyfirst.nei.org.s3.amazonaws.com/wordpress/wp-content/uploads/2011/11/IndianPointBatteryPower.jpg

Would love to drop a crow bar across those battery terminals.

 

[Astronuc]

I suppose I should feel happy. Only 3 years past Fukushima and some in US nuclear industry start to think they need to be prepared for SBO.

I guess only short 20 years to wait more and US plants will actually have procedures in place to survive SBO. Just about time when most of them will be closing down.

(angry unproductive rant mode off)

The US nuclear industry has been thinking about station blackout (SBO) for decades.

Reevaluation of Station Blackout Risk at Nuclear Power Plants (NUREG/CR-6890) - 2005
Note: Vol. 1, Analysis of Loss of Offsite Power Events: 1986-2004 (PDF - 10.97 MB)
◦Vol. 2, Analysis of Station Blackout Risk (PDF - 5.93 MB)
◦Vol. 3, Resolution of Comments (PDF - 3.87 MB)

http://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr6890/

This report is an update of previous reports analyzing loss of offsite power (LOOP) events and the associated station blackout (SBO) core damage risk at U.S. commercial nuclear power plants. LOOP data for 1986–2004 were collected and analyzed. Frequency and duration estimates for critical and shutdown operations were generated for four categories of LOOPs: plant centered, switchyard centered, grid related, and weather related. Overall, LOOP frequencies during critical operation have decreased significantly in recent years, while LOOP durations have increased. Various additional topics of interest are also addressed, including comparisons with results from other studies, seasonal impacts on LOOP frequencies, and consequential LOOPs. Finally, additional engineering analyses of the LOOP data were performed. To obtain SBO results, updated LOOP frequencies and offsite power nonrecovery curves were input into standardized plant analysis risk (SPAR) models covering the 103 operating commercial nuclear power plants. Core damage frequency results indicating contributions from SBO and other LOOP-initiated scenarios are presented for each of the 103 plants, along with plant class and industry averages. In addition, a comprehensive review of emergency diesel generator performance was performed to obtain current estimates for the SPAR models. Overall, SPAR results indicate that core damage frequencies for LOOP and SBO are lower than previous estimates. Improvements in emergency diesel generator performance contribute to this risk reduction.

And we reassess when some major event occurs.

I remember covering LOOPs about 30+ years ago, and it was not a new concept then, but something that had been around since at least the 60s.

http://nrcoe.inel.gov/resultsdb/LOSP/

Loss Of Offsite Power
It is recognized that the availability of ac power to commercial nuclear power plants is essential for safe operations and accident recovery. A loss of offsite power (LOOP) event, therefore, is considered an important contributor to total risk at nuclear power plants. In 1988, the NRC published NUREG-1032 to report on an evaluation of the risk from actual LOSP events that had occurred at nuclear power plants within the United States up through 1985. NUREG/CR-5496 documents a similar study whose primary objective was to update the LOOP model parameters, frequency, and recovery time, using plant event data from 1980 - 1996. An additional objective was to re-examine the engineering insights concerning LOSP events.

http://www.nei.org/Master-Document-...gh-the-Decades-History-of-US-Nuclear-Energy-F (only back through 1992)Clearly there were a number of deficiencies at the Fukushima Daiichi site. It should have been clear that the region was at risk of a 30 m tsunami or so - because it had happened before. On the other hand, much of the coastline north and south was not protected against such a tsunami.

http://en.wikipedia.org/wiki/1964_Alaska_earthquake
http://wcatwc.arh.noaa.gov/about/64quake.htm

Leaving the diesel generators and oil storage tanks so vulnerable is to me mind boggling.

Leaving the switch gear in a vulnerable location is also mind boggling.

Ignoring studies that indicated the need to identify such vulnerabilities is unconscionable.

 

[jim hardy]

Would love to drop a crow bar across those battery terminals.

Somebody at another plant got an aluminum ladder across their battery... once a DC arc is started it's hard to extinguish. Made a real mess of that battery room.

We didn't allow aluminum ladders on the property.

But it would be exciting from a safe distance.

 

[LabratSR]

They appear to finally be moving forward with the long talked about Muon Detectors


Cosmic rays to pinpoint Fukushima cores

http://www.world-nuclear-news.org/RS-Cosmic-rays-to-pinpoint-Fukushima-cores-1108144.html

 

[Sotan]

They appear to finally be moving forward with the long talked about Muon Detectors


Cosmic rays to pinpoint Fukushima cores

http://www.world-nuclear-news.org/RS-Cosmic-rays-to-pinpoint-Fukushima-cores-1108144.html

This short article from the IRID site also relates to this subject. It reports about a test carried out in order to establish the shield thickness needed to isolate the muon measuring devices from the influence of the gamma radiation present at the site.

 

[Sotan]

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201408280043

Asahi Shinbun article with a quick update and some numbers related to the contaminated water issue.

"As of Aug. 26, 367,000 tons of highly contaminated water sat in tanks placed inside plant grounds awaiting treatment."

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140901_04-j.pdf
(In Japanese)

On Aug. 29, during the remote-controlled operations of removing debris from the Spent Fuel Pool of Reactor 3, a ~570 kg piece of debris (the operating console of the Fuel Handling Machine and part of its platform) fell into the Spent Fuel Pool.

