1. No category

STATUS OF THE
FUKUSHIMA DAIICHI SITE
AND THE REMAINING
RISKS
NURIS 2015
1st INRAG Conference on Nuclear Risk
16 - 17.04.2015 BOKU, Vienna
Dr. G. Kastchiev
Member of INRAG
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STATUS OF THE FUKUSHIMA SITE /1/
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FUEL DEBRIS
The fuel containing masses in units 1-3
блок include total about 257 t HM /2/ more than Chernobyl:
- More than 2800 кг isotopes of Pu; - Almost 540 кг Cs-137;
- About 362 кг Sc-90;
- About 1280 кг other long–lived isotopes;
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Fuel debris create very high radiation fields in
units 1 -3, assess of personal in the buildings is
limited;
Geometrical shape and physical properties of
debris unknown, as well as their locations
containing. Re-criticality?
February 2015, unit 1 –
experimental use of “muon”
detection device, that could
detect how much of the debris
remains in the vessel;
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The solidified fuel containing masses
continue to generate heat, air cooling is
still not possible;
The water cooling cycle is semi open,
every day 320 m3 water /2/ are injected
in units 1 – 3, after cleaning half of it is
reused;
The basements of units 1 – 3 contain
huge amount (about 65 000 m3) highly
contaminated water;
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No real plans for their removal.
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SPENT FUEL IN SPENT FUEL POOLS IN UNITS 1-4
Before the accidents the amount of spent fuel in the spent fuel
pools:
Unit 1 – 292 spent fuel assemblies (about 40 tons HM)
Unit 2 – 587 spent fuel assemblies (about 97 tons HM)
Unit 3 – 514 spent fuel assemblies (about 63 tons HM)
Unit 4 – 1331 spent fuel assemblies (about 219 tons HM)
Removal of spent fuel from unit 4 completed in December
2014.
Removal of spent fuel from unit 3 (planned) - first half of 2017
/3/. Severe radiation fields. Works to remove the large pieces
of debris that fell into the pool in an accident August 2014;
Removal of spent fuel from unit 3 – plans unclear;
Removal of spent fuel from unit 1 (planned): 2018 - 2019.
Dismantling of the existing cover scheduled March 2015.
Application of an anti-dispersal agent;
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RADIOACTIVE WATER IN THE BASEMENTS OF
UNITS 1 -3
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To cool fuel debris every day about 320 tons water is injected /4/ in reactors 1-3. Part of
injected water is in direct contact with the debris and becomes highly radioactive. In
addition during typhoons and heavy rains rain water goes inside the buildings;
In the end of March 2015 approximately 49 400 m3 water is accumulated in the
basements of units 1 – 3 /1/;
The total activity of the accumulated water is huge, but not known. An assessment /5/
shows that the activity of Cs-137 in the water accumulated in the basements of units 1 -3
could be more than 1 E17 Bq. This is more than Chernobyl releases of Sc-137 (about 8,5
E16 Bq) to the atmosphere /3/.
If this radioactive inventory would be released to the environment this will represent
another INES Level 7 accident;
The water in the basements of units 1 – 3 contains sea salt, boron acid, oil and other
chemicals and is chemically aggressive. Metal and other structures subject to corrosion.
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RADIOACTIVE RELEASES TO THE ATMOSPHERE
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Radioactive waters, contaminated surface and
equipment, removal of debris and other activities
generate aerosols, containing Cesium, Strontium,
Tritium and other radioactive nuclides;
End March 2011 - the rate of Cs emissions hundreds to thousand billion Bq/h /10/;
March 2012 - the rate of Cs emissions from
damaged units - about 10 million Bq/h /11/;
NGO /12/ - the present rate of Cs emissions is
about 10 million Bq/h (quoting TEPCO);
Even with a rate 1 million Bq/h the annual
release of Cs would be 8,76 billion Bq;
In 2003 the total annual release of long-lived
aerosols including Cs from 42 operating reactors
in Germany, Spain, Switzerland, Belgium and
Finland was 0,4 billion Bq /13/;
Fukushima site is a source of continuous and long
term tremendous contamination of the ocean.
