Saturday Morning Videos: Interstellar Journeys, Reality vs. Hollywood

Freeman Dyson (podcast) vs Matthew McConaughey (trailers)   -see also the reference entries featured on Nuit Blanche on the technical aspects of going fast in space -


Related references:

• Catch my gamma rays if you can
• The Technical Side of the Nuclear Rockets Option
• The "Don't even think about it, kid" Lever
• The high stakes of Curiosity's Entry, Descent, and Landing (EDL)
• The Cost of Success or Failure versus Complexity in Space Voyages

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The Fukushima Inverse Problem - implementation -

The following paper asks an interesting question and puts sparsity/positivity promoting algorithms in a positive light. Instead of using Least Squares for overcomplete systems, one can use a different inversion based on LASSO that provides something useful. The field of atmospheric science being so empirical, one always wonder if something interesting can be gotten out of forward simulation models. And indeed as they say in the paper, the difference between sensor readings and computer models could provide some sorts of correlation but, sometines,  " the variability is considerable—often orders of magnitude." It turns out that if the current result of the paper holds, there is an interesting question at the end of this paper that should have a bearing on the current imaging of the deteriorated cores (see Imaging Damaged Reactors and Volcanoes ). But first, here is the paper, go read it, I'll read it :The Fukushima Inverse Problem by Marta Martinez-Camara, Ivan Dokmanic, Juri Ranieri, Robin Scheibler and Martin Vetterli, Andreas Stohl

Knowing what amount of radioactive material was released from Fukushima in March 2011 is crucial to understand the scope of the consequences. Moreover, it could be used in forward simulations to obtain accurate maps of deposition. But these data are often not publicly available, or are of questionable quality. We propose to estimate the emission waveforms by solving an inverse problem. Previous approaches rely on a detailed expert guess of how the releases appeared, and they produce a solution strongly biased by this guess. If we plant a nonexistent peak in the guess, the solution also exhibits a nonexistent peak. We propose a method based on sparse regularization that solves the Fukushima inverse problem blindly. Together with the atmospheric dispersion models and worldwide radioactivity measurements our method correctly reconstructs the times of major events during the accident, and gives plausible estimates of the released quantities of Xenon.

The attendant code is here, it features the transport matrix A and the cleaning code. The code uses CVX. I find it fascinating that one needs to enforce the positivity of the solutions. I wonder if by using the Xe and the Cs data there would not be a way to figure out where out of the three or four potential sources, the ones that emitted shortly after the earthquake.
Relevant links:

• Sunday Morning Insight: Enabling the "Verify" in "Trust but Verify" thanks to Compressive Sensing
• Sunday Morning Insight: Muon Tomography as a Moore's Law Enabled Technology
• Imaging Damaged Reactors and Volcanoes
• Deconvoluting a Radiation Field using a Webcam and Robust PCA
• It never was noise; Just a different convolution
• Robust Denoise This!
• An Interesting Inverse Problem
• Where Are The Clouds ?

Join the CompressiveSensing subreddit or the Google+ Community and post there !
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The Technical Side of the Nuclear Rockets Option

from xkcd, Gravity wells

So there is a petition on the White House site for a Nuclear Rocket initiative. No big news as this comes back and forth every once in while. Such a technical solution was considered as recently as JIMO/Prometheus. One wonders if it will be in consideration for a Mars mission with humans given the large size of hydrogen tank needed. The staggering numbers are in part due a combination of the low efficiency of chemical rockets and the need for better space plumbing. 

Of great importance and a subject I never see really mentioned anywhere: after six months in space, humans are really incapable of doing anything under gravity for a little while. It's one thing to land on Mars, it will be another before they can leave their seats. For that reason only and if one is serious about landing people on Mars and unless we find a pill to get space travelers to not deteriorate too much, getting there faster is really the only way. Hence the nuclear rocket option.

