Faulty Thermometer Likely Cause of Fukushima Temperature Rise

Last week, we alerted our readers to reports out of Japan that the temperatures inside Unit #2 at Fukushima Daiichi were rising. At the time, we noted that some of the reports of the news were, "rather breathless." That judgment has been borne out, as we received the following welcome news from Japan overnight:

A faulty thermometer is likely to blame for rising temperatures inside a stricken nuclear reactor at the Fukushima-Daiichi plant, authorities said Monday, as Japan prepares to mark one year since a devastating earthquake and tsunami triggered a nuclear meltdown.

[...]

A nuclear expert agreed that a faulty temperature gauge inside the Unit 2 reactor is the most likely cause for the higher heat reading.

Tokyo mega-quake prediction Inside the Japan nuclear exclusion zone Japan considers restarting two reactors Japan exclusion zone's lone resident
Michael Friedlander, a former senior operator at U.S. nuclear power plants, told CNN that the prospect of another catastrophic explosion at the Fukushima-Daiichi is "virtually zero."

"If the reactor was going to become critical it would have become critical in March of last year, not now," he said.

We'd be remiss if we didn't not that the first person who raised the possibility of the faulty thermometer was none other than Will Davis at Atomic Power Review.

On the Temperature Increase at Fukushima Daiichi Unit #2

Over the past 24 hours we've seen a number of account concerning rising temperatures inside reactor #2 at Fukushima Daiichi. While we noted this item over at SafetyFirst.nei.org yesterday morning, some accounts of the news have been rather breathless.

If you'd like a sober account of what's actually happening there right now, I'd suggest reading the following account from World Nuclear News. Here's the relevant passage:

This stability of unit 2 was disturbed for a few days, however, when Tepco tried to improve cooling further by tuning the rates of water injection.

[...]

After making this change, Tepco noted a tendency for increasing temperature at the bottom of the reactor vessel. Within a matter of hours the company decided to reverse the change and restore the previous injection rates, but the temperature continued to slowly rise.

Two of the three temperature sensors at the bottom of the reactor vessel edged up by about 2 degrees C. The third, however, rose by around 20 degrees C to hit 72.2 degrees at 5.00am today. Tepco acted to stem this increase by injecting an extra cubic metre of water per hour through the feedwater line, and this stabilised the sensor at about 70 degrees C. It has since decreased to 68.5 degrees C, while the other two sensors were at a new low of around 41 degrees C.

Tepco was able to discount recriticality as a potential cause of the temperature rise after conducting an analysis of charcoal filters in the containment gas control system. These showed very low traces of fission products that were below the threshold that would indicate criticality. Nevertheless Tepco this morning injected boric acid into the reactor vessel as a precaution and increased the core spray injection rate by three cubic metres per hour.

The bottom line here: at no time did the temperature of the bottom of the reactor vessel exceed, or even approach, 100 degrees C, which was one of the important conditions TEPCO has to maintain for cold shutdown conditions.

We're keeping an eye on this and will report back if events warrant.

The President of Thorium

Power from thorium:

This is [Bob] Greene's first time running [for President], and he's not sure if it's his last, but he certainly wants the world to know his position on thorium — a natural radioactive chemical element he hopes can change the nation's dependence on foreign oil.

Why thorium?

This energy source is used to create nuclear energy, much like uranium. However, he said it is safer to use and produces a waste product with a shorter radioactive life span. Like nuclear power, thorium would not create a huge carbon footprint, such as burning coal or oil, he said.

The writer gets a little muddled about nuclear energy here, but Greene has his arguments for thorium down pat. But why a single issue candidacy revolving around thorium?

He said he doesn't think President Barack Obama is taking advantage of the possibilities of thorium.

"I see this as an issue of national security," he said. "We can stop oil wars if we do this. We can change our import economy to an export economy."

Not sure why this isn’t equally true of uranium, but who are we to quibble? As the first thorium-boosting Presidential candidate we know of, we can only salute him at this crossing.

Right now, he’s only on the Democratic primary ballot in New Hampshire – against President Obama – but if things go well, who knows?

His campaign web site is here.

