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ABWR Safety

PRA, Containment Response & Severe Accidents

J. Alan Beard April 13, 2007

Enhanced Safety

Rugged and simplified design Modern C&I systems and control room Safety systems are more redundant and diverse Meet USNRC requirement for Severe Accidents Meet utilities' ALWR requirements Pre-engineered, pre-licensed total plant design Shorter, predictable construction schedule Reduced capital and O&M costs

Core Damage Frequency

Advanced Typical Operating Nuclear Plants in U.S. Nuclear Plants

10-3 1010-4 10-

10-5 10-

10-6 10-

10-7 10-

Zion SequoyahSurry Peach Grand SequoyahSurry Bottom Gulf

APWR ABWR

Improvements in Nuclear Plant Designs Source: "Severe Accident Risks: An Assessment for Five U.S. Nuclear Power Plants, NUREG-1150, June 1989.

Copyright © 2007 by GE Energy / Nuclear

2 GE Energy / Nuclear April 2007

ABWR Safety Challenges Reduced

· LOCA challenges reduced

> Eliminated external recirculation loops ­ No large pipes below core > Increased rating of low pressure piping (ISLOCA) > Added backup Reactor Water Cleanup System shutoff valve > Core always covered for DBAs > High Pressure Core Flooder has capability even with inlet water at saturation

Copyright © 2007 by GE Energy / Nuclear 3 GE Energy / Nuclear April 2007

ABWR Safety Challenges Reduced

·ATWS challenges reduced

> Accumulator-driven scram without Scram Discharge Volume > FMCRD electric run-in > Alternate Rod insertion ­ Diverse logic for scram function > Automated mitigation ­ Recirculation and feedwater runback ­ boron injection

Copyright © 2007 by GE Energy / Nuclear 4 GE Energy / Nuclear April 2007

ABWR Safety Challenges Reduced

·Shutdown challenges reduced

> 3 dedicated RHR shutdown loops > 2 trains of Fuel Pooling Cooling ­ RHR can be manually aligned to provide cooling of the Spent Fuel Pool > All core cooling pumps potentially available > Large water inventory over fuel

Copyright © 2007 by GE Energy / Nuclear

5 GE Energy / Nuclear April 2007

PSA Scope

·Internal Events, Power Operation > Level 1, 2, and 3 ·Internal Events including Low Power and Shutdown > Level 1 > 99% SD CDF in mode 6, so no level 2 required ·External Events > Does not include seismic > Fire Using the FIVE Methodology > Internal Floods ­ Screening shows no impact on risk

Copyright © 2007 by GE Energy / Nuclear 6 GE Energy / Nuclear April 2007

PSA Scope (cont)

·Seismic > Seismic margins analysis identified no outliers ­ High Confidence Low Probability of Failure (HCLPF) ­ At least 1.67 times design · 0.6 g > Most critical equipment is located low in their buildings ­ Even greater capability

Copyright © 2007 by GE Energy / Nuclear 7 GE Energy / Nuclear April 2007

PSA Quality

·Follows ASME Standard Principles > Where applicable, meets capability category 3 > Some plant specific information not available until COL or construction ·PSA Capability > Determine that ABWR meets risk goals > Determine importance at a system level > Determine overall importance of operator action ·Can be used for operational assessments

Copyright © 2007 by GE Energy / Nuclear 8 GE Energy / Nuclear April 2007

Design Features Resulting from PRA

·3-division ECCS ·AC independent water addition ·Combustion turbine generator ·RWCU filter demin bypass to permit decay heat removal at high pressure ·Containment overpressure protection ·Automation of Suppression pool cooling ·Automation of ATWS mitigation

Copyright © 2007 by GE Energy / Nuclear 9 GE Energy / Nuclear April 2007

Design Features Resulting from PRA (cont)

·ADS drywell pressure bypass timer ·RCIC capability for local control ·4th SRV added to Remote Shutdown Panel ·Increased rating of low pressure piping to eliminate ISLOCA concerns ·RWCU drain line isolation valve ·Service Water and Circ Water pump trips and isolation on flood ·Improved RHR heat exchanger supports

Copyright © 2007 by GE Energy / Nuclear 10 GE Energy / Nuclear April 2007

ABWR Internal Events CDF

Copyright © 2007 by GE Energy / Nuclear

11 GE Energy / Nuclear April 2007

ABWR Response to Feedwater Line Break- Short Term

80 70 180 170 Containment Design Limit Drywell Wetwell 160 150 140 130 120 110 100 140

12 GE Energy / Nuclear April 2007

Suppression Pool Temp (°F)

Containment Pressure (psia)

60 50 40 30 20 10 0

Feedwater stopped

0

20

40

60

80

100

120

Time (sec)

Copyright © 2007 by GE Energy / Nuclear

ABWR Response to Feedwater Line Break

80 260 240

Maximum Drywell Pressure (psia)

70 60 50 40 2 RHR 1 RHR 30 20 10 0 10 0 10 1 10 2 10 3 10 4 10 5 Containment Spray Containment Design Limit

Suppression Pool Temp (°F)

220 200 180 160 140 120 100 10 6

Time (sec)

Copyright © 2007 by GE Energy / Nuclear 13 GE Energy / Nuclear April 2007

ABWR Passive Severe Accident Mitigation Features

Containment overpressure protection

ABWR passive features which mitigate severe accidents: · Inerted containment · Lower drywell flood capability · Lower drywell special concrete and sump protection · Suppression pool - fission products scrubbing and retention · Containment overpressure protection

Containment Pressure vessel

Core

Fusible valve Basaltic concrete

Sump cover

High degree of public protection High degree of public protection

14 GE Energy / Nuclear April 2007

Copyright © 2007 by GE Energy / Nuclear

AC Independent Water Addition

MO Reactor Building Wall Diesel Driven Fire Pump (Existing)

MO Drywell Spray

LPFL Pump

MO

Drywell Standpipe

Outdoor Fire Truck Connection (New)

Reactor Vessel

15 GE Energy / Nuclear April 2007

Copyright © 2007 by GE Energy / Nuclear

ABWR Severe Accident

- Fire Water Addition

1.0 Rupture Disk Opens 0.8 Lower Drywell Dries Out Firewater Spray Starts Lower Drywell Refloods 0.4 120 100 80 60 40 20 Firewater Spray Stops Vessel Fails 0.0 0 10 20 30 40 50 60 70 0

Pressure (MPa)

0.6

0.2

Time (hrs)

16 GE Energy / Nuclear April 2007

Copyright © 2007 by GE Energy / Nuclear

Pressure (psig)

ABWR Whole Body Dose at 1/2 Mile

1x10 Annual Probability of Exceedence

-5

1x10

-6

1x10

-7

· Minimum 48

1x10

-8

hours

· Nominal site

weather

0.1 1 10 100 Early Whole Body Dose, Rem 1000

1x10

-9

0.01

Probability of large release is < 11in a billion Probability of large release is < in a billion

Copyright © 2007 by GE Energy / Nuclear 17 GE Energy / Nuclear April 2007

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