A nuclear rocket is singularly different from other kind of space nuclear projects that are (were)   currently in use

• The Soviets flew in low Earth Orbit more than 30 Rorsats that had nuclear reactors in them, The underlying reason for the need for much power was the relative unsophistication of the signal processing that could be done on-board. With no compression, one had to resort to larger power levels to send out all those signals. At the end of the cold war, the US sought to buy a different and advanced technology from the Russians (TOPAZ).
• There are simpler systems however. Most of the probes beyond Low Earth Orbit require power levels that cannot be provided by the Sun. Currently the rather large Curiosity rover is getting its energy from the decay of Plutonium-238 that heats up elements and produce electricity through the reverse of the Peltier effect.

Nuclear Rockets that have been tested in the past, and that I am aware of, fall in a different category altogether. They use a reactor core and the propellant as its coolant. That gas coolant climbs in temperature as it goes through the reactor and then exits from the core and eventually a rocket nozzle. Unlike a chemical rocket, the temperature of the hydrogen can go higher and therefore can raise substantially the ISP of said rocket. Back in the 1960s, such program was conducted and went through several prototypes. A very nice technical summary of that story can be found in this write-up: Application of Proven Rover/NERVA Nuclear Thermal Rocket Technology for NearFuture Manned Planetary Missions by Stanley Gunn and Ernest Robinson. The ISP of those rockets can be double that of any chemical rockets. The Achille's heel of these system is their scrubbing mechanism i.e. make sure none of the reactor core material is stripped from its location and sent outside through the nozzle system. 
For the technically inclined data is sparse so it of substantial interest to find the results of some of the tests of the XE-Prime engine which was probably the most advanced engine in the Technology Readiness Level ladder of that program. You can find some of the reports here (search for "XE-Prime" in DOE's database.) that feature some of the most technically advanced data I have seen on the subject.

from [1]

I note the following segment from the first reference:

"...Then, after the Kiwi TNT safety reactor test was conducted (to learn how destructive the reactor assembly would be if its control rods went wildly out of control) and the reactor assembly was self-destructed, the Los Alamos NRDS Assistant Director, two of his associates, and again Rocketdyne's NTR  Section Chief were exposed to the after-test radiation surrounding the destroyed reactor assembly.  The measured environment radiation was approximately 10 rem. Fifty years have passed, and the health of the above-defined test programs participants (as determined  by the NTS Medical Surveillance Project Office's evaluation) remain unaffected by  radiation...."

Some videos of the tests can be found on Youtube:  

 h/t Various Consequences

[1]  XE-prime EP-4A startup tests. SPEAR report

Compressed Sensing for the multiplexing of PET detectors

Following up on yesterday's paper and one of the author that had already shown up my radar screen earlier this summer,  Craig Levin forwarded me their use of compressive sensing that quite simply could replace Anger Logic. This is big news.

Here is the paper: Compressed Sensing for the multiplexing of PET detectors by Peter Olcott , Garry Chinn and Craig Levin . The abstract reads:

Compressed sensing can be used to multiplex a large number of individual readout sensors to significantly reduce the number of readout channels in a large area PET block detector. The compressed sensing framework can be used to treat PET data acquisition as a sparse readout problem and achieve sub-Nyquist rate sampling, where the Nyquist rate is determined by the pixel pitch of the individual SiPM sensors. The sensing matrix is fabricated by using discrete elements or wires that uniquely connect pixels to readout channels. By analyzing the recorded magnitude on several ADC channels, the original pixel values can be recovered even though they have been scrambled through a sensing matrix. In a PET block detector design comprising 128 SiPM pixels arranged in a 16 x 8 array, compressed sensing can provide higher multiplexing ratios (128:16) than Anger logic (128:32) or Cross-strip readout (128:24) schemes while resolving multiple simultaneous hits. Unlike Anger and cross-strip multiplexing, compressed sensing can recover the positions and magnitudes of simultaneous, multiple pixel hits. Decoding multiple pixel hits can be used to improve the positioning of events in light-sharing designs, inter-crystal scatter events, or events that pile up in the detector. A Monte-carlo simulation of a compressed sensing multiplexed circuit design for a 16 x 8 array of SiPM pixels was done. Noise sources from the SiPM pixel (dark counts) and from the readout channel (thermal noise) were included in the simulation. Also, two different crystal designs were simulated, a 1x1 coupled design with 128 scintillation crystals, and a 3:2 light-sharing design with 196 crystals. With an input SNR of 37dB (experimentally measured from a single SiPM pixel), all crystals were clearly decoded by the compressed sensing multiplexing with a decoded SNR of the sum signal a 30:6 0:1 dB SNR for the one-to-one coupling, and 26:1 0:1 dB three-to-two coupling. For a 10% energy resolution, and SNR of greater than 20 dB is needed to accurately recover the energy.

