1. Nuclear Accident in Japan: A Summary
4/1/2017 3:13 PM
Nuclear Accident in Japan: A Summary
Dennis Quinn, CHP
DAQ, Inc.
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

2. Fukushima Nuclear Reactors

3. Fukushima Nuclear Reactors

4. Fukushima Daiichi Nuclear Reactors

5. Boiling Water Reactor Basic Flow
Use this slide to show the general Rx design, flow of water, steam, heat. And show where the radioactivity is.
Starting with feedwater pumped into reactor
Reactor provides heat
Feedwater converted to steam and directed to steam turbines
Turbines spin and connected to electrical generator
Steam is directed downward to condenser, where it is condensed back into water
A separate loop of water (e.g., ocean water) cools the condenser and is discharged back to ocean
Condensed water is heated and pumped back into reactor as feedwater.

6. Boiling Water Reactor Design
Reactor vessel is within the primary containment vessel (drywell). Reactor vessel is thick steel, and the drywell is a steel shell surrounded by reinforced concrete.
The secondary containment structure has the function to maintain the components out of the weather, but it is not a robust containment structure.
The wetwell, also called the torus or suppression pool, has a purpose to take the steam being created after shutdown and condense it.
Describe a normal operating cycle and refueling: plant operates for months, then is shut down for refueling. The top of the reactor and the containment are removed and the fuel (some of the fuel) is moved from the reactor vessel into the spent fuel pool.
Note that the spent fuel pool is located in the secondary containment, and contains spent fuel from previous refuelings under water.
en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Power_Plant

7. Nuclear Reactor Fuel Design
Fuel is important because it contains almost all of the radioactivity. The safety systems are designed to maintain cooling to the fuel – if the fuel is maintained cool, you cannot release large quantities of radioactivity.
Describe the fuel as about feet long and less than a foot square. There is a large surface area to improve heat transfer.
The fuel itself is uranium oxide and is slightly radioactive before it is put into the reactor and becomes extremely radioactive after it has fissioned in the reactor.
The fuel is changed out about once per months, and 1/3 is removed, 1/3 new, and the remainder is “shuffled”.
A Fukushima reactor (unit 2 or 3) had about 2740 MWth of power (at 100%) and this produced about 765 MWe.
~96 rods per assembly
~ assemblies per Rx

8. Key Points
The nuclear fuel contains almost all of the radioactivity (>99%).
The nuclear fuel continues to generate heat after the reactor is shut down.
19 MW after 1 day
12 MW after 1 week
7 MW after 3 months
The fuel must be cooled, or there is a risk of fuel damage and release of radioactivity.
Fuel is important because it contains almost all of the radioactivity. The safety systems are designed to maintain cooling to the fuel – if the fuel is maintained cool, you cannot release large quantities of radioactivity.
So, all the safety systems are designed to pump in water and keep the fuel cool – or else there could be a large release of radioactivity.

9. Stainless Steel Melts Activity Available for Release (Curies)
Fuel Temperature (oF)
Stainless Steel Melts
Activity Available for Release (Curies)
Reactors 2 and 3 at Fukushima are 2380 MWth reactors. Assumptions for release fractions from USNRC NUREG Decay to 7.5 days after shutdown. Values listed are those estimated to be released from the core to the coolant, and release from coolant to containment and release from containment to environment are not included in this estimate. Ci shown above are for 100% fuel melt, 100% fuel overheat, and 100% fuel gap. It is likely that a value less than 100% will occur – for example, there may be 100% fuel gap plus 50% fuel overheat plus 10% fuel melt.
The temperatures listed are for when fuel clad damage is expected – about 1300 oF, with resultant release of some noble gases and volatile fission products.
Fuel Overheat- about 3,000 degrees F, release of 50% of noble gases and volatile fission products and some less volatile fission products (Tellurium, Barium, Strontium)
Fuel Melt: about 4,500 degrees F, release of 100% NG and volatile fission products, and larger percentages of non-volatiles such as barium and strontium.
Note that the stainless steel that hold the fuel together, spacers, etc. melts at about 2,500 degrees F, so the cladding and steel will be damaged or melted resulting in fuel pellets in a pile in the reactor with molten materials – all before the fuel itself is melted.