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When the Soviet Union ended, then-Secretary of Defense Dick Cheney was asked what would become of the country’s nuclear arsenal:

"If the Soviets do an excellent job at retaining control over their stockpile of nuclear weapons and they are 99% successful, that would mean you could still have as many as 250 that they were not able to control."

The story by Huffington Post’s Graham Allison shows what actually happened to those 250 vulnerable missiles – and all the other missiles, too: nothing bad. This was due to two U.S.-Russia programs, one to help Russia gather all nuclear materials from the former soviet republics and a second, called Megatons to Megawatts, that downblended the gathered nuclear materials in those missiles to be used by domestic nuclear energy facilities. The missiles were not only rendered harmless, but their payloads were used for constructive purposes.

Nice to be reminded of programs that worked exactly as they should have.

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Tokyo Electric Power Co. (TEPCO) may face nationalization:

Yesterday, shares in Tepco plunged to the lowest in at least 37 years after Trade and Industry Minister Yukio Edano said the company needs to consider being nationalized. Edano, who served as chief cabinet secretary and government spokesman in the months following the March 11 earthquake and tsunami, now runs the ministry overseeing the nuclear power industry.

That makes it sound voluntary. The story also suggests that how TEPCO moves forward will depend on an energy plan being worked on by the government.

The same day he spoke of a government takeover, Edano’s ministry said in a statement it was studying changing rules governing Japan’s electricity industry to make distribution networks independent of power generators to spur competition. Those studies will form part of a new national energy policy to be drawn up by summer.

The story doesn’t say that there would be any attempt to limit compensation to those affected by the accident at TEPCO’s Fukushima Daiichi facility.

Bottom line: there’s no evidence that nationalizing TEPCO would have any impact on the clean-up or on the work being done at Fukushima.

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Happy New Year from your friends at NEI Nuclear Notes. 2011 proved to be two years in 365 days. The most impressive event – leaving the accident at Fukushima Daiichi in a category of its own – to me was the extremely thorough and diligent response to the accident by the industry, the NRC, the U.S. government.

No one – at least who didn’t speak deutsch - looked at the accident and said “That’s it. Pull the plug.” But no one said, “This can’t happen here” either, even if the specifics of the Japan accident were unique.

But everything stayed at a level – the value of nuclear energy was almost universally acknowledged, but the need to take every lesson that could be learned from Fukushima and apply them to the American industry took center stage. Even attempts by anti-nuclear energy advocates to seize the moment fell flat – if anything, they became more shrill not less.

So – a tough year with a fair measure of heartening moments.

Welcome, 2012.

Bob Greene

What Is “Cold Shutdown?”

Several news articles late this week have reported that Japan’s Fukushima Daiichi nuclear plant may be in “cold shutdown” by mid-December. Although the reports are mostly accurate, there is a difference between the traditional “cold shutdown” of a nuclear plant and what is happening at Fukushima.

First, what is cold shutdown? The U.S. Nuclear Regulatory Commission defines it as:

The term used to define a reactor coolant system at atmospheric pressure and at a temperature below 200 degrees Fahrenheit following a reactor cooldown.

In non-nuclear speak, it basically means the conditions within the nuclear reactor are such that it would be impossible for a chain reaction to occur. This term usually comes into play whenever a reactor is shut down periodically for refueling or for the final time prior to the long-term before it is decommissioned. When a reactor is in cold shutdown, the reactor pressure vessel (RPV) can be safely opened with great care and additional water is added to the cavity above the vessel for shielding to permit safe handling of the fuel for refueling (replacing depleted fuel elements) or defueling (removing the entire core).

In Fukushima Daiichi’s case, achieving the strict definition of “cold shutdown” is not possible because the RPVs have been breached. This means that the RPVs will not hold water (currently the cooling water is flowing through them) and some of the melted fuel may not be in the vessel, but rather on the floor below, which is still within the primary containment. To clean up the plant, Tokyo Electric Power Company (TEPCO), the plant’s owner and operator, will work with the Japanese government and other parties to develop a long-term plan that will include removing the damaged fuel.

