Subject: Fukushima Update 7-7-11 - Impact on Nuclear by Fukushima

See Last Story First!

From: Chris in Delaware

Date: Thu, 7 Jul 2011 12:32:33 -0400

Fukushima Update with Commentary

Nitrogen injection could be delayed at Fukushima

http://www3.nhk.or.jp/daily/english/07_18.html

The operator of the troubled Fukushima Daiichi power plant is having trouble injecting nitrogen gas into one of the reactors to prevent a hydrogen explosion.

Tokyo Electric Power Company on Wednesday examined the No.3 reactor to see if it can connect injection pipes to the containment vessel.

A camera-mounted robot was used for the operation because high radioactive levels are preventing workers from remaining in the reactor building for long periods.

But TEPCO failed to confirm the situation because the robot couldn't reach the necessary part of the reactor.

Radiation levels as high as about 50 millisieverts per hour were registered in the area.

The reading means a worker would be exposed to radiation on par with the government-set 250-millisievert safety limit in 5 hours.

TEPCO is now considering sending personnel or a robot into the reactor building to conduct another survey. The new survey would happen on Friday at the earliest.

There is a growing likelihood that the planned nitrogen injection will be delayed.

Thursday, July 07, 2011 12:58 +0900 (JST)

Commentary:

It is extremely important that Unit 3 is inerted with nitrogen to prevent another hydrogen explosion. The damage, temperature, humidity, and radiation fields are thwarting all attempts to get the nitrogen equipment hooked up to a suitable injection location deep within the bowels of the Reactor Building directly surrounding the Containment.

I also believe that the readings of 50 millisieverts per hour is too low. Fuel elements, either from the Spent Fuel Pool or the Reactor Vessel is much HOTTER than that. Electronic Equipment IS malfunctioning due to high radiation against which they are not protected.

Please see the following Article from the MOST Respected electrical and electronics organization, the IEEE about Radiation's effects on micro-processors

I do not know if this is the cause of the T-Hawk UAV crash onto Unit 2 Reactor Building on June 23.

Radiation Hardening 101: How To Protect Nuclear Reactor Electronics

http://spectrum.ieee.org/tech-talk/semiconductors/design/radiationhardening-101

Radiation Hardening 101: How To Protect Nuclear Reactor Electronics

POSTED BY: The IEEE Spectrum editorial staff / Tue, March 22, 2011

Tucked behind shielding, most of the electronics in a working nuclear reactor are no more exposed to radiation than the humans that operate them. Problems like the loss of coolant in Japan’s damaged Fukushima reactors can change that, boosting radiation to levels that can threaten control systems and robots that might be sent in for repairs.

How do you protect or “harden” electronics to prevent radiation damage? And are the electronics at the Fukushima Dai-1 nuclear power plant tough enough? IEEE Spectrum Associate Editor Rachel Courtland asked Dan Fleetwood, an expert in radiation-resistant devices at Vanderbilt University in Nashville, Tennessee, to take us through the basics.

How does radiation pose a problem for electronics?

Radiation can ionize atoms and disrupt a semiconductor's crystal structure. For electronics that are very close to a reactor, neutrons will create physical damage to the semiconductor crystal. But most chips will fail first because of leakage that’s associated with the charging of insulators. In something like a metal-oxide-semiconductor device, for example, gamma rays and X-ray radiation will knock electrons off atoms in an insulator to create electron-hole pairs. The resulting trapped positive charges will shift the operating characteristics. Devices are designed to turn on and off at a well-defined point of operation, and if that operating voltage shifts, this can create difficulties.

How do you protect or “harden” electronics against radiation in a nuclear reactor?

It involves all aspects of design, process, and testing. At a power plant there are usually design criteria to keep the most basic operating and control electronics relatively simple and relatively robust so that you can have an event like a loss of coolant and maintain control of the plant.

There are special processing techniques that are used to make the insulators more resistant to the consequences of having electrons knocked out. There are ways to process insulators, for example, so that there are fewer defects, which reduces the number of sites where positive charges can be trapped, and there are ways to dope the regions between transistors to make devices more resistant to the effects of radiation.

Nuclear power plants may also have the most critical electronics shielded in enclosures made of lead or some other very dense material that can help protect them from radiation.

