Text

Incident Investigation Team Rept, Plant Shutdown Due to Circulating Water & Essential Svc Water Intake Icing
	ML20100R429
Person / Time
Site:	Wolf Creek
Issue date:	02/28/1996
From:	; WOLF CREEK NUCLEAR OPERATING CORP.
To:	;
Shared Package
ML20100R408	List: ML20100R404; ML20100R429;
References
	96-002, 96-2, NUDOCS 9603120413
	Download: ML20100R429 (82)
	v • d • e

1 Incident Investigation Team Report 96-002

" Plant Shutdown Due To Circulating Water and Essential Service Water Intake icing"

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Wolf Creek Nuclear Operating Corporation Issued February 28,1996 9603120413 960308 '~

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INCIDENT INVESTIGATION REPORT 96-002

" Plant Shutdown Due To Circulating Water And Subsequent Essential Service Water Intake Icing" Wolf Creek Nuclear Operating Corporation (WCNOC) signed copy on file 2/28/96 signed copy on file 2/28/96 IliTeam Leader Date llT Team Leader Date Engineering Subcommittee Operations Subcommittee Approved By: signed copy on file 2/28/96 Incident Investigation Team (IIT) Leader Date Distribution: President / Chief Executive Officer Vice President Plant Plant Sofety Review Committee Operations Choirman Manager Performance Primary Investigation Secondary investigation Assessment Coordinotor Coordinator Nuclear Sofety Review Nuclear Sofety Review Manager Engineering Support Committee Secretary Committee Chairman Monoger Training

INCIDENT INVESTIGATION REPORT 96-002 Index Report Section Title Page Section l l l Executive Summary 1 Il Introduction 1 Ill Description Of Event 2 IV Analysis Of Event 15 l

l V Determination Of Root Cause 58 ,

l l VI immediate Actions Taken 65 Vll Additional Actions Taken 66 Vlli Recommended Corrective Actions 67 IX Recommended Enhancements 70 X Appendices: 77 i

A) Incident investigation Team Member List N/A

' 1 B) List Of Performance Improvement Requests !

C) List Of Documents Reviewed By llT D) Photographs (regular and thermal-imaging)

E) Root Causal Factor Charts and Chronological Listing Of Actions Taken Following Icing Event F) Interviews, Personnel Statements, And Telecons l

Summary List G) [U.S. Army Corp Engineers - Consultant] Frazil Ice Report l H) Performance improvement Requests initiated by llT - vaulted copy only 1

l L ' l) Trend Data Charts and Information (climatic data, fore bay level data)'- vaulted copy only J) Interviews, Personnel Statements, Telecons - j vaulted copy.only - .)

l K)! Team Resumes -Lvaulted copy only L) . Operation and Engineering Sub-Team Notes -

vaulted copy only -

M) Engineering and Operations ESW Watch Logs --

i vaulted copy only N) Simplified ESW Drawings - vaulted' copy only O) Correspondence (internal and external) -

vaulted copy only P) Contingency Plan Information - vaulted copy j only

- Q) Bechtel Hydraulic Model-' vaulted copy only 4

R) Cold Regions Technical Digest NO. 91-1, March 1991, "Frazil Ice Blockage Of Intake Trash 1

! - Racks," - [U.S. Army Corp Engineers - )

Consultant] - vaulted copy only '

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i INCIDENT INVESTIGATION REPORT 96-002 '

" Plant Shutdown Due To Circulating Water And Subsequent Essential Service Water Intake Icing (IIT 96-002)" l I

TEAM l.EADER: [name deleted) i TEAM MEMBERS: See Appendix "A" for Team Assignment ASSESSMENT PERIOD: This incident Investigation Team investigation activities occurred from February 3,1996, through February 17,1996. Follow-up activities and report development continued into the week of February 26,1996.

l. EXECUTIVE

SUMMARY

This report documents the findings of the Incident Investigation Team (IIT) (96-002) and gives recommended corrective action and the 4 recommended enhancements for the various areas evaluated. The .

basic report and its recommendations concern the Essential Service Water (ESW) trash rock frazilice formation and the Circulating Water (CW) traveling screens freezing problems. In addition the report addresses a number of issues found during the llT such as the initial misalignment of valves during the operation of the ESW system.

The inherent root cause of this event is the inadequate design of the CW and ESW systems to operate in the cold environment existing on January 30,1996, through February 1,1996. This report addresses the recommended corrective action to preclude this event in the future.

II. INTRODUCTION:

At 0337 hours0.0039 days 0.0936 hours 5.57209e-4 weeks 1.282285e-4 months on January 30,1996, Wolf Creek Generating Station (WCGS) was manually tripped following ice build-up on the Circulating Water (CW) traveling screens. Ice build-up on the Essential Service Water (ESW) trash racks later caused the loss of the "A" ESW pump on two separate occasions. Twice during this event the Wolf Creek Nuclear Operating Corporation (WCNOC) declared a Notification of . Unusual Event (NUE).

IIT 96-002 Page 1 of 78

f The Vice' President Plant Operations, through letter :WO 96-0024, chartered on incident Investigation Team (IIT) to investigate the plant shutdown due to CW intake icing, the ESW intake icing,' and subsequent events relating to these conditions. The WCNOC Nuclear Safety; Review Committee (NSRC) Chairman was appointed as the

' team leader. The first team meeting was conducted at 0800. hours on-February 3,1996. The team was split into two groups, one to evaluate ,

engineering and design issues, and the other to investigate- '

Operations and Emergency Planning issues. The Manager Supp~ ort Engineering was appointed to lead the Engineering Team and the Manager Training. was appointed to lead the. Operations . Team.

Consultants were . brought in from both Bechtel Engineering and Sargent & Lundy (S&L), respective designers of the ESW, Ultimate Heat

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Sink (UHS) and Train Systems. ' Personnel were also brought in .from Cooper Nuclear Station, Callaway Nuclear Station, and the Institute !

Of Nuclear Power Operations. Additionally, a Hydraulic Engineer from l the United States Army Corps of Engineers, Cold Regions Research and Engineering Laboratory, participated in the investigation. See ;

Appendix "A" for a listing of the team composition and expertise.

Specific concerns associated with the Turbine Driven Auxiliary Feed '

4 Water Pump (TDAFWP) and the failure of some control rods to fully insert were not included in this investigation. Incident Investigation llT 1 96-001 was' chartered with investigating the TDAFWP concerns and the control rod problems are being investigated under significant PIR.

96-0268.

111. DESCRIPTION OF EVENT:

Overview:

On . January 30,1996, Wolf Creek Generating Station (WCGS) initiated ;

a plant shutdown due to the loss of all CW because of ice build up on the traveling screens. To gain a broader perspective of this event, this description will encompass specific events occurring prior to, during, and subsequent to this plant shutdown.

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llT 96-002 Page 2 of 78

4 i Historical Develooments: i 2

L In. August of 1975 S&l. performed calculations (Calc WR-WC-DT-3) for- ;

determining flow rates for the CW warming lines. During April and May of 1976,.Bechtel performed an evaluation on the potential for frazilice formation at the WCGS ESW pumphouse. As a result of this 4

evaluation Bechtel changed the location of the warming line from in e

front of the pumphouse to inside the pumphouse. Bechtel also i

instructed the individual performing the evaluation to assume that the Service W:ater (SW) would enter the ESW Screenhouse through the i warming line at 35 F (Calc K-20-01-F), when lake water temperature is i sub-cooled to less than 32 F. The Bechtel calculation (Calc K-20-01-F) also determines a flow of 4000 gallons per minute (gpm) is required through the warming line to prevent frazil ice formation. A later Bechtel calculation (Calc M-EF-13) determined. the actual flow

! through the warming lines will be 4413 gpm with valves EF HV-39,40,

) 41, and 42 closed, and EF HV-37, and 38 open. This calculation

assumes the line would be full.

STN GP-001, Revision 0, " Plant Winterization," is released in October-1985. Initially it does not contain any steps to winterize either the CW

, Screen House (CWSH) or the ESW Pumphouse. These were added to l the procedure in Revision 3 (1990) in response to PMR 2149 modifications. These modifications were to allow SW flow through the i warming lines when the ESW system is not in operation to control Microbiologically Induced Corrosion -(MIC). In October 1988, with regards to the CWSH side, the setup includes putting the traveling

] screens in " manual slow".

2 STN GP-001 was initiated on September 22, 1995, and the steps associated with the CWSH and the ESW pumphouse were completed on October 30,1995. During winter conditions the shift crews begin i

receiving briefings when the temperatures are predicted to be extremely low, aimed at heightening awareness of problem areas created by the cold weather.

On January 24,1996, maintenance was performed on the TDAFWP. It j was confirmed that Maintenance personnel had removed the

! packing gland follower, and that it was not reinstalled correctly.

~i llT 96-002 Page 3 of 78

January 29,1996: '

Preventive Maintenance (PM) was performed on the CWSH traveling l

screens and the "B" CW Pump Motor. The work on the traveling l screens was completed 'successfully around 1430 hours0.0166 days 0.397 hours 0.00236 weeks 5.44115e-4 months . The lead i mechanic has indicated.that there was a little ice on the traveling l scre. ens, and on the screen cover backsplash, but nothing out of the i ordinary for that time of year and the existing weather conditions. He y also noted that the ice on the lake was closer in toward the pump l fore bays than he had previously seen, but it did not raise any. undue

-concern in his mind. The traveling screens were left in_the "as-found" condition which was, all running in " manual slow speed."

L The PM work on the "B" CW Pump Motor was completed successfully at about 1500 hours0.0174 days 0.417 hours 0.00248 weeks 5.7075e-4 months . However, the electricians had noticed that there was a bushing on a potentiometer that might be a potential problem.

The supervisor was contacted, and it was agreed that the pump would be left " tagged out" until the following day. They would then pull a spare from the warehouse to compare with the installed problem part. The A" and "C" CW Pumps were not affected by the PM on."B," and thus were running the entire time. They were also running when the electricians left the CWSH that afternoon.

January 30,1996:

At 0000 hours0 days 0 hours 0 weeks 0 months the plant status was as follows: MODE 1, Power level 98.3% with Reactor Coolant System (RCS) Average Temperature at 584.6 F and RCS Pressure at 2235 psig. The lake elevation was at 1086' (Technical Specification (T/S) Limit for UHS is 1070'). The lake temperature was between 32.2 F and 32.8 F (CW inlet temperature).

The air temperature was 8 F with wind speeds of 16 MPH. The "B" Component Cooling Water (CCW) pump was carrying all the CCW loads. The "A" and "C" SW pumps were supplying SW, and, as noted I above, the "A" and "C" CW pumps were running with the "B" pump tagged out. The CWSH traveling screens were in the manual mode on slow (per Procedure STN GP-001).

llT 96-002 Page 4 of 78 l - - - -.

l Icina Event

Description:

l At 0149 hours0.00172 days 0.0414 hours 2.463624e-4 weeks 5.66945e-5 months on January 30,1996, the following sequence of events l began. The control room receives CWSH trouble alarms. At 0154 hours0.00178 days 0.0428 hours 2.546296e-4 weeks 5.8597e-5 months the site watch reports high differential pressure (AP) in bay #3. A i couple of minutes later (0158 hours0.00183 days 0.0439 hours 2.612434e-4 weeks 6.0119e-5 months ) Annunciator (ANN) SA, CWSH alarms. The Shift Supervisor (SS) instructs the operator to immediately start "A" & "B" ESW, at 0159 hours0.00184 days 0.0442 hours 2.628968e-4 weeks 6.04995e-5 months , based on a drop in SW pressure and an increase in load temperatures. l The operator is directed to do this without the System Procedure (SYS) due to the need for urgency. Thus, the following actions were accomplished without the use of the procedure. The "B" ESW Pump is started at 0159 hours0.00184 days 0.0442 hours 2.628968e-4 weeks 6.04995e-5 months , followed by the "A" ESW Pump at 0211 hours0.00244 days 0.0586 hours 3.488757e-4 weeks 8.02855e-5 months . At approximately the same time (0200 hours0.00231 days 0.0556 hours 3.306878e-4 weeks 7.61e-5 months ) the site watch reports traveling screens in "A" and "C" CWSH bays are frozen. Operators open ESW return to SW isolation valves EF HV-39,-40,-41 and -42. They close ESW to UHS isolation valves EF HV-37 and -38, aware that the valves will still be 90% and 67% open, respectively, by design.

l l The site watch notes that the traveling screens in CWSH "B" bay are

! clear of ice, but the pump is " tagged out" and not running at 0223 hours0.00258 days 0.0619 hours 3.687169e-4 weeks 8.48515e-5 months . He places the traveling screens in " manual fast" to prevent I freezing, and, at the direction of the Control Room, clears the " tag out". The "B" CW Pump and the Low Flow SW Pump are started and the "A" CW Pump and the "A" SW Pump are secured due to low bay level. Two minutes later, 0225 hours0.0026 days 0.0625 hours 3.720238e-4 weeks 8.56125e-5 months , the site watch reports bay "B" traveling screens are frozen and level in bay "B" and "C" are decreasing. The CW valves are throttled to stop level decrease.

The SS contacts the Manager Operations at 0212 hours0.00245 days 0.0589 hours 3.505291e-4 weeks 8.0666e-5 months , to apprise him of the situation and to request additional support. In addition, support is requested from Mechanical Maintenance (MMA) at 0200 hours0.00231 days 0.0556 hours 3.306878e-4 weeks 7.61e-5 months , plant support at 0238 hours0.00275 days 0.0661 hours 3.935185e-4 weeks 9.0559e-5 months , Electrical Maintenance at 0312 hours0.00361 days 0.0867 hours 5.15873e-4 weeks 1.18716e-4 months and i Reactor Engineering at 0326 hours0.00377 days 0.0906 hours 5.390212e-4 weeks 1.24043e-4 months .

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The Operators start the standby condenser vacuum pumps at 0252 l hours in response to decreasing condenser vacuum. With the i decrease in condenser vacuum and the continued degradation of l the CWSH conditions, the decision is made to begin decreasing IIT 96-002 Page 5 of 78

Icina Event

Description:

At 0149 hours0.00172 days 0.0414 hours 2.463624e-4 weeks 5.66945e-5 months on January 30,1996, the following sequence of events began. The control room receives CWSH trouble alarms. At 0154 hours0.00178 days 0.0428 hours 2.546296e-4 weeks 5.8597e-5 months the site watch reports high differential pressure (AP) in bay #3. A couple of minutes later (0158 hours0.00183 days 0.0439 hours 2.612434e-4 weeks 6.0119e-5 months ) Annunciator (ANN) SA, CWSH alarms. The Shift Supervisor (SS) instructs the operator to immediately start "A" & "B" ESW, at 0159 hours0.00184 days 0.0442 hours 2.628968e-4 weeks 6.04995e-5 months , based on a drop in SW pressure and an increase in load temperatures.

