ML110480295

Attachment to E-mail, Willoughby to Miller, NRC Conference Call on Friday - Seabrook Annulus Debris Interceptor Approach Velocity

ML110480295
Person / Time
Site:	Seabrook
Issue date:	02/15/2011
From:	Willoughby P NextEra Energy Seabrook
To:	Office of Nuclear Reactor Regulation
Shared Package
ML110480290	List: ML110480280 ML110480295
References
Download: ML110480295 (4)

Text

Seabrook Annulus Debris Interceptor Approach Velocities During our January 21, 2011 conference call with the NRC concerning fiber erosion testing for Seabrook using a method that was acceptable to the NRC (ML101540221), the NRC requested the bases that the test velocities used in the Seabrook tests are applicable to the Seabrook containment and debris interceptors.

The basis is described below.

• Containment annulus flow rates are calculated as described in Seabrook response to RAI 15.

• The RAI 15 response appeared acceptable to the NRC. (ML093350036).

• All ECCS and CS flow is conservatively assumed to enter inside the bioshield area. Flow exits the annulus area and splits to the North and to the South to the sump strainers.

• Containment annulus water height is conservatively low. Large breaks would result in a water height of 3.01 feet instead of the 2.21 feet given in the example below.

• Path flow rate, annulus debris interceptor length and containment water depth determine the debris interceptor approach velocity.

• Example:

o DI at azimuth 250, Length = 18.5 feet, water height = 2.21 ft, flow rate =7635 gpm o Velocity = 7635 gal/min

• min/60 sec

• ft³/7.4805 gal / (18.5 ft

• 2.21 ft) = 0.416 fps.

• Debris hold up is based on testing at debris interceptor approach velocities that bound or exceeds the actual debris interceptor approach velocity.

Seabrook Annulus Debris Interceptor Approach Velocities.doc Page 1 R. J. Faix, February 2, 2011

Typical fiber debris hold-up at 0.517 fps Annulus Debris Interceptor Test Photos 5C-1025-2H Final (01) 5C-1025-2H Final (02)

Typical fiber debris hold-up at 0.384 fps Annulus DI Tests at 762 gpm Seabrook Annulus Debris Interceptor Approach Velocities.doc Page 2 R. J. Faix, February 2, 2011

Typical fiber debris hold up at 0.252 (500 gpm test flow rate) and 0.318 fps (635 gpm test flow rate)

Annulus Debris Interceptor Test Photos 6-500F-2H (01) 6-500F-2H (02) 4-630F-2H (01) 4-630F-2H (04)

• At 0.318 fps and less, the debris hold up occurred ahead of the debris interceptor. The debris piled up and sunk to the floor as the flow field passed through the debris. This type of debris holdup would expose small fines to the full approach velocity.

• At 0.384 fps and above, the debris hold up occurred at the debris interceptor and formed a triangular debris pile against the debris interceptor. The face of the debris pile is exposed to the debris interceptor approach velocity.

• Of the 8 annulus debris interceptors, 5 operate at an approach velocity that exceeds 0.384 fps based on the maximum ECCS and CS recirculation flow rate. Of these, one debris interceptor is not credited for debris hold up for the maximum recirculation flow case since its approach velocity exceeds the values used in the debris interceptor tests. The remaining 3 debris interceptors fall in the 0.318 fps category.

Seabrook Annulus Debris Interceptor Approach Velocities.doc Page 3 R. J. Faix, February 2, 2011

Conclusion Based on the type of debris piles formed behind the debris interceptors, the conservative water heights used to determine the debris interceptor approach velocity and the as-tested approach velocities, the 0.42 to 0.43 fps velocity fields used to test and determine the fines erosion fraction for Seabrook are conservative and bound the expected debris interceptor approach velocities.

Seabrook Annulus Debris Interceptor Approach Velocities.doc Page 4 R. J. Faix, February 2, 2011