112th day!
Dear Coleagues:
I. Recapping on photos and a dose map of 1F4 SFP (5th floor)
Th new clear photo, taken on June 29, was released from TEPCO showing
that a team is coming out from the pool surface. The pool temperature was
85 derees? at 4:00 PM on June 30. This photo is ve interesting since it
is clearly showing an evidence of boiling steam coming out of the filled
spent fuel rack. Please visit
http://www.tepco.o.jp/en/news/110311/index-e.html and downlord:
http://www.tepco.co.jp/en/news110311/images/110701_1.jpg
Spent Fuel Pool in Reactor Building (5th floor),Unit 4, Fukushima Daiichi
Nuclear Power Station (pictured on June 29, 21)
This phenomena is consistent with the two calculation summarized in Earhtquake
(93). Attached please find the Spen Fuel Data (1F4).
In the two phase natural circulation heat transfer, the pool water
enters from the bottom of the fuel, rising inside of the fuel assembly,
started to boil as oon as the temperature on the surface of the fuel rods
reached to the boilin point and then outflows into the bulk of pool water
as 100°C steam bubbles. he residence time is computed through a heat
balance necessary to remove th decay heat by heat of vaporization minus the
specific heat to raise th inlet water temperature to 100?.
Flow Rate (m3/s) = (decay heat, J/s)/((225 - 4.2*(100 Tpool))*1.E+06,
J/m3)
Importantssue here is that the steam from the spent fuels comes out
even when the bulk of pool water is not at the boiling point bt at a
temperature as high as 70-90?. It appears that the bulk pool temperatre
did never reached to the boiling temperature.
II. Recapping on cleaning odebris from the 1F3 reactor building.
Since the dose rate at the first foor in 1F3 Reactor Building is as
high as 170 mSv/h, TEPCO could not recove the nitrogen gas injection to
prevent anther hydrogen explosion. Today, TPCO started removing solid
debris by using a new robot, Worrier, with a bg ³crab tong," manufacture by
the US iRobot Company, and a robot vcuum cleaning system.
III. Air cooler installed in 1F3.
Late on June 0, it was announced that the air cooler installed in 1F3
started to wok. It is expected that the current pool water temperature,
currently ashigh as 70?, will drop down to around 40 degrees in a matter of
a few days. his is the second successful operation, following 1F2.
IV. Recapping onthe water purification system
In view of the repeated troubles in water prification system, TEPCO is
trying to update and improve the instruction mnuals for this system.
The leakage detected in AREVA¹s temporally storage tan was announced due to
a miss in an automatic level control valve wich was inadvertently set to 3%
level, near empty, instead of 30% for startupcondition. By this erroneous
setting, the pump flow was choked to tranfer the water.
Well, let me stop here,
Genn Saji
________________________________________________________________________
(Previous e-mail senat 09:38 PM on June 30 as Earthquake (111))
Dear Colleagues:
111th day!
I. Waste water management
Today TEPCO released an English version of ³Siuation of storing and
treatment of accumulated water including highly concentrated radioactive
materials at Fukushima Daiichi Nuclear Power Station(1st Release)² through
http://www.tepco.co.jp/en/press/corp-com/elease/11062911-e.html. The
attached flow sheet is explains a forecast of a ass balance of contaminated
water generated in Fukushima Daiichi as of June . Please note the
³concentrated sea water² receiving tank receiving discharge stream from
the reverse osmosis process. This stream seems to cotain radionuclide that
were not adsorbed or co-deposited in the ³treatment facility,² likely
containing significant amount of Sr-89 and Sr-90.
As a matter of fact, at the ³concentrated sea water² receiving ank, a 50
tons of leakage occurred yesterday. The leaked water showed a contact dose
rate of 50 microSv/h. This leakage seems to occurred at 9:30 AM of June 29,
from a drain at the bottom of the temporally storage tank. By applying an
end cap the leakage was stopped at 10:30 AM.
Also at 2:49 PM of June 29, anoter leakage was detected in AREVA¹s
temporally storage tank due to a mis operation in an automatic flow control
valve which was inadvertently set t a manual closed position. The system
restarted at 9:15 PM. Such mino trouble still brought over to June 30. At
2:30 PM, the AREVA system trpped due to a malfunction of ³gas purge line²,
potentially releasing hdrogen generated through water radiolysis.
Since the operation of the conaminated water treatment system is so
critical, the operation hasbeen performed in parallel with
pre-commissioning test. However, due to the repeated water leakagesand
miss operations, the availability of the system went down to only 50-60%.Currently, TEPCO is targeting to keep the most critical trench water leveldown below 1 meter from the ground level to avoid leakage to the sea.