How good can radiation hardening get?

The annual, whole-body limit for radiation workers is usually set in the range of 20-50 millisieverts, or 2-5 rads. Most commercial electronics can survive radiation levels in silicon of at least 500 to 1000 rads. Some commercial devices can survive levels higher than that but you’re just never sure when it’s going to lose functionality unless detailed testing has been done in advance. The most radiation-hardened electronics can survive levels of radiation that are hundreds of thousands of times greater than what a human can survive, more than a million rads.

The higher the dose the less likely you will be able to find a commercial integrated circuit to handle it. Radiation-hardened electronics are typically anywhere from two to four generations behind commercial electronics in terms of their performance. It takes extra time to do the additional engineering.

Can a reactor’s electronics survive a meltdown?

Certainly in the 1960s [when the first Fukushima reactors were built], people were very aware of the risks due to radiation and there were choices of electronics that could be made that would increase the resistance to radiation by a lot.

Very basic control circuits can be made to withstand exceedingly high levels of radiation, but they’re very simple in terms of function. They’re not the kinds of electronics that you could use to run the entire plant. They would just be used to maintain the capability of being able at some point to turn cooling systems on or perform critical switching and control functions.

Is it possible that electronics in the damaged Fukushima reactors could be used to boot the cooling system back up?

That’s a question of how bad the damage is. My guess is the electronics are probably not the weak link there. The mechanical systems could be the weak link, just because of the physical damage that appears to have occurred as a result of the explosions that have been reported. It’s also possible that there could be some failures in the electronics that might recover with time. Not all the effects of radiation exposure are permanent.

TAGS: Japan // Japan NUCLEAR EMERGENCY // Nuclear emergency // earthquake // nuclear energy // nuclear power // radiation // radiation-hardened // tsunami

This excellent synopsis describes how Radiation adversely affects electronic chips.

This explains why Robotics are not successful in these conditions. . .

http://www.dailykos.com/comments/987847/42121057#c103?mode=alone;showrate=1%23c103

As for the new Japanese designed Quince robot that also just failed, inside the plant...Probably, the Quince robot has super-duper maximum radiation hardening; plus other task-related enhancements that have, evidently, made it more operationally challenging than the previous U.S. radiation hardened robot workhorses -- which may have been sidelined because they were not designed to perform the upcoming series of tasks under unknown conditions. Suffice to say, there are unique complexities and complications at Fukushima, which pose more monumental demands than robots have had to deal with in prior nuclear crises. (Oh, we know, robots have done all kinds of whiz-bang things in fantastically inhospitable environments. Now we'll see what they can do here.)

----------------------------------------------------------------------------------

Reactor cooling to be accelerated in August

http://www3.nhk.or.jp/daily/english/07_07.html

The operator of the Fukushima Daiichi nuclear plant says a new cooling system is now working well so it will accelerate the cooling of the plant's reactors in August.

The system, which recycles decontaminated radioactive wastewater, suffered a series of problems at its launch in late June.

But Tokyo Electric Power Company says it has been working almost as planned since the start of this month.

The utility says that with radioactive water still leaking from 3 reactors, it had to limit the amount of wastewater used in the system. The leaks mean that the level of toxic water already accumulated is not decreasing.

The utility says if the water decontaminator keeps working properly, the water level will drop over one meter below the risk of overflowing by next month.

That in turn would allow it to ease restrictions on the amount of water used to cool the reactors.

But the company is still concerned about the extent of damage to the reactor containment vessels. Injecting more water into the damaged vessels could release more radioactive steam into the environment.

Thursday, July 07, 2011 07:57 +0900 (JST)

Commentary:

The Cooling System is a medley of Filters, Demineralizers, Pumps, Hoses, Tanks, Valves, and Control Circuits, hastily tossed together with Duct Tape and Glue. It is a joint venture between Areva and GE and is NOT performing as Advertised:

- Promised a Cesium Reduction of 1000 times - Delivers Cesium Reduction of 10 times or thereabouts.

Further, this "system" is becoming highly radioactive as it collects particles and that means it is impossible to maintain and operate. What a mess, but TEPCO has declared a success –

http://www3.nhk.or.jp/daily/english/24_35.html

Decontamination system meets performance target

The operator of the Fukushima Daiichi nuclear plant says a trouble-hit system for decontaminating highly radioactive water at the facility is working as planned.

