Fukushima Daiichi – Issues at Unit 5
There have been concerns that something is going on at Unit 5 (and possibly 6) at Fukushima Daiichi. A number of reports of pieces of information have been coming out. While there is no clear theory about exactly what is going on at units 5 and 6, much of the activities seem to focus on the water intake systems.
Unit 5
Photos of quake damage at unit 5 http://mainichi.jp/select/
Videos of intake damage (taken by TEPCO)
Unit 5 auxiliary sea water intake http://www.youtube.com/watch?v=T2igL2Jz5Yc
Unit 5 RHRS sea water intake http://www.youtube.com/watch?v=MjPWWZWXhCc
Unit 6 auxiliary sea water intake http://www.youtube.com/watch?v=WYM6lKI3CVo
Unit 6 RHRS sea water intake http://www.youtube.com/watch?v=8QpDuEYkVKk
Some damage was noted on the intakes including broken pipes below the intakes at unit 5 and what appears to be a broken wall on the concrete sump box for the auxiliary sea water intake at unit 5. These intakes sit behind the filter screens that block fish and large debris in a concrete sump box/pool. You should see a concrete floor instead they look like sea floor full of sand and debris. This indicates the screens may have been damaged during the tsunami or otherwise filled up with garbage during the tsunami. The broken pipes seen at unit 5’s intakes indicate the impellers and any underwater pump equipment is likely damaged and not operable.
Images of above water damage on the dock area of units 5 and 6 (end of page) http://cryptome.org/eyeball/daiichi090911/daiichi090911.htm
Page 3-7 describes the cooling circulation systems being used at unit 5 http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf
Details on this kind of pump as described from another BWR reactor system similar to Fukushima
A number of other issues have been brought up related to units 5 and 6
- A local resident claimed workers have mentioned concerns at the plant with units 5 and 6 in a video interview.
(translated bits of interview http://fukushima-diary.com/2011/10/news-a-raged-fukushima-citizen-talks-about-everything/)
- Levels of cesium being detected outside the intakes at 5 and 6 have increased. (documented with TEPCO reports)
- A unverified report that cesium levels near Ibaraki went up on October 16.
- Unverified mention (in the same video interview above) that Hitachi is building up staff near Fukushima Daiichi to conduct some emergency work at the plant.
A list of ongoing incidents at unit 5 mostly and a few at unit 6 that are reported by TEPCO, most having to do with cooling systems.
May 30 – A water pump at unit 5 failed and had to be replaced, this caused an increase in reactor temps. http://www.joewein.net/blog/2011/05/30/fukushima-1-unit-5-water-pump-fails/
More on the May 29-30 pump failure http://www.beyondnuclear.org/home/2011/5/29/fukushima-daiichi-unit-5-loses-cooling-for-15-hours.html
July 3rd split hose that carried seawater to unit 5 had to be repaired. http://www.upi.com/Top_News/World-News/2011/07/03/Fukushima-reactor-cooling-problem-fixed/UPI-67951309736486/
Possibly the hoses used to get around the damaged intake system and provide sea water to RHRS and auxiliary seawater side of those systems?
Below are known events reported by TEPCO for unit 5 and then unit 6. Some things of note is the ongoing issue at unit 5 with the components of the cooling system.
UNIT 5
1. Off-site power has been connected to Units 1 to 6 by March 22, 2011.
2. At approximately 8:00 am on May 31, we confirmed oil leakage to the sea around
the curtain wall of the water intake canal of Unit 5 & 6 and reported the issue to
Futaba Wide-area Fire Headquarters and Fukushima Coastguard Office. As a
result of our investigation, we confirmed that oil leaked from pipes around seawall
to the port through holes of steel sheet piles and that the leakage already stopped.
Since the diffused area was just around the curtain wall and the surface of the sea
around Shallow Draft Quay and the oil film was very thin, we confirmed that there
is no spread to the outer sea. We completed installing oil-absorbing mat around
seawall at approximately 2:00 pm and also completed installing oil fences at 4:50
pm. We plan to protect pipes around seawall and collect the oil. At 10:00 am on
June 14, we closed the open part at the bottom of curtain wall, through which the
oil leaked
3. Unit 5 (Outage due to regular inspection)
-Sufficient level of reactor coolant to ensure safety is maintained.