This is a very nice paper. Let us note a few things. Their measurement matrix is very sparse and different from the ones we have heard about so far. I note also that in the extreme noiseless case, using the Donoho-Tanner phase transition, a 128x16 measurement matrix like the one implemented here , we therefore have N = 128, m = 16 or delta = 0.125 and using Jared Tanner's app, we can estimate the optimal number of simultaneous detectable events to be about 0.26*16 (Weak Simplex) or about 4. In the noisy case, we should expect a number lower than four. 

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Deconvoluting a Radiation Field using a Webcam and Robust PCA

Just as we used the videos provided by TEPCO on their website to figure out if a robust PCA could decompose the image field into a full image (the low rank component) and a sparse component that would pick up the radiation hits only, we were faced with another issue: water droplets. Those droplets would alternatively be part of the sparse component or the noisy component of the Robust PCA decomposition and therefore make it difficult for us to simply evaluate the radiation field based on this decomposition. Additional complex filtering would need to be performed. Yes, I know what you are about to say:

 "You poor little things, the endoscopic camera looking into one of the reactors at Fukushima did not allow for a simple demonstration of what Robust PCA can do" 

and you would be right. But our take is more along the lines of: the following: Next time some endoscopic camera is used into reactor 1, 2 or 3 at Fukushima, it ought to do certain things like wait a few seconds every once in a while and in a view free of flying droplets to get a easy sense of the radiation level at those locations.

But in order to provide a more compelling example and as part of Cable And Igor's adventures in the evaluation of Matrix Factorization for Images and Videos (CAI),  Cable and I went through some YouTube videos who could help us make that point clearer. And here we are presenting to you a video featuring the illumination of a webcam with a 230 MeV proton beam (it looks like this beam was used to calibrate an experiment that eventually flew on the Lunar Reconnaissance Orbiter -LRO-)

There is no movement in the video just a static scene with the random hit from the radiation with the webcam CMOS. Here is the Robust PCA decomposition:

We could not visually see much so we focused on using Matlab's imagesc instead of imshow for the sparse and noisy components and here what we have::

focusing only on the sparse component, I believe we nailed it:

 

As we have done in the previous examples, the Robust PCA was implemented using GoDec one of the recent Advanced Matrix Factorization solver.

You can find more about  Cable And Igor's adventures in the evaluation of Matrix Factorization for Images and Videos (CAI) at:   http://nuit-blanche.blogspot.com/search/label/CAI

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It never was noise; Just a different convolution

One of the difficulties working with video material is that suddenly everything gets bigger and computations go slower fast. This is the reason we had to crop the scene in the Fukushima endoscopic videos. The scene analyzed was essentially a cropped version of the next 12 seconds of the following video

(at one minute into the video)



That yielded this result :

Obviously, random projections as implemented in SpaRCS would be helpful. A compressive sensing of the dynamical scenes of this video might also give us a way to think of the type of important parameters a compressive sensing system were to use in this type of situation. One of the interesting feature of these shots is that the "noise" or blips observed on the focal plane array, are not unlike what one would see in a hyperspectral video a la CASSI where a third dimension (spectral information) is embedded in each 2D shot through a hardware based convolution. Here, the hardware based convolution is the interaction between the radiation field and the hardware instance of the focal plane array which result in these "noisy" or more exactly radiation modulated images.