Using underwater cameras it was found that the fallen item is now standing above the other debris, mostly supported by a spent fuel rack and it is assumed that about 10 fuel assemblies are directly underneath. It was not possible to examine the assemblies themselves directly due to the large amounts of debris present in the area. Still, they seem inclined to believe that the assemblies are fine, as no changes in monitored parameters have been observed and the racks are designed to withstand 750kg of weight. They will continue to monitor the area and investigate the cause of the incident.

 

[LabratSR]

Ex-Skf has video of them dropping the console

http://ex-skf.blogspot.com/2014/09/fukushima-i-npp-reactor-3-sfp-debris.html

 

[zapperzero]

I did NOT expect it to look exactly like those carnival machines with the stuffed toys inside.

 

[Hiddencamper]

Unlike the carnival machine, these ones are designed to not drop stuff.

The grapple is sets of J hooks that interlock with each other when they are in the grapple position. Once they pull up on the fuel bundle, the bail handle on the bundle itself physically prevents the grapple from opening (passively safe) because to open up would require shearing through the bail handle.

As you begin to lift the crane, there is a weight gauge which can determine if fuel is loaded. If it is, then the control rods are all locked out and cannot move (if they aren't all in then the crane will lock out). If the reactor mode switch is not in REFUEL, then if it senses a fuel bundle on the handle it locks the crane out to prevent a core alteration while the control room is not prepared for monitoring the core during refuel ops.

There are also smaller auxiliary crane for lifting control rods, dry tubes, fuel/top guide support pieces, and other in core objects. These all lock out if they sense the weight of a fuel rod on them to prevent the aux hoist from lifting one up on accident.

 

[nikkkom]

The video isn't showing a standard refueling crane, it shows something like construction/demolition equipment (a big grapple, it seems) currently in use at Unit 3 for debris cleanup.

 

[Sotan]

http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0026_03.pdf
The link above leads to a short document in Japanese, dated Aug. 18, presented in a NRA (Japanese Nuclear Regulation Authority) meeting, which contains some considerations regarding the need for defense measures against the potential damaging effects of external phenomena such as earthquakes and tsunamis on the crippled facilities in Fukushima Daiichi plant.

But the fragment I want to post here is actually something else: a quick list of objectives and the terms for their accomplishment. Recently I at least felt a bit lost when it comes to "what exactly are they doing now and what are the plans and the deadlines"; this list reminded me of how slow the work will proceed.

Short term objectives: achievable in 1-2 years:
- removing the spent fuel assemblies from the SFP of Reactor 4 (by the end of 2014);
- removing the spent fuel assemblies from the SFP of Reactor 3 (from mid fiscal 2015, meaning ~September 2015, to last for about a year);
- cleaning the RO concentrated salty water stored in tanks on site, by means of decontamination facilities such as ALPS (until March 2015);
- removal of contaminated water from the trench on the sea side (until or perhaps before winter of 2014);
Medium term objectives (to be achieved in 3-5 years):
- removal of the spent fuel assemblies from the SFP of Reactor 1 (to start in April 2017 and take about a year);
- removal of the spent fuel assemblies from the SFP of Reactor 2 (planned to start around April 2019);
Long term objectives (to be accomplished later than 5 years from now):
- removal of the contaminated water stored in the reactor buildings and turbine buildings (will take 7 years after the establishment of the frozen soil wall);
- removing the molten fuel debris (planned to start sometime in 2020).

 

[jadair1]

http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0026_03.pdf
The link above leads to a short document in Japanese, dated Aug. 18, presented in a NRA (Japanese Nuclear Regulation Authority) meeting, which contains some considerations regarding the need for defense measures against the potential damaging effects of external phenomena such as earthquakes and tsunamis on the crippled facilities in Fukushima Daiichi plant.

But the fragment I want to post here is actually something else: a quick list of objectives and the terms for their accomplishment. Recently I at least felt a bit lost when it comes to "what exactly are they doing now and what are the plans and the deadlines"; this list reminded me of how slow the work will proceed.

Short term objectives: achievable in 1-2 years:
- removing the spent fuel assemblies from the SFP of Reactor 4 (by the end of 2014);
- removing the spent fuel assemblies from the SFP of Reactor 3 (from mid fiscal 2015, meaning ~September 2015, to last for about a year);
- cleaning the RO concentrated salty water stored in tanks on site, by means of decontamination facilities such as ALPS (until March 2015);
- removal of contaminated water from the trench on the sea side (until or perhaps before winter of 2014);
Medium term objectives (to be achieved in 3-5 years):
- removal of the spent fuel assemblies from the SFP of Reactor 1 (to start in April 2017 and take about a year);
- removal of the spent fuel assemblies from the SFP of Reactor 2 (planned to start around April 2019);
Long term objectives (to be accomplished later than 5 years from now):
- removal of the contaminated water stored in the reactor buildings and turbine buildings (will take 7 years after the establishment of the frozen soil wall);
- removing the molten fuel debris (planned to start sometime in 2020).

I would be extremely surprised if they met any of those objectives in the time frame they outline.

Indeed, I do not think they are even working on, or have any idea how to achieve some of them.

I firmly believe that everything TEPCO says should be taken with a huge grain of salt!