The operator is directed to do this without the System Procedure (SYS) due to the need for urgency. Thus, the following actions were accomplished without the use of the procedure. The "B" ESW Pump is started at 0159 hours0.00184 days 0.0442 hours 2.628968e-4 weeks 6.04995e-5 months , followed by the "A" ESW Pump at 0211 hours0.00244 days 0.0586 hours 3.488757e-4 weeks 8.02855e-5 months . At approximately the same time (0200 hours0.00231 days 0.0556 hours 3.306878e-4 weeks 7.61e-5 months ) the site watch reports traveling screens in "A" and "C" CWSH bays are frozen. Operators open ESW return to SW isolation valves EF HV-39,-40,-41 and -42. They close ESW to UHS isolation valves EF HV-37 and -38, aware that the valves will still be 90% and 67% open, respectively, by design.

The site watch notes that the traveling screens in CWSH "B" bay are clear of ice, but the pump is " tagged out" and not running at 0223 hours0.00258 days 0.0619 hours 3.687169e-4 weeks 8.48515e-5 months . He places the traveling screens in " manual fast" to prevent freezing, and, at the direction of the Control Room, clears the " tag out". The "B" CW Pump and the Low Flow SW Pump are started and the "A" CW Pump and the "A" SW Pump are secured due to low bay level. Two minutes later, 0225 hours0.0026 days 0.0625 hours 3.720238e-4 weeks 8.56125e-5 months , the site watch reports boy "B" traveling screens are frozen and level in bay "B" and "C" are decreasing. The CW valves are throttled to stop level decrease.

The SS contacts the Manager Operations at 0212 hours0.00245 days 0.0589 hours 3.505291e-4 weeks 8.0666e-5 months , to apprise him of the situation and to request additional support. In addition, support is requested from Mechanical Maintenance (MMA) at 0200 hours0.00231 days 0.0556 hours 3.306878e-4 weeks 7.61e-5 months , plant support at 0238 hours0.00275 days 0.0661 hours 3.935185e-4 weeks 9.0559e-5 months , Electrical Maintenance at 0312 hours0.00361 days 0.0867 hours 5.15873e-4 weeks 1.18716e-4 months and Reactor Engineering at 0326 hours0.00377 days 0.0906 hours 5.390212e-4 weeks 1.24043e-4 months .

The Operators start the standby condenser vacuum pumps at 0252 hours0.00292 days 0.07 hours 4.166667e-4 weeks 9.5886e-5 months in response to decreasing condenser vacuum. With the decrease in condenser vacuum and the continued degradation of the CWSH conditions, the decision is made to begin decreasing IIT 96-002 Page 5 of 78

turbine load ~ at 1/2% per minu'te (0255 hours0.00295 days 0.0708 hours 4.21627e-4 weeks 9.70275e-5 months ) by manually inserting. '

l rods and borating. ]

With CW bay levels still decreasing, the SS and the Supervising-

' Operator (SO) discuss a plan of action for tripping the plant (0334 j hours). At 0335 hours0.00388 days 0.0931 hours 5.539021e-4 weeks 1.274675e-4 months the SW Pressure Low Alarm comes in and the site 1

watch reports auto start of the electric fire pump. 'Also, the low flow SW pump is making a lot of noise.

System Operations is contacted, the plant announcement is made

, and the reactor is manually tripped at 0337 hours0.0039 days 0.0936 hours 5.57209e-4 weeks 1.282285e-4 months . The Operators enter Emergency Operating Procedure (EMG) E-0, " Response .To Reactor Trip Or Safety injection," and begin monitoring the Critical Safety Function trees, break condenser vacuum and remove CW from -

service. The following control rods failed to fully insert: H2 (12 steps), F6 ,

(18 steps), K6 (6 steps), K10 (6 steps), and H8 (12 steps).

The Auxiliary Feedwater started on lo Lo Steam Generator (S/G). Level .

i and the Operators manually initiate the Main Steam Isolation Signal at 0338 hours0.00391 days 0.0939 hours 5.588624e-4 weeks 1.28609e-4 months .

! ' At 0341 hours0.00395 days 0.0947 hours 5.638227e-4 weeks 1.297505e-4 months the Control Room transitions from the EMG E-0 and then-entered EMG ES-02, " Reactor Trip Response." In the' process 'of the transition it was discovered that' the Control Room did not have a

copy of EMG ES-02 on hand. Fourteen minutes later, (0355 hours0.00411 days 0.0986 hours 5.869709e-4 weeks 1.350775e-4 months ) the Operators begin emergency boration, using ES-02 and Off Normal Procedure (OFN) BG-009, " Emergency Boration."

AT 0430 hours0.00498 days 0.119 hours 7.109788e-4 weeks 1.63615e-4 months the Control Room Operators begin Attachment "A" of

! General Operating Procedure (GEN)00-005, " Minimum Load To Hot i Standby," in accordance with EMG ES-02. AT 0432 hours0.005 days 0.12 hours 7.142857e-4 weeks 1.64376e-4 months the SS makes the event notification to the Nuclear Regulatory Commission (NRC) per 10CFR50.72, Reactor Protection System (RPS) actuation. At 0439 hours0.00508 days 0.122 hours 7.258598e-4 weeks 1.670395e-4 months operators halt emergency boration, all rods having settled on the bottom of the reactor without operator action. Emergency boration is halted with concurrence of the Reactor Engineer, but without completion of a shutdown margin calculation (Surveillance c Procedure (STS) RE-004, " Shutdown Margin Determination") as q required by OFN BG-009.

, llT 96-002 Page 6 of 78

l At 0503 hours0.00582 days 0.14 hours 8.316799e-4 weeks 1.913915e-4 months Security reports that the TDAFWP is spraying water on the wall. The turbine building watch confirms that the TDAFWP is' leaking.

about 20-25 gpm from the shaft gland packing. At 0505 hours0.00584 days 0.14 hours 8.349868e-4 weeks 1.921525e-4 months , MMA is notified. Operations ~ personnel use the Motor Driven- Auxiliary Feedwater Pump (MDAFP). to control S/G levels. The TDAFWP is

. ' secured and declared inoperable at 0514 hours0.00595 days 0.143 hours 8.498677e-4 weeks 1.95577e-4 months . The plant enters T/S 3.7.1.2, and is in'a 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months Limiting Condition for Operations (LCO). :

The SS instructs. Chemistry to obtain a sample to determine the Dose Equivalent lodine (DEI) so the Emergency Action Levels (EALs) can be. :

reviewed. At.0528 hours0.00611 days 0.147 hours 8.730159e-4 weeks 2.00904e-4 months Chemistry reports DEI at 2.16 C/gm. -This is 1 L high enough to enter T/S 3.4.8, but not high enough to require L notifications.

The Operations shift change occurs at 0700 hours0.0081 days 0.194 hours 0.00116 weeks 2.6635e-4 months . The oncoming Reactor Operator (RO) recognizes that the ESW volve lineup is '

improper, but takes no immediate action to correct the condition. ,

l At'0747 hours0.00865 days 0.208 hours 0.00124 weeks 2.842335e-4 months operators secure the "A" ESW Pump [ place the pump in

" Pull-To-Lock" (PTL)] due to low discharge' pressure and high strainer l AP. Operations enters OFN-33, "ESW Malfunctions," and the plant 1 enters T/S 3.7.1.2,3.7.4 and 3.8.1.1. This puts the plant in a 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months LCO. j l The SO continues working' GEN'00-005, Attachment "A," before '

beginning GEN 00-006, " Hot Standby To Cold Shutdown." The TDAFWP l is tripped locally.at 0750 hours0.00868 days 0.208 hours 0.00124 weeks 2.85375e-4 months and AL HV-36 is closed to reduce condensate loss from the TDAFWP inboard packing seal. About fifteen minutes later the SO directs the ESW line-up to be corrected using SYS

'EA-120, " Service Water System Startup." Operators also start SGK04B and secure SGK04A to provide more heat to the "B" Train ESW.

Notification Of Unusual Event (NUE): '

At 0845 hours0.00978 days 0.235 hours 0.0014 weeks 3.215225e-4 months the Emergency Plan pagers are activated, but the recording on the Automatic Dialog System (ADS) states that there is

.no emergency. A minute later, and after consultation with the Shift Engineer, the Manager Operations, the Vice President Plant Operations, and the Manager Emergency Planning on the EALs, the SS declares a NUE due to "A" ESW and TDAFWP being out of service. This is done in accordance with the Emergency Action Level (EAL)

Administrative Tree 1,2.

llT 96-002 Page 7 of 78

_ . . _ - . . _ ~ . _ _ . _ . _ _ _ _ _ _ _ ~ . _ . _ ______ _ _ ._

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l A report comes in.that the "D" S/G Safety valve ABV045 is. lifting at '

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'0900 hours0.0104 days 0.25 hours 0.00149 weeks 3.4245e-4 months . The current S/G pressure is -1100 psig and the Safety valve setpointlis 1185 psi. Operations declares ABV045 inoperable and i

. enters T/S 3.7.1.1.

L Electrical Maintenance sets Up temporary heaters for both "A" and "B" ESW fore bays at 0925 hours0.0107 days 0.257 hours 0.00153 weeks 3.519625e-4 months . At 1013 hours0.0117 days 0.281 hours 0.00167 weeks 3.854465e-4 months Operations authorizes L

l Emergency Temporary Modification (TMO). 96-005-NG and TMO 96-004-NG to install' heaters from spare breakers in NG056 and NG06E.

System Engineering determines this. does not render either train l inoperable, and this is verified by the Call Superintendent per Step 6.8 l of Administrative Procedure (AP) 211-001, " Temporary Modifications."

L l At 1107 hours0.0128 days 0.308 hours 0.00183 weeks 4.212135e-4 months operators commence cooling down-the RCS to 350 F per GEN 00-006 (T/S 3.7.1.2). At this point the plant was a little over three (3) hours into the six (6) hour LCO. This delay is due to the SO having difficulty completing Attachment "A" of GEN 00-005.

l The site watch reports that the CW Warming Line Valve 1CW002 is i open. Operators close the valve at 1211 hours0.014 days 0.336 hours 0.002 weeks 4.607855e-4 months . They also close NG06E HF1 to supply temporary _ heaters at ESW. About ten (10) minutes later, in response to reports that five (5) traveling screen pane!s have buckled on the "A" CW screen, the Low Flow and "A" SW pumps, and the "A" CW pump, are put in PTL. Operators close breaker NG05E GF2 to supply temporary heaters.

[ The SS logs that operations has failed to reach MODE 4, RCS less than

.350 F, as required by T/S 3.7.1.2. Operations continues the cooldown, while the SS prepares an RER and PIR at 1347 hours0.0156 days 0.374 hours 0.00223 weeks 5.125335e-4 months .

Operations commences boration of the RCS at 1433 hours0.0166 days 0.398 hours 0.00237 weeks 5.452565e-4 months . The RCS will be borated to 900 parts per million (PPM) to facilitate Rod Drop Testing,if needed.

The SS notifies the Call Superintendent, at 1521 hours0.0176 days 0.423 hours 0.00251 weeks 5.787405e-4 months , of having missed the 6-hour limit to be in Hot Shutdown (MODE 4). Ten minutes later (1531 hours0.0177 days 0.425 hours 0.00253 weeks 5.825455e-4 months ) WCGS enters MODE 4. The "A" ESW Pump is started and l

placed in service per SYS EF-200, " Operation Of The ESW System," at l 1543 hours0.0179 days 0.429 hours 0.00255 weeks 5.871115e-4 months .

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IIT 96-002 Page 8 of 78

The operators secure "A" Reactor Coolant Pump (RCP) to allow oil addition at 1645 hours0.019 days 0.457 hours 0.00272 weeks 6.259225e-4 months . The "A" Train containment coolers are filled, vented and placed in service with the ESW flow through them at 1704 hours0.0197 days 0.473 hours 0.00282 weeks 6.48372e-4 months .

By 1710 hours0.0198 days 0.475 hours 0.00283 weeks 6.50655e-4 months the System Engineers have established that ABV 045 was I not leaking. The evidence of steam was due to entrainment of steam !

from the S/G Atmospheric Relief Valves (ARV's). The S/G Safety Valve is determined to be operable per System Engineering recommendations and Operations exits T/S 3.7.1.1 NUE Terminated:

At 1745 hours0.0202 days 0.485 hours 0.00289 weeks 6.639725e-4 months the NRC requests continuous Emergency Notification System (ENS) communications be maintained through the night. Per discussions with the Manager Operations, the Vice President Plant Operations and the System Engineer, the ESW "A" Train can be considered fully operable for the following reasons: 1) The system is !

filled and vented and running properly; 2) Supplemental heating is l available and functioning (one diesel fired heater per train, ducted )

and tented to the back of the ESW and two electric heaters per train in the pump room ducted to the fore bays); and,3) Continuous Fire Watches stationed to observe fore bay levels, watch for icing and to monitor diesel fired heaters. Per an engineering evaluation, as long as the ESW strainer AP's are within allowable values (i.e., not alarming) the ESW system is operable. The contingencies taken above are to ensure ESW AP's remain in the normal range. Currently ESW "A" and l

"B" Trains are fully Operable. The PSRC reviewed and concurred, prior fo implementation, with the above discussed actions and decisions.

Continuous ENS communications were maintained throughout the night per NRC request. Based on this reasoning, the NUE is terminated at 1758 hours0.0203 days 0.488 hours 0.00291 weeks 6.68919e-4 months .

Shift Turnover occurred at 1900 hours0.022 days 0.528 hours 0.00314 weeks 7.2295e-4 months with the plant in MODE 4; "A" and "B" ESW Pumps running, "A" and "B" MDAFP are running, "B" RHR Pump is in service, "A" RCP is Out Of Service, "B", "C", & "D" RCPs are running.