10. Prior to Accident Spent Fuel Pool
Reactor Service Floor (Steel Construction)
Concrete Reactor Building (secondary Containment)
Reactor Core
Reactor Pressure Vessel
Containment (Dry well)
Containment (Wet Well) / Condensation Chamber
Spent Fuel Pool
Fresh Steam line
Main Feedwater
Normal operation and just after shutdown – normal flow of water and steam, reactor is being cooled by flowing feedwater being heated into steam.
From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun

11. Earthquake and Loss of Electric Power
Earthquake causes loss of offsite power.
Emergency Diesel Generators supply power
Tsunami disables EDGs
Steam dumps to wet well
Water level in reactor decreases
Fuel heats up
Cladding is damaged and releases noble gases and volatile isotopes (cesium and iodine)
~3/4 of the core exposed, Cladding exceeds ~1200°C
Zirconium in the cladding starts to burn under Steam atmosphere
Zr + 2H20 ->ZrO2 + 2H2
Exothermal reaction further heats the core
Generation of hydrogen Unit 1: kg Unit 2/3: kg
Hydrogen gets pushed via the wet-well, the wet-well vacuum breakers into the dry-well
> 99.9% of radioactivity is in the fuel
From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun

12. Accident Progression
Large volume in wet well eventually heats to boiling and no more pressure suppression
Pressure increases
Hydrogen created by high temperature reaction of cladding & steam
Operators decide to vent primary containment gas to secondary containment
Gas has fission products and hydrogen
From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun

13. Hydrogen Explosion Unit 1 und 3
Hydrogen burn inside the reactor service floor
Destruction of the steel-frame roof
Reinforced concrete reactor building seems undamaged
Lower Flammability Limit (LFL) for Hydrogen = 4% in air, UFL = 75% in air
Lower Explosive Limit (LEL) for Hydrogen = 17% in air, UEL = 56%
From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun

14. Early Releases and Dose Rates
Background is – 0.01 mR/hr
Fukushima Daiichi Main Gate dose rates dependent on wind direction & events:
3/14: 50 mR/hr
3/15: 300 mR/hr due to venting from Unit 2
3/15: 1200 mR/hr due to explosion & fire on Unit 4
3/16: 850 mR/hr explosion on Unit 2
3/17: 1100 mR/hr – releases from Units 2 and 3 of plant
U.S. 7th Fleet ship contaminated helicopter crew.
US news crews returning after 2 wks have contaminated equipment.
The situation was very confusing in the first two weeks. It was uncertain why the dose rates were going up then down – although now it appears to all be explainable based on venting of the primary containments and hydrogen explosions – and the wind direction.

17. Emergency Planning Actions
Date, Time
Evacuate
Shelter
March 11, 15:42 - Loss of power in Nuclear Power Plants
March 11, 21:23
3 km
10 km
March 12, 05:44
March 12, 18:25
20 km
March 15, 11:06
30 km
March 21 – First food restrictions: spinach, kakina, & milk
April 22 – Selected areas km termed Planned Evacuation Zones if estimated dose > 20 mSv (2 rem)
On April 22, the area within 20 km officially declared as a “no-entry Zone”. The planned evacuation zones from km are generally to the northwest of Fukushima Daiichi. Those who are expected to get 20 mSv in a year must leave within a month.
Other actions: April 30, interim policy on whether to use school buildings or outdoor areas.
April 22: Radiation measurements in ports in Japan to provide info on shipping containers, decontamination criteria, reporting.
Considering exchanging soil layers as a way to lower radiation levels in affected areas.