-At 5:00 am on March 19, we started the Residual Heat Removal System Pump
in order to cool the spent fuel pool.
-At 2:30 pm on March 20, the reactor achieved cold shutdown.
-At 2:45 pm on July 15, we started the operation of the original Residual
Heat Removal System (System B) by its original seawater pump.
-At this time, we don’t think there is any reactor coolant leakage inside
the primary containment vessel.
4. -At 2:06 pm on October 7, we started to spray purified accumulated water
brought from Unit 5 and 6 continually in order to prevent dust scattering
and potential fire outbreaks from the cut down trees.
5. <Treatment of Accumulated Water>
– From 2:06 pm on October 7, in order to prevent from spontaneous combustion of cut
trees and dust dispersing we started to sprinkle water in the site of Fukushima
Daiichi Nuclear Power Station with cleared-up accumulated water of Unit 5 and 6.
We measured radioactivity density in advance and confirmed to meet requirement of
the guideline suggested in “Guideline regarding radioactive materials on bathing area”.
6. <Others>
From 10:03 am to 10:43 am on August 8, we stopped the residual heat removal system
pump (D) in order to switch the power source of the pump (C) as well as conducting its
commissioning (C)
7. – In order to repair the outlet valve of Unit 5 residual heat removal system seawater
pump (D), from 9:45 am to 10:42 am, September 26, we switched the seawater
pump from B system (permanently installed) to A system (temporarily installed).
8. – On September 30, as the repair work for the outlet valve of Unit 5 Residual Heat
Removal System Sea Water Pump completed, between 11:30 am and 11:34 am on
the same day, the Residual Heat Removal System was switched from A system to B
(the Residual Heat Removal System Sea Water Line was also switched from A
system to B).
9. – For the purpose of Unit 5 water intake inspection, at 9:05 am October 20, unit 5
seawater pump of Equipment Water Cooing System was shutdown, and stopped
cooling the spent fuel pool. At 9:13 am, Residual Heat Removal System (D) was
stopped and stopped cooling the reactor. As the inspection was completed, at 2:32 pm,
seawater pumps of Equipment Water Cooing System was resumed, which resumed
cooling the spent fuel pool. At 3:02 pm, Residual Heat Removal System (D) was
resumed, which resumed cooling the reactor. Due to this stop, reactor water
temperature temporarily rose from 22.2℃ to 31.1℃. Spent fuel pool water temperature
temporarily rose from 25.5℃ to 26.2℃.
Details for Unit 6
Unit 6
1. Off-site power has been connected to Units 1 to 6 by March 22, 2011.
2. At approximately 8:00 am on May 31, we confirmed oil leakage to the sea around
the curtain wall of the water intake canal of Unit 5 & 6 and reported the issue to
Futaba Wide-area Fire Headquarters and Fukushima Coastguard Office. As a
result of our investigation, we confirmed that oil leaked from pipes around seawall
to the port through holes of steel sheet piles and that the leakage already stopped.
Since the diffused area was just around the curtain wall and the surface of the sea
around Shallow Draft Quay and the oil film was very thin, we confirmed that there
is no spread to the outer sea. We completed installing oil-absorbing mat around
seawall at approximately 2:00 pm and also completed installing oil fences at 4:50
pm. We plan to protect pipes around seawall and collect the oil. At 10:00 am on
June 14, we closed the open part at the bottom of curtain wall, through which the
oil leaked
3. -Sufficient level of reactor coolant to ensure safety is maintained.
4. -At 10:14 pm on March 19, we started the Residual Heat Removal System Pump
of Unit 6 to cool down Spent Fuel Pool.
5. -At 7:27 pm on March 20, the reactor achieved cold shutdown.
6. -At 2:33 pm on September 15, we started separately cooling the reactor
through the Residual Heat Removal System and the spent fuel pool through
Equipment Cooling Water System and Fuel Pool Cooling System.
7. -At this time, we don’t think there is any reactor coolant leakage inside
the primary containment vessel.
8. -At 2:06 pm on October 7, we started to spray purified accumulated water
brought from Unit 5 and 6 continually in order to prevent dust scattering
and potential fire outbreaks from the cut down trees.
9. < Treatment of Accumulated Water>
– Following start of transferring of low radioactive accumulated water from temporary
tank to Mega Float, we restarted the transferring of accumulated water at the
underground of Unit 6 turbine building to temporary tank, as shown below.