I. Cleaning of debris from the 1F3 reactor building.
Tomorrow, TEPCO willstart removing solid debris by using a new robot,
Worrier, with a big ³crab ong², and a robot vacuum cleaning system as shown
in the attached illustration. Additional photos are also available at
http://www.tepco.co.jp/en/news/110311/index-e.html. Pease download
Cleaning system for Unit 3, Fukushima Daiichi Nuclear Power tation
Cleaning system
(pictured on June 28, 2011)
Robot (Worriar)
(pictured May, 2011)
III. Transfer of low level contaminated water from 1F5 and 1F6 o the
MegaFloat
Please visit http://www.tepco.co.jp/en/news/110311/ndex-e.html and
download
[Reference] Transfer of the low level accumulate water to Megafloat
Megafloat tied up to around Shallow Draft Quay (Bck of the picture)
(pictured on June 25, 2011)
Megafloat tied up to around Shllow Draft Quay (Front of the picture)
(pictured on June 25,11)
IV. Photos and a dose map ofF4 SFP (5th floor)
TEPCO¹s crew of 6 people went inside of the SFP area of the 1F4 to check
conditions of Pool Water Cleaning and Circulation Cooling system, looking
for an alternate cooling pass. Although the 4 member crew stayed there for
almost one hour, the accumulated doses were only 0.21-0.31 mSv.
Well, lt me stop here tonight!
Genn Saji
___________________________________________________________________________
(Previous e-mail sent at 11:13 PM n June 29 as Earthquake (110))
Dear Colleagues:
110th day!
I. Recapping othe water purification system
Although the system resumed its pre-commisioning test at 2:36 PM
yesterday, a miniscule water leak was noticed in apipe joint at the feedig
pump. TEPCO is keeping a close eye as to its operation. At 11:00 AM, the
operation was suspended, since additional two mniscule leaks were detected.
TEPCO exchanged the faulty pipe and resume operationat 13:30. However, I
do not think the miniscule leakages are of immediate afety concern, since I
believe there should be no radiological safety issuesin the purified water
after going through the reverse osmosis (RO) process It is because the
ionic diameters of radioactive species are much larger tan the MWCO (
Molecular Weight Cut Off, which refers to the lowest moleclar weight solute
in which 90% of the solute is retained by the membrne, or the molecular
weight of the molecule that is 90% retained by the membrne) in the
commercially available membranes. As a matter of fact, seeral companies
tested their commercial water purifiers by using the slightly contaminated
tap water i Fukushima and confirmed that no radioactivity passed through.
Before treatmnt the tap water contained as high as 10?32Bq/kg of Cs-137 and
600Bq/kg ofI-131. I do not think TEPCO should be so nervous of the
miniscule leak of te purified water. In stead, try to construct a more
robust pipeline.
The real headache is in the waste disposal issues of the ³concentrate
sea water,² which should have been discharged from the RO being rich in salt
and contaminated with non-cesium radionuclide, typically Sr-89 and Sr-90.
Even for this, it is likely not necessary to go that far as to
vitrification, s long as the wastes are mainly contaminated with strontium.
The ³concentraed water² will go through a series of evaporators which seem
to have been used in reprocessing facilities. This stream of waste water
may still be level when non-cesium radionuclide is assumed to come out
in thi stream.
Many Japanese scientists, including me, thought of putting desalintion
process first so that some kind of zeolite can be used for adsorption of
wide range of radioactive species. It was because of disappointingly low
DF in the salty water. However, with the Kurion¹s and AEVA¹ system in
front of RO for desalination, it is not necessary to improve he current
water purification system by trying further to reduce concentrtion of
radioactive species. TEPCO made a good choice for the water purification
process, I believe. Although its operation is not stable at this moment,
this should be improved by further optimization and enforcement of pipe
lines.
As a matter of fact, a leakage as much as 50 tons of the ³concentrated
sea water² also occurred in its strage tank, showing a contact dose rate of
50 microSv/h. This indicatesthat some non-cesium radioactivity is actually
being concentrated as a dscharge from the RO process. The leakage is a
real issue with its radiactive species.
II. Recapping on the ³melt-through² scenario
SinceI covered this issue on June 7 as Earthquake (87), I did not
re-visit tis topic for last three weeks, mainly because there are no
significan release of news or reports on this issue in Japan. At that
time NISA reeased their calculation to estimate the initiating time of melt
down. Theresults were summarized below.