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Robust Denoising Fukushima Endoscopic Videos

[ このビデオは東京電力によって公開された、福島第一原発の第5核融合炉の内部を映したものです。
我々は新しく考案したRobust PCA等を用いた新しいアルゴリズムを用いて、水滴や放射線等によるノイズを除去しました。

 http://nuclear.tamu.edu/~kurwitz/

The following videos were released by TEPCO. They show the inside of reactor 5 at Fukushima Daiichi. We processed these videos using new techniques such as Robust PCA to evaluate the algorithm's capabilities to separate background information from more dynamic information such as water droplets and radiation hits on the focal plane array. Thank you Julien, Yasuda-san and Tsuji-san for the translation.  ].

In Robust Denoise This! I wondered if there was a way to denoise the videos coming out of endoscopic visualization of the containment vessel of reactor 5 at Fukushima Daiichii. One of the impediment of videos being inserted in this area is clearly related to the radiation field and water droplets that render the video very noisy. We are here well outside the comfortable academic benchmarks used to figure out the quality of denoising algorithms. However, I am of the opinion that any of the Robust PCA or other advanced Matrix Factorization techniques can only be field tested with actual footages that have not been carefully prepared like these endoscopic shots. 

For this reason, Cable Kurwitz and I were thinking about what could be obtained from this sort of shots. Let us first realize that these endoscopic shots were performed on one of the least damaged reactor and so radiation issue for this survey would be more like what could be expected from a reactor that has gone through a  normal cold shutdown operation  

The GoDec solver was used for this preliminary trial. It performs a low rank decomposition added with a sparse and noisy component. We were wondering if the radiation field (mostly bleeps occurring at every frame at different locations) would be caught by the noisy component. By the way, they are not truly blips because the videos themselves seem to have been transform coded with MPEG: i.e every hit has become more like small crosses. We hypotethized that the droplets would mostly be in the sparse component so that the noisy component would provide a proxy for the radiation level seen by the endoscopic Focal Place Array. In other words, we could use the video also as radiation detector.. Here is the result so far from about 800 frames at 1 minutes into video 2:

Here is what we can see:

• The low rank component (1) is pretty nice and steady and seems to be able to catch different illuminations
• The noisy component (3) does indeed catch most of the the radiation hits but
• it also catches some of the droplet component (so the noisy component cannot be used right away as a proxy to the radiation level). 
• The sparse components (2) picks up most of the droplets 

Additional processing would need to be performed on the noisy component to catch only the radiation hit  component.





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An Interesting Inverse Problem

[ The folks at University of Washington know about this opportunity ]

In the fog of data coming out of the Fukushima plant and the numerous sensor networks (government, university and citizen centered), one faces the interesting inverse problem of figuring out the specific failure mechanism of each of the reactors depending on whether the plume goes over a specific sensor and location. Forward simulations at Texas A&M provides some clues to determine the where and what for a specific sample obtained in Seattle at University of Washington. Not only is the inverse problem about plume trajectory determination but it goes further and provides a clue on the actual failure of the nuclear system. Today, it looks we may have a chance of figuring out what's in Unit 3 with its attendant grey and black smokes.

Back in the days of nuclear testing, this sort of inverse problem was generally solved by nuclear States to watch out what type of devices others were implementing. Nowadays, this task is also taken up by entities such as the CTBT organization. However, in the case of accidents, this task can be taken up other entities.

Failure was not a option

 All my instruments are gone. My lights are gone. And I can't even tell now what my altitude is. I know I'm running out of fuel, so I'm thinking about ditching in the ocean. And I, I look down there, and then in the darkness there's this uh, there's this green trail. It's like a long carpet that's just laid out right beneath me. And it was the algae, right? It was that phosphorescent stuff that gets churned up in the wake of a big ship. And it was - it was - it was leading me home. You know? If my cockpit lights hadn't shorted out, there's no way 

So uh, you, uh, never know... what... what events are to transpire to get you home.

from here:

"...The Fukushima power plants were required by regulators to withstand a certain height of tsunami. At the Daiichi plant the design basis was 5.7 metres and at Daini this was 5.2 metres.

