ET 10-0031, Response to Supplemental Information Request for License Amendment Request Deviation from Fire Protection Requirements - Reactor Coolant System Subcooling During Alternative Shutdown

Response to Supplemental Information Request for License Amendment Request Deviation from Fire Protection Requirements - Reactor Coolant System Subcooling During Alternative Shutdown

ML103340290
Person / Time
Site:	Wolf Creek
Issue date:	11/22/2010
From:	Garrett T Wolf Creek
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ET 10-0031, TAC ME4757
Download: ML103340290 (21)

Text

W0LF CREEK NUCLEAR OPERATING CORPORATION Terry J. Garrett Vice President Engineering November 22, 2010 ET 10-0031 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Reference:

Letter ET 10-0026, dated September 22, 2010,.from T. J. Garrett, WCNOC, to USNRC

Subject:

Docket No. 50-482: Response to Supplemental Information Request for License Amendment Request Deviation from Fire Protection Requirements - Reactor Coolant System Subcooling During Alternative Shutdown (TAC NO. ME4757)

Gentlemen:

The Reference provided Wolf Creek Nuclear Operating Corporation's (WCNOC) License Amendment Request (LAR) to make changes to the approved fire protection program as described in the Wolf Creek Generating Station (WCGS) Updated Safety Analysis Report (USAR). Specifically, a revision to USAR Table 9.5E-1 was proposed to include information on Reactor Coolant System process variables not maintained within those predicted for a loss of normal ac power as evaluated in Evaluation SA-08-006 Rev.1, "RETRAN-3D Post-Fire Safe Shutdown (PFSSD) Consequence Evaluation for a Postulated Control Room Fire."

The Nuclear Regulatory Commission (NRC) staff initiated an acceptance review of the Reference and concluded that supplemental information is necessary to enable the NRC staff to make an independent assessment regarding the acceptabilityof the proposed amendment request in terms of regulatory requirements and the protection of public health and safety and the environment. A phone call between WCNOC and the NRC staff was held on October 26, 2010, to discuss the information required to supplement the amendment request. The requested supplemental information was provided by electronic mail from the NRC Project Manager on November 3, 2010 with the supplemental information to be submitted by November 22, 2010.

P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HC/VET

ET 10-0031 Page 2 of 3 This letter contains no commitments. If you have any questions concerning this matter, please contact me at (620) 364-4084, or Mr. Richard D. Flannigan at (620) 364-4117.

The Attachment provides a copy of the supplemental information needed with WCNOC's response following each requested item. The information provided in the Attachment does not impact the conclusions of the No Significant Hazards Consideration provided in the Reference.

In accordance with 10 CFR 50.91, a copy of this submittal is being provided to the designated Kansas State official.

Sincerely, Terry J. Garrett TJG/rlt Attachment I- Response to Supplemental Information Request for License Amendment Request Deviation from Fire Protection Requirements - Reactor Coolant System Subcooling During Alternative Shutdown II - Results for Scenarios 1, 1A, 2, and 2A With PORV Open Greater Than 3 Minutes cc: E. E. Collins Jr (NRC), w/a T. A. Conley (KDHE), w/a G. B. Miller (NRC), w/a B. K. Singal (NRC), w/a Senior Resident Inspector (NRC), w/a

ET 10-0031 Page 3 of 3 STATE OF KANSAS )) s COUNTY OF COFFEY )

Terry J. Garrett, of lawful age, being first duly sworn upon oath says that he is Vice President Engineering of Wolf Creek Nuclear Operating Corporation; that he has read the foregoing document and knows the contents thereof; that he has executed the same for and on behalf of said Corporation with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.

Vice Engineering SUBSCRIBED and sworn to before me this day of fnDvimber ,2010.

Notary Public

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Expiration Date .(}( n1*, , 1L*rf)I'-/

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Attachment I to ET 10-0031 Page 1 of 2 Response to Supplemental Information Request for License Amendment Request Deviation from Fire Protection Requirements - Reactor Coolant System Subcooling During Alternative Shutdown The Nuclear Regulatory Commission (NRC) staff initiated an acceptance review of Reference 1 and concluded that supplemental information is necessary to enable the NRC staff to make an independent assessment regarding the acceptability of the proposed amendment request in terms of regulatory requirements and the protection of public health and safety and the environment. A phone call between Wolf Creek Nuclear Operating Corporation (WCNOC) and the NRC staff was held on October 26, 2010, to discuss the information required to supplement the amendment request. The requested supplemental information was provided by electronic mail from the NRC Project Manager on November 3, 2010. The specific NRC staff request for information is provided in italics.

1. Please describe what happens if the PORVs are not closed in 3 minutes. Since the current licensing basis may allow five minutes, without having considered loss of subcooling, If NRC staff approves this amendment, staff may need to unapprove the five minutes in theirprogram.