TEPCO understood this important nuance to achieving “cold shutdown” early on this year when it developed its initial recovery plans and developed a new term, “cold shutdown condition,” which applies to how they are bringing the reactors to stable condition. Their definition is as follows:

• Temperature of RPV bottom is, in general, below 100 degrees Celsius.
• Release of radioactive materials from PCV is under control and public radiation exposure by additional release is being significantly held down. (Not exceed 1 mSv/y at the site boundary as a target.)

By their definition, the Fukushima Daiichi reactors will reach “cold shutdown condition” once they are below boiling point and are no longer releasing significant amounts of radiation into the atmosphere. This new definition, thus, has an important distinction between the more commonly used “cold shutdown,” which typically takes place at a nuclear plant under normal conditions.

Reaching “cold shutdown conditions” at Fukushima Daiichi, however, has been an extremely difficult task for TEPCO workers given the conditions at the site and is a very significant milestone in their recovery efforts. TEPCO expects to reach this condition in just a few weeks by the end of 2011.

Graphic: Schematic of Reactor Design at Fukushima Daiichi

On The Containment Vessel Damage at Fukushima Daiichi Unit 1

Early on Wednesday morning, the Dow Jones News Wire first reportedthe following from Japan, before the rest of the mainstream media got holdof the story today:

The melted nuclear fuel within the No. 1 unit at the FukushimaDaiichi power plant was of such intensity that it eroded through 2 meters ofthe 2.6 meter (8.5 feet) concrete base, plant operator Tokyo Electric Power Co.said in a report issued on Wednesday. 

Yesterday here at the office, we huddled with a representative ofTEPCO to get a better understanding of the report, and share some additionalfacts that puts this information into the proper context. What's been reported isa very conservative mathematical analysis that has yet to be physicallyconfirmed. In other words, this is a worst case scenario. And as we've seen inour industry, even in the worst case scenario, there is still a verysignificant safety margin.

A quick read ofthe article could give one the impression that the melted core was a littlemore than half a meter -- about 2 feet -- from reaching the externalenvironment. I think it’s important to note that according to the TEPCO analysisonly .7 meters (a little more than two feet) of concrete was actually eroded.  In addition, as we've written before, plantshave multiple redundant safety systems in place to protect the public, andthat's exactly the case with Fukushima Daiichi Unit 1.

In addition to the2.6 meters (about 8.5 feet) of steel reinforced concrete inside the containmentvessel, underneath the steel shell of the containment vessel lies another 7.6meters (about 25 feet) of basemat reinforced concrete and steel. Altogether,that means there was 10.2 meters (about 33.5 feet) of reinforced concrete andsteel standing between the reactor core and the outside of the plant before theaccident.

Even if 2 meters (about6.5 feet) of that structure has been eroded, another 8.2 meters (almost 27feet) of reinforced steel and concrete lies between the melted fuel and the externalenvironment.

It’s also important to note that according to tests of air samplesfrom inside containment, it appears that the process of erosion – called coriuminteraction – has essentially ceased and no further damage is occurring at thistime. If that process is still continuing, it is doing so at such a slow ratethat TEPCO has more than enough time to develop a mitigation strategy.

NEI's Tony Pietrangelo Gives Overview of INPO Timeline

In addition to the published INPO timeline, NEI CNO Tony Pietrangelo also recorded a video overview, one that includes a brief look at how American industry is applying the lessons learned from Fukushima to enhancing safety at U.S. plants:

INPO Compiles Timeline of Fukushima Events After Japan Earthquake, Tsunami

Just a few minutes ago, the Institute of Nuclear Power Operations published a detailed timeline of events at the Fukushima Daiichi nuclear power station following the March 11 earthquake and tsunammi (click here for the PDF of the report). The full text of the Nuclear Energy Institute news release announcing the publication follows below:

INPO Compiles Timeline of Fukushima Events After Japan Earthquake, Tsunami
4-Day Chronology Provides Common Baseline of Facts To Inform Response Activities by U.S. Industry, Government
WASHINGTON, D.C., Nov. 11, 2011—The Institute of Nuclear Power Operations has compiled a detailed timeline of events at the Fukushima Daiichi nuclear power station after the March 11 earthquake and tsunami in Japan. The detailed report, prepared as part of the integrated response to the Japan events, was delivered today to U.S. industry executives, the Nuclear Regulatory Commission and to members of Congress.

