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Japan Nuclear Watch, Mon Nite (JST): Power! Unit 3 Smoking, Radiation Spreads

5:12 am in Uncategorized by Scarecrow

Reactor Containment & Fuel Storage from UCS; (h/t commenter lobster)

Update: Monday 5:30 pm (EDT): AP reports utility officials say some of the pumps in Unit 2 are damaged and must be replaced. They’re on order.

It’s Monday morning in the US; it’s Monday evening in Japan.

Quick Summary: Over the weekend, hopes of getting the reactors and spent fuel storage pools cooled rose significantly at the Fukushima Daiichi Nuclear Station, although on Monday, new smoke rose from Unit 3 (see NYT photo) forcing another evacuation there. They’re not sure whether there was another explosion (none was heard) nor do they know the source/cause of the smoke.

Rising hopes are attributed to getting power connected to some Units, though cooling systems have not yet been restated, and their improving ability to target sea water spray into the spent fuel storage pools and sustain it for several hours. This appears to be lowering temperatures at the critical hot spots.

In the meantime, they’re finding higher radation levels in surrounding communities, creating concerns about milk, local produce and tap water.

Power to the Units. Over the weekend, plant officials were able to complete laying transmission cables to transmit electric power from the grid to Units 1 and 2; they’re now completing connections to Units 3 and 4. There are reports they were able to connect to terminal/hubs providing power to a central control room between Units 1 and 2.

As of 8:30 am Monday (EDT), they have not attempted to turn on the cooling systems at Units 1 and 2. They’re still testing gauges, water temps, and other equipment to determine water levels and temperatures, and thus which pumping/cooling equipment needs to be tested for restarting. So even though they have power, the normal cooling systems are not yet functioning and we don’t yet know what equipment will work.

As we feared, the New York Times reports this morning (EDT) that workers are finding critical equipment, including a ventilation system, that must be repaired before they can restart the cooling systems at Unit 2. Recall that all four units suffered explosions, but Unit 2 suffered minimal exterior wall/roof collapse, whereas Units 1, 3, and 4 were extensively damaged.

After connecting the transmission line on Sunday, engineers found on Monday that they still did not have enough power to fully run the systems that control the temperature and pressure in the building that houses the reactor, officials from the nuclear safety agency said.

Engineers were also trying to repair the ventilation system in the control room that is used to monitor conditions in the No. 1 and No. 2 units. When that work is completed, possibly on Monday, it will allow the power company, also known as Tepco, to begin cleansing the air in the control room so that workers can eventually re-enter and begin using equipment inside to monitor conditions in the two reactor units.

At the same time, they’ve restored back-up generation at Units 5 and 6. With restored cooling functions, those two reactors and their spent fuel storage pools are out of danger, at least for the moment.

Continued spraying of sea water at Units 3 and 4. With the normal cooling functions still unavailable at units 1-4, they’ve continued spraying water from high-pressure fire hoses. They’ve brought in more crews and equipment, including a large crane that pictures show getting a hose above a reactor building and focusing spray down towards the fourth floor spent fuel pools. The ability to do this remotely (thus limited worker exposure next to the reactor) and to continue for several hours at a time has greatly increased their ability to inject water into the reactor buildings.

On Sunday, there was a report they had determined the spent pool fuel at Unit 4 was full. What accounts for this? Recall that last week, US Nuclear Regulatory Commission officials disagreed with the Japanese by insisting that Unit 4′s spent fuel pool was dry — all the water had either evaporated from the rising heat/boiling (which meant uncovering and damage to fuel and fuel cladding) or had leaked from cracks to the pool walls or floor. [One NHK TV segment interviewed a plant worker who, at the time of the quake, was near one of the pools; he and others were splashed with water as the quake sloshed the storage pool water.] The US claim led to a hypothesis by Union of Concerned Scientists that pool water could also have escaped through a breach in the “gate” that allows transfer of fuel assemblies between the reactor core and the spent fuel pool. [See my previous update].

Now, however, plant officials are claiming the Unit 4 spent fuel pool is full. If true, was it ever damaged or dry? Or is this simply the result of continuing efforts to spray sea water into the pool? Whatever, it’s a good sign that sufficient water is there and temperatures have fallen.

One issue we touched on early last week but haven’t heard much about lately is the corrosive effect of sea water on containment structures and pumping equipment. Remember that the decision to start injecting sea water was interpreted at the time as a decision to give up on any hope of saving the plant for future operation, since the sea water would over time destroy critical equipment. But it was necessary given the need to prevent a wider meltdown and public health hazard.

They have now spent over a week pumping sea water into units 1-4 (and Units 5-6?), both into the cooling systems circulating through the reactors and into the spent fuel storage pools. When does that necessary emergency action become the corrosion that causes the next system breakdown, even if they are able to restore pumps and other cooling mechanisms? And what will they do to prevent this inevitable breakdown?

Increasing concern about area radiation and public health. Dozens of plant workers have now received dangerous levels of radiation, possibly lethal for many of the “Fukushima 50″ who stayed at the plant when others were evacuated. They’ve continued to cycle in new workers, particularly those who can operate the fire trucks and other sea water pumping equipment.

Yesterday, various radiation monitoring systems near Fukushima and another plant were reporting spikes in radiation readings, but it’s unclear what caused this. Another event at Fukushima? Another plant? Rain? Commenter lobster was tracking last night.