Unit Approximate time of RPV filure
1F1 8 PM of March 11
1F2 10:50 PM of March 14
F3 10:10 PM of March 14
These results were presented at the IAEA inisterial level meeting.
Their results are certainly conservatie, by ignoring the ³feed and
Bleed² cooling which I believe played an importnt role, since the rector
core cooling can be made by automatically releasingthe steam through the
³Steam Release and Safety Valves.² The ³safety vave² function should have
been available without battery power. I have ot continue my study on his
since then. However, I had a chance to exchange some discussion as o the
mechanism of melt down and recalled the study made by Professor Burkov and
his colleagues of Radium Institute. ( B.E. BURAKOV et al. , 1996. Te
Behavior of Nuclear Fuel in First Days of the Chernobyl Accident, MRS 199
Fall Meeting, Boston, MA, USA. Symposium II, December 2, 1996 ³Scienific
Basis for Nuclear Waste Management XX², Mat. Res. Soc. Symp. Proc. Vol. 65
(1997), pp. 1297-1308.) They studied various types of Chernobyl fuel
conaining masses named black ³lava², brown ³lava², porous ³ceramic² and
³hot² prticles that formed during first days of the accident at the
Chernobyl PP 4th Unit by methods of optical and electron microscopy,
microprobe and X-ay diffraction. One of the most important lessons
learned was that the eltdown sequence follows the melting points of the
structural materials nvolved in forming the corium.
If I aly there findings to the Fukushima Daiichi, the following sequence
can e predicted during the meltdown.
(1) The first structural material starte to melt must have been the
stainless steel components in core, includng control rods and poison
curtain with the melting temperature of 1371-1400?or SUS 316. In the
Chernobyl reactor, the spacer grids were made from the tainless steel,
therefore, among the initially released hot particles by th steam
explosion, some of them were found entrapped in the Fe-Cr-Ni melts.
(2) When the temperature reached as high as 1900?, zirconium started to melt
with its melting emperature of 1852?. This should be the initial source of
corium togther with the molten stainless steel. Into the mass of molten
metals, somefraction of fuel particles should have been included. By
melting the fuel ladding, the fuel assembly loses the self-standing
configuration, and pileup on the core support plate by forming a
non-uniform mixture of ³cold² sructural and ³hot² fuel materials with the
melt in the zone of direct contat, as in the Chernobyl accident.
(3) Since the melting point of UO2 is aroun 2800?, the melting of fuel
matrix is less likely just by decay heat. It ws confirmed with the
Chernobyl lava that the temperature of the silicate mel in the Chernobyl
³lava² center did not exceed 1660-1700 °C the limitof zircon's thermal
stability.
I believe this kindof sequence occurs when the water inside of the reactor
vessel is completelydried out. In my ³back of an envelop² calculation,
such a situation did not occur in 1F1 which sems to have survived until
water injection became successful. Since many extensive LOCA/ECCS code
systems have been developed for BWRs in late 1970th, this kind of the
problem should be investigated from tht point of view instead of overly
simplified core melt analysis.
III. ecapping on the dose maps and observation of highly contaminated water
n 1F2
As introduced in Earthquake (103), the basement of the 1F2 Reactoruilding was filled with radish water as observed in the picture presented
i http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110622_01-j.pd
The following electrochemical assessment was made to understand this
phenomna.
The pH of the water was near neutral with 7.1.
http://www.tepco.cojp/nu/fukushima-np/images/handouts_110522_04-j.pdf
Perhaps it is becausethere is no appreciable concrete debris in 1F2 Reactor
Building. Assume tat the equilibrium potential is determined by the oxygen
in the air atmophere, through an electrochemica reaction:
2H2O = O2 + 4H+ + 4e- Eo = 1.228 - 0.0591pH + 0.0147log (P-O2)
given in the Pourbaix Diagram ( Atlas of Electrochemical Equlibria in
Aqueous Solutions by Marcel Pourbais, Pergamon Press 1966 ). Theequilibrium potential of this accumulated water is 0.8 V/SHE. When
consuting with the Pourbaix diagram, at pH = 7.1 d Eo = 0.8 volt, it is
within the equilibrium state of FeO3 (hematite). In the more recent text
book, this region is designated with FeO(OH) [red-brown] ( G.K. Schweitzer
and L.L. Pesterfield, 200. The Aqueous Chemistry of the Elements, Oxford
University Press)
Well, let me stop here tonight!
