Text

NRC Bulletin 2003-01 Response to NRC Request for Additional Information
	ML042920066
Person / Time
Site:	San Onofre
Issue date:	10/13/2004
From:	Scherer A; Southern California Edison Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	BL-03-001
	Download: ML042920066 (13)
	v • d • e

SOUTHERN CALIFORNIA EDISON An 0

Compn A. Edward Scherer Manager of Nuclear Regulatory Affairs October 13, 2004 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

Subject:

Docket Nos. 50-361 and 50-362 NRC Bulletin 2003-01 Response To NRC Request For Additional Information San Onofre Nuclear Generating Station Units 2 and 3

References:

1)

Letter from A. E. Scherer (SCE) to the Document Control Desk (NRC) dated August 1, 2003;

Subject:

San Onofre Nuclear Generating Station Units 2 and 3, Docket Nos. 50-361 and 50-362, 60-Day Response to NRC Bulletin 2003-01, "Potential Impact of Debris Blockage on Emergency Sump Recirculation at Pressurized-Water Reactors"

2)

Letter from Bo M. Pham (NRC) to Harold B. Ray (SCE) dated September 7, 2004;

Subject:

San Onofre Nuclear Generating Station (SONGS) - NRC Bulletin 2003-01 re: Potential Impact of Debris Blockage on Emergency Sump Recirculation at Pressurized-Water Reactors (TAC NOS. MB9610 and MB9611)

Dear Sir or Madam:

By Reference 1, Southern California Edison (SCE) submitted a 60-day response to NRC Bulletin 2003-01, "Potential Impact of Debris Blockage on Emergency Sump Recirculation at Pressurized-Water Reactors."

By Reference 2, NRC staff has requested additional information regarding our submittal in order for the staff to continue its review of the submittal.

Enclosed is the SCE response to the request for additional information.

P.O. Box 128 San Clemente, CA 92674-0128 949-368-7501 Fax 949-368-7575 1io3

Document Control Desk October 13, 2004 If you have any questions or require any additional information, please contact Mr. Jack Rainsberry at (949) 368-7420.

Sincerely, Enclosure cc: B. S. Mallett, NRC Region IV, Regional Administrator B. M. Pham, NRC Project Manager, San Onofre Units 2 and 3 C. C. Osterholtz, NRC Senior Resident Inspector, San Onofre Units 2 and 3

ENCLOSURE SCE RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION SAN ONOFRE NUCLEAR GENERATING STATION. UNITS 2 AND 3 SOUTHERN CALIFORNIA EDISON COMPANY NRC BULLETIN 2003-01 DOCKET NOS. 50-361 AND 50-362 The following questions are provided after a preliminary review of Southern California Edison's (SCE's) submittal dated August 1, 2003 (Reference 1), in response to NRC Bulletin 2003-01 of June 9, 2003.

1.

On page 5 of Attachment I of your Bulletin 2003-01 response, you state:

"Licensed operator requalification training will be completed by November 30, 2003 to address loss of flow/loss of pump suction while in [the] recirculation mode of emergency core cooling. The training will address indications of sump clogging and subsequent Severe Accident management Guidelines."

However, your response does not completely discuss the operator training to be implemented. Please provide a detailed discussion of the operating procedures to be implemented, the indications of sump clogging that the operators are instructed to monitor, and the response actions the operators are instructed to take in the event of sump clogging and loss of ECCS recirculation capability.

Response to question number 1:

Licensed operator requalification training was conducted from October 7, 2003 through November 4, 2003. Acronyms used in this response include:

CS Containment Spray EOI Emergency Operating Instruction FS Floating Step HPSI High Pressure Safety Injection LOCA Loss Of Coolant Accident LPSI Low Pressure Safety Injection RAS Recirculation Actuation Signal, or, in some contexts, Containment Emergency Sump RWST Refueling Water Storage Tank SBLOCA Small Break Loss Of Coolant Accident SFSC Safety Function Status Check Si Safety Injection WOG Westinghouse Owners Group Page 1 of 11

Operating Procedures The training emphasized that at the time of the training, no changes to SONGS procedures had yet been made in response to NRC Bulletin 2003-01. Possible procedure changes then under consideration were discussed, including the 10 possible changes proposed by Westinghouse (PA-SEE-085):

1) Throttle / Stop Containment Spray, 1 or both trains.