Tepco has now released tentative assessments of the scale of the tsunami putting it at over 10 metres at Daiichi and over 12 metres at Dainii.

The plant sites were inundated, causing the loss of residual heat removal systems at both sites as well as emergency diesel generators at Daiichi....."

Cooling Issues

We'll see how the explosion at Unit 2 is affecting the cooling of that unit. The fire at Unit 4 seems to also be connected to a cooling issue as well (remember these cores were shutdown before the earthquake but they and their attendant spent fuel pools still need to be cooled) which basically means that we ought to hear about cooling issues in Unit 5 and 6 as well. Of concern is that the removal of non-essential personnel from the site allows for potential mishandling.

Water is being poured again in Unit 2 !

from here. I get all these infos from wikipedia and so you can too!

What is the condition of the crew at Fukushima Unit 2?

At some point in time, we will need to understand how people can discard basic thermodynamic concepts. In the latest on Unit 2, this caught my attention:

Air pressure inside the reactor rose suddenly when the air flow gauge was accidentally turned off, operator TEPCO said, adding that this blocked the flow of cooling water into the reactor, leading to full exposure of the rods.

Maybe they're tired and need some sleep. (from here)

TEPCO's charts. Still No Japanese Nuclear Armageddon Today (part III)

[ Update: Updated charts can be found here.As expected they are about to put sea water in unit 2 ]

At long last, here is some informative piece from TEPCO (via Barry's blog).

As one of Barry's commenter noted this chart is outdated as the RCIC system has failed today, that leaves them with the option of getting sea water if the decay heat is still an issue. Looks like they will be relieving pressure like they did for unit 1 and 3. 

The Sum of All Click-Throughs: An 8.9 Earthquake, a Tsunami and an Explosion at a Nuclear Power Plant

Do you think this headline is optimized for click-throughs ?

With this type of headlines how can you not think that 9500 people are casualties of a nuclear accident ?

Contrast this with the post I would have loved to write: Why I am not worried about Japan’s nuclear reactors

Fukushima Daiichi, Situations at Unit 1, 2 and 3.

From TEPCO's latest press release:

Fukushima Daiichi Nuclear Power Station:

Units 1 to 3: shutdown due to earthquake

Units 4 to 6: outage due to regular inspection

* The national government has instructed evacuation for those local residents within 20km radius of the site periphery.

* The value of radioactive material (iodine, etc) is increasing according to the monitoring car at the site (outside).

* Since the amount of radiation at the boundary of the site exceeds the limits, we decide at 4:17PM, Mar 12 and we have reported and/or noticed the government agencies concerned to apply the clause 1 of the Article 15 of the Radiation Disaster Measure at 5PM, Mar 12. After that, the radiation dose at the monitoring post decreased once. Today, the measured value revamped and the radiation dose measured at site boundary exceeded the limiting value again. As such, at 8:56AM, today, it was determined that a specific incident stipulated in article 15, clause 1 occurred and at 09:10AM, today, notified accordingly.

* In addition, a vertical earthquake hit the site and big explosion has happened near the Unit 1 and smoke breaks out around 3:36PM, Mar 12th.

* Unit 1: We started injection of sea water into the reactor core at 8:20PM, Mar 12 and then boric acid subsequently.

* Unit 2: Reactor has been shut down and Reactor Core Isolation Cooling System has been injecting water to the reactor. Current reactor water level is lower than normal level, but the water level is steady. After fully securing safety, we are preparing to implement a measure to reduce the pressure of the reactor containment vessels under the instruction of the national government.