Over the weekend, there were reports of officials finding unsafe radiation levels in milk and increased levels in local produce, first spinach and now other foods grown in Fukushima and neighboring prefectures. There is a ban on exporting produce from these areas, and they are continuing to monitor for food contamination. Also, there is warning against drinking tap water in a community about 30 miles away. That signals a spreading public health problem. As of Monday, more than 29,000 people have been evaculated from the area.

The NHK live tv feed (English) has been showing frequent updates on radiation levels at various locations, comparisons with normal exposure levels and recommended precautions.

And it’s been raining in northern Japan. So, for people still there, it’s stay indoors, don’t go out in the rain, avoid contaminated produce and wash everything.

More updates as warranted.

Sources:
NHK World TV

New York Times, New Repairs Delay Work at Crippled Nuclear Plant

New York Times, Status of Each Unit, with timelines

Breakthrough Institute, Situation Report

Union of Concerned Scientists, All Things Nuclear; and Daily Briefings

Radiation dose chart (please note disclaimers)

Japan Nuke Watch, Sat Nite (JST): Power to Site, Radiation in Food

5:38 am in Uncategorized by Scarecrow

Reactor Containment & Fuel Storage from UCS; (h/t commenter lobster)

It is Saturday morning here; Saturday night in Japan.

Some important developments that provide rays of hope and areas of concern. Concerns first.

First, some local produce has become contaminated with radiation. The New York Times reports authorities finding unacceptable levels of radiation in food in Fukushima:

The government said on Saturday that they had found levels of radioactive materials above safe limits in spinach and milk in Fukushima and Ibaraki prefectures, the first confirmation by officials that the nuclear catastrophe unfolding at power plants nearby has affected the nation’s food supply.

Yukio Edano, the chief cabinet secretary, said that the radioactivity contained in the average amount of spinach and milk consumed during an entire year would be equal to the amount received in a single CAT scan. Mr. Edano said that abnormal amounts of radioactivity were found only in these two products, though other foods were tested.

It was not known how much affected milk and spinach had already been shipped.

Subsequent reports indicate the government has banned the sale of produce grown in the Fukushima prefecture. They are still maintaining their 20 kilometer evacuation zone with warnings to stay indoors out to 30 km from the site.

[Update: Kyodo News reports findings of slightly higher levels of radioactive iodine in water samples in Tokyo and above legal limits in tap water at Fukushima prefecture.]

Second, they’re about to test the new electrical connection from the grid. TEPCO reports they have completed installing the new power connection from the grid to the site and then on to Units 1 and 2. They’re also working to extend to Units 3 and 4, though it’s unclear whether that implicates radiation levels near those two units.

As I suspected, not only did they need a new line from the grid; they needed to bypass much of the original interconnection points on the site that link to each of the Units and other buildings. These interconnection points were vulnerable to the tsunami and may be unusable. Recall that the back-up diesel generators used whenever grid power is lost were located in a low elevation building closer to the sea and were inundated by the tsunami.

Authorities say they now have power connections to the station, but have not tested the electrical components. They’ll need to make sure the interconnections to the individual Units are sound first, then carefully test connected electrical equipment, control panels and switching. Only then will we know whether the pumps and other critical cooling equipment that require electric power are still operable. Those tests are supposed to occur on Sunday.

Third, they’re bringing in the robots! If you watch the periodic reports on the NHK tv feed, they show an unmanned fire truck with water cannon shooting water into Unit 3. The truck is connected by a hose 800 meters long so they can constantly feed water into the unmanned truck-cannon, rather than expose workers with manned hoses. (Authories also report they are bringing in emergency fire crews from other regions to relieve those who have already reached their exposure limits.)

The remotely supplied water cannon allowed several hours (seven?) of continuous spraying on Saturday, and officials claim they sent 1260 tons of water aimed at Unit 3′s spent fuel storage pool. They also claim to have slightly lowered the temperature in the pool to below boiling, but it’s not clear whether they’ve confirmed this.

In addition, American and other western nations are sending in robots that can perform certain tasks in nuclear emergencies, including dragging fire hoses. From the NYT (h/t 4cdave):

At the request of the Japanese military, a Massachusetts company, iRobot, said it put four robots on a plane for Japan on Friday. Colin Angle, the chief executive, said it had sent two small robots that could measure radiation levels close to the reactors and two larger ones that could pull hoses to spray water on the fuel rods. He said Japanese soldiers could operate the robots from a protected vehicle.

Fourth, they’ve restarted another generator at Unit 5. This appears to be a generator on site, not power from the new power line extensions from the grid. The added generation has allowed them to resume more water pumping into Units 5 and 6 storage pools.

Both reactors were down form maintenance when the quake/tsunami struck, but they both have fuel in their reactor cores (per NYT Unit summaries) and more in their spent fuel storage pools. The generators can help keep the units cooled, so those units are now at significantly lower risk.

More: Could Unit 4 Storage Pool be leaking? US authorities have argued that the loss of cooling water in Unit 4′s spent fuel storage pool could be at least partially explained by a leak or damage to the storage pool walls or the “gate” that opens to allow transfer of fuel rod assemblies between the pool and the reactor vessel.

Union of Concerned Scientists has an explanation of one plausible reason for a leak in the “gate.” The gist is, the gate is normally sealed by an air pressurized seal driven by an electric air pump. The pump gets its power from the grid. Lose that and the air pump can’t seal the gate to ensure against leakage of water from the pool. As UCS notes, this scenario actually occurred at a US reactor, the Hatch facility in Georgia in 1986. It’s worth reading for the clear explanation, diagrams and actual pictures from other BWR plants.

More updates as we get them, and I want to thank our commentors who continue to bring in reports and updates. Thanks especially to 4cdave and others who maintained the late night vigils.