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RADIOACTIVE LEAKAGES TO THE OCEAN
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The site is at the bottom of the hills, every day 800-1000 tons of underground water drain
down to units 1-4. At least 300 tons /4/are going into the basements of units 1 - 3 through
cable/pipe penetrations and small cracks, mixing with the heavily contaminated water used
to cool the debris. Part of the radioactive water is leaving the buildings in similar ways to the
port causing high levels of contamination to be found in the test wells near the sea;
During typhoons and heavy rains the underground water flow and its activity is increasing,
rain water is also contaminated. Highly contaminated water flows from buildings into the
trenches on the sea side. TEPCO failured to stop the flow of contaminated water;
Following typhoon ”Uifa”, on 19.10.2013 the record activity (isotopes of cesium, strontium,
tritium) measured in the underground water (east unit 2) – 1,3 million Bq/l /7/. After two
weeks heavy rains on 17.10.2014 the activity measured in the sample of groundwater (east
unit 1 and 2) – 267 thousands Bq/l /8/ (accuracy of measurements questionable);
In addition there are leakages of radioactive water stored in the thanks (“peaks of the
iceberg” - August 2013 - about 300 tons, 9 October 2013 - about 10 tons);
Samples of water taken from the Pacific Ocean of the U.S. and Canada West Coast already
contain Cesium /14/, even in very small amount, far below the limits;
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RADIOACTIVE LEAKAGES TO THE OCEAN
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TEPCO - activity of Strontium, Cesium and
Tritium in the daily radioactive releases to the
sea (2013 and the projection for 2014 and
2015) is in order of billions Bq/day (see the
figure on the right). No data about releases of
Barium, Molybdenum, Technetium, etc.;
In 2013 the total annual release of Strontium90 and Cesium-137 to the sea - about 13 TBq
(using TEPCO data);
According to TEPCO the difference between
”last year”(2013) and “this year”(2014) is due
to the movement of the survey point;
Even after start of operation of sub-drain
system, wall of frozen soil and sea-side wall
TEPCO plans to release about 325 billion Bq of
Cesium and Strontium to the ocean;
Fukushima site is a source of long term
tremendous contamination of the ocean.
INES scale doesn’t consider radioactive
releases to the ocean.
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RADIOACTIVE WATER STORED AT THE SITE
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The total volume of water with different
activity stored at the Fukushima site all the
time is steadily increasing;
In the end of 2013 г. more than 350 000
tons are stored in more than 1000 tanks;
In March 2015 the total amount of stored
water with different activity is more than
600 000 tons, the total storage capacity is
about 800 000 tons /6/;
TEPCO demonstrated insufficient ability to
manage the contaminated water.
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STORAGE OF RADIOACTIVE WATER
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STORAGE OF RADIOACTIVE WATER
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The thanks are sitting on poor
concrete foundation too close to
each other. In case of strong
earthquake and collapse of one
thank “domino” effect is possible;
Still some thanks are made from
bolted steel sheets and have to be
replaced with welded thanks;
Still some thanks are without level
measuring devices;
Every 1-3 days a new 1000 tons
tank has to be installed and
connected to the system.
There are too many joints, pipes,
pumps, etc. System too big to be
effectively controlled and managed;
Leakages of contaminated water
from the thanks. Last incident –
March 2015, leak of more than 700
m3 highly contaminated water.
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CLEANING OF CONTAMINATED WATER
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Every day about 320 tons water are injected in units 1-3
to cool the debris;
Water is contaminated, much of it is pumped out and
passed through Cesium cleaning systems;
Water contaminated with other radioactive nuclides is
cleaned with “Advanced Liquid Processing System”
(ALPS), capacity 250m3/day x 3 systems;
Additional expanded high performance ALPSs
(250m3/day x 3 systems) and high-performance ALPSs
(500m3/day) installed /7/ with government subsidies;
ALPS removes all radioactive nuclides without tritium.
The waste water is stored on the site;
After installing the new systems approximately 2000 tons
of water a day could be processed /6/;
In addition several strontium removal systems;
End of 2014 - about 245 000 m3 already treated. TEPCO
plans to clean highly contaminated water till the end of
May 2015;
The problem with the treatment of salt water (about 20
000 m3) is not resolved;
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OTHER FACILITIES
Groundwater bypass system
Groundwater is pumped from 12 wells inland from units
1-4 and stored in thanks. This system could reduce the
ingress of water to the basements by 100 tons per day.
The activity of released water must be below 10 Bq/l.