“The U.S. nuclear energy industry is committed to learning from Japan’s experience and applying relevant lessons to make U.S. nuclear energy facilities even safer. We are sharing this report with the widest possible audience because it is important that we all work from the same set of facts in determining the appropriate response,” said NEI’s senior vice president and chief nuclear officer, Tony Pietrangelo. “It is of paramount importance that we learn from it and take our facilities to even higher levels of safety and preparedness.”

U.S. nuclear power plants operating in 31 states produce 20 percent of U.S. electricity, with a unique combination of 24/7 production, industry-leading reliability and zero carbon emissions or air pollution.

The report presents a chronology of activities at the Fukushima Daiichi station in the first four days after the earthquake and tsunami. It does not provide analysis, draw conclusions or include recommendations on the events. Most of the information in the report has been previously released, but in a piecemeal fashion. The Institute of Nuclear Power Operations, an industry organization whose mission is to promote the highest levels of safety throughout the U.S. nuclear industry, worked closely with the Tokyo Electric Power Co., the plant’s operator, to develop the timeline. Information was compiled from multiple sources, including the Japanese government, the International Atomic Energy Agency, and several Japanese nuclear and safety organizations.

The U.S. nuclear energy industry has established a leadership model among major electric sector organizations – including NEI, the Electric Power Research Institute, reactor vendors and INPO – to integrate and coordinate the nuclear industry’s ongoing response to the Fukushima Daiichi accident.

This Fukushima Response Steering Committee already has identified five areas that warrant action or further examination:

Seismic and flooding inspections

Maintaining safety during a prolonged loss of AC power

Assuring the accessibility and functionality of reactor containment vent valves assuming loss of AC power

Enhanced training in guidelines to manage severe accidents

Enhanced monitoring of used fuel storage pools at reactors

“This timeline doesn’t tell us why events unfolded – a comprehensive root cause analysis will likely take several months if not years to achieve that understanding. However, the facts presented in this timeline reinforce the industry’s and the NRC’s independent assessments on what our response priorities should be,” Pietrangelo said.

The timeline is available here and at NEI’s “Safety First” website, http://safetyfirst.nei.org.

More to come.

Wednesday Update

From NEI’s Japan earthquake launch page:

Plant Status

• Tokyo Electric Power Co. continues to deal with water management issues at the Fukushima Daiichi site. The company is plugging concrete enclosures at the plant to retain contaminated water and is studying the feasibility of building a system to purify seawater. The Japan Nuclear and Industrial Safety Agency has ordered TEPCO to complete a plan for storing and treating contaminated water at the Fukushima Daiichi site by June 1.

• TEPCO has begun to build a concrete structure to provide additional support to the used fuel storage pool for reactor 4 at the Fukushima Daiichi facility. Work is planned for completion by the end of July.

Industry/Regulatory/Political Issues

• The Japanese government announced plans to appoint a panel to investigate the accident at Fukushima Daiichi. The head of the committee will be Yotaro Hatamura, a professor emeritus at the University of Tokyo.

• A delegation from the International Atomic Energy Agency has arrived in Japan for a fact-finding mission on the nuclear accident. Its objective is to make a preliminary assessment of safety issues at the facility and identify areas that need further study. The team is composed of 20 international and IAEA experts from a dozen countries and is to complete its work June 2. Leading the team is the United Kingdom’s chief nuclear inspector, Mike Weightman, who will present a report on the mission at IAEA’s Ministerial Conference on Nuclear Safety June 22-24.

• NEI President and CEO Marvin Fertel will speak at a public meeting of the Nuclear and Radiation Studies Board of the National Academy of Sciences on the aftermath of Fukushima, beginning at 12:45 p.m. EDT May 26 in Washington, D.C. Other speakers include the Natural Resources Defense Council’s Thomas Cochrane and the Union of Concerned Scientists’ Ed Lyman.

• NEI Senior Vice President and Chief Nuclear Officer Tony Pietrangelo will participate in a briefing for NRC's Advisory Committee on Reactor Safeguards on events at Fukushima, beginning at 1 p.m. EDT May 26 at NRC headquarters in Rockville, Md.