At 1923 hours0.0223 days 0.534 hours 0.00318 weeks 7.317015e-4 months the Operators secure "A" ESW Pump due to fluctuating discharge pressure and flow. The Plant enters T/S 3.7.1.2, 3.7.4 and llT 96-002 Page 9 of 78

3.8.1.1; which require the plant to be in Cold Shutdown (<200 F within 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months ). Ten minutes later the site watch reports that the level of the "A" ESW After Bay _is 10' lower than normal. At 1931. hours the NRC Resident and the ENS are notified that the "A" ESW has been secured.

The SS and the Shift Engineer (SE)_ review the EAL's. No EAlis made at this time (1936 hours0.0224 days 0.538 hours 0.0032 weeks 7.36648e-4 months ) since the "B" ESW is still operating properly, and ,

with the plant in MODE 4 no Auxiliary Feedwater (AFW) is required.

At 2002 hours0.0232 days 0.556 hours 0.00331 weeks 7.61761e-4 months the Site Watch notifies the SS that the level in the "B" ESW fore bay is slowly decreasing. The SS, the SE and the Manager Operations discuss the potential for the loss of the "B" ESW. If "B" ESW is lost both Emergency Diesel Generators (EDG) will be inoperable which will require a NUE declaration. The SS directs the SO to commence the cooldown using the "B" RHR system at 2012 hours0.0233 days 0.559 hours 0.00333 weeks 7.65566e-4 months , and to cooldown to 200 F at 2019 hours0.0234 days 0.561 hours 0.00334 weeks 7.682295e-4 months . By 2021 hours0.0234 days 0.561 hours 0.00334 weeks 7.689905e-4 months the "B" ESW fore bay Levelis recovering. The thought is that the recovery may be 1 due to hotter water returning through the warming line. The fore bay levelis at 1077.'

At 2024 hours0.0234 days 0.562 hours 0.00335 weeks 7.70132e-4 months the Call Superintendent directs the SS to cool the plant down to 190 F.

The operators place the "A" EDG master transfer switch in " Local" as the "A" EDG is inoperable at 2041 hours0.0236 days 0.567 hours 0.00337 weeks 7.766005e-4 months . The Site Watch reports to the !

SS that the "A" ESW fore bay levelis normal, and that he will be rolling the traveling screens in slow speed. About fifteen (15) minutes later, 2058 hours0.0238 days 0.572 hours 0.0034 weeks 7.83069e-4 months , with the "A" ESW traveling screens rotating freely in slow speed, the site watch reports that the "B" ESW fore bay level is

, fluctuating below normal level, but still greater than T/S Level. This leads to a discussion between the SS, the SE and the Call Superintendent (at 2100 hours0.0243 days 0.583 hours 0.00347 weeks 7.9905e-4 months ), that if the "B" fore bay level decreases below 1070', or if the pump cannot be run, the proper EAL will be a Site Area Emergency (SAE) from Block 7 of the Safety System Functions Chart. At 2128 hours0.0246 days 0.591 hours 0.00352 weeks 8.09704e-4 months the site watch reports that both "A" and "B" ESW fore bay levels are equal with Lake Level.

At 2141 hours0.0248 days 0.595 hours 0.00354 weeks 8.146505e-4 months operators isolate ESW flow to the "A containment coolers to allow venting of the "A" Train ESW. In the meantime the Superintendent of MMA updates the SS on status of maintenance on llT 96-002 Page 10 of 78

"C"/"D" CWSH traveling screens. Once all of the "A" Train ESW high points, with the exception of containment, are vented, the "A" ESW pump is started at 2214 hours0.0256 days 0.615 hours 0.00366 weeks 8.42427e-4 months . Fourteen (14) minutes later, at 2227 hours0.0258 days 0.619 hours 0.00368 weeks 8.473735e-4 months , operators secure the "A" ESW pump due to fluctuating

-discharge and pressure. The discharge pressure went to O psig and the flow decreased. The site watch says the levelis about 12' below where it was when the pump was started.

At 2325 hours0.0269 days 0.646 hours 0.00384 weeks 8.846625e-4 months the clearance order on the "A" RCP is restored. t January 31,1996: >

-The operators start the "A" RCP at 0047 hours5.439815e-4 days 0.0131 hours 7.771164e-5 weeks 1.78835e-5 months . At the same time, the' Call Superintender,t is directed to leave the control room to man the Technical Support Center (TSC). The Outage Shift Manager notifies j the Engineering team to move to the TSC, along with the Outage ;

Control Center (OCC) at 0103 hours0.00119 days 0.0286 hours 1.703042e-4 weeks 3.91915e-5 months . A manual callout of ERO Team 4 "A" personnel is initiated at 0208 hours0.00241 days 0.0578 hours 3.439153e-4 weeks 7.9144e-5 months .

The SS authorizes Clearance Order 96-175-EF to allow diver inspection 1 of the "A" ESW fore bay at 0238 hours0.00275 days 0.0661 hours 3.935185e-4 weeks 9.0559e-5 months . At 0357 hours0.00413 days 0.0992 hours 5.902778e-4 weeks 1.358385e-4 months MMA reports, via the TSC, that "C" and "D" CWSH traveling screens are working properly and rotating in slow speed. About a hour later (0454 hours0.00525 days 0.126 hours 7.506614e-4 weeks 1.72747e-4 months ) the "D" CWSH traveling screens are turned off. The "A" ESW Train is filled and vented outside containment and containment coolers "A" and "C" are isolated.

. Second NUE:

. At 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months the SS declares a NUE using Administrative Tree 1.2. This was due to the excessive ice build-up in the "A" ESW fore bay. Thirty-five minutes later,1035 hours0.012 days 0.288 hours 0.00171 weeks 3.938175e-4 months , follow-up notifications to the county and state are initiated. These are done at approximately 30 minute intervals.

The diver exits the ESW fore bay around 1255 hours0.0145 days 0.349 hours 0.00208 weeks 4.775275e-4 months . At 1435 hours0.0166 days 0.399 hours 0.00237 weeks 5.460175e-4 months MMA initiates sparging air to "A" ESW return line using a temporary air compressor. The air is introduced into a vent line on the chemical injection line. A little more than an hour later,1548 hours0.0179 days 0.43 hours 0.00256 weeks 5.89014e-4 months , the divers re-enter the "A" ESW fore bay. At 1610 hours0.0186 days 0.447 hours 0.00266 weeks 6.12605e-4 months the TSC informs the control room that the effect of the air sparge has moved the ice block 2' IIT 96-002 Page 1.1 of 78

L L back from the trash racks. The plan is to do the following things: 1) l Disconne~ct the air sparge to connect a flange to the ESW chemical l- injection spool piece to inject heated water from a portable _ tanker L (truck) heater; 2) Then reconnect the air sparge to the ESW. vent line and force heated water and air into the ESW warming line. Once this is accomplished TMO 96-006 will be implemented which will direct SW return to the UHS via the _"A" ESW warming line. -

Thirty minutes later the decision is made to not implement TMO 96-006.

This decision is made because of the flange configuration. Since there is no isolation valve on the truck or the flange, the modification l would require the warming lines to be closed to change trucks. A telecon is held between the TSC staff and the NRC, to update the NRC on the plant status and plans of action. ,

L At 1730 hours0.02 days 0.481 hours 0.00286 weeks 6.58265e-4 months , the control room starts hourly logging the ESW return l temperatures on a local Fluke temperature meter. Inputs for the l

meter are from Valves EF HV-37 and EF HV-38. (Between 1730 hours0.02 days 0.481 hours 0.00286 weeks 6.58265e-4 months , on January 31,1996, and 1005 hours0.0116 days 0.279 hours 0.00166 weeks 3.824025e-4 months , on February 2,1996, the

_ temperatures ranged between 39.9 F and 41.1 F for HV-37, and l between 56.0 F and 57.2 F for HV-38.) -

L By 1821 hours0.0211 days 0.506 hours 0.00301 weeks 6.928905e-4 months Maintenance resumes injecting air into the ESW vent L line. They will follow this with injection of hot water from the tanker heater. Thirty minutes (1932 hours0.0224 days 0.537 hours 0.00319 weeks 7.35126e-4 months ) after they went into the "A" ESW fore-bay, the divers are out. At 2000 hours0.0231 days 0.556 hours 0.00331 weeks 7.61e-4 months Operators secure the hot water flush of "A" ESW to allow the truck to be refilled. The TSC notifies the SS that the ice under the water at the "A" ESW is cleared.

I At 2100 hours0.0243 days 0.583 hours 0.00347 weeks 7.9905e-4 months , SW flow to "A" ESW is established in accordance with l TMO 96-006. However, when the Operator attempts to close EA HV-6 electrically. It does not close the all the way.' The site watch is instructed to manually shut the valve. (Action Request (AR) #12238 is j initiated) The SW pressure is 104 psig. The watch at the ESW sees more 1

turbulence in the "A" ESW fore bay. It appears that two of the warming line valves, EF-V264 and EF-V262, are leaking by. At 2113 hours0.0245 days 0.587 hours 0.00349 weeks 8.039965e-4 months , Operators close EF-V318, secure the air purge of the "A" ESW

! fore bay and the venting header, and disconnect the air hose.

t IIT 96-002 Page 12 of 78

h I The Outage Shift Manager informs the SS at 2123 hours0.0246 days 0.59 hours 0.00351 weeks 8.078015e-4 months , of a discussion g held previously between representatives from Wolf Creek, .the NRC,'

the State, - the County and Federal Emergency Management Administration (FEMA). The decision was made that if a SAE l ' declaration was.made based on loss of functions needed to maintain Hot Shutdown (i.e., Loss of all ESW), and no release occurred, that

-John Redmond Reservoir (JRR) would not be evacuated. " NOTE A" on EPP 01-10.1 would be applicable in this situation only.

At 2148 hours0.0249 days 0.597 hours 0.00355 weeks 8.17314e-4 months Operations recommence hot water flush to "A" ESW

fore bay. The SS directs the SO to take the plant to MODE 5 at 2205 hours0.0255 days 0.613 hours 0.00365 weeks 8.390025e-4 months .: At 2248 hours0.026 days 0.624 hours 0.00372 weeks 8.55364e-4 months , Operations makes the announcement that the plant is in MODE 5. This allows the exiting of T/S 3.7.4 on the ."A" ESW-pump. The control room directs the watch at ESW to open both "A" warming valves, EF-V262 and EF-V264 at 2303 hours0.0267 days 0.64 hours 0.00381 weeks 8.762915e-4 months . The watch L reports to the TSC that on opening the volves he did not hear any L flow. The air sparge is realigned to go through EF-V318, and the l watch reports that. warming line flow can be'seen in the "A" fore bay.

o February 1,1996:

l The SS approves TMO 96-008 to establish air sparging to the ESW fore-bays at 0120 hours0.00139 days 0.0333 hours 1.984127e-4 weeks 4.566e-5 months . TMO 96-007 is also approved at 0230 hours0.00266 days 0.0639 hours 3.80291e-4 weeks 8.7515e-5 months . This l TMO adds a hot water connection and sparging air to the ESW warming lines. At 0243 hours0.00281 days 0.0675 hours 4.017857e-4 weeks 9.24615e-5 months Operators open EA-HV6 and start the "A"-

ESW pump. Both discharge pressure and flow are normal. After starting the "A" pump, operations closes out TMO 96-006. About an hour later (0351 hours0.00406 days 0.0975 hours 5.803571e-4 weeks 1.335555e-4 months ) the watch reports that Maintenance has commenced putting bubbling air on the bar grill on the "B" ESW fore bay. This is slowly breaking up the ice in the "B" fore bay. There is no ice in either the fore or after bay of the "A" ESW.

l At 0527 hours0.0061 days 0.146 hours 8.713624e-4 weeks 2.005235e-4 months the "A" and "C" Containment Coolers are vented and i ESW flow through them is reestablished. Maintenance commences hot water flush of the "B" ESW fore bay at 0811 hours0.00939 days 0.225 hours 0.00134 weeks 3.085855e-4 months . About an hour later,0910 hours0.0105 days 0.253 hours 0.0015 weeks 3.46255e-4 months , the "B" ESW hot water sparging is secured for about thirty-seven minutes and then restarted at 0947 hours0.011 days 0.263 hours 0.00157 weeks 3.603335e-4 months . At 1140 hours0.0132 days 0.317 hours 0.00188 weeks 4.3377e-4 months

the hot waterinjection at the ESW fore bays is secured. No further hot L water injection will be done for now, however the system will remain in i hot standby. The air sparging to the "A" ESW warming line is also llT 96-002 Page 13 of 78

secure'd at~ 1200 hours0.0139 days 0.333 hours 0.00198 weeks 4.566e-4 months and EF-V318 is closed. About a half hour later -

EF-V262 and EV-V264 ore closed to install new flanges at the "A" ESW.

These valves are open again by 1340 hours0.0155 days 0.372 hours 0.00222 weeks 5.0987e-4 months .

~

At l'358 hours0.00414 days 0.0994 hours 5.919312e-4 weeks 1.36219e-4 months the divers enter the fore bay at the CWSH to inspect the-

"F" screen. They' are entering the area between the screen and the t

trash rack. The divers are aware that a pump is running in the fore ,

. bay.. Maintenance installs TMO 96-009-ZC. This' puts air sparging on the lake side of each of the CW Traveling Screens.

The "B" CW pump is started at 1650 hours0.0191 days 0.458 hours 0.00273 weeks 6.27825e-4 months with t'he traveling screens in manual slow and the discharge valve is throttled to achieve 21.5 psig discharge pressure. At 1702_ hours, the watch station at the CWSH reports that the level in the "B" fore bay initially dropped about two j inches, then stabilized. The fore bay level will be continually ;

monitored until ANN 6B, "CWSH. Screen Bloc" is cleared. An AR has I been submitted. The Operators open 1CW 002, CW warming line volve at 1708 hours0.0198 days 0.474 hours 0.00282 weeks 6.49894e-4 months . Forty minutes later "C" and "D" CWSH traveling ,

screens are placed-in " Auto" per an On-The-Spot-Change (OTSC) to l SYS SW-121, " Circulating Water Screen Wash System."