* Unit 3: High Pressure Coolant Injection System automatically stopped. We endeavored to restart the Reactor Core Isolation Cooling System but failed. Also, we could not confirm the water inflow of Emergency Core Cooling System. As such, we decided at 5.10AM, Mar 12, and we reported and/or noticed the government agencies concerned to apply the clause 1 of the Article 15 of the Radiation Disaster Measure at 5:58AM, Mar 13. In order to fully secure safety, we operated the vent valve to reduce the pressure of the reactor containment vessels (partial release of air containing radioactive materials) and completed the procedure at 8:41AM, Mar 13 (successfully completed at 09:20AM, Mar 13). After that, we began injecting water containing boric acid that absorbs neutron into the reactor by the fire pump from 09:25AM, Mar 13.

* We continue endeavoring to secure the safety that all we can do and monitoring the periphery.

Looking back at the previous press release, they now talk about the failure of one of the cooling systems (unit 3). The borated water quenches any chain reaction so that this water cools the decay heat from the reactor and also stops any potential chain reaction from occurring. Here are some guesses from some folks working in nuclear power plants on what happened for the explosion on top of unit 1 yesterday (i.e. hydrogen or pressure explosion), again those are just guesses.  But as far as I can tell there is no way anybody can say anything about the inside conditions of any of the three cores. In particular, the wording Partial Meltdown seems to be overly used in the media when in fact the fuel rods may have been just damaged. It is indeed a serious situation but there is no need to be hysterical about it mostly because of the containment around the vessel that houses the reactor core. By the way, they seem to have used pure water not sea water in unit 3 showing to me that they seem to very much control that aspect of the process.

When this is over, I'll be buying the book on how the operators went about sustaining a 8.9 earthquake and a tsunami.

Still No Japanese Nuclear Armageddon Today (part II)

The new TEPCO press release provides additional insight into the current situation. Out of all the power plants, one that seems to be the most problematic is unit 1.

All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.
Unit 1(Shut down)
- Reactor has been shut down. However, the unit is under inspection due to  the explosive sound and white smoke that was confirmed after the big quake occurred at 3:36PM.
- We have been injecting sea water and boric acid which absorbs neutron into the reactor core. 

Other sources seem to confirm that the reactor containment vessel has not been breached which allows the second step highlighted above: i.e. flood the containment with water to continue the cooldown of  the decay heat. The use of borated water is unusual in that boron is never used in Boiling Water Reactor's (BWR, looks like a GE design) coolant.  Boron is a neutron poison that stops any chain reactions very quickly as it has a very large cross section for thermal neutrons (the particles enabling chain reactions).. Some of that boron may come from a US source. I am guessing that they want to be on the safe side besides cooling the reactor core. That also means that this reactor will be out of business for a long while. One can also read about the two other units:

Unit 2(Shut down)

- Reactor and Reactor Core Isolation Cooling System have been shut down.

Current reactor water level is lower than normal level, but the water level is steady. After fully securing safety, we are preparing to implement a measure to reduce the pressure of the reactor containment vessels under the instruction of the national government.

Unit 3(Shut down)

- Reactor has been shut down and we continue injecting water by High Pressure Core Injection System. After fully securing safety, we are preparing to implement a measure to reduce the pressure of the reactor containment vessels under the instruction of the national government.

- Currently, we do not believe there is any reactor coolant leakage inside the reactor containment vessel.

If I read this correctly, the current main concerns are therefore for units 1 and 2 with unit 1 being the most concerning. From their description, it looks like they have the means of cooling these units. 

Still No Japanese Nuclear Armageddon Today

According to the BBC, the Japanese Nuclear Regulatory Agency has rated this accident as a level 4 on the IAEA INES scale and seems to mention that the containment has not been breached which is consistent with the previous interpretation of TEPCO's press release. Let me be specific, this containment is one of the key difference between a Chernobyl type of reactor and the light water reactors being used in Japan.

If this is a level 4 accident, then a similar incident occurred in France at the nuclear power plant in Saint Laurent des Eaux in 1980 as a cooling incident led to the melting of one channel of fuel in the reactor. There was no release outside the site. The fuel rods were eventually removed. Nobody was hurt. If things have been done properly, I would not be surprised if this accident at Fukushima is eventually de-rated when we discover the real physical interior of the core. By the way, that French power plant is was still producing power to the electric grid for 23 years after this accident.

