fukushima daiichi nuclear power station accident april19 2011

By

Joseph S. Miller

EDA, Inc

Introduction Over 35 Years in the Nuclear Power Industry

MS Nuclear, BS Mechanical, BS Industrial

Worked at a BWR Nuclear Power Station for 9 years.

Responsible for Fuel, safety analyses and PRA.

Responsible for Nuclear Steam Supply Systems

Technical Support Manager for Emergency Response Organization.

Supported the Nuclear Regulatory Commission (NRC) in reviewing Nuclear Power Plant Safety Systems.

Acknowledgements Thanks to Japanese Industrial Atomic Forum (JIAF)

Tokyo Electric Power Company (TEPCO)

AREVA PowerPoint- The Fukushima Daiichi Incident – Dr. Matthias Braun

Nuclear and Industrial Safety Agency (NISA) & Japan Nuclear Energy Safety Organization (JNES) on Plant Data

Lake H. Barrett- Foundation For Nuclear Studies Briefing

General Electric

The Fukushima DaiichiAccident

1. What Happened?

2.Plant Designs

3.Accident Progression

4.Spent fuel pools

5.Radiological releases

6.Impact on US

What Happened?

Tsunami Size Was Accident Cause 3/11 15:45 at Fukushima I

Plant Designs - Fukushima Dai-ichi

Unit 1 is BWR/3

Units 2-4 are BWR/4

BWR is a Boiling Water Reactor

There are 52 Reactors in Japan and 104 Reactors in the USA (35 BWRs & 69 PWRs)

The Fukushima I reactors began operation in the 1970’s so they are all thirty - forty years old.

They all are early vintage Mark I Containment Designs

Fukushima Dai-ichi – Tokyo Electric Power Co.

Reactor No. Net MWe Reactor ModelCommercial

Start

Reactor

Supplier

Unit 1 439 BWR-3 3/71 GE

Unit 2 760 BWR-4 7/74 GE

Unit 3 760 BWR-4 3/76 Toshiba

Unit 4 760 BWR-4 10/78 Hitachi

Unit 5 760 BWR-4 4/78 Toshiba

Unit 6 1067 BWR-5 10/79 GE

Fukushima Dai-ichi Site Reactor and Fuel Specifications

PWR – Pressurized Water Reactor

What happened?

•The plant was immediately shut down (scrammed)

when the earthquake first hit. Off-Site power was lost.

•Emergency Diesel Generators (EDGs) started to

provide backup electrical power to the plant’s backup

cooling system. The backup worked.

•All AC power to the station was lost when the Tsunami

flooded the EDGs.

•The diesel generators ceased functioning after

approximately one hour due to Tsunami induced

damage.

•At that point, the plant experienced a complete

blackout (no AC electric power at all). Commonly

called a “Station Blackout”.

Operating BWR

When it Started

Containment Isolation

The Tsunami Hits

What happened (cont.)?•Initially the Isolation condenser (IC) for Unit 1, which uses the condensate as a heat sink, was used to remove the decay heat from the shutdown reactors. After 1 or 2 hours, the 29,000 gallons of water in the IC is hot, the condensate heat sink was not available and no heat removal was available for Unit 1.•Reactor Core Isolation Cooling (RCIC) system for Units 2 & 3, which operate on steam from the reactor, were used to cool reactor core water, however, the battery‐supplied control valves lost DC power after the prolonged use.•DC power from batteries was consumed after approximately 34 hours.•Hours passed as primary water inventory was lost and core degradation occurred (through some combination of zirconium oxidation and clad failure).

Isolation Condenser (Unit 1) and RCIC (Units 2 & 3) Were Used to Cool the Plants

RCIC Works for About 8 Hours

RCIC Stops Cooling Plants

What happened?

•Hydrogen in reactor building exploded causing it to collapse around the containment.•The containment around the reactor and RPV were reported to be intact.•Pressure in the containment drywell rose as wetwell became hotter.•Hydrogen produced from zirconium oxidation was vented from the containment into the reactor building.

Fuel in Top of Core is Uncovered

Zr-Water Begins at

What happened?

•Portable diesel generators were delivered to the plant site.•AC power was restored allowing for a different backup pumping system to replace inventory in reactor pressure vessel (RPV).•The decision was made to inject seawater into the RPV to continue to the cooling process, another backup system that was designed into the plant from inception.•Radioactivity releases from operator initiated venting appear to be decreasing.

Melting of the Fuel

Release of Fission Products

Containment is Last Barrier

Venting the Containment

Unit 1 Primary Containment Pressure (D/W) & Reactor Pressure (3/11 – 3/16)

Decay Heat

Hydrogen Explosion Units 1 & 3

Damage to Torus Unit 2

Looking Down Units 3, 2 & 1

Units 4 & 3 Looking Down

Radiation Levels

Fukushima I Fuel Pools

Surry 1 & 2 Surry Power Station, Unit 1 &2 II PWR-DRYSUB 2,546

06/25/1968

Virginia Electric and Power Co. WEST 3LP 05/25/1972

Surry, VA S&W 12/22/1972 90

(17 miles NW of Newport News, VA) S&W 03/20/2003

050-00280 05/25/2032

www.nrc.gov/info-finder/reactor/sur1.html 94

Current Event -Surry Power Station Shuts Down After Apparent Tornado Cuts Off-site Electricity

Apparent tornado damages switchyard adjacent to nuclear units

Loss of Off-Site Power

Emergency Diesel Generators Activated

Dominion Virginia Power crews have restored off-site power to station

Back-up diesel generators functioning to supplement electrical supply

Units are in a safe and stable condition

US Reactors

Three Mile IslandMarch 28, 1979

TMI Core ConfigurationEvening 3/28/1979

Three Mile Island History Reactor Scram: 04:00 3/28/79

Core melt and relocation: ~ 05:00 –07:30 3/28/79

Hydrogen Deflagration: 13:00 3/28/79

Recirculation Cooling: Late 3/28/79

Phased Water Processing: 1979‐1993

Containment Venting 43KCi Kr‐85: July 1980

Containment Entry: July 1980

Reactor Head removed and core melt found: July 1984

Start Defuel: October 1985

Shipping Spent Fuel: 1988‐1990

Finish Defuel: Jan 1990

Evaporate ~2M gallons Processed Water: 1991‐93

Cost: ~$1 Billion

Impact on US Reactors US has implemented B.5.b requirements in 2008

Beyond Severe Accident Guidelines

Onsite high pressure portable pump

Procedures and appropriate staging areas and requirements for fire hoses and equipment on site

MOUs with fire local fire stations to establish the plant as a priority in case of an emergency.

Impact on US Reactor Some of the things that should be reviewed

Review all external events, i.e., fire, flooding, explosions and earthquake, to ensure that there is backup emergency equipment that can support a station black out.

Review training for extreme station Blackout events and procedure.

Ensure that emergency batteries are qualified for worst case events for fl0od, fire, explosions and seismic.

The portable high pressure pump and associated equipment that was required because of B.5.b should be housed in a structure that is qualified for worst case fire, flood, explosion and seismic events.