At 2300 hours0.0266 days 0.639 hours 0.0038 weeks 8.7515e-4 months Mechanics lower the sparging header in the '!A" ESW fore bay from its present position of about 15' below the water level to !

the bottom of the fore bay. The "A" ESW pump parameters were I monitored during this evolution to verify that pump performance would be acceptable with the sparging header at any elevation in <

the fore bay. Ten minutes later it is returned to its original level. No changes were observed on the "A" ESW pump discharge pressure or current. The System Engineer reports that with the'sparging header on the bottom of the fore bay the observed turbulence was the same as, or greater than the turbulence with the header at the (-)15 foot level.

i This indicates that the air supplied through the sparging header is not

being ingested into the ESW pump, at 2310 hours0.0267 days 0.642 hours 0.00382 weeks 8.78955e-4 months .

The Outage Shift Manager reports that the day shift completed a temporary procedure to collect data on the ESW pump. All measured parameters were found to be acceptable. These parameters were measured to ensure "A" ESW was operated properly. STS EF-100A, "ESW System inservice Pump A Test And ESW A IIT 96-002 Page 14 of 78

Service Water Cross Connect Valve Test," is current and will not need ,

to be performed as a prerequisite to. calling "A" ESW operable.

February 2,1996:

The ESW sparging headers are placed on the bottom of "A" ESW fore -

bay at the direction of the System Engineer at 0200 hours0.00231 days 0.0556 hours 3.306878e-4 weeks 7.61e-5 months . Operations personnel complete venting of the "A" Train ESW via selected vents (per SYS EF-203, " Fill And Vent Of A(B) Train-ESW," - partial procedure performed). The OCC had requested this action be taken. The only air found was about a 1/2 second release from GK V71. This information is forwarded to the OCC.

At 0800 hours0.00926 days 0.222 hours 0.00132 weeks 3.044e-4 months the SS, the SE, the SO, the Superintendent of Operations and the System Engineering Supervisor review the AP 28-001,

" Evaluation Of Nonconforming Conditions Of Installed Plant -

Equipment," operability evaluation of the ESW system. The SS signs concurrence with the evaluation, but will hold on making an operability call until after the Plant Safety Review Committee (PSRC).

has reviewed the evaluation.

e Termination Of The Second NUE:

At 1005 hours0.0116 days 0.279 hours 0.00166 weeks 3.824025e-4 months with the review, and approval of the "A" ESW Operability evaluation per AP 28-001 by the PSRC, the SS reviews the contingencies, actions taken and the present status of the ESW fore

' boys and declares the "A" ESW Operable. T/S 3.7.4 and T/S 3.8.1.1 are exited and the NUE is terminated.

The ESW fore bays are free of ice and there is a tent installed over the :

grating of the fore bay. Two air compressors are located at the ESW !

with one in service supplying air sparging to the "A" ESW fore bay. The second compressor is idling in standby. If ice formation is detected in the fore bays while the pumps are secure, they will be started and maintained running untilice free conditions are restored.

At 1005 hours0.0116 days 0.279 hours 0.00166 weeks 3.824025e-4 months on February 2,1996, the second NUE was terminated.

IV. ANALYSIS OF EVENT:

The llT was established to perform an analysis of the icing event by initially addressing the questions posed by the Vice President Plant '

IIT 96-002 Page 15 of 78

Operations in letter WO 96-0024, dated February 2,1996. This was followed up by root cause analysis of the icing event, contributing causes, and a related event concerning the failure to meet a T/S Action Statement cooldown time. In addition, questions posed by the NRC Augmented Inspection Team (AIT) were also addressed.

Questions posed by the NRC in regard to how close the operability margin associated with "B" ESW Pump was during the event and the adequacy of the first operability determination of ESW Pump "A" will be addressed at the end of this section.

This Section will summarize the questions addressed as well as discuss the evaluations and their conclusions. Corrective Actions will be summarized in the Recommended Corrective Action Section and the Recommended Enhancement Section.

QUESTIONS / ANSWERS:

How will ESW operability be assured under the icing conditions experienced during this event? What are the proposed temporary modifications, administrative controls, and compensatory measures that will be used to anticipate and mitigate the ESW Intake icing conditions? l A comprehensive and critical review was performed of the l Engineering Evaluation performed for Work Package (WP) 109199 Task 1 dated February 2,1996, to mitigate the ESW intake . icing conditions. The Engineering Team found the Evaluation to be thorough, conservative and reflected good Engineering judgment. However,it was evident from the review that those involved with the Evaluation did not fully understand the mechanisms that initiate frazil ice formation and the root cause for it. PIR 96-0367 was initiated to document the llT review of the Operability Evaluation. With the knowledge gained from conducting this investigation, the llT Engineering Team has recommended enhancements to System Engineering for incorporation into the WP 109199 Task 1 to ensure frazilice blockage of the ESW intake trash racks does not occur.

Incorporation of these enhancements gives additional assurance for frazilice mitigation into the ESW Pumphouse:

IIT 96-002 Page 16 of 78

L i

.1. Verify proper valve'and system' lineup to maximize warming flow'to the ESW fore boys whenever ESW pumps are running.

2. Install temporary heating equipment to the ESW screen bay area to reduce the likelihood of ice formation to the traveling j l

screens. i

3. Provide a means to clean the front of the ESW trash racks. This can be accomplished by installing temporary air sparging in each fore bay.to " broom" the front of the trash rack and/or !

by use.of a trash rock rake. j 4.To provide early detection of active frazilice formation while.

the ESW pumps are running, immerse a metal chain several !

l feet into the trash rack fore bay water and monitor for ice '

accumulation.

l 5. Install tents over the grating of the fore bay to provide wind protection to personnel assigned to monitor ESW fore bay conditions and to prevent surface ice formation. This is to i

! assist in detection and cleaning of the trash racks should frazil l ice begin to form.

l

! 6. Station a dedicated cognizant individual at the ESW pumphouse while the ESW pumps are operating. This 1 individual will: 1) Monitor the sparging air compressors, 2) 1 Monitor the tents, and 3) Watch for formation of ice on the traveling screens, screen wash discharge, and trash racks. 1 Notification of the Control Room should occur immediately upon compressor failure, tent degradation or detection of ice j formation. i

7. Install high intensity lights for observing and cleaning of trash racks and traveling screens.

Actions 1 through 7 above will be performed on both ESW trains when:

1) Actual lake temperature is 33 F and decreasing, as measured at the intake of the ESW Pumphouse. ,

i IIT 96-002 Page 17 of 78

2) An ice cover does not exist from the ESW UHS to the Owner Controlled Area Boundary.

NOTE: In evaluating whether a substantial ice cover does i exist, a small amount of open water adjacent to the pumphouse structure is not of concern.

What is the Justification for using these temporary modifications to provide for system operability?

The justification for the use of temporary modifications is based l upon the design deficiency to provide adequate warming line l heat as determined through the root cause investigation. Use of the above temporary measures adequately compensates for the inability of the design to mitigate the affects of frazilice by providing:

1. Indication of the changing environmental conditions necessary to take actions

2. Early detection of any frazilice ingress 1

3. A means to remove the frazil ice should it begin to '

accumulate on the trash racks.

4. Protection for personnel performing work and surveillance ,

activities during frazilice conditions. I Performance of these measures within the WCNOC procedural control program and from the experience gained from the icing event provides assurance that these temporary measures are adequate compensation until the design deficiency can be corrected.

Is the installed warm-up line adequate to mitigate the icing conditions experienced? If so, why didn't it prevent the icing condition from occurring?

The ESW warming line is inadequate to mitigate the icing ,

conditions as experienced. The system hydraulics will not i provide 4000 gpm at 35 F minimum as originally designed. PIR l 96-0263 was initiated to document the "A" ESW pump IIT 96-002 Page 18 of 78

- . ~ -- .. - - .. - . ._ ~ . . -..- . _ _ . - - . . .

r becoming -inoperable due to low water level in the fore bay due to icing.

A design calculation performed in 1976 specified a warming- t line flow rate of 4000 gpm for the prevention of frazil ice. This was determined using valid, conservative methods, but assumed that the temperature of the warming line flow would '

be at least 3 F above freezing. During the time that the icing occurred the estimated actual warming line temperature rise from Train "A" was on the~ order of 1 F. This situation is due to ,

the only substantial heat load on Train "A" being the "A" Train Containment Coolers. CCW Heat Exchangers are the only.

other significant heat load to ESW in addition to the Containment -Coolers. During the event the CCW Heat Exchanger "B" was valved in to reject heat to "B" Train ESW in

. addition to the "B" Train Containment Coolers. Although, a greater amount of heat input was being delivered to the "B" Train ESW, than "A" Train ESW, neither train was. delivering' the amount of heat specified by the original design to the ESW Pumphouse warming lines. PIR 96-0316 was initiated to document the design deficiency and to develop corrective actions.

Using present day United States Army Corps of Engineers-minimum recommendations, the flow required to prevent frazil ice for a warming line flow temperature of 1 F above freezing would be 2,700 gpm. Using this _ methodology the 4000 gpm design flow rate might have been adequate even with the lower than assumed warming temperature.

The UHS and warming lines are open ended piping runs to the UHS and ESW Pumphouse respectively. The piping diameters and elevations are such that portions of these lines operate with partial pipe flows due to the low driving head and with the dry portions not vented. This condition was apparently not foreseen by the piping designer, and makes the calculation methodology used for sizing the warming line inadequate and resulted in a much lower than required flowrote. PIR 96-0334 was initiated to document the lower than required flowrate and llT 96-002 Page 19 of 78

i l

l to develop corrective actions. The warming line flow rate during an accident line-up for the piping as-built configuration cannot be readily calculated or measured with a high degree I of certainty, but is estimated to be about 2500 gpm.

, The "B" Train ESW warming line was operating with a known nonconformance. Valve EFV-0263 is one of two manual butterfly valves in series located in the "B" ESW warming i discharge line at the ESW Pumphouse. From previous work l history, EFV-0263 was mechanically frozen in the 50% open position. Engineering had been quoted in company l correspondence that this nonconformance was acceptable for !

system operation as the partial open position did not affect flow appreciably. However, no formal disposition by Engineering of ,

this nonconformance could be found. Furthermore, had the {

"B" ESW been operating as the original design intended, the !

pressure drop across this partially open valve could have l impeded flow by approximately 600 gpm. PIR 96-0430 was 1 initiated to document the nonconformance and provide corrective actions. The llT Engineering team concluded from )

the hydraulic analyses and partial pipe fill conditions that the partially open butterfly valve EFV-0263 actually had negligible l affect to further reduce the flow. However, PIR 96-0438 was i initiated to ensure that the outstanding repair activities for the l four warming line valves, EFV-0262, 0263, 0264 and 0265 be completed in order to accommodate the corrective actions 1 being developed to alter the ESW System hydraulic I characteristics for satisfactory warm as well as cold weather operation.

During the approximately six hour period preceding the first time "A" ESW pump had to be secured due to the ice blockage, ESW return to SW return cross tie isolation valves were ;

open and the ESW return to the UHS valve was throttled. This i l caused some of the ESW return flow to be diverted from UHS i through the normal SW discharge line. It is estimated that this caused warming line flow to be reduced to about two thirds of what it would have been, or about 1700 gpm. This flow l

IIT 96-002 Page 20 of 78

diversion merely hastened the icing event on "A" ESW trash rack and did not change the eventual outcome.

is there a need for any additional operator training or any changes to operating procedures?

The following recommendations are made based on needs identified during interviews, investigation, and root cause analysis, a) Simulator Training on MODE 3 to 4 cooldown in 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . PIR 96-0370 b) General Operating Procedures (GEN)00-005 and 00-006 !

l needs clarification for " rapid cooldown." PIR 96-0369 c) Recommendation to include Reactor Engineers in selected simulator scenario's. PIR 96-0416 d) include frazil ice formation in applicable training material.

PIR 96-0415 i e) Review clarity of management's expectations for communications when crew composition changes. PIR 96-0371 f) Contingency Plans should be incorporated into the winterization procedure. PIR 96-0376 and PIR 96-0398 g) The Alarm Response Procedure (ALR's) should be reviewed with emphasis on actions required where expeditious actions may be required. In these cases specific steps could be added to minimize the references to separate procedures.

PIR 96-0375 h) Review guidelines for Axial Flux Control. PIR 96-0362 i) Review clarity of management expectations for verification after performing urgent system line-ups. PIR 96-0373 j) Review clarity of management expectations for procedure adherence when completing GENS for rapid cooldown. PIR l 96-0372 l

IIT 96-002 Page 21 of 78 l

l k) Enhance Control Room crew communications. PIR 96-0374 l l 1 l} Review the adequacy of the Shutdown Margin (SDM) computer program. PIR 96-0406 m) Evaluate Auxiliary Boiler Trips for reliability of boiler. PIR 96-0417 n) Delete Technical Specification Clarification 88-003 which I

promulgated incorrect frazilice formation. PIR 96-0366 o) Procedure SYS SW-121 needs revision to delete requirement to operate the traveling screens in slow for cold weather i operations. PIR 96-0376 and 96-0482- I p) STN GP-001 needs revision to require controlotron setup and zero adjustment prior to opening the CW warming line valve each winter season. PIR 96-0316, and 96-0482 q) SYS SW-121 needs revision to provide guidance on the use of air bubblers to assist in breaking up surface ice around the CW traveling screens. PIR 0398,96-0316, and 96-0482 r) ALR 00-006C needs revision to eliminate requirement to place traveling screens in fast if icing conditions are encountered. PIR 96-0399 s) EPP 01-4.1 needs revision to ensure that minimum staffing requirements for the TSC/OSC activation are clear, concise and consistent with the Radiological Emergency Response Plan (RERP). PIR 96-0428 Is Wolf Creek's Cold Weather Protection Plan adequate?

To answer this question two approaches were pursued.

First, operations personnel were interviewed to determine if they felt that the program was adequate and to determine the reasoning behind their answer. The responses received provided their reasoning for believing the program was adequate. In addition to the preparatory actions taken at the j beginning of the cold weather season, frequent reminders were

! provided at shift briefings when the weather was anticipated to IIT 96-002 Page 22 of 78

i !

i I be severe. These were usually directed at a'reas of known or expected vulnerability; areas with vent ducts and uninsulated piping, specific areas with a history of freezing problems, etc. ]

This'wts being done during shift briefings at this time because of l l the low temperatures being experienced. When questioned l about possible concerns 'with the. CW and ESW System, the answer was always in the negative. Despite equally cold conditions having occurred in the past, no problems of this kind l had ever occurred previously. In addition, it was documented that questions had been previously directed to engineering

. concerning potential problems with "frazil icing". Per a- 1990 Engineering Letter, NP 90-2162, to Operations, frazil ice.was not

a. concern since the ESW pumphouse is heated and the traveling screens are enclosed by the building structure. PlR 96-0366 was initiated to address the error in judgment regarding frazil ice potential and to develop corrective actions.