• NEI Vice President of Regulatory Affairs Doug Walters will speak at Preparing for the Unthinkable: Joint Crisis Leadership in the Event of an Energy Systems Breakdown, at 5:30 p.m. EDT May 26, at the Center for Strategic and International Studies in Washington, D.C.

Media Highlights

• NEI media relations is making outreach calls to reporters and editors about the recent testimony of John Boice before the House Committee on Science, Space and Technology’s Energy and Environment and Investigations and Oversight subcommittees. In a hearing on the aftermath of the Fukushima accident, Boice, a radiation epidemiologist and professor in the Department of Medicine at Vanderbilt University, said that “the health consequences [of radiation] for Japanese workers and public appear to be minor” and “the health consequences for United States citizens are negligible to nonexistent.”

New Products

• NEI has updated its frequently asked questions about issues relating to the Fukushima Daiichi nuclear accident.

• A new NEI fact sheet is available on used fuel pools.

Upcoming Events

• Challenges of Nuclear Spent Fuel Management: Lessons from Around the World, 3 p.m. EDT June 3 at American Association for the Advancement of Science Headquarters, 1200 New York Ave., NW, Washington, D.C.

TEPCO’s Plans to Stabilize Fukushima-Daiichi

Yesterday, TEPCO released their plans on how to stabilize the plant in the short term. Below is a one-page overview of the plans (pdf).

Nuclear Street has a good description of some of the main objectives:

TEPCO said that after 3 months it expects radiation levels to decline at the plant, followed by cold shutdown in reactors 1 though 3 within six months. Also in that timeframe the company plans to cover units 1, 3 and 4 using a temporary “scaffolding” to minimize the escape of radioactive elements from damaged reactor buildings.

In the near-term, TEPCO will strengthen the walls and base of the spent fuel tank in unit 4. Unit 2 will continue to be drained of irradiated water believed to contribute to some of the highest dose readings at the plant. Eventually, the company will flood the containment vessels of units 1 through 3, with unit 2 requiring additional work to seal its containment vessel beforehand.

At TEPCO’s press release, you can find more links and descriptions of the plan. The link to Appendix 2 (three-page pdf) is the most detailed document and highlights the risks of the actions in red. As well, the countermeasures are numbered in Appendix 2 and are conveniently matched to the plant overview image above.

Friday Morning Update

From NEI’s Japan earthquake launch page:

UPDATE AS OF 9:30 A.M., MARCH 25:
Japanese officials are investigating the source of higher radiation readings at reactor 3 at the Fukushima Daiichi nuclear power plant after two workers were contaminated while laying cable in the turbine building. Tests of the water in which the workers were standing contained a concentration of radioactive material many times the level normally found in water circulating in the reactor, the Nuclear and Industrial Safety Agency said.

"When we looked into the composition of the water, the source seems to be the reactor core," said NISA's Hidehiko Nishiyama. "Another possibility is the spent fuel, and we cannot rule out that possibility either."

Several possibilities could account for the presence of radioactive materials in the turbine building. Seawater sprayed onto the fuel pool area may have washed over the floor of the fuel pool area onto the turbine building and leaked through the damaged roof into the basement of that building. Other possibilities include a problem with an interconnected system to the primary containment, such as the main steam system, or a small opening in the reactor containment structure.

Japanese authorities recommended residents within 30 kilometers of the plant evacuate voluntarily, extending the recommendation from 20 kilometers. Damage to infrastructure in the area from the earthquake severely limits the ability to provide water, food and other necessary supplies to people sheltering in their homes for the coming weeks.

Tokyo Electric Power Co. is stepping up efforts to switch from sea water to fresh water for cooling the reactors and used fuel storage pools. The United States government has urged the switch to fresh water as soon as possible and is providing two U.S. Navy barges, each of which can carry up to 1,000 tons of water. The ships are scheduled to reach port about 60 kilometers from the Daiichi plant in about three days. Japanese workers at the site will install pipes and hoses to carry the water to the plant.

New Web Page on 'Health and Radiation'
NEI has created a new web page, "Health and Radiation Safety," which provides information and links to additional resources.