Genn Saji
Dear Coleagues:
I. Recapping on photos and a dose map of 1F4 SFP (5th floor)
Th new clear photo, taken on June 29, was released from TEPCO showing
that a team is coming out from the pool surface. The pool temperature was
85 derees? at 4:00 PM on June 30. This photo is ve interesting since it
is clearly showing an evidence of boiling steam coming out of the filled
spent fuel rack. Please visit
http://www.tepco.o.jp/en/news/110311/index-e.html and downlord:
http://www.tepco.co.jp/en/news110311/images/110701_1.jpg
Spent Fuel Pool in Reactor Building (5th floor),Unit 4, Fukushima Daiichi
Nuclear Power Station (pictured on June 29, 21)
This phenomena is consistent with the two calculation summarized in Earhtquake
(93). Attached please find the Spen Fuel Data (1F4).
In the two phase natural circulation heat transfer, the pool water
enters from the bottom of the fuel, rising inside of the fuel assembly,
started to boil as oon as the temperature on the surface of the fuel rods
reached to the boilin point and then outflows into the bulk of pool water
as 100°C steam bubbles. he residence time is computed through a heat
balance necessary to remove th decay heat by heat of vaporization minus the
specific heat to raise th inlet water temperature to 100?.
Flow Rate (m3/s) = (decay heat, J/s)/((225 - 4.2*(100 Tpool))*1.E+06,
J/m3)
Importantssue here is that the steam from the spent fuels comes out
even when the bulk of pool water is not at the boiling point bt at a
temperature as high as 70-90?. It appears that the bulk pool temperatre
did never reached to the boiling temperature.
II. Recapping on cleaning odebris from the 1F3 reactor building.
Since the dose rate at the first foor in 1F3 Reactor Building is as
high as 170 mSv/h, TEPCO could not recove the nitrogen gas injection to
prevent anther hydrogen explosion. Today, TPCO started removing solid
debris by using a new robot, Worrier, with a bg ³crab tong," manufacture by
the US iRobot Company, and a robot vcuum cleaning system.
III. Air cooler installed in 1F3.
Late on June 0, it was announced that the air cooler installed in 1F3
started to wok. It is expected that the current pool water temperature,
currently ashigh as 70?, will drop down to around 40 degrees in a matter of
a few days. his is the second successful operation, following 1F2.
IV. Recapping onthe water purification system
In view of the repeated troubles in water prification system, TEPCO is
trying to update and improve the instruction mnuals for this system.
The leakage detected in AREVA¹s temporally storage tan was announced due to
a miss in an automatic level control valve wich was inadvertently set to 3%
level, near empty, instead of 30% for startupcondition. By this erroneous
setting, the pump flow was choked to tranfer the water.
Well, let me stop here,
Genn Saji
________________________________________________________________________
(Previous e-mail senat 09:38 PM on June 30 as Earthquake (111))
Dear Colleagues:
111th day!
I. Waste water management
Today TEPCO released an English version of ³Siuation of storing and
treatment of accumulated water including highly concentrated radioactive
materials at Fukushima Daiichi Nuclear Power Station(1st Release)² through
http://www.tepco.co.jp/en/press/corp-com/elease/11062911-e.html. The
attached flow sheet is explains a forecast of a ass balance of contaminated
water generated in Fukushima Daiichi as of June . Please note the
³concentrated sea water² receiving tank receiving discharge stream from
the reverse osmosis process. This stream seems to cotain radionuclide that
were not adsorbed or co-deposited in the ³treatment facility,² likely
containing significant amount of Sr-89 and Sr-90.
As a matter of fact, at the ³concentrated sea water² receiving ank, a 50
tons of leakage occurred yesterday. The leaked water showed a contact dose
rate of 50 microSv/h. This leakage seems to occurred at 9:30 AM of June 29,
from a drain at the bottom of the temporally storage tank. By applying an
end cap the leakage was stopped at 10:30 AM.
Also at 2:49 PM of June 29, anoter leakage was detected in AREVA¹s
temporally storage tank due to a mis operation in an automatic flow control
valve which was inadvertently set t a manual closed position. The system
restarted at 9:15 PM. Such mino trouble still brought over to June 30. At
2:30 PM, the AREVA system trpped due to a malfunction of ³gas purge line²,
potentially releasing hdrogen generated through water radiolysis.
Since the operation of the conaminated water treatment system is so
critical, the operation hasbeen performed in parallel with
pre-commissioning test. However, due to the repeated water leakagesand
miss operations, the availability of the system went down to only 50-60%.Currently, TEPCO is targeting to keep the most critical trench water leveldown below 1 meter from the ground level to avoid leakage to the sea.