2) Pre-align 1 train to RAS, other train to remain on RWSTs.

3) Terminate 1 train SI after RAS (assumes both are running).

4)

Review LPSI early termination prior to RAS.

5) Refill RWST from all possible sources.

6) Injecting water from a refilled / dilute source.

7) Aggressive cooldown I depressurization for SBLOCA.

8) Add guidance on symptoms / identification of Sump blockage.

9) Add contingency actions in response to blockage.

10) Evaluate changing SI Throttle I Stop criteria (earlier termination)

At the time, the WOG was reviewing this information for possible impact and change to the EOls. Simulator training re-emphasized these 10 items and allowed the operators to perform the " RAS Actuation"attachment.

Indications of Sump Clogging The instructor reviewed generic Containment Emergency Sump concerns with the operators and solicited suggestions on recognition of sump degradation. The instructor was provided with key points that identified symptoms of cavitation on pumps taking suction from the sump, namely, low or oscillating pump flow and motor amps.

Response Actions The lesson plan reemphasized that at the time of the training, no changes had been made to the SONGS EOls in response to NRC Bulletin 2003-01. The lesson plan reviewed the following actions.

o The WOG is looking at possible procedure changes that might delay switchover to containment sump recirculation (e.g., shutting down redundant pumps that are not necessary to provide required flows to cool the containment and reactor core, and operating the Containment Spray System intermittently).

o Actions that already exist in the E0ls that could assist:

-FS-14, TERMINATE Containment Spray Operation (allows stopping CS Pumps and extends time to RAS)

-FS-20, MONITOR RWST Level (maintains awareness of RWST inventory)

-FS-21, VERIFY RAS Conditions Established (initiates Attachment 14, RAS Actuation, which includes HPSI Protection - flow requirement)

Page 2 of 11

-Attachment 14, RAS Actuation (If inadequate Sump Level, evaluates need for RWST inventory)

-SFSC (Figure 1 provides minimum Si flow requirements during Cold Leg Injection and Figure 2 provides minimum HPSI flow during simultaneous hot/cold leg injections.)

-SFSC (LOCA) for Containment Pressure/Temperature (gives minimum CS flows with or without Emergency Cooling Units) o SONGS already has proceduralized methods to refill the RWST or to otherwise provide inventory to inject into the reactor core and spray into the containment atmosphere (direction from Floating Step 20 'Monitor RWST Level" as well as S023-12-9 main body Step 15 to initiate makeup as required):

- S023-3-2.2 "Makeup Operations" (can fill at approximately 150 GPM)

- SO23-3-2.11.1 "SFP Level Change and Purification Crosstie Operations" (splits flow from a pump that has a capacity of about 150 GPM) o SONGS already has Severe Accident Management Guidelines (SAMG)

(Note that 1 OCFR50.54 (x) & (y) apply.)

Allows for filling the Reactor Cavity using un-borated water (firewater system)

Throttles Si flow

2.

On page 1 of Attachment I of your Bulletin 2003-01 response you state:

"Additionally, Westinghouse is evaluating potential changes to the guidance in CEN-162. SCE plans to review the potential changes after they become available and make procedural modifications as appropriate." The Westinghouse owners Group (WOG) has developed operational guidance in response to Bulletin 2003-01 for Westinghouse and Combustion Engineering type PWRs. Please provide a discussion of your plans to consider implementing this new WOG guidance. Include a discussion of the WOG recommended compensatory measures that have been or will be implemented at your plant, and the evaluations or analyses performed to determine which of the WOG recommended changes are acceptable at your plant. Provide technical justification for those WOG recommended compensatory measures not being implemented by your plant. Also include a detailed discussion of the procedures being modified, the operator training being implemented, and your schedule for implementing these compensatory measures.

Response to question number 2:

Backaround

SONGS has performed an analysis for emergency sump operability in A-98-NM-002, "Post-LOCA Emergency Sump operability in presence of loose coatings and other Page 3 of 11

debris." The analysis shows that the containment emergency sump would be able to supply a sufficient amount of water to the Emergency Core Cooling System (ECCS) and Containment Spray System (CSS) in the recirculation mode.