The Tokyo Electric Power Company, or TEPCO, said on Friday that the system can reduce the density of radioactive substances in the water to the targeted level of one-100,000th.

The system is seen as the key to reducing the amount of contaminated water threatening to overflow from the plant's compound.

TEPCO said a US-made device for absorbing radioactive cesium continues to perform at one-tenth its intended capacity, even after workers readjusted a faulty valve setting.

But the firm says test runs have shown that the targeted level can be achieved when the device is used with a French decontaminator.

TEPCO says about 2,500 tons of radioactive water has been decontaminated so far. On Friday, workers began sending the water through salt-removing equipment.

The firm plans to return the treated water to reactors this month, to establish a stable cooling system that involves circulating the water.

But TEPCO says resuming full operation of the decontamination system may take several more days.

Friday, June 24, 2011 19:59 +0900 (JST)

------------------------------------------------------------------------------------

Press Release (Jul 07,2011)

Detection of Radioactive Materials from Subsurface Water near the Turbine Buildings of Fukushima Daiichi Nuclear Power Station

http://www.tepco.co.jp/en/press/corp-com/release/11070708-e.html

Press Releases

Press Release (Jul 07,2011)

Detection of Radioactive Materials from Subsurface Water near the Turbine Buildings of Fukushima Daiichi Nuclear Power Station

On March 28 2011, we were advised from Nuclear Safety Commission of Japan to enhance sampling surveys regarding water accumulated in underground floor of the turbine buildings of Fukushima Daiichi Nuclear Power Station. In order to verify any leakages to underground and sea, and safety, we have been implementing the sampling surveys of subsurface water and seawater.

Regarding sampling surveys of sub-drains, based on the instruction from Nuclear and Industry Safety Agency (NISA) on April 14th, we will continue conducting the same kind of sampling surveys three times a week, and inform the result on the next day of the survey.

Previously announced

As a result of Nuclide analysis from the sample regarding sub-drains (subsurface water obtained and managed in the site) near the turbine buildings of Fukushima Daiichi Nuclear Power Station collected on July 6, radioactive materials were detected as shown in the attachment and today, we reported to NISA and the government of Fukushima Prefecture.

We also conducted analyses of plutonium in the subsurface water on June 13, 2011. As a result, plutonium was not detected as shown in the Appendix.

Appendix1: Results of Nuclide Analyses of Sub-drains

Appendix2: Result of Plutonium analysis on Sub-drain water at Fukushima Daiichi nuclear power plant

Appendix3: Radioactivity Density of Sub-drain (PDF 24.6KB)

All Rights Reserved. Copyright 1995-2011 TEPCO

Commentary:

There is no question that there is leakage from the structure. This may be part of the Melt-Through scenario that requires further attention.

-------------------------------------------------------------------------------------

NRC Quietly Acknowledges Worsening Weather/Earth Changing Patterns - With Nuclear Power Safety, Its All About The Grid

From the extremely conservative weekly trade publication, "PLATTS WEEKLY," (named for its founder Warren Platt, energy entrepreneur), article caught my attention . . . posted here for your convenience (for Reference Verification Inside NRC 07-04-11 Page 5 and 6).

NRC, industry differ over degraded voltage protection issues

"NRC is seeking to clarify regulations that protect nuclear power plants from drops in voltage on the power grid, but the nuclear industry says the effort imposes new requirements and could force units to switch to backup diesel power more often."

"Patrick Hiland, director of the division of engineering in NRC’s Office of Nuclear Reactor Regulation, said June 29 the agency will decide soon what to put in the RIS, in order to try bring clarity to the subject. “We’re giving it [the grid] a lot more attention today than we did five years ago,” he said." "While overall grid reliability has increased in recent years, extreme weather and a growing dependence on intermittent power sources have the potential to bring instability to electrical transmission networks, he said."

Commentary:

This is very sobering, when you read between the lines. What is being proposed here by the NRC is that more and diverse electrical power supplies will be REQUIRED at existing nuclear power plants. The industry is of course, whining. I'm with with the NRC on this one.