Furthermore, PIR 96-0377 was-initiated to find and remove documentation referring to frazil ice as not.being a credible event.

The second approach was to review STN GP-001 including the history of revisions. A review was also done of SYS EA-120, which is used for the winterization alignment of the ESW system.

ESW and CW winter alignments were added to STN GP-001 in Revision 3 released in 1990. No changes were found in the section dealing with ihe winterization of the Circulating Water Screenhouse (CWSH) from the time it was included (Rev. 3), until the revision in use at the time of the icing event.- Changes were found in the section dealing with the winterization of the ESW pumphouse. Most of the changes made in this section during the life of the procedure did not affect the basic warming valve line-ups. However, for several years the procedure carried a

" Note" dealing with the throttling of certain valves in the ESW (EF) system to maintain system AP and temperature across the CCW heat exchanger. The ' Note' was eventually deleted when the requirement to throttle for system AP was removed. l These changes were also reflected in SYS EA-120. These basic {

activities of the procedure for winterization of the CWSH and j llT 96-002 Page 23 of 78

ESW pumphouse appear to have been adequate within the constants of the postulated winter conditions and the assumed system performance with respect to the design basis heat transfer and flow conditions. These conclusions were also verified with a review of the winterization portions of SYS EA-120.

l In addition to this review of the procedures and interviews with !

operations personnel, the team reviewed Quality Evaluation i (QE) Surveillance Reports K15-003 S-3056 and K15-003 S-3130.

These surveillances covered the implementation of the Plant j Winterization program for the winter of 1994 and 1995. While there was no specific mention of the CWSH or the ESW pump houses, the overall conclusion of the reports was that the actions taken, as part of STN GP-001, were satisfactory and i

adequate.

i

it should also be noted that no other equipment covered by 4

STN GP-001 encountered freezing problems during the period surrounding this event. Thus, our conclusion is that the conditions that occurred within the CWSH, and the ESW i

pumphouse, were not due to inadequacies in STN GP-001, but attributable to other considerations.

Was there equipment, either individually or in combination, that was degraded or out of service that had on impact on the event or could have provided better mitigation?

A review of the Equipment Out of Service log, plant logs, and Operatorinterviews were utilized. ;

The "B" CW Pump (preventive maintenance)and the "B" SW -

Pump (seized bearing) were both out of service. As the j

traveling screens were freezing this limited the crews ability to shift pumps away from the most problematic bay. Even though the crew was switching pumps, with all three Circulating /SW Pumps available, the crew could have rotated pumps more

effectively in conjunction with shutting down the plant. It took 34 minutes to get the " Danger-Do-Not-Operate" Tags removed

! from the "B" CW Pump. The crew noted decreasing condenser

vacuum and increasing return temperatures on the Main Lube lit 96-002 Page 24 of 78

Oil Systems. The Low Flow SW Pump was reported to be making cavitation sounds, and the Electric Fire Pump started on low pressure. The potential loss of these systems caused great concern for the ability of the unit to remain on the line.

Significant equipment damage in the Turbine building was a certainty if SW was lost for a prolonged period. These facts led to the crew decision to trip the unit at 0337 hours0.0039 days 0.0936 hours 5.57209e-4 weeks 1.282285e-4 months on January 30, 1996. Even though a plant trip was inevitable, the status of the CW and SW system impacted the mitigation strategies.

The most significant post trip problem was the combination of the TDAFWP and the loss of the "A" ESW pump. These events, coupled with the very real possibility of losing the "B" ESW would result in lose of primary safety related cooling systems. In that i condition, secondary means of cooling remain available.

Is the design of the Circulating and Service Water Systems, and their !

auxiliary equipment adequate for the climatic conditions?

No. The llT has determined that CW Traveling Screens are not adequately protected from the environmental conditions. PIR 96-0265 was initiated to address ice buildup on the CW Traveling Screens.

The CWSH is provided with a 42" Warming Line supplied from l the CW Discharge Header and routed to the area just in front of 1 the structure's trash racks. The line delivers 34,000 gpm of water heated 30 F above lake temperature, during 3 CW Pump operation, and 30,000 gpm of water heated to 40 F above lake temperature, for two pumps. Therefore, even though the flow is l less, more heat is actually transferred to the Circulating Intake !

Bay during 2 pump operation than in 3. The head pressure which drives the warming line flow is a factor of Circulating Discharge Weir water level. This level varies by less than 3' between 2 and 3 pump operation. Thus the change in warming line flow between 2 and 3 pumps is relatively minor.

Since throttling of the CW Pump discharge valves to prevent pump runoui does not reduce the weir level by any significant amount, this practice actually helps increase the heat input to the bay by increasing the condenser outlet temperature even llT 96-002 Page 25 of 78

more. Simple heat balance calculations show that there is sufficient warming line heat input to prevent frazil ice during either mode of CW Pump operation with the plant on-line.

l These calculations were verified by measuring the warming line l flow rate during two pump operation using an ultrasonic flow meter. The lack of any substantial build-up of ice on the trash racks also indicates that the Warming Line's design is adequate.

l Travelina Screen Operation:

l The CW Traveling Screens are a series of stainless steel wire l mesh basket assemblies with 3/8" openings. The traveling screens are chain driven by a two speed motor (1800/450 RPM).

In the Manual slow mode of operation, one complete basket cycle takes 36 minutes. Fast speed can complete the cycle in 9 l minutes. While operating in Manual slow, as procedurally required, the traveling screens are exposed to the environment for approximately 7 minutes during the 36 minute cycle. While exposed the traveling screens are backwashed by sprays supplied by SW at near lake temperature. This spray, when exposed to the environmental conditions present on January ,

30,1996, caused an initial ice build-up on the steel mesh. As '

the traveling screens continued through their cycle they were exposed to the water coming into the CW Bay. This incoming water was believed to be warmed sufficiently to prevent ice buildup on the trash racks in front of the traveling screens, yet near enough to freezing that the initial ice build-up caused a rapid growth of ice to block the traveling screens completely.

PIR 96-0376 documents the " Manual slow" mode of Traveling Screen operation as a causal factor to the ice blockage of the CW Traveling Screens. PIRs 96-0399 and 96-0482 also address additional procedural controls in regard to the CW Traveling !

Screens. ,

is the design of the Ultimate Heat Sink, (UHS), adequate for the climatic conditions? Was the potential for this situation to occur recognized in the plant design basis? Why is there a level indication installed in the "B" ESW fore bay and not the "A" fore boy?

l IIT 96-002 i

Page 26 of 78

f

^

l The design was found to be deficient in providing adequate warming line heat to the ESW Pumphouse intake to prevent

! frazil ice blockage. The design of the UHS by itself was not

found by the llT Engineering T.eam to be a contributor to the

, deficiency other than the source of the frazil ice. During the .

L original design, the potential for frazil ice was recognized, but j was thought to be addressed adequately by the design of the l ESW warming line and the spacing of the trash rack bars.

I Spacing of the trash rack bars influences the ability of frazilice to " bridge" and thus block flow through the trash rack.

Reference literature included in the design calculations at 'the time of the ESW Pumphouse and warming line design t

development recommended four inches between trash rack l bars to prevent frazilice " bridging". The design chosen was to use three inches center to center of bars based on the potential l of foreign material- ingress into the ESW Pump suction.

Therefore, the three inch center to center bar spacing criteria chosen was non-conservative in regard to frazilice blockage.

More recent evaluation on frazil ice formation has found that the size of the spacing actually will not prevent bridging (4" versus 3") but will significantly delay the formation of a bridge.

Although the 3" versus 4 was non-conservative at the time with the knowledge available, it is not significant to the recommended corrective actions to preclude recurrence' of this event at WCGS.

The design basis of the water levelindicator in the "B" ESW Fore bay is to monitor the UHS level. The ESW Pumphouse structure provides a convenient location to mount and maintain the sensor. It was not designed with the intent to monitor ESW Pump suction water level. PIR 96-0329 was initiated to address the current provision of ESW Fore bay water levelindication.

The instrument operates by sending out a series of ultrasonic pulses, transmitted and received. When the pulses " bounce" (reflect) off of the water surface, the instrument calculates a level by comparing the difference in the transmitted time versus the received time. If the return signal is interfered with, the llT 96-002 Page 27 of 78

I proper time and pattern will not be achieved and a false l indication will result. Per the vendor, Sensall Instruments, Inc.,.

L surface turbulence or something in the water at the water '

surface, such as frazil ice, may cause this type of erratic response.

Data was gathered and analyzed for approximately 1 year on

the operation of both "A" and "B" pumps. Normal operation of.

l the UHS levelindicator was observed.

.l Accounts of eyewitnesses at the ESW Pumphouse during the- !

l event, were that the fore boy level varied approximately 8' to )

10.' It is believed that the trend of levelindicated by the level l

instrument follows the pattern of actuallevel. The minimum and i

maximum spikes observed appear to be from turbulent water, !

including frazil ice mixtures, in the fore bay. However, the l l periods of instability for the level instrument coincide with the i securing of "A" ESW Pump. l AR 12261 was initiated to investigate the operation of the

! instrument. As stated in the Technical Manual, turbulence' affects the operation of the instrument as well as electrical interference. Results of the AR revealed that the electronics of the instrument operated within specification. However, I turbulence at the water surface incurred by the "B" ESW Pump operating caused water level fluctuations of several-inches, '

and prevented instrument indications to come within tolerance.

Thus, it is concluded that the trend was indicative of the fore bay level fluctuation, and that the high and low spikes observed were caused by the signal being reflected in an :

uneven pattern.

L Recommendations for ESW Fore bay level indication is !

, addressed in PIR 96-0316.

l l

l IIT 96-002 Page 28 of 78

1

- Were surveillances and/or preventive maintenance - procedures .

adequate and up to date?

A determination was made early in the review that Preventive Maintenance (PM). activities had been conducted in the CWSH l

on January 29, 1996, the day prior to the event. WP 107621. '

covered. MPM SW-001, PM of the "B" CWSH Traveling Screens. l

'An interview was conducted with the lead mechanic. He !

stated that while they did notice a small amount of ice on the

~

traveling screens, and some on the backsplash of the screen cover, this was not unexpected considering the temperature and had been seen previously. Only one of the . traveling screens was stopped for some minor adjustments. Though not-part of the procedure, the traveling screens are taken to fast speed to expedite inspection. Each screen was done in ' turn-and then returned to slow speed. This information was provided to the engineering team to evaluate the potential impact on ice formation on the traveling screens.' The mechanic remarked that the only thing of notice to him was how close the lake ice was to the fore bay. He also remarked that he had thought about it a lot since the event, trying to think if there was anything that would have indicated a - potential problem.-

However, he could not recall anything. They completed the PM sometime between 1400 hours0.0162 days 0.389 hours 0.00231 weeks 5.327e-4 months and 1500 hours0.0174 days 0.417 hours 0.00248 weeks 5.7075e-4 months .

This practice for conducting PM's was evaluated by Engineering for the potential of icing to have initiated upon the i traveling screens. It was determined that it did not. Due to the short duration of the speed change and no evidence of AP change across the traveling screens following the work, it was concluded that PM activity had no significance towards the event.

The other PMs being worked that day were on the "B" CW !

Pump Motor. One was an electrical check-out of the motor (WP107587,'to perform MPM E00P-05) and the second was a ,

sampling of the motor's oil (WP 107586, to perform MPM OS-001).

IIT 96-002 Page 29 of 78

4 An interview was conducted with the lead electrician performing the pump motor PMs. He stated that the PMs were completed satisfactorily around 1500 hours0.0174 days 0.417 hours 0.00248 weeks 5.7075e-4 months on January 29,1996.

They had noted, however, a potential problem with a bushing on a potentiometer in the control circuit. The electrician contacted his supervisor to confirm the decision to leave the I

motor tagged out and do a comparison of the part with one in the warehouse the next day. The electrician was called in early the next morning to clear the tag due to the icing event.

In an interview with Maintenance Planning personnel, the PM schedule was reviewed for equipment in both the CWSH, and the ESW Pumphouse. The review showed that with the

, completion of the PMs noted above, all PM's were up-to date as of the date of the event. In all other respects the PM's

appeared to be adequate.

A review was also done for all applicable Surveillances. Several were found for the ESW system. STS EF-001 is the ESW Valve Check surveillance. It was last completed on January 24,1996.

This surveillance manipulates valves in the system to ensure their operability. Included in these are EF HV-51, -52, -59, & -60. The procedure notes that for normal operation these valves are open, but may be throttled during cold weather, and can be opened at the operator's discretion. The other valves manipulated by this procedure that are involved in the winterization procedure are EF HV-39,-40,-41,-42. For the latest completion of this STS, EF HV-51 and -52 were listed as "Open,"

and EF HV-59 and -60 were listed as " Closed." This was determined to be a correct line-up for the valves. The remainder of the valves were returned to their proper 'as-found' condition.

STS EF-100A and -100B, " Inservice Pump A(B) And A(B)/ Service Water Crossconnect Valve Test," were completed on October 18,1995, and January 3,1996, respectively. As the title implies, this test ensures operability of the ESW pumps and the associate crossconnect to the SW system.

IIT 96-002 Page 30 of 78

- The last Surveillance reviewed was STS EF-201 A and -201B, ESW Inservice Valve Test. This ensures the operability of all the major valves in the system. Both surveillance's were last completed on December 17,1995.

When asked why these procedures were done during the winter ,

rather than the spring or fall, the Maintenance Planner noted that our outages come in the spring or the fall, every other year.

Performing the tasks in the winter unloads the amount of work that might have to be done during an outage. This coupled I with the need to fit things within the thirteen week rolling schedule are the determining factors for when the maintenance and surveillance's are performed.

In conclusion, the team found that all PM and surveillances for the equipment involved in this event were both adequate and !

current. Valve EF-0263 is a nonconformance, for which the !

decision for acceptability is being investigated in PIR 96-0430 as opposed to a PM or surveillance problem.