From 11:00 am to 4:00 pm on August 2
From 11:00 am to 4:00 pm on August 3
From 11:00 am to 4:00 pm on August 5
From 11:00 am to 4:00 pm on August 6
From 11:00 am to 4:00 pm on August 8
From 11:00 am on August 9 to 5:00 pm on August 10
From 10:00 am to 4:00 pm on August 11
From 10:00 am to 4:00 pm on August 12
From 11:00 am on August 15 to 9:00 am on August 15
From 10:00 am to 5:00 pm on August 18
From 10:00 am to 1:00 pm on August 19
From 10:00 am on August 23 to 4:00 pm on August 24
From 10:00 am to 4:00 pm on August 25
From 10:00 am to 4:00 pm on August 26
From 10:00 am to 4:00 pm on August 29
From 10:00 am to 4:00 pm on September 1
From 11:30 am to 4:00 pm on September 12
From 10:00 am to 4:00 pm on September 13
From 10:00 am to 4:00 pm on September 15
From 10:00 am to 4:00 pm on September 20
From 10:00 am to 4:00 pm on September 21
From 10:00 am to 4:00 pm on September 22
From 10:00 am to 4:00 pm on September 24
From 10:00 am to 4:00 pm on September 26
From 10:00 am to 4:00 pm on September 28
From 10:00 am to 4:00 pm on September 29
From 10:00 am to 4:00 pm on September 30
From 10:00 am to 4:00 pm on October 3
From 10:00 am to 4:00 pm on October 5
From 10:00 am to 4:00 pm on October 7
From 10:00 am to 4:00 pm on October 12
From 10:00 am to 4:00 pm on October 14
From 10:00 am on to 4:00 pm on October 18
From 10:00 am on to 4:00 pm on October 22
– We transferred low level radioactive accumulated water, which had been transferred
from the turbine building to the temporary tank, from the temporary tank to Mega Float,
as shown below.
From 10:00 am to 5:00 pm on August 2
From 10:00 am to 5:00 pm on August 3
From 10:00 am to 5:00 pm on August 5
From 10:00 am to 5:00 pm on August 6
From 10:00 am to 5:00 pm on August 8
From 10:00 am to 4:00 pm on October 19
From 2:00 pm to 3:00 pm on October 20
From 10:00 am to 4:00 pm on October 21
– We transferred accumulated water from the basement of Unit 6 reactor building to
the turbine building as shown below.
From 11:05 am to 12:00 pm on September 2
From 8:30 am to 9:55 pm on September 3
From 1:20 pm to 2:45 pm on September 8
From 10:15 am to 11:30 am on September 12
Transfer from September 13 onwards, will be considered depending on the
water level at the building.
10. – At 10:00 am on August 9, we resumed transferring low-level accumulated water to
Mega Float from a temporary tank where we had transferred from the turbine
building of Unit 6. At 10:12 am the transfer was suspended, as we confirmed
accumulated water was leaking from the transfer hose. At 1:35 pm on the same day,
we restarted the transfer after replacing the hose. At 5:00 pm on the same day, we
completed the transfer. After that, the results of the transfer are shown below.
From 5:00 pm on August 13 to 10:00 am on August 14
11. – From 2:06 pm on October 7, in order to prevent from spontaneous combustion of
cut trees and dust dispersing we started to sprinkle water in the site of Fukushima
Daiichi Nuclear Power Station with cleared-up accumulated water of Unit 5 and 6.
We measured radioactivity density in advance and confirmed to meet requirement
of the guideline suggested in “Guideline regarding radioactive materials on bathing
area”.
12. – At 9:27 am on August 9, as we conducted plumbing connection work to Unit 6 residual
heat removal seawater system (System A), we stopped the power source of residual
heat removal seawater system (System B) and cooling of the reactor and the spent fuel
pool was temporarily suspended. At 2:01 pm on the same day, we completed the work
and restarted cooling the reactor and the spent fuel pool by the residual heat removal
seawater system (System B).
