Workers Inspect Inside Unit 1
Video has been released of the an extended entry into unit 1 on October 18th. Previously, workers had expressed concerns about high radiation levels inside the building. Radiation readings as high as 4 sVh were found in areas of the building making work even more high risk. Workers inspected the isolation condenser and an area on the floor(s) below. Details about the isolation condenser provided by Dean at the end of the article.
The drawing to the left is from Oyster Creek NPP. This unit is very similar to unit 1 at Fukushima Daiichi. The isolation condenser tanks are highlighted in red. The area labeled “8A” is the rough vicinity of the last part of the video where you can see the outside of the containment bulb concrete.
After the video below are photos from the video showing some of the damage and some of the key pipes and valves. Various gauges and valves are labeled with the general area they were found in. If you have more data on these please leave a comment with what you know. It did appear that one set of gauges for a tank or valve was holding pressure while the other was at zero.
The video is extremely loud, you may want to turn down the sound before it plays. The loud leaking steam sound was not identifiable in the video. The beeping and alarm sounds heard throughout the video are the workers dosimeters going off to warn them that they are in a high radiation area.
Photos from the video:
(if you want larger copies of the images contact us at info (at) fukuleaks.org/web
Open area opposite the IC tanks, lots of mangled metal and equipment.
Outside reactor containment concrete below the IC tank level
Turn in the containment concrete near 8A section, containment concrete appears intact in this area.
Collapsed concrete, rebar and steel near the stairwell past the IC tanks.
Left IC tank valve & gauge located between the two tanks (left being while looking at the red ends with the insulation knocked off)
Same valve & gauge, better view.
Valves under right IC tank
Overhead pipes between IC tanks
Valves below left IC tank
Left IC tank about 60 on the gauge
This is from the right tank at about 80%
Overhead pipe connection
Valve by the right IC tank
This gauge was behind the IC tanks near the stairs, opposite the red ends.
This was also behind the IC tanks
Second gauge behind IC’s – the other one is max’ed out.
Front of one of the IC tanks with the insulation knocked off.
Equipment panels to the right of the two IC tanks – damaged
Scraps of sheet metal a frequent find.
Isolation Condenser Information:
Isolation Condenser (IC)
Some reactors, including notably the (E)SBWR series of reactors, have a passive system called the Isolation Condenser. This is a heat exchanger located above containment in a pool of water open to atmosphere. In operation, decay heat boils steam, which is drawn into the heat exchanger and condensed; then it falls by weight of gravity back into the reactor. This process keeps the cooling water in the reactor, making it unnecessary to use powered feedwater pumps. The water in the open pool slowly boils off, venting clean steam to the atmosphere. This makes it unnecessary to run mechanical systems to remove heat. Periodically, the pool must be refilled, a simple task for a fire truck. The (E)SBWR reactors provide three days’ supply of water in the pool.  Some older reactors also have IC systems, including Fukushima Dai-ichi reactor 1, however their water pools may not be as large.
Under normal conditions, the IC system is not activated, but the top of the IC condenser is connected to the reactor’s steam lines through an open valve. Steam enters the IC condenser and condenses until it is filled with water. When the IC system is activated, a valve at the bottom of the IC condenser is opened which connects to a lower area on the reactor. The water falls to the reactor via gravity, allowing the condenser to fill with steam, which then condenses. This cycle runs continuously until the bottom valve is closed
In some BWRs, such as Fukushima’s Unit 1, an isolation condenser (IC) provides heat removal if the main condenser is unavailable or isolated from the reactor. ICs condense steam from the core and return condensate directly to the core, rejecting the heat to an external pool of water through natural circulation. During isolation condenser operation, the water on the shell side of the condenser boils and needs to be replenished. Makeup water is typically provided from on-site water storage tanks through pumps powered by either off-site power or on-site emergency diesel generators if off-site power is unavailable. Other sources of water—from, say, the fire protection system—could also be used. However, their use will likely require manual actions.
Newer designs, such as those at Fukushima Units 2, 3, and 4, employ a steam turbine-driven reactor core isolation cooling (RCIC) system to control primary system inventory during abnormal transient events, including the loss of off-site power and conditions known as “station blackout” where both on-site and off-site power is lost. Energy from the reactor may be removed through the safety relief valves to the suppression chamber, a toroidal-shaped chamber located within the reactor building that is an integral part of the Mark 1 containments, the kind used by Fukushima Units 1 through 4.
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