What was the proximate cause to the event, and was the response l

appropriate?

l The apparent cause to this event was the formation of ice on the CW traveling screens, and ESW trash racks. This caused CW screen trouble and CW bay emergency alarms to be received i in the Control Room. Because of a decrease in SW pressure along with an increase in cooling load temperatures, Operators made the decision to start the ESW system. A continued ;

downward trend In CW bay levels, caused Operators to secure 1 the CW pumps, and trip the Reactor. Approximately five and one-half hours after the ESW pumps were started, ice formation ,

on the "A" ESW fore bay trash rack reduced inlet flow to that pump, forcing Operators to secure it. This, together with the {

1 TDAFWP being out of service, placed the plant in T/S 3.7.1.2 b, which required a six hour Cooldown to <350 F. A misalignment during the initiation of the ESW system, and a failure to verify and correct this misalignment, may have contributed to the speed in which the ice reduced inlet flow to the "A" ESW fore bay.

IIT 96-002 i Page 31 of 78

Responses to problems in fluctuation of CW and SW bay levels-included the following:

When CW screen. trouble alarms were received by Operators, the Site Watch was dispatched .to verify these. -

Shortly after receiving. a report from the site watch, that. '

traveling screens at CW were frozen, the Shift Supervisor-(SS)'

notified the Manager Operations of the plant status.

Throughout the progress of.the event, timely and accurofe reports were relayed to the Control Room, aiding Operators in evaluating the situation.' SW pumps were. started and-secured-as conditions warranted to. maintain a continuous-p flow of SW to plant equipment. These actions were prudent 3

although complicated by the "B" pump being out of service and unavailable.

As conditions deteriorated, "Do-Not-Operate" -tags were removed from the "B" .CW pump. The pump was

subsequently placed in service _ with the traveling screens in fast in an attempt to prevent freezing. .This was done when ,

Operators were forced to secure the "A'.' pump because'of ice blockage at the traveling screens, and a loss of fore bay level. The ESW system was started in response to a drop in SW pressure and an increase in load temperatures. ESW systems were started without the use of the a procedure due to the gravity of the situation.

Management expectations and standard operating 4

practices dictate that if a continuous use procedure is not i

used during the manipulation of plant equipment, a i

verification of the manipulation will be performed in a reasonable amount of time. With the amount of activity going on in the Control Room, after this evolution took place, !

this verification was overlooked. Attempts to perform this verification were begun, but were never completed. This failure to verify is addressed in PIR 96-0338.

When the loss of CW was imminent, Operators manually tripped the plant off-line and secured all CW pumps. RCS temperatures were controlled by auxiliary feed to the S/Gs llT 96-002 Page 32 of 78

and steam release through the atmo' spheric relief valves. This i

represented proper decision making.

Five control rods failed to completely insert after the reactbr trip. Emergency boration was commenced by the RO's. The.

control rods subsequently dropped to the bottom, and adequate shutdown margin was confirmed by Reactor Engineering. The boration was' secured prior to completingLa shutdown margin calculation (STS RE-004) as required by OFN BG-009, however, the surveillance was later completed. This sequence was proper, noting the subsequent completion.

and verification of. shutdown margin by the appropriate procedure.

A report was received by Operators'at 0503 hours0.00582 days 0.14 hours 8.316799e-4 weeks 1.913915e-4 months 'that the-TDAFWP was spraying water across the room. Operators sent the turbine building watch to confirm this report, and' requested assistance from MMA. MMA reports stated that part.of the packing was blown out and the leak could not be .

stopped. Operators secured the pump and declared it inoperable. The pump was later secured locally to_ conserve _

condensate water. These were appropriate actions. The 1 adequacy of maintenance performed on this pump is being pursued by another llT. ,

1 At turnover on the morning.of the January 30,1996, the on- i coming RO noticed that the line-up for the ESW system was not correct. This was communicated to the on-shift RO, but the issue was not pursued. A note was made in the on- l coming RO's personal note book to discuss this with the oncoming SO offer turnover, but again deteriorating plant conditions led to this being forgotten. This failure is addressed in PIR 96-0338.

Formation of ice on the "A" Train ESW trash racks caused fore bay levels to decrease and pump discharge pressures to drop. In order to avoid damage to the pump, Operators secured the pump and placed it in PTL. This placed the plant i in T/S 3.7.1.2 b, requiring a six hour Cooldown to <350 F. An I additional Licensed Operator in the Control Room, while l LIT 96-002 Page 33 of 78

.,.-s -

- - - , ..n,. - - - , - - _ . - - + -w--- w

checking on various plant parameters, noticed that the ESW line-up was not in the correct position. This was brought to the attention of the SO, and the RO restored the line-up to the correct configuration. Operations issued PIR 96-0281 to address this. These were prudent actions.

Additional Operators were assigned to various tasks in order to free the Control Room staff for plant stabilization. In addition, plant management assisted with some of the administrative emergency plan responsibilities assigned to the SS, to aid him in overall plant control. This was a good utilization of resources.

The plant Cooldown specified in T/S 3.7.1.2 b was not completed within the required 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . Several factors that may have contributed to this include the following:

No past plant experience or training with six hour Cooldowns.

A relatively inexperienced SO, working with an SS who was not a normal member of that crew.

GEN procedures that may contain steps that are not absolutely necessary for a rapid Cooldown.

Operations expectations for procedure compliarice may have contributed to sequential performance.

When it was realized that the six hour requirement would not be met, the decision was made to ensure the safety of the plant and not try to rush the Cooldown. The decision to continue in a safe manner, when it was realized that the T/S could not be met, is considered a safe and proper decision. Missing a required T/S Cooldown is not an acceptable practice, however, and is addressed in PIR 96-0264.

Were subsequent actions taken prudent with respect to protection of the UHS?

IIT 96-002 Page 34 of 78

i j A common feeling among. Operators was that the UHS was a j tool designed to protect safety related systems at all times. . This feeling was still predominant after the loss of CW. When the

incorrect line-up of the ESW warming line was discovered by an

! extra Licensed Operator, it was promptly corrected to restore

. full flow. After the loss of the "A" ESW pump, initial actions

included ensuring heat loads remained on the "B" Train, l'

installation of temporary heaters in the ESW fore bays, and continuous watch on fore bay water levels. Additional actions i

that were taken as resources became available included the i erection of tents with heaters blowing on the fore bays,

! injection of hot water and air to break-up and dissipate the ice

} at the trash racks, and adding additional heat loads to the "B" r Train ESW.

Descriotion of actions taken to orotect the UHS

i i The~ initial ESW train line-up, although not correct, was i performed with the understanding that flow to the warming line

! would be maintained. Valves EF HV-37 and -38 when closed electrically are maintained in a throttled position. At this time j the mind-set of Operators was that the UHS was designed to be l the ultimate cooling source, and would not be susceptible to l

freezing. This is substantiated by letter OP 90-0235, stating that i "Their (Engineering) position is that since traveling screens at ESW are inside and pump-house is heated that Frazil ice is not a l concern." This letter had been sent to all SS's in December of 1990.

{

An additional Licensed Operator in the Control room on the morning of January 30,1996, noted that the line-up of the ESW system was not correct. This was brought to the attention of the

! on-shift SO and promptly corrected. However, this correction

was not performed in time to provide full flow to the "A" Train l ESW warming line prior to a loss of fore bay level, and the 1 securing of the pump. Because the majority of heat loads were

on the "B" Train, the correct line-up would not have prevented j the restriction of flow from ice build-up, but could have delayed it.

4 IIT 96-002 Page 35 of 78 a

After the loss of the "A" ESW pump, at 0747 hours0.00865 days 0.208 hours 0.00124 weeks 2.842335e-4 months on the l January 30,1996, immediate actions taken to protect the "B" pump included, ensuring heat loads remained on the "B" Train, and the installation of temporary heaters in the ESW fore bays.

Heaters installed consisted of, one. diesel fired heater per train tented and ducted to the fore boys, and two electric heaters '

, per train ducted to the fore boys. This was accomplished through the. approval of temporary modifications TMO 96-005-l NG and TMO 96-004 NG, at 1013 hours0.0117 days 0.281 hours 0.00167 weeks 3.854465e-4 months . These heaters were l operating by 1230 hours0.0142 days 0.342 hours 0.00203 weeks 4.68015e-4 months . ROs stated, during interviews, that ,

they were concerned a majority of efforts were being concentrated on restoring the "A" pump and not on ensuring the "B" pump remained in service. When questioned about this

! Operations Management responded by saying that this was not l the case. RO's were not informed of all activities because they wanted them to focus on stabilization and protection of the plant. The SS was kept current of all activities in progress and in

j. the planning stage; however, feeding the RO's information, that l was not really necessary, might have taken them away from i their primary responsibility.

Efforts to clear the ice from the ESW fore bays, in addition to the l

portable heaters included, portable boilers and compressors brought in to dissipate and melt the ice from in front of the ESW fore bays. These efforts commenced at 1435 hours0.0166 days 0.399 hours 0.00237 weeks 5.460175e-4 months , on January L 31,1996. Continuous watches were placed on this equipment to ensure non-stop operation. By 2045 hours0.0237 days 0.568 hours 0.00338 weeks 7.781225e-4 months on January 31, l 1996, the ice had cleared. Operability of the "A" ESW pump l was declared at 1005 hours0.0116 days 0.279 hours 0.00166 weeks 3.824025e-4 months on February 2,1996.

Included in. but not primarily related to protection of the UHS, were efforts to ensure that if the UHS were lost, plant safety would be maintained. This included repair of the TDAFWP. At 1411 hours0.0163 days 0.392 hours 0.00233 weeks 5.368855e-4 months on January 30, 1996, the TDAFWP was declared functional. An additional action taken in this area was the procurement of a make-up water system. This would ensure l that an adequate water supply for plant cooling through the

! S/Gs was maintained.

3 IIT 96-002 Page 36 of 78

At some time between 2002 hours0.0232 days 0.556 hours 0.00331 weeks 7.61761e-4 months and 2010 hours0.0233 days 0.558 hours 0.00332 weeks 7.64805e-4 months reports were received from the Site Watch that the "B" ESW fore bay levels were decreasing. In response to this Operators placed the "B" Train Residual Heat Removal (RHR) system in operation. This increased the amount of heat sent to the ESW warming line and the fore bay level begin to recover. This quick action definitely had a direct positive effect in preventing the loss of the "B" Train ESW pump.

Did plant equipment respond appropriately to and throughout the event, and were known exceptions adequately dealt with?

A review of the Post Trip report, plant logs, Operator interviews and NPIS revealed that equipment that failed to operate as expected were the CW system, the SW system, the Control Rods, the TDAFWP, the ESW system, and the Auxiliary Boiler. ;

The CW system experienced icing conditions on the traveling screens. This icing led to the eventual loss of the CW System ,

and degraded SW System performance. The Crew attempted i to alternate running CW and SW pumps while shutting down the Unit. These were prudent actions.

Five Control Rods failed to fully insert following the Manual !

Reactor Trip. The crew noted this immediately. Per the l requirements of'the emergency procedure network the crew correctly referenced the Off Normal procedures and .

commenced Emergency Boration.

The TDAFWP developed a leak on the inboard packing giand.

The Crew removed the pump from service, tagged it out, and directed repairs. The "A" ESW pump was placed in PTL and j declared inoperable at 0747 hours0.00865 days 0.208 hours 0.00124 weeks 2.842335e-4 months on the morning of January 30,1996. Reports of low fore bay levy, fluctuating discharge pressure, and strainer AP alarms led tci this determination. This l action placed the Unit in T/S 3.7.1.2, action b. l The operating crew initially determined one of the "D" Main Steam Line Safety Valves to be inoperable. This determination I was made based on a report from outside the Control Room and a comparison of the operating parameters of all S/Gs.

IIT 96-002 Page 37 of 78

1 r.

Though initially declared inoperable, it was later determined by !

an Engineering Evaluation that the Safety Valve was operable- ;

throughout the event. The inoperable determination was I conservative, and had no impact on the mitigation strategy. I

! The Auxiliary Boiler trips caused the crew to be concerned with the loss of outside tanks and other components that would be !

required to shutdown the plant. The boiler was tripping j because the fuel oil was cold and the boiler was operating under low load. The Auxiliary Boiler has a history of. trips when switching from the ' auxiliary to main gun. An Engineering L Evaluation should be conducted to resolve reliability issues. PIR 96-0417 was written for this condition.

Were procedures correct and were they adhered to?

To answer this question the Post Trip review was utilized. Both

- the Night Shift Crew and Day Shift Crew were interviewed.

Procedures were generally correct, with numerous On The Spot Changes (OTSC) ' required. During the course of this investigation several opportunities for procedure improvements were noted. They are addressed in the above discussed question (Is there a need for any additional operator training or any changes to operator procedures?). EMG ES-02 was not in its correct location. PIR 96-0278, was written to address this condition. Two instances of procedure non-compliance were identified.

. Upon receipt of various CWSH alarms the crew referred to and l 4

carried out the actions of the ALR's. Included in this event 1 sequence was placing traveling screens in fast, (ALR 00-006B, "CWSH Screen Block," and ALR 00-006C, "CWSH Fast Wash") !

and placing the ESW System in service (ALR 00-008B, " Service Water Pressure Hi/Lo"). The ESW system was placed into service without reference to SYS EF-200, " Operation Of The ESW System." PIR 96-0281 was written to document this event. It is l expected that in some cases, in-hand procedure use is not the most conservative action. It is also, however, clearly Management's expectation that all system manipulations be llT 96-002 Page 38 of 78 3

___ . _._._ _ __ _ _ _ _ . _ . _ - - . _ . . . , , _ , . ~ - - . _ _ _ . ,

l l

verified by procedure in a timely manner. This action did not occur for approximately 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . This was inappropriate. A root cause evaluation was conducted for this event. See PIR 96-1 0338. The evaluation identified the root cause to be a failure to verify the actions against procedural requirements in a timely l manner. There are several contributing factors to this root cause that will be addressed through the PIR process. They are:

PIR 96-0373, 96-0374, 96-0375 and 96-0541. PIR 96-0362, was l

generated as a result of this root cause evaluation to determine l if written guidance and expectations from Reactor Engineering -

caused the Operators to place undue emphasis on control of ,

Axial Flux Difference during plant maneuvers. A separate ;

question was identified with regard to the reliability of Limitorque valves. At question was the confidence level of the !

