ML14139A165

Response to Questions Regarding NRC Documents Describing Our Oversight of Seabrook Containment Liner Examination Activities (EDATS: RegionI-2014-0122)

ML14139A165
Person / Time
Site:	Seabrook
Issue date:	05/19/2014
From:	Mel Gray Engineering Region 1 Branch 1
To:	Grinnell D C-10 Foundation
Gray M
References
EDATS: RegionI-2014-0122, IR-12-005
Download: ML14139A165 (2)

Text

From: Gray, Mel Sent: Monday, May 19, 2014 9:21 AM To: Debbie Grinnell Cc: Barkley, Richard; Dentel, Glenn; Cook, William; Heater, Keith

Subject:

Response to Questions Regarding NRC Documents Describing our Oversight of Seabrook Containment Liner Examination Activities Based on your conversations with Mr. Rich Barkley of NRC Region I, the following responds to specific questions related to NRC reviews of the containment liner at the Seabrook Station.

Specifically, the following questions are associated with NRC Inspection Report 05000443/2012005 dated February 11, 2013 (ADAMS ML3042A058) and NRC Safety Evaluation Report with Open items Related to the License Renewal of Seabrook Station, (ML12160A374), pages 3-28 to 3-32.

If you have further questions, please contact myself at 610-337-5209 or Mr. Rich Barkley at 610-337-5328.

Myself and Mr. Bill Cook are also available today to discuss our recent NRC inspection report regarding Seabrook Station. Please contact me at the above number.

Sincerely, Mel Gray Chief, Engineering Branch 1 NRC Region I Office

1) What was the elevation of the water in the Containment Enclosure Building and at what azimuth?

Response: The bottom of the Containment Enclosure Building is -30 feet; the bottom floor of containment is -26 feet. The water level in the annulus area was found to be up to 6 feet deep.

Thus the water in the annulus was at most 2 feet above the floor level of the containment. The annulus runs 360 degrees around containment, with the exception of areas where there are penetrations into the containment, such as the fuel transfer tube and its associated concrete shielding. The containment is described in terms of angular measurement (azimuth) from 0 to 360 degrees.

2) In 2009, NextEra noted an area of the containment liner near the fuel transfer tube that was corroded and had a thickness of between 0.484 - 0.411 inches (a variation of 18 percent). You indicated that you had seen another document which indicated an area of the containment liner (presumably this same one) was 0.409 - 0.400 inches in early 2011. You also noted that in a February 2013 Inspection Report that another area was 0.375 inches thick, although we verified that this location (-26 foot elevation at azimuth 317 degrees) was definitely different than the 2009 measurement. You asked the location of all of these measurements, as well as whether the 2009 measurement would be repeated 3 times as indicated in an NRR license renewal document?

Response: The fuel transfer tube passes through the containment liner inside the transfer tube shielded vault. This area is located at azimuth 180 degrees near the containment floor. A

reinforcing transition plate, welded to the transfer tube, is then welded to the containment liner.

The transition plate is 0.75 inches thick and the liner plate is 0.375 inches thick. The weld joining these two pieces varies in thickness; however, the welded area thickness is greater than the required 0.375 inch thickness of the containment liner.

In 2009, the licensee noted an area of the containment liner near the fuel transfer tube was inspected and surface rust was evident. UT thickness readings verified that all areas with surface rust or coating anomalies showed thicknesses greater than 0.375 inches. The 0.484 and the 0.411 thickness readings were not taken in the same location. The two thickness readings were taken at different locations in the fuel transfer tube area, which varied in thickness due to the weld. However, both locations had thickness greater than the required 0.375 inches.

You indicated that you had seen another document which indicated an area of the containment liner (presumably this same one) was 0.409 - 0.400 inches in early 2011. Without knowing the document that identifies these numbers, we cannot provide a location or the context for these numbers.

3) You asked about a commitment by NextEra to inspect much more extensive portions of the containment liner, as well as urged the NRC to require NextEra to UT examine the thickness of 100% of the liner to detect any possible degradation as you do not feel the required visual inspection of the internal surface of the liner is adequate. You asked the location of all of these measurements, as well as whether the 2009 measurement would be repeated 3 times as indicated in an NRR license renewal document?

Response: As part of our ongoing license renewal review process, the NRC issued a Safety Evaluation Report (SER) with open items (ML12160A374). The NRC SER pages 3-30 and following describe licensee commitments to measure specific areas of the containment liner.

Regarding the fuel transfer tube vault area measured in 2009, the licensee stated that it will complete augmented exams of this area under Subsection IWE,Section XI of the ASME B&PV Code for the next three exam cycles (every 3 1/3 years). The licensee also committed to complete inspections of the containment liner area within 10 inches of the moisture barrier at the containment basement floor (-25 to -26 foot elevation). This was the area of the liner potentially affected by standing water in the annulus which is now maintained in a dewatered state. The licensee committed to measure the liner thickness at 10 degree increments and complete these examinations by December 31, 2015, and thereafter at intervals of no more than five refuel outages as described in the SER. The licensees containment liner examination actions during the recent April 2014 refuel outage will be described in the next NRC inspection report for the Seabrook Station to be issued in early August 2014.

NRC safety requirements for completing inservice inspections of the containment liner are located in 10CFR50.55a, paragraph g which requires licensees implement ASME Section XI of the Boiler and Pressure Vessel Code inservice inspections related to containment liners. Our reviews at the Seabrook Station to date have determined the licensee has complied with our requirements related to containment liner inspections.

I would note that while the thickness of the containment liner is not extensively measured, the integrity of the containment liner is confirmed via periodic testing during a Containment Integrated Leak Rate Test (ILRT). This test verifies the ability of the containment to withstand the highest pressure expected following a design basis accident by pumping up the building with high pressure air. It also verifies that when at this pressure, the containment will not leak more

than a very small fraction of its volume per day. The main purpose of the liner is to ensure the containment structure is able to meet this stringent leakage provision as noted in 10 CFR 50, Appendix J.