I. Cleaning of debris from the 1F3 reactor building.
Tomorrow, TEPCO willstart removing solid debris by using a new robot,
Worrier, with a big ³crab ong², and a robot vacuum cleaning system as shown
in the attached illustration. Additional photos are also available at
http://www.tepco.co.jp/en/news/110311/index-e.html. Pease download
Cleaning system for Unit 3, Fukushima Daiichi Nuclear Power tation
Cleaning system
(pictured on June 28, 2011)
Robot (Worriar)
(pictured May, 2011)
III. Transfer of low level contaminated water from 1F5 and 1F6 o the
MegaFloat
Please visit http://www.tepco.co.jp/en/news/110311/ndex-e.html and
download
[Reference] Transfer of the low level accumulate water to Megafloat
Megafloat tied up to around Shallow Draft Quay (Bck of the picture)
(pictured on June 25, 2011)
Megafloat tied up to around Shllow Draft Quay (Front of the picture)
(pictured on June 25,11)
IV. Photos and a dose map ofF4 SFP (5th floor)
TEPCO¹s crew of 6 people went inside of the SFP area of the 1F4 to check
conditions of Pool Water Cleaning and Circulation Cooling system, looking
for an alternate cooling pass. Although the 4 member crew stayed there for
almost one hour, the accumulated doses were only 0.21-0.31 mSv.
Well, lt me stop here tonight!
Genn Saji
___________________________________________________________________________
(Previous e-mail sent at 11:13 PM n June 29 as Earthquake (110))
Dear Colleagues:
110th day!
I. Recapping othe water purification system
Although the system resumed its pre-commisioning test at 2:36 PM
yesterday, a miniscule water leak was noticed in apipe joint at the feedig
pump. TEPCO is keeping a close eye as to its operation. At 11:00 AM, the
operation was suspended, since additional two mniscule leaks were detected.
TEPCO exchanged the faulty pipe and resume operationat 13:30. However, I
do not think the miniscule leakages are of immediate afety concern, since I
believe there should be no radiological safety issuesin the purified water
after going through the reverse osmosis (RO) process It is because the
ionic diameters of radioactive species are much larger tan the MWCO (
Molecular Weight Cut Off, which refers to the lowest moleclar weight solute
in which 90% of the solute is retained by the membrne, or the molecular
weight of the molecule that is 90% retained by the membrne) in the
commercially available membranes. As a matter of fact, seeral companies
tested their commercial water purifiers by using the slightly contaminated
tap water i Fukushima and confirmed that no radioactivity passed through.
Before treatmnt the tap water contained as high as 10?32Bq/kg of Cs-137 and
600Bq/kg ofI-131. I do not think TEPCO should be so nervous of the
miniscule leak of te purified water. In stead, try to construct a more
robust pipeline.
The real headache is in the waste disposal issues of the ³concentrate
sea water,² which should have been discharged from the RO being rich in salt
and contaminated with non-cesium radionuclide, typically Sr-89 and Sr-90.
Even for this, it is likely not necessary to go that far as to
vitrification, s long as the wastes are mainly contaminated with strontium.
The ³concentraed water² will go through a series of evaporators which seem
to have been used in reprocessing facilities. This stream of waste water
may still be level when non-cesium radionuclide is assumed to come out
in thi stream.
Many Japanese scientists, including me, thought of putting desalintion
process first so that some kind of zeolite can be used for adsorption of
wide range of radioactive species. It was because of disappointingly low
DF in the salty water. However, with the Kurion¹s and AEVA¹ system in
front of RO for desalination, it is not necessary to improve he current
water purification system by trying further to reduce concentrtion of
radioactive species. TEPCO made a good choice for the water purification
process, I believe. Although its operation is not stable at this moment,
this should be improved by further optimization and enforcement of pipe
lines.
As a matter of fact, a leakage as much as 50 tons of the ³concentrated
sea water² also occurred in its strage tank, showing a contact dose rate of
50 microSv/h. This indicatesthat some non-cesium radioactivity is actually
being concentrated as a dscharge from the RO process. The leakage is a
real issue with its radiactive species.
II. Recapping on the ³melt-through² scenario
SinceI covered this issue on June 7 as Earthquake (87), I did not
re-visit tis topic for last three weeks, mainly because there are no
significan release of news or reports on this issue in Japan. At that
time NISA reeased their calculation to estimate the initiating time of melt
down. Theresults were summarized below.