RO when he went to the close position on the ESW returns to the 1

UHS. Discussion with the MOV Engineer and review of all l Limitorque failures at Wolf Creek Nuclear Operating l Corporation (WCNOC) revealed that the confidence was i justified. There is no Wolf Creek Generating Station (WCGS) !

l history of Limitorque valves failing to stop at the set position due l 1 to limit switch failures. :

The unit was not placed at an average RCS temperature of ,

<350 F in the requisite 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . While the decision making and i

control of the cooldown were prudent, events leading up to that situation warrant attention. PIR 96-0264 was generated to )

document this event. A separate root cause analysis was conducted for this event and PIR 96-0264 was amended to include the root cause evaluation. The root cause is identified as belief of the SO that GEN-005 Attachment "A" had to be complete prior to cooldown. Several actions in the controlling procedures could have been performed in parallel. Although I

the SS expressed his desire to commence the cooldown, thus complying with T/Ss, no method for achieving that end was L

presented or discussed. Other causal factors are identified in I

the root cause analysis and are addressed by PIR's 96-0264,96- ,

0369, 96-0370, 96-0371, & 96-0372. WCNOC has never experienced the pace of operations required to achieve Hot IIT 96-002 Page 39 of 78

Shutdown (MODE 4) in the requisite 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months while operating within the procedure network designed for a normal controlled cooldown to 350 F. A review of the Outage Schedule with all equipment and personnel staged, shows a ten hour window allotted to maneuver the plant from MODE 3 to MODE 4.

Emergency Boration was terminated after all control rods were fully inserted. Procedure OFN BG-009 requires a Shutdown Margin be performed using STS RE-004 to terminate emergency boration flow. While a SDM calculation was not performed until later, the crew terminated emergency boration flow with the concurrence of the Reactor Engineer. Interviews with the crew and the Reactor Engineer were conducted. It is believed that the actions taken by the Crew were prudent and justified based on plant conditions. PIR 96-0406 was written to address the computer problems encountered when attempting to perform SDM calculations.

Was the Emergency Response Plan Followed?

Prior to the declaration of the first NUE, the SS began calling out additional support beginning at 0200 hours0.00231 days 0.0556 hours 3.306878e-4 weeks 7.61e-5 months on January 30,1996.

These personnel included the Manager Operations (notified at 0212 hours0.00245 days 0.0589 hours 3.505291e-4 weeks 8.0666e-5 months ), Supervisor Facilities Maintenance (notified at 0238 hours0.00275 days 0.0661 hours 3.935185e-4 weeks 9.0559e-5 months ), Supervisor Maintenance (notified at 0312 hours0.00361 days 0.0867 hours 5.15873e-4 weeks 1.18716e-4 months ) and Supervisor Reactor Engineering (notified at 0326 hours0.00377 days 0.0906 hours 5.390212e-4 weeks 1.24043e-4 months ). In turn, the Manager Operations notified the Vice President Plant Operations, Superintendent Operations, Superintendent Work Authority, and Manager Plant Support. During an interview, the SS stated that these individuals were crucial to his ability to handle the plant situation and that these particular personnel possessed the necessary expertise. Further, the assistance provided by these individuals allowed the SS to focus his full attention toward the changing plant conditions.

Two declarations of a NUE occurred. The first NUE was declared at 0846 hours0.00979 days 0.235 hours 0.0014 weeks 3.21903e-4 months on January 30,1996, and the second NUE was declared at 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months on January 31,1996. The responsibilities identified on Form EP 01-1.0-1, " Shift Supervisor Task List" were completed as is evidenced by Control Room, Security, and llT 96-002 Page 40 of 78

TSC/OCC logs and copies of Immediate and Follow-up Notification Forms. Control Room personnel completed notification to Security, Coffey County, and the State of Kansas within 15 minutes, as required. Plant personnel were notified through pager activation and over the plant's gaitronics public !

address system. However, required announcements were delayed 30-40 minutes in buildings accessed by another plant address system following the declaration of the first NUE (PIR 96- !

0216 was initiated to address this issue). Building walk-through announcements were completed in buildings not serviced by any public address system. Several paged personnel expressed i confusion at receiving the message "No Emergency Declared" when calling into the ADS to acknowledge having received the pager (PIR 96-0260 was initiated to address this issue). As ,

initial corrective action for this event, the ADS message has '

been changed to state that the " ADS has not been activated."

Pagers are activated manually for emergency classifications ,

declared during normal working hours. Other elements !

inclusive to the implementation of the Emergency Response l Plan are as follows:

All Immediate Notifications associated with the termination of both NUEs were completed as required by Form EP 01-1.0-1,

" Shift Supervisor Task List," for NUE. During interviews the SS stated that Form EP 01-3.1-1, "Immediate Notification Form,"

proved to be a cumbersome tool for event termination as much of the specified information on the form is not consistent with NUE termination conditions (PIR 96-0296 was initiated to address this issue and to recommend further evaluation of event termination guidance).

As evidenced by Control Room logs and interviews of plant personnel, an open line of communication with the NRC was established over the ENS !ine. This line was manned by various Operations personnel, including the Manager Operations, thereby relieving the SS of this task so he could focus his full attention upon plant conditions. At 1745 hours0.0202 days 0.485 hours 0.00289 weeks 6.639725e-4 months on January 30, 1996, this line, at the request of the NRC, was maintained throughout the night after the NUE was terminated at 1758 IIT 96-002 Page 41 of 78

hours. This line was later manneci by the TSC ENS Communicator who informed the NRC of the second !

declaration of the NUE at 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months on January 31,1996. In l addition, specific data was requested by the NRC to be !

communicated at either 30 minute intervals or upon !

occurrence, as appropriate. At the request of the NRC the l transmittal of this information was later changed to hourly.

Information requested at 30 minute intervals (later hourly) were l Tavg, Pressurizer level / temperature / pressure, S/G pressure / level i prior to RHR cooling, ambient temperature, wind l speed / duration, CST level prior to RHR cooling; data requested l upon occurrence included major equipment changes, updates I on control rod issue, radical change in weather, major l maintenance performed, and problems with temporary I heating at ESW.

" Followup Notifications" to Coffey County and the State of l Kansas were conducted in accordance with EPP 01-3.2, !

" Follow-up Notifications." Eighteen (18) Immediate and 95 Follow-up Notifications were made during the first and second I NUE classifications, respectively. Minor inconsistencies, errors, and improvement items were identified on the completed l forms. However, none of these errors resulted in adverse I consequences, or reportability issues. PIR 96-0346 was initiated to document minor inconsistencies, errors, and improvement items identified on the completed forms.

The Onsite Public Information Coordinator performed the duties assigned to his position following the declaration of the first NUE !

in accordance with EPP 01-1.6, "Public Information )

Organization." This position continued to be staffed throughout the second declaration of a NUE.

Following the declaration of an emergency classification, four responsibilities are assigned to the SS. These responsibilities are l transferred to the Duty Emergency Director upon the activation i of the TSC. These responsibilities may not be delegated. Two of these responsibilities, authorizing emergency exposures and making protective action recommendations, were not required !

IIT 96-002 Page 42 of 78

___s a .,_ _.

1 I

l with these two NUE classifications. The third, authorizing offsite I notifications was clearly satisfied. Because of the duration and nature of the plant conditions, and the pursuant involvement of non-control room personnelin these events, the responsibility of assumption of command-and-control requires specific ,

explanation. Interviews with the two SSs who were on duty l when the NUE's were declared, the Vice President Plant Operations, Manager Operations, and one of the Outage iift Managers revealed the following results:

a) Both NUE's were declared by the on-duty SS who continued to have command-and-control of the emergency 1 throughout the events. In addition to possessing command- l and-control, the SSs possessed full authority with regard to the operation of the plant and associated licensee requirements.

b) The Outage Shift Managers supported the SSs by establishing the OCC within the TSC. This established a central point of contact for responding to the Control Room needs, to coordinate engineering and maintenance activities and to ensure that information regarding engineering and-maintenance activities was communicated to the SS. In addition, the TSC/OCC was manned by additional personnel assigned to the TSC Emergency Response Organization, '

including the TSC ENS Communicator who provided an additional source to the NRC for emergency related information.

c) The Manager of Operations supported the SS by maintaining a continuous line of communication with the NRC, thereby allowing the SS to focus his attention upon the plant. The Manager of Operations and his direct report, the Superintendent Operations, also traveled between the TSC/OCC and Control Room to ensure that the needs of both facilities were satisfied.

d) The Vice President Plant Operations provided executive management support and ensured the provision of all WCNOC resources.

IIT 96-002 Page 43 of 78

Are changes to the Emergency Action Levels, (EAL's), needed to better classify the event?

Event Classification:

Throughout the initial transient, shutdown, and cooldown of the plant, the SS evaluated the plant condition according to established plant procedures. The Emergency Classification procedure (EPP 01-2.1) indicated, at two separate times, that a NUE could be declared based upon the Administrative. These declarations were made by the SS. In addition to the SS classifying and declaring the two NUEs, the Shift Engineer also performed an independent review of the plant status and EAL classification as required by plant procedures.

The SS consulted at various times with other plant staff and management. These discussions were effective, and supportive of the decisions made by the SS. Interviews were conducted with the SSs, Executive Management, Manager Operations, Manager Emergency Planning, Outage Shift Manager (TSC),

Shift Engineers, and Emergency Planners. From these interviews, it was determined that the SS did indeed have command and control of the plant throughout the event.

Emeraency Action Level (EAL) Charts:

The WCGS EAL Charts (for event based and initiating condition based decision making - Charts 1-12) led to a classification of

'No Action This Category' throughout the event. Potential paths to higher classifications were recognized by the SS, and discussed at various times with other plant staff and management.

The EAL charts most applicable to the classification (at various times) were the Administrative Chart (13-ADM), and the Safety System Failure or Malfunction Chart (8-SSFM). The Loss of Electrical Power / Assessment Capability Chart (6-LEP/AC) would have been important for classification if offsite power had been lost. The EAL Administrative Chart performed its function in

, raising the level of awareness and plant preparedness by llT 96-002 Page 44 of 78

classifying an event that did not meet any of the criteria on the first twelve charts.

By following the Charts as they were written it was possible to proceed directly from no classification to a Site Area Emergency (e.g.,8-SSFM1,4,7). On January 31,1996, a specific "B" ESW fore bay level was assigned and plans were made to enter an Alert based upon reaching an ESW fore bay level of 1083.' In addition, a Site Area Emergency would still be declared upon a fore bay level of 1070' (as listed in EPP 01-2.1-2, referenced from 8-SSFM7). By establishing ESW fore bay level guidance, the emergency response activities could be escalated in a step-wise manner. The action taken by management to strengthen the approved, written EALs was appropriate because it moved the decision to an objective point rather than a subjective point. Such guidance should be evaluated for incorporation into the EAL Charts (See PIR 96-0432).

Draft EAL Chart Chanaes:

After the event and during the llT investigation, a draft set of 1 EAL Chart changes was prepared by the Manager Emergency Planning. The initial draft changes: 1) Remove a page referred to from the Safety System Failure or Malfunction and place the criteria within the EAL logic flowchart,2) Add additional basis regarding Safety System Failures and examples of Natural Phenomena. The draft changes do'not alter the basic logic or intent of the currently approved EAL Charts. However, the draft EAL Chart changes, along with additional basis guidance, are expected to add significantly to the decision making process by minimizing subjective decision making.

Performance improvement Reauests:

Three PIRs were written during the evaluation of the Emergency Action Level classification process. PIR 96-0287 was written to evaluate the declaration of a NUE based upon the EAL Administrative Chart. Based upon the review for ilT 96-002, it was determined that the use of the EAL Administrative Chart IIT 96-002 Page 45 of 78

l was the appropriate means to classify the event. The llT 96-002 recommended that PIR 96-0287 be closed based upon the proper use of the procedures and evaluation of plant conditions.

l The subject of the second PIR was EAL enhancements. PIR 96-L 0432 was written to evaluate ESW fore bay level guidance for l l incorporation into the EAL Charts, and to document and track l l

the proposed draft changes to the EAL Charts.

The third PIR was written against the UHS level indicator, physically located in the "B" ESW pump fore bay. PIR 96-0365 l was written to investigate the erratic readings of the ESW fore L bay level indicator (EF LIT-0027).

Were Communications adequate with the NRC, State, County, Public and employees?

Communications with offsite agencies were conducted in

accordance with emergency planning procedures. Interviews i and logs of various plant personnel generally depict the communication to be thorough and appropriate. An interview conducted with officials from the State of Kansas and Coffey 1 County concluded that both agencies were satisfied with '

communications.

l As discussed elsewhere in this report, an open-line of communication was established with the NRC over the FTS-2000

ENS line. This open line was maintained throughout both L emergency classifications and, at the NRC's request, through j the period of time between classifications.

l Immediate notifications were made to Coffey County and the l State of Kansas within fifteen minutes as required. All followup l notifications were conducted as required. Interviews with l

Control Room personnel did not reveal that personnel receiving these notifications at the offsite agencies had any concerns during the notification processes. Following the manning of the TSC, personnel had several phone conversations with various State and County officials for the purpose of updating them personally. Further, a teleconference discussion occurred on llT 96-002 Page 46 of 78

._ - -. . .. - - . _ . . - ._- ..- . - . . - = --

4 January 31, 1996, between officials of the State of Kansas, ,

Coffey County, NRC Headquarters, NRC Region IV, FEMA l i

Region Vil and the President and Chief Executive Officer, the Chief Administrative Officer, the Manager Community and Government Affairs and an Emergency Planning Engineering Specialist of WCNOC concerning the potential declaration of a

Site Area Emergency in the event "B" ESW pump became inoperable. It was mutually agreed that the most appropriate

action to take under these particular circumstances was to not ,

evacuate JRR at the SAE (PIR 96-0405 was initiated to address I j this issue). The agreement was to use Note "A" on the Protective Action Recommendation chart as the highest priority )

guidance based upon the current weather conditions and the fact that no one had been seen at John Redmond Reservoir by the Army Corps of Engineer. The County raised the issue of not activating the sirens at the SAE. FEMA strenuously objected. It was agreed that if an SAE was declared, the sirens would be ,

activated and a news statement would be released that l evening concerning what actions the public should take if the

sirens sounded. An Emergency Alert System (EAS) statement would also be revised to identify the proper actions to be taken I

by the public. Everyone agreed these actions only applied to -

this particular situation. The teleconference ended with the regulators, licensee and offsite officials feeling very positive about the discussion. They felt it was noteworthy to have such communications prior to reaching the point where evacuations may have been implemented rather than waiting until the decision was upon us.