There is no Japanese Nuclear Armagedon today.

More technical information from can be found here.

No Japanese Nuclear Armageddon Today

I am a Nuclear Engineer by trade and I am not sure I see a reasonable coverage of the current situation going on in Japan. For instance this type of reporting is bad (I mean come on, using Ukrainian "specialists" as experts and compare the Japanese plants to the RBMK reactors in Chernobyl is just unconsciounable.). I am not working for TEPCO or any of its affiliates or any nuclear related entities but here is my take and explanation of their latest press release:

Press Release (Mar 12,2011)
Impact to TEPCO's Facilities due to Miyagiken-Oki Earthquake (as of 3PM)


Below is major impact to TEPCO's facilities due to the Miyagiken-Oki Earthquake that occurred yesterday at 2:46PM.

*new items are underlined

[Nuclear Power Station]
Fukushima Daiichi Nuclear Power Station:
Units 1 to 3: shutdown due to earthquake
Units 4 to 6: outage due to regular inspection

Good only three power plants to pay attention to.

* The national government has instructed evacuation for those local residents within 10km radius of the periphery.

I am guessing this is a conservative move by the authorities. Nothing more.

* Measurement of radioactive material (Iodine, etc.) by monitoring car indicates increasing value compared to normal level. One of the monitoring posts is also indicating higher than normal level. We will continue monitoring discharge of radioactive material from exhaust stack and discharge canal, etc.

Higher than normal does not mean it is unsafe in one post. In particular, I am guessing the language would be different if the levels were above "safe" levels ( by safe I mean as set by national standards, i.e. it does not mean that one gets sick, but that's a different story). Now let's get to the meat of the press release:

* Reactor of Unit 1 has been shut down and steam in reactor has been cooled by isolation condenser, but it is now stopped. Because pressure level in reactor containment vessel is increasing, following the national government instruction, we have done the measure to reduce the pressure of the reactor containment vessels in order to fully secure safety and we understand that we have succeeded it at 2:30PM.
At present, reactor water level is becoming lower and we are injecting water accordingly.
* Reactor of Unit 2 has been shut down and we continue injecting water by Reactor Core Isolation Cooling System. Current reactor water level is lower than normal level, but the water level is steady. Following the national government instruction, we are preparing to implement a measure to reduce the pressure of the reactor containment vessels in order to fully secure safety.
* Reactor of Unit 3 has been shut down and we continue injecting water by Reactor Core Isolation Cooling System. Following the national government instruction, we are preparing to implement a measure to reduce the pressure of the reactor containment vessels in order to fully secure safety.

The main problem with shutting down a reactor is generally not in shutting down the neutron population (criticality issues) in the core but rather after that has been done, it is to remove the remaining heat produced by the decaying reactor core. The heat produced by the core is large but it is decaying. All safety systems in a reactor plant are designed to address specifically that issue. What is said above is that the three cooling systems are in play to remove that decay heat. What this also says is that the control rods have done their jobs and now we have a cooling issue only. The issue to pay attention to is whether the cooling systems would fail. I don't see any of that in the press release.  Over time, this issue is slowly going away as the reactor decay heat decreases.

* We are implementing a measure to reduce the pressure of the reactor containment vessels, but, one of our employees working in the Unit 1 was irradiated at over 100mSv level(106.3mSv). He received a medical treatment by a special physician.

The high pressure is just a side effect of that large amount of heat released in the containment section of the core. With regards to the employee receiving 106mSv, that's 10.6 rem, he has received less than 50 times  the annual dose of a radiation worker. See here in the Health Physics Society website:

The most recent report (November 1999) indicates that the average annual measurable dose to a radiation worker at a commercial nuclear power plant in 1998 was 180 millirem.

That dose is also twice the legal limit for a year as defined by the U.S. Nuclear Regulatory Commission:

Dose Limits for Radiation Workers

Title 10, Part 20, of the Code of Federal Regulations (10 CFR Part 20), "Standards for Protection Against Radiation," establishes the dose limits for radiation workers. Although the limits vary, depending on the affected part of the body, the annual total effective dose equivalent (TEDE) for the whole body is 5,000 mrem (5 rem).