From April 2014 till February 2015 about 73 800 m3
released;
Sub-drain system
Set of wells on the site to decrease the level of
underground water. Damaged in March 2011 and
restored, new pits installed (total42). Includes collecting,
purification and transfer equipment. Could capture 500700 m3 water per day with subsequent cleaning. Start of
pumping – August 2015. TEPCO expects that this will
reduce groundwater inflow into the buildings by up to
150 m3 per day. No final decision about disposition or
discharge of treated water. Difficult to prevent radioactive
contamination of wells as well as the water in them;
Seaside Impermeable Wall
Barrier between units 1-4 and the port in order to prevent
leakages of contaminated water. Steel pipe sheet pile
wall constructed, 20-30 m deep inside the seabed, about
5 m from the coast. Total length about 780 m, and 4-5 m
above the sea level. Initially planned to close it in the end
of September 2014 (postponed till May 2015).
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ICE WALL
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The approved plan is to isolate units 1-4 from the
flow of the groundwater and to prevent leakages by
freezing the soil around the damaged units;
1549 chiller pipes will be installed (approximately
30m deep underground) at 1m intervals /7/. The
total length of the wall would be about 1500 m, the
volume of frozen soil would be about 70 000 m³ ;
The soil-freezing technology used in tunnel and
mining industry, but never in such large scale;
No feasibility studies;
Vulnerable to earthquakes and accidents with heavy
equipment;
Potential negative consequences not thoroughly
evaluated;
In April 2015 the ice wall will be partially frozen,
overall freezing in the mountain side to be started in
May after approval from the NRA. Very small progres
on the sea side;
Initial investments – more than $ 320 million (with
government subsidies);
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OTHER PROBLEMS
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Metal and other structures in the buildings are subject to corrosion processes;
Buildings are vulnerable to earthquakes, typhoons, heavy rains and combinations of
extreme external events;
The site territory is contaminated, radiation dose rates above the natural background.
Protective measures needed;
The port is heavily contaminated;
Long-term management of generated radioactive waste with different activity not resolved,
only temporary storages on the site;
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Big amount of treated water that contains tritium;
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Lack of skilled workers because of dose limits;
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Lack of trust between the main shareholders – TEPCO, Japanese nuclear regulator, public;
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It looks that Japanese government, TEPCO and IAEA underestimate the severity of the
situation.
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S0URCES
1. TEPCO, Status of the Fukushima Daiichi Nuclear Power Station Nuclear Power Station, January 2014
http://www.tepco.co.jp/en/nu/fukushima-np/water/images/140127_01.pdf
2. The National Diet of Japan Fukushima Nuclear Accident Independent Investigation Committee (NAIIC) Report
3. Nuclear Regulation Authority, Japan, Measures for Mid-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS, 18.02.2015
http://www.nsr.go.jp/data/000098679.pdf
4. Situation of Storage and Treatment of Accumulated Water including Highly Concentrated Radioactive Materials at Fukushima Daiichi Nuclear
Power Station (194th Release), March 27, 2015
5. Errico Cazzoli, Estimate of Consequences from the Fukushima Disaster
6. TEPCO, Schedule of Main Targeted Events at Fukushima Daiichi Nuclear Power Station, March 2015
7. TEPCO Nuclear Safety Reform Plan Progress Report, February 3, 2015
8. http://www.itar-tass.com/proisshestviya/808888
9. http://www.vesti.ru/doc.html?id=2059701&tid=88854
10. Estimation of radioactive release resulting from Fukushima Dai-ichi NPS accident, 7.23.2012, Hiroya SHIRAKI, TEPCO
https://www.nsr.go.jp/archive/nisa/shingikai/700/14/240723/AM-3-2.pdf
11. Current Status of Fukushima Dai-ichi NPS, Masaya Yasui, International Experts Meeting on Reactor and Spent Fuel Safety in the Light of the
Accident at the Fukushima Daiichi Nuclear Power Plant, March 2012, Vienna, Austria
12. Current State of Post-Accident Operations at Fukushima Daiichi, Hajime Matsukubo, March 31, 2015
http://fukushimaupdate.com/current-state-of-post-accident-operations-at-fukushima-daiichi/
13. National Reports to the Convention on Nuclear Safety, http://www-ns.iaea.org/conventions/nuclear-safety.asp?s=6&l=41
14. Fukushima Daiichi NPS Prompt Report (Nov 11,2014), http://www.tepco.co.jp/en/press/corp-com/release/2014/1243939_5892.html
15. Efforts to ensure ocean protection, TEPCO, August 11, 2014, http://www.tepco.co.jp/en/nu/fukushimanp/handouts/2014/images/handouts_140811_03-e.pdf
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