Eleven (11) news statements were released during the event.

Numerous live interviews were granted to various media by official WCNOC Spokespersons. Executive Management considered the quality of information released to the media to have been very good.

Employees were kept informed of the plant situation through plant announcements of emergency classifications and '

' distribution of news statements through electronic mail. In addition, a meeting was conducted at 0840 hours0.00972 days 0.233 hours 0.00139 weeks 3.1962e-4 months on January llT 96-002 Page 47 of 78

l 31, 1996, to brief Team "B" Emergency Response Organization personnel on the requirements of second shift TSC/OCC and Public Information staffing. Personnel to staff the Emergency Offsite Facility (EOF) and augment the Public Information Organization to full staffing status also reported for second shift availability.

Are restart plans thorough, well understood and well communicated?

This question was included when the original intention was to bring the plant back on line prior to going into the RFVlli outage. Since the decision was subsequently made to start the outage early rather than bring the plant on line, this question is no longer valid in its original context.

1 Were the Emergency Response Facilities, which were manned, l adequate and appropriately staffed? l In the early morning hours of January 31,1996, the decision was made to staff the TSC/OCC in order to parallel the heightened response staffing at the NRC Region IV and Headquarters facilities. At 0103 hours0.00119 days 0.0286 hours 1.703042e-4 weeks 3.91915e-5 months , the Outage Shift Manager notified engineers already on site in response to the plant conditions to centrally locate in the TSC/OCC. At 0208 hours0.00241 days 0.0578 hours 3.439153e-4 weeks 7.9144e-5 months , a manual callout commenced of Emergency Response Organization !

(ERO) Team "A" personnel assigned to the TSC. Those personnel l reported to the TSC/OCC during the next two hours. At no time I was an emergency classification considered in order to activate the TSC, nor did the need arise. During interviews, the Outage Shift Manager revealed that additional Chemistry Technician, Health Physics Technician and Maintenance craft personnel were not called out to augment the existing back-shift staffing levels. Because of the non-radiological nature of the event, the Outage Shif t Manager felt that he had adequate ,

personnel to perform all necessary operational functions.

However, he also stated that in order to activate the facility, additional personnel beyond those on back-shift (primarily Health Physics Technicians) would have been required. Further, plans were developed for second shift and subsequent shift staffing for a prolonged period of time not only for TSC llT 96-002 Page 48 of 78

l

personnel but also EOF and Public Information Organization l personnel. EOF manning was never required. Selected l individuals in the Public Information Organization did perform the duties of their positions in support of the public information effort, in summary, the emergency response facilities were adequately staffed to respond to the needs of the given event.

However, interviews with other personnel revealed that the procedural requirement which establishes the minimum staffing for activation of the TSC/OCC is not clear (PIR 96-0424 was initiated to ensure the clarity and completeness of procedural guidance for the activation of the TSC/OSC). ;

l Why did this icing situation occur now, but not during any past operations?

To answer this question, one first must consider the environmental conditions for frazilice to form. These conditions are as follows:

1. Water temperature just above the freezing point

2. Rapidly dropping air temperature below 22 F. i

3. Sufficient wind to preclude the formation of surface ice and allow supercooling of the surface layer of water (the neutral buoyancy of frazil ice crystals coupled with the turbulence

, created by the wave action allows the frazil ice to travel to great depths in the already near-uniformly cooled water column. This then promotes further cooling of the water at depth to the point where frazil ice formation is possible at depth).

These conditions existed the evening of January 29,1996, and

! into the morning of January 30, 1996. Recorded lake temperatures indicated that the water may have reached a supercooled condition at approximately 0246 hours0.00285 days 0.0683 hours 4.06746e-4 weeks 9.3603e-5 months on the morning of January 30,1996. This time is given as this is the point when the CW inlet water temperature sensor recorded its lowest value (32.2 F). The other sensor, which consistently recorded higher values than the first, recorded its lowest value (32.6 F) at l LIT 96-002 l Page 49 of 78 l

l 0201' hours. 'Obviously, the accuracy of the readings are i suspect, and the actual lake water temperature may have ,

gone below the freezing point prior to either one of these times, but this data gives a good reference point as to approximately l what time frazilice could have begun forming in the lake water i immediately in front of the CWSH. Normally, frazil ice l development will--cease during the daylight hours' due to sufficient solar radiation to prevent: the decrease in !

temperature below 32 F necessary for frazil ice to form. l Documentation does not exist to know. exactly how much of the lake surface, in the vicinity of the intake structures, was frozen over by the evening of January 30,1996. Apparently, sufficient open water existed in proximity to-the ESW intake structure to allow for formation of.frazilice the night of January 30,1996, and into the morning of January 31, 1996. Frazil ice has- been documented to travel under surface ice for-some distance. Continued high winds throughout the day and into .

the morning of January 31,1996, coupled with decreasing air temperatures during that period would have been conducive

-to frazil ice formation again. Actual lake temperature data is not available after 0337 hours0.0039 days 0.0936 hours 5.57209e-4 weeks 1.282285e-4 months on the morning of January 30, 1996, until.approximately 1700 hours0.0197 days 0.472 hours 0.00281 weeks 6.4685e-4 months on February.1,1996, as the CW System was not operating, and the temperature sensors that provide the lake water temperature are located in the CW piping in the Turbine Building. Wind speeds decreased during l

the daylight hours of January 31,1996, allowing surface ice to form in'the vicinity of the intake structures. During the night of 1 January 31,1996, and the morning of February 1,1996, with very )

light winds and temperatures, it is unlikely that frazil ice production could have continued. Based on recorded lake temperatures and the increased amount of surface ice, after 1700 hours0.0197 days 0.472 hours 0.00281 weeks 6.4685e-4 months on February 1,1996, it is unlikely that any additional frazilice could have been produced near enough to the intake structures for it to be drawn into the intake of either CW or ESW.

i To summarize, based on the available data, conditions

! conducive to frazil ice formation in the vicinity of the intake j structures existed during the early morning hours of January 30, i

llT 96-002 Page 50 of 78

, . ~ _ , - , _ . . _ . - - .._ _ - -

l 1996, and continued into the early morning hours of January 31, 1996.

Research into why frazil ice had not previously caused intake problems found that since the winter of 1992-1993, recorded lake temperature from the :CWSH intake has been less than I 32.4 F only once. This occurred during the early morning hours l of January 30,1996, (the time of the icing problems at CWSH and ESW) when the lake temperature was recorded at 32.2 F.

This fact alone may account for the absence of any icing l problems on trash racks or traveling screens from the winter of I 1992-1993 up to January 30,1996. Prior to the winter of 1992-

1993 beginning with the winter of 1985-1986 (the first

operational winter), nine time frames were identified when lake '

temperatures could have approached 32 F. For six. of these nine time frames, sufficient surface ice cover was documented l l to preclude the occurrence of frazilice in the area of the intake l structures. During the remaining three time frames, c review of Control Room Operator Logs gave no indication of ESW pump !

l operation on those dates. !

Was the first operability determination of ESW Pump "A" odequate?

The team concluded that the Operability Review performed was inadequate due to inadequate engineering review of the j l actual plant conditions. dSW "A" Pumphouse fore bay level fluctuations, prior to securing the pump, should have made it

obvious that flow blockage was occurring upstream of the i pump suction. The cause of the blockage was not conclusively i determined nor steps taken to ascertain that the blockage had cleared.

! Based upon the knowledge base and information on icing I l

utilized by the personnel at the time, the decision made by the Duty SS to declare the pump operable appeared to be valid.

Procedural controls were correctly followed and the chain of command was well utilized in making the operability decision.

l The pump operation for the previous two hours was within 4

normal parameters and met the performance criteria specified.

IIT 96-002 Page 51 of 78 l l

l

L i l Supplemental-he'ating to the ESW Pumphouse' fore boys and-continuous site watch surveillance appeared to provide. i

adequate ' assurance to maintain the pump operable. The l review and: concurrence of:the PSRC was obtained prior to

. i declaring the pump operable. l However, the suction to ESW Pump "A" was being restricted by continuing frazilice buildup on the trash rack from the lake. This )

i phenomenon was not recognized by the personnel. involved !

and was therefore not taken into consideration during the-decision making process regarding ESW Pump "A" operability.

A visual inspection of the ESW fore bay during the incident incorrectly concluded that the ice present existed only at the l

surface.

Although visual inspection into the ESW fore bay could determine the presence of surface ice, the depth or degree of coverage of. ice on the trash. racks could not be positively determined. Nor was it known or recognized that the quantity of warming line flow and temperature was less than the given design values. Previous correspondence from Engineering to Operations had established a basis of understanding that frazil' ;

ice b!ockage was not a credible event. This . event i demonstrates that a good questioning attitude is necessary'to sometimes break a mindset prevalent at the time of the initial investigation. If the cause of the blockage is not thoroughly determined, then assurance of it not reoccurring again cannot be guaranteed. PIR 96-0368 addresses the concern of not recognizing the potential of frazil ice accumulation. PlR 96- !

0377 was initiated to find and remove documentation referring to frazilice as not being a credible event. Furthermore, PIR 96-0412 addresses the concern of not modeling the SW/ESW !

warming lines into the Wolf Creek Individual Plant Examination for the same reason.

How close did the "B" ESW Pump come to becoming inoperable j during the event?

! "B" ESW pump was operable throughout the entire period when 1 i frazil ice blockage was being experienced on "A" ESW, llT 96-002 Page 52 of 78

l

delivering the required flow and pressure. However, due to ;

l design. problems and operational valve lineup problems, the <

j - amount of warming line heat input to the "B" ESW pump intake appears to have been marginal. Ice was visible on the surface i upstream of the trash rocks, but the depth of this ice was not j - verified as divers did not inspect the "B" trash racks since the-4 pump was running. Abnormallevel variations were observed at '

times in the "B'? ESW pump suction bay, and some "B" ESW i pump discharge pressure variations occurred. These variations l were not to the point of making the ' pump inoperable but Indicated that some frazilice blockage had occurred.

The closest to losing "B" ESW appears to have been at about ,

the time that "A" ESW pump was secured for the second time, !

1925 hour0.0223 days 0.535 hours 0.00318 weeks 7.324625e-4 months s- on Tuesday January 30, 1996. Reports from ESW

' - indicate that "B" ESW pump suction level was trending downward. The . site watch observed that the lowest level reached was below the lower platform (<1072'). Minimum .

pump submergence is 9(about 1068'). From the site operator-1and control room logs additional RHR heat load was put on "B"

CCW by the. Operators in an attempt to reverse falling "B" ESW j suction bay levels at about 2015 hours0.0233 days 0.56 hours 0.00333 weeks 7.667075e-4 months . This was effective in reversing dropping levels within about 15 minutes and suction ;

levels were fully restored to normal by about 2130 hours0.0247 days 0.592 hours 0.00352 weeks 8.10465e-4 months . .

Recognition of the downward trend of "B" ESW Fore bay level and the timely response in increasing the heat load onto "B" .

ESW via the RHR System reflects a strength on the part of the Operating crew. The trend of decreasing fore bay level can also be detected in "B" ESW pump discharge pressure trend.

Had the Operating crew not increased the heat load onto the f i

"B" ESW Train, the "B" ESW Pump fore bay would have likely continued to drop to the 1068' elevation further resulting in degraded or eventual loss of the "B" ESW Pump discharge ,

pressure and flow.

Personnel at ESW also reported level fluctuations of up to 9' below normal on ESW "B" during the day on Tuesday, January llT 96-002 Page 53 of 78

1 30,1996. From the written reports it appears that the lowest' l level during the day would have been about elevation 1077.'

l UHS ultrasonic. level indicator was: erratic much of the day,

! presumably due 'to oscillating levels. - Communications between the TSC and ESW during the day indicate that this indicator was not tracking level very well. This indicator is

normally steady even when ESW pumps are running. Its l behavior seems to be representative of level in that its indication is erratic when actual level is erratic, but it can not I track actual level when levels are erratic. It is noteworthy that- 1 4

in the evening, when level at the "B" ESW pump suction was 'l

[ reported to be decreasing, that U-27 seems to track level fairly l well.

l i

"B" CCW dwarfs other ESW loads present on "B" Train ESW on l Tuesday, January 30,1996. A plot of "B" CCW Heat Exchanger A-temperature is attached. It remained steady throughout the j . day until late afternoon when it decreased slightly. From site

! operator and control room logs o'dditional RHR load was put on

"B" CCW by Operators in an attempt to reverse falling "B" ESW -

! suction fore bay levels at about 2015 hours0.0233 days 0.56 hours 0.00333 weeks 7.667075e-4 months .

h L !

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IIT 96-002 Pago 54 of 78

i 1

1 1

ESW Inlet Bay Elevations l

1087' Normal Lake Level m 1086' Platform and Approximate Actual Lake Level on Tuesday 1/30/96 e

n 1072' Lower Platform 1068 minimum level N d Bottom of Pumo Acoroximate Bottom of Pit i

IIT 96-002 Page 55 of 78 i

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V. DETERMINATION OF ROOT CAUSES:

Summary:

The root cause of both of the icing events is inadequate design. The i CW system and the ESW system are expected to be able to operate under the environmental conditions experienced on the morning of 1 January 30,1996. Failure to verify design assumptions resulted in an l inadequate ' design of these systems and their inability to operate I satisfactorily during this event. l Process for identifyina Root Cause:

The identification of the root causes associated with this event were done with the processes outlined in procedures Al 28B-003, Rev. 4,

" Incident Investigation Team," and Al 28B-004, Rev. O, " Guidelines For Performing Root Cause Analysis " As with any in-depth root cause investigation, the process involved a large amount of data collection and formal industry-accepted methods for ensuring the event and its causes are thoroughly understood.

An initial Event and Causal Factor (E&CF) chart was the first step in understanding the sequence of events. This information was obtained l from a review of the Shift Supervisor and Control Room Logs. At the same time, decisions were being made on who to interview and what questions to ask. Procedures, drawings, calculations and a wide variety of other documents were reviewed (as described below). As more information was obtained, important events or activities were '

added to lhe E&CF chart. For each event or activity, the question was asked: "Was this action appropriate for the given circumstances 9" was formulated. Those identified as inappropriate are identified on the chart.

Once inappropriate actions were identified, efforts were made to understand why they occurred. This was