The maximum velocity through a large, unblocked passage toward the emergency sump would be 0.13 feet per second. The SONGS emergency sumps were tested and analyzed in full scale model testing and hydraulic model studies contained in two reports, S023-611-1-7, 'Final Report on Hydraulic Model Studies of Containment Emergency Sump Intakes,"

Western Canada Hydraulic Laboratories, 1979, and SO23-611-1-2, "Hydraulic Model Studies of Containment Emergency Sump Recirculation Intakes with Revised Operating Water Levels," Western Canada Hydraulic Laboratories, 1990.

The insulation of the Reactor Coolant System piping, the pressurizer, and the primary side of the steam generators at SONGS is Reflective Metal Insulation (RMI) as described in UFSAR Section 6.2.2.1.2.6. The secondary side of the steam generators is insulated in stainless steel encapsulated mineral wool also described in the same UFSAR section.

NUREG-0897, "Containment Emergency Sump Performance", Revision 1, states in Section 3.3.1(5): 'Both fibrous insulation and reflective metallic insulation (RMI) debris fragments transport at low velocities (0.2 to 0.5 ft/sec).". Since the maximum approach velocity to the sump is 0.13 feet per second it is unlikely that insulation debris generated by the LOCA will be transported to the sump.

The aforementioned Western Canada Hydraulic Laboratories studies performed two separate full-scale tests of SONGS emergency sumps in 1979 and 1990 to demonstrate that SONGS 2 & 3 containment emergency sump recirculating intakes will not be subjected to degrading effects on sump performance. The most recent and limiting test was performed in 1990, and the results were documented in S023-611-1-2. The first two portions of this test were performed to identify blockage configurations that were most prone to vortex formation and air ingestion. The three worst-case configurations, which were used in third stage tests, had blockage ratios of 67%, 75.5% and 83.5%. The blockage in the third stage tests was simulated by fixing vertical metal plates to the trash rack surrounding the sump. These tests were performed at higher flow rates than those for LOCA conditions at SONGS. The tests examined the maximum water level where air bubble ingestion occurred. For each of the three scenarios, the water level was between 18.5 and 18.8 feet.

Calculation CCN-4 to N-0240-006 gives the minimum post-LOCA water level inside of containment as 19.078 feet, which is greater than the maximum water level that caused air ingestion in the three scenarios.

Based on the preceding discussion it is considered unlikely (compared with LOCA events) that the SONGS emergency sumps will be prevented from performing their safety function following a LOCA.

CEN-152 Revision 5.3 Assessment SONGS has determined that some of the procedural modifications recommended by the Westinghouse Owners Group (WOG) in Revision 5.3 to CEN-152 may be risk adverse at Page 4 of 11

SONGS. Qualitative risk assessments considered potential risk-negative aspects of procedural modifications that would reduce the Safety Injection flow during containment sump recirculation. Comparisons were made with potential risk-positive aspects of procedural modifications. Potential risk-negative aspects include the increase in the likelihood of operator error and the increase in the likelihood of failure of equipment that is redundant to equipment that experiences a random single failure. In some cases, the risk-negative aspects were judged to outweigh the risk-positive aspects.

In those cases, SONGS is not adopting the procedural steps recommended in Revision 5.3 to CEN-1 52. Technical justification is provided on a step-by-step basis later on in this Enclosure. The WOG-recommended measures that SONGS will be adopting and their supporting analyses are discussed below.

CEN-1 52 Revision 5.3 Steps That WILL Be Implemented Loss of Coolant Accident Recovery Guideline

1. LOCA Step 12B Containment Spray Termination Criteria Action to be Taken: No action required to EOI S023-12-3, Loss of CoolantAccident.

The only change that will be required is in the bases document. CEN-1 52 addresses this step as a "Continuously Applicable Step or Non-Sequential Step" and moved it up to Step 12, from Step 37; SONGS has this incorporated as Floating Step FS-14, TERMINATE Containment Spray Operation and does not need to make any change.