Unit Approximate time of RPV filure
1F1 8 PM of March 11
1F2 10:50 PM of March 14
F3 10:10 PM of March 14
These results were presented at the IAEA inisterial level meeting.
Their results are certainly conservatie, by ignoring the ³feed and
Bleed² cooling which I believe played an importnt role, since the rector
core cooling can be made by automatically releasingthe steam through the
³Steam Release and Safety Valves.² The ³safety vave² function should have
been available without battery power. I have ot continue my study on his
since then. However, I had a chance to exchange some discussion as o the
mechanism of melt down and recalled the study made by Professor Burkov and
his colleagues of Radium Institute. ( B.E. BURAKOV et al. , 1996. Te
Behavior of Nuclear Fuel in First Days of the Chernobyl Accident, MRS 199
Fall Meeting, Boston, MA, USA. Symposium II, December 2, 1996 ³Scienific
Basis for Nuclear Waste Management XX², Mat. Res. Soc. Symp. Proc. Vol. 65
(1997), pp. 1297-1308.) They studied various types of Chernobyl fuel
conaining masses named black ³lava², brown ³lava², porous ³ceramic² and
³hot² prticles that formed during first days of the accident at the
Chernobyl PP 4th Unit by methods of optical and electron microscopy,
microprobe and X-ay diffraction. One of the most important lessons
learned was that the eltdown sequence follows the melting points of the
structural materials nvolved in forming the corium.
If I aly there findings to the Fukushima Daiichi, the following sequence
can e predicted during the meltdown.
(1) The first structural material starte to melt must have been the
stainless steel components in core, includng control rods and poison
curtain with the melting temperature of 1371-1400?or SUS 316. In the
Chernobyl reactor, the spacer grids were made from the tainless steel,
therefore, among the initially released hot particles by th steam
explosion, some of them were found entrapped in the Fe-Cr-Ni melts.
(2) When the temperature reached as high as 1900?, zirconium started to melt
with its melting emperature of 1852?. This should be the initial source of
corium togther with the molten stainless steel. Into the mass of molten
metals, somefraction of fuel particles should have been included. By
melting the fuel ladding, the fuel assembly loses the self-standing
configuration, and pileup on the core support plate by forming a
non-uniform mixture of ³cold² sructural and ³hot² fuel materials with the
melt in the zone of direct contat, as in the Chernobyl accident.
(3) Since the melting point of UO2 is aroun 2800?, the melting of fuel
matrix is less likely just by decay heat. It ws confirmed with the
Chernobyl lava that the temperature of the silicate mel in the Chernobyl
³lava² center did not exceed 1660-1700 °C the limitof zircon's thermal
stability.
I believe this kindof sequence occurs when the water inside of the reactor
vessel is completelydried out. In my ³back of an envelop² calculation,
such a situation did not occur in 1F1 which sems to have survived until
water injection became successful. Since many extensive LOCA/ECCS code
systems have been developed for BWRs in late 1970th, this kind of the
problem should be investigated from tht point of view instead of overly
simplified core melt analysis.
III. ecapping on the dose maps and observation of highly contaminated water
n 1F2
As introduced in Earthquake (103), the basement of the 1F2 Reactoruilding was filled with radish water as observed in the picture presented
i http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110622_01-j.pd
The following electrochemical assessment was made to understand this
phenomna.
The pH of the water was near neutral with 7.1.
http://www.tepco.cojp/nu/fukushima-np/images/handouts_110522_04-j.pdf
Perhaps it is becausethere is no appreciable concrete debris in 1F2 Reactor
Building. Assume tat the equilibrium potential is determined by the oxygen
in the air atmophere, through an electrochemica reaction:
2H2O = O2 + 4H+ + 4e- Eo = 1.228 - 0.0591pH + 0.0147log (P-O2)
given in the Pourbaix Diagram ( Atlas of Electrochemical Equlibria in
Aqueous Solutions by Marcel Pourbais, Pergamon Press 1966 ). Theequilibrium potential of this accumulated water is 0.8 V/SHE. When
consuting with the Pourbaix diagram, at pH = 7.1 d Eo = 0.8 volt, it is
within the equilibrium state of FeO3 (hematite). In the more recent text
book, this region is designated with FeO(OH) [red-brown] ( G.K. Schweitzer
and L.L. Pesterfield, 200. The Aqueous Chemistry of the Elements, Oxford
University Press)
Well, let me stop here tonight!
Genn Saji
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