Response: Four of the Evaluation SA-08-006 Rev.1 Post-Fire Safe Shutdown (PFSSD) scenarios (1, 1A, 2, and 2A) pertaining to inside control room fires have been analyzed considering an open pressurizer power operated relief valve (PORV) for three minutes. The scenario descriptions are:

Scenario 1 - Loss of off-site power, PORV open Scenario 1A - Loss of off-site power, PORV open, auxiliary feedwater (AFW) pumps auto start for unplanned cooldown Scenario 2 - No loss of off-site power, PORV open Scenario 2A - No loss of off-site power, PORV open, AFW pumps auto start for unplanned cooldown Results of the analysis for an open PORV for greater than 3 minutes determined that two-phase flow developed in the Reactor Coolant System (RCS) pumps for Scenarios 2 and 2A. Since the RETRAN reactor coolant pump (RCP) model has only been benchmarked for single-phase flow, once two-phase flow develops, the model cannot accurately predict the results for Scenarios 2 and 2A with a PORV open for five minutes. However, through a sensitivity study, it was determined that Scenarios 2 and 2A could be analyzed with the PORV open for 3.5 minutes without achieving two-phase flow in the RCP model. Therefore, Scenarios 2 and 2A were analyzed with the PORV open for 3.5 minutes.

As shown in the Figures in Attachment II, the thermal-hydraulic process variables (Core Power, Core Mass Flowrate, Steam Generator Pressure, Pressurizer Pressure, and Pressurizer Level) for all four cases, are maintained within those predicted for a loss of normal ac power, with the exception that some voiding occurs in the upper core and upper head in Scenarios 1 and 1A.

Those results show that natural circulation can be sustained and adequate core cooling is maintained, as sufficient core flow continues and the core exit temperature is less than 712 0 F.

Attachment I to ET 10-0031 Page 2 of 2 In the Scenario 1 and 1A cases with the PORV open for 5 minutes, the peak upper core void fraction is less than 19% and occurs approximately 5 minutes after the PORV opens. The maximum upper head void fraction is less than 60%. The core mass flowrates are slightly higher with a higher pressurizer level and lower pressurizer pressure than the 3 minute cases.

The continued positive core mass flowrates and the core exit temperatures below 7121F demonstrate that unrestorable conditions will not be reached.

For Scenarios 2 and 2A, no voiding occurs in the upper core or the upper head with the PORV open for 3.5 minutes. Comparing with the original case (PORV open for 3 minutes), core mass flowrates are essentially unchanged and pressurizer pressure is very similar to the 3 minute case. The continued positive core mass flow rate and the core exit temperature below 712°F demonstrate that unrestorable conditions will not be reached.

2. With the apparentsensitivity of 3 minutes, what indicationsare available to the operators, unaffected by the postulated fire, the make the decision to close the power operated relief valves (PORVs).

Response: For a control room fire prompting control room evacuation, WCNOC does not credit diagnostic instrumentation to determine the need to close the pressurizer power operated relief valves (PORVs). Isolation of the PORVs is an immediate action step in procedure OFN RP-017,"Control Room Evacuation," and is one of the first steps performed upon evacuation of the control room during a fire. This is a preemptive action that is performed regardless of the actual PORV position and, while it will close an open PORV, it is intended to prevent the PORV from opening due to potential fire-induced cable damage.

Prior to the 2008 Triennial Fire Protection Inspection (Inspection Report 05000482/2008010),

the immediate action step to isolate the PORVs was timed in preparation for a revision to procedure OFN RP-017. Three operators were timed with times of 1 minute 35 seconds, 2 minutes, and 1 minute 50 seconds. Procedure Al 21-017, "Timed Fire Protection Actions Validation," was developed in September 2010. This procedure requires validation of the immediate action step on a 3 year frequency.

References:

1. WCNOC Letter ET 10-0026, "License Amendment Request (LAR) for Deviation from Fire Protection Requirements - Reactor Coolant System Subcooling During Alternative Shutdown," September 22, 2010.

Attachment II to ET 10-0031 Page 1 of 16 Results for Scenarios 1, IA, 2, and 2A With PORV Open Greater Than 3 Minutes 1: Scenario I Results (PORV Open 3 vs. 5 minutes) 3000 2400 1800 o.

1200 600 AI L .....