So it looks like he is going on some extended paid vacation by TEPCO as a result but tit is very likely not lethal  Let us go back to the press release:

Fukushima Daini Nuclear Power Station:

Units 1 to 4: shutdown due to earthquake

* The national government has instructed evacuation for those local residents within 3km radius of the periphery and indoor standby for those local residents between 3km and 10km radius of the periphery.

same as before. Authorities are being conservative.

* At present, we have decided to prepare implementing measures to reduce the pressure of the reactor containment vessel (partial discharge of air containing radioactive materials) in order to fully secure safety. These measures are considered to be implemented in Units 1, 2 and 3 and accordingly, we have reported and/or noticed the government agencies concerned.

* Unit 3 has been stopped and being "nuclear reactor cooling hot stop" at 12:15PM.

Out three units, one has its decaying heat been removed. The two other plants continue the process of removing the decaying heat from the core.

Kashiwazaki Kariwa Nuclear Power Station:
Units 1, 5, 6, 7: normal operation
Units 2 to 4: outage due to regular inspection

Good news.

[Thermal Power Station]
Hirono Thermal Power Station Units 2 and 4: shutdown due to earthquake
Hitachinaka Thermal Power Station Unit 1: shutdown due to earthquake
Kashima Thermal Power Station Units 2, 3, 5, 6: shutdown due to earthquake
Ohi Thermal Power Station Units 2, 3: shutdown due to earthquake
Higashi-Ohgishima Thermal Power Station Unit 1: shutdown due to earthquake

If anything this is not good with regards to providing some electrical baseload to the national grid.

[Hydro Power Station]
4 stations in Fukushima Prefecture were shutdown due to earthquake.
Power stations in Yamanashi Prefecture have been restored.

[Transmission System, etc.]
5 substations shown below have been shutdown:
- Naka Substation
- Shin Motegi Substation
- Joban Substation
- Ibaraki Substation
- Nishi Mito Substation

[Blackout in TEPCO's Service Area]
Total of about 0.6 million households are out of power.
Tokyo: 0
Kanagawa Pref.: 0
Tochigi Pref.: 30,389
Chiba Pref.: 36,456
Saitama Pref: 0
Gunma Pref.: 0
Ibaraki Pref: 537,288
Yamanashi Pref: 0
Shizuoka Pref: 0 (east of Fuji River)

[Supply and Demand Status within TEPCO's Service Area to Secure Stable
Power Supply]
Backup supply from Shinshinano Conversion Station: 600MW
Backup supply from Sakuma Conversion Station: 300MW
Backup supply from Higashi Shimizu Conversion Station: 100MW

Because TEPCO's facilities have been seriously damaged, power shortage may occur. TEPCO appreciates customers' cooperation in reducing electricity usage by avoiding using unnecessary lighting and electrical equipment.

With all the thermal power stations off-line, no wonder they are asking people to curb their use of electricity.

We are taking all measures to restore power, however, we expect extremely difficult situation in power supply for tomorrow as well. We kindly ask our customers to cooperate with us in reducing usage of power.

Please do NOT touch cut-off electric wires.

Words of wisdom!

No Comment (Part II)

(From here)

When Modeling Reality Is Not An Option (The Robust Mathematical Modeling Blog)

Some of you know this but others may not. I sometimes blog about robust mathematical modeling (when modeling reality is not an option is the motto). The reason I say this is because I just wrote an entry there about a workshop I attended last week on issues related to modeling and its pitfalls. One of the issue discussed (the MOX talk) used to be an issue we struggled with in the Excess-Weapons Plutonium disposition program back in the late nineties.  The entry  SCM Talks: Electricity Production Management and the MOX Computational Chain features the fascinating problematic of planning electricity production for France and the computational difficulties stemming from performing experiments and computational calibration exercises outside the real region of operation of a nuclear reactor.