18. Radiation Measurements
This graph is in uSv/hr. If you multiply by 0.1, then it is converted to mR/hr.
In Ibaraki prefecture, the dose rate (average) was about 0.04 uSv/hr on 3/24, which is about 5-10 times background.
Early on, the results from Fukushima province were not shown on the public websites.
The reason for showing this is to show the reduction over time – the dose rates are due to deposition on the ground, and the reduction is the decay of I-131, which was the major radionuclide in the first few weeks after the accident.
Note –no significant deposition events noted after 3/19

19. Water and Food Products
I-131, Cs-134, Cs-137
Milk
Produce (leafy vegetables, spinach, etc.)
Drinking water (peak at 3x 30 km, now below limits).
Seawater, fish products
Initially prevented sale of food & seafood within 30 km radius
Recent identification of beef with Cesium contamination.

20. Percent above Action Level for I-131
Type of Sample
Percent above Action Level for I-131
Percent above Action Level for Cs-134 and Cs-137
Meat and Eggs 0%
Milk 4%
0.2%
Produce 2% 5%
Seafood
0.4% 7%
Tea Products
14%
Total
Data from April - July After this synopsis of data on the WHO website, some samples of beef were found above the 500 Bq/kg limit for meat.

21. Food and Drinking Water Japan Limits (Bq/L or Bq/kg)
Nuclide
Water, Milk
Vege-tables
Meat, Fish
IAEA for all food
I-131
300*
2,000
3,000
Cs-134
200
500
1,000
Cs-137
IAEA values are those that will result in 10 mSv per year (1 rem)
Limits are based on Notice No Article 3 of the Dept of Food Safety, March 17, 2011.
Note that the effluent limit (release to the ocean) is less than drinking water limit.
Note that Bq/kg x = pCi/g.
2000 Bq/kg = 54 pCi/g; 500 Bq/kg = 13.5 pCi/g
Water Effluent limits are 40 Bq/L I-131, 60 Bq/L Cs-134, and 90 Bq/L Cs-137
IAEA GSG-2, Criteria for Use in Preparedness and Response for a Nuclear or Radiological Emergency
*Infant water and milk limit is 100 Bq/kg
IAEA Limits based on 1 rem per year to most restrictive individual (generally infant) if consuming food for 1 year at the limit

22. Workers Meeting for Recovery 4/1

23. Bags of Radwaste (PPE, Plastic, etc.)

24. Contaminated Water and Soil Control Issues
Resin Spraying for Soil Control
Rx 2 – Leak to the Sea

26. Contamination Control Silt Fence

27. Mega Float Arriving Yokohama

28. Remote Operated Vehicle

29. Remote Monitoring & Protection
Remote operation of equipment and dose rates. Note Protective Clothing and Respirators.

30. International Nuclear and Radiological Event Scale (INES)
Chernobyl
Level 7
Fukushima Daiichi
TMI
Level 5

31. Status according to World Health Org
As of July 2011

32. So How Bad Was It?
As a nuclear or industrial accident, it was major – resulted in evacuation, loss of a major electricity source, and uncertainty in the public for months.
It was not a major health catastrophe, and it is not likely that there will be significant health effects.
Why? – The emergency plan actually worked. Despite the initial confusion, people were evacuated, controls were placed on food, etc.
Note that this is my personal opinion.

33. 4/1/2017 3:13 PM
Key Points:
It was a bad accident from a nuclear safety aspect and a major industrial accident. They are are at the edge of the woods, but not out of the woods yet.
It was not a major health issue, and is not likely to be, even in the future. That is not to say that there will be absolutely no health effects, but the Emergency Plan worked, people were evacuated, and controls were placed on food.
n the picture above, the artist replaced Mt. Fuji with an image of Fukushima Nuclear Power Plant from the original “The Great Wave of Kanagawa”. Woodblock prints and Bunjinga: The school of art best known in the West is that of the ukiyo-e paintings and woodblock prints.
Originally created as a Japanese Ukiyo-e woodblock printing, “the Great Wave of Kanagawa” is a study of contrasts between thundering waves and the small but mighty Mt. Fuji. Artist Katsushika Hokusai ( ) often used the mystical mountain as a centerpiece in his art. In a novel interpretation of a traditional theme, Mt. Fuji’s significance and power is hardly minimized by its diminished size.
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.