0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 1-1 Core Power 40000 35000 30000 25000 20000 o 15000 10000 5000 600 1200 1800 2400 3000 3600 System Elapsed Time (see)

Figure 1-2 Core Mass Flowrate

Attachment II to ET 10-0031 Page 2 of 16 1150 -

1100 S1050 a.

1000 950 900 0.0 600.0 1200.0 1800.0 2400.0 3000.0 3600.0 System Elapsed Time (sec)

Figure 1-3 Steam Generator Pressure 600 Core Exit (PORV open 5 minutes) Core Exit (PORV open 3 minutes) 580 570

• 560 Core Inlet (PORV open 5 minutes)

Vessel Average(PORV open 5 minutes) Core Inlet (PORV open 3 minutes) 550 540 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 1-4 RCS Temperature

Attachment II to ET 10-0031 Page 3 of 16 2400 2200 2000 1600 2` 160 PORV open 3 minutes

0. 14oo00 -,-

1200 PORV open 5 minutes 1000 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 1-5 Pressurizer Pressure 100 90 80 0PORV open 5 minutes S70 60 I50 i POR open3 minutes 40 30 206 0600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 1-6 Pressurizer Level

Attachment II to ET 10-0031 Page 4 of 16 1.0 0.9 0.8 0.7 0.6 0

, 0.5 0.4 0.3 0.2 PORV open 3 minutes PORV open 5 minutes 0.1 0.0 -I_ -

0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 1-7 Upper core void fraction 1.0 0.9 0.8 0.7 PORV open 5 minutes 0.6-L 0.5 0.4 0.3 0.2-PORV open 3 minutes 0.1 0.0 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 1-8 Upper head void fraction

Attachment II to ET 10-0031 Page 5 of 16 2: Scenario 1A Results (PORV Open 3 vs. 5 minutes) 3200-2800 -

2400 -

2000 -

0IL 1600-U 1200 -

800 -

400 L

ý,i 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure IA-I Core Power 40000 35000 30000

" 25000 I 20000 o 15000 C.)

10000 5000 600 1200 1800 2400 3000 3600 System Elapsed Time (sac)

Figure IA-2 Core Mass Flowrate

Attachment II to ET 10-0031 Page 6 of 16 1200 1150 1100 PORV open 5 ninutes

• 1050 0.

1000 9500 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure IA-3 Steam Generator Pressure 600 Core Inlet (PORV open 5 minutes) 590, 590 Core Exit (PORV open 3 minutes)

• Vessel Average(PORV open 3 minutes) 56 .Core Exit (PORV open 5 minutes) 560 iCore Inlet (PORV open 3 minutes)

Vessel Average(PORV open 5 minutes) 550 540 0600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure IA-4 RCS Temperature

Attachment II to ET 10-0031 Page 7 of 16 2400 2200 2000

. 1800 e

1600 PORV open 3 minutes 1400 -

1200 PORV open 5 minutes 1000 0 600 1200 1800 2400 3000 3600 System Elapsed lime (sec)

Figure 1A-5 Pressurizer Pressure 100 90 80-70 PORV open 5 minutes 0.

~60 Nl PORV open 3 minutes S40 30 20 10 0 600 1200 1800 2400 3000 3'60(

System Elapsed lime (see)

Figure IA-6 Pressurizer Level

Attachment II to ET 10-0031 Page 8 of 16 1.0 0.9 0.8 0.7

._20.6 0.5 2*

0.4 0.3 PORV open 5 minutes 0.2 -PORV open 3 minutes 0.1 0.0 ,c-0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 1A-7 Upper core void fraction 1.0 0.9 0.8 PORV open 5 minutes 0.7 0.6 L. 0.5 0.4 0.3 0.2 0.1 PORV open 3 minutes 0.0 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 1A-8 Upper head void fraction

Attachment II to ET 10-0031 Page 9 of 16 3: Scenario 2 Results (PORV Open 3 vs. 3.5 minutes) 3000 2400 It lw 0

1200 600 0

0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2-1 Core Power 35000 30000

• 25000 20000 15000 10000 5000 0

0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2-2 Core Mass Flowrate

Attachment II to ET 10-0031 Page 10 of 16 1200 1150 1100 1050 CD 1000 950 900 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2-3 Steam Generator Pressure 2400 2200 2000 1800 0)1600 1400 1200 1000 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2-4 Pressurizer Pressure

Attachment II to ET 10-0031 Page 11 of 16 620 Figure 2-5 RCS Temperature

Attachment II to ET 10-0031 Page 12 of 16 100 90 80 PORV open 3 minutes 70 5 60

• 50 S40 30 PORV open 3.5 minutes 20 10 01 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2-6 Pressurizer Level

Attachment II to ET 10-0031 Page 13 of 16 4: Scenario 2A Results (PORV Open 3 VS. 3.5 minutes) 3600 3200 2800 2400 2000 o- 1600 0

1200 800 400 0

0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2A-1 Core Power 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2A-2 Core Mass Flowrate

Attachment II to ET 10-0031 Page 14 of 16 (5

• 8 S

0 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2A-3 Steam Generator Pressure 2400 2200 2000 1800 1600 1400 1200 1000 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2A-4 Pressurizer Pressure

Attachment II to ET 10-0031 Page 15 of 16 Figure 2A-5 RCS Temperature

Attachment II to ET 10-0031 Page 16 of 16 100 90 80 70 PORV open 3.5 minutes e

S60

• 50 PORV open 3 minutes S40 30 20-10-0 0 600 1200 1800 2400 3000 3600 System Elapsed Time (sec)

Figure 2A-6 Pressurizer Level