13. – From 9:55 am to 12:39 pm on September 8, in order to fill Residual Heat Removal
System seawater system cooling pump (A) of Unit 6, we stopped Residual Heat
Removal System (B). With this, cooling of Reactor and Spent Fuel Pool were also
temporarily suspended
13. – At 2:29 pm on September 10, we stopped the residual heat removal system (B) of
Unit 6. At 3:12 pm we started (A) of the same system. (Cooling of the spent fuel
pool was temporarily suspended, however, there was no change in the water
temperature in the pool before and after the suspension.) The water in the reactor
and in the spent fuel pool will be alternately cooled by the residual heat removal system (A).
14. – At 9:56 am on September 15, we restored and restarted the seawater pump of
Equipment Cooling Water System of Unit 6. At 2:33 pm on the same day, we
completed the adjustment of the flow rate of Fuel Pool Cooling System and started
cooling the spent fuel pool. Consequently, the reactor and the spent fuel pool are
now separately cooled through Residual Heat Removal System and Fuel Pool
Cooling System respectively.
15. – At 11:05 am on September 27, on the second floor of the turbine building of Unit 5,
while draining lubricant oil of overhead crane to drums for inspection of the crane,
one of our employees found lubricant oil was leaked on the floor. The amount of the
leaked oil was approximately 8 liters, and at about 1:00 pm, we wiped the oil from
the floor.
16. – Because a decrease in the amount of water was confirmed at the residual heat
removal system seawater pump (C), the cooling of the reactor using residual heat
removal system (A) was stopped at 11:20 am on October 3, and we implemented
the inspection of the residual heat removal system seawater pump (C) and the
related system. The inspection result confirmed its normal function. Thus, at 12:44
pm on the same day, we resumed cooling the reactor by residual heat removal
system (A).
17. – At 1:41 pm October 6, We stopped pumping at auxiliary cooling seawater system
Unit 6 since we found slow decreasing trend in pressure of pump header at that
system. At 2:07 pm October 6, we restarted the pump and confirmed that the
pressure was normal value.
18. – As confirming downward tendency on flow rate at Residual Heat Removal system
sea water pump (C) of Unit 6, we stopped cooling reactor by Residual Heat
Removing system (A) and conducted check-out the pump and related system at
11:55 am on October 7. The result of check-out , we confirmed no abnormalities
and restarted cooling reactor with Residual Heat Removal system (A) at 12:41 pm on the same day.
19. – At 9:42 am on October 13, we stopped the residual heat removal system (A) in
order to check operation of residual heat removal system temporary pump (B) of
Unit 6. We started the residual heat removal system (B) at 9:54 am on the same day.
After completion of the check, we stopped the residual heat removal system (B) at
10:07 am, and restarted residual heat removal system (A) at 10:17 am.
20. – Because a decrease in the amount of water was confirmed at the residual heat
removal system seawater pump (C) of Unit 6, the cooling of the reactor using
residual heat removal system (A) was stopped at 2:42 pm on October 14, and after
that we stopped the residual heat removal system seawater pump (C). Later on, we
restarted the residual heat removal system seawater pump (C) and confirmed that it
returned to a predetermined performance. Thus, we restarted to cool the reactor
using residual heat removal system (A) at 3:23 pm on the same day. Due to this
suspension, the water temperature of the reactor temporarily rose to 23.3℃ from 22.6℃.
21. – At 2:30 pm on October 19, we stopped seawater line pump of residual heat removal
system (C) after stopped cooling reactor by residual heat system (A) due to the
downward trend on the flow rate and pressure of the Unit 6 residual heat removal
system. After that we restarted sea water pump of residual heat removal system (C)
and as we confirmed the related pump returned to running at specified performance,
we restarted cooling reactor by residual heat removing system (A) at 3:02 pm on the
same day. The temperature of the reactor water is rose 21.6 deg C to 22.1 deg C
temporarily by this suspension.
22. – For the purpose of Unit 6 water intake inspection, at 9:05 am October 21, unit 6
seawater pump of Equipment Water Cooing System was shutdown, and stopped
cooling the spent fuel pool. At 9:13 am, Residual Heat Removal System (A) was
stopped and stopped cooling the reactor. After the inspection was finished, the cooling
for the reactor was resumed by restarting the pump of Residual Heat Removal System
(A). At 4:01 pm, the cooling for spent fuel pool was resumed by restarting the seawater
pump of Equipment Water Cooling System. As a result of this interruption, the water
temperature in the reactor increased temporarily from 24℃ to 32.1℃. The water
temperature for the spent fuel pool increased temporarily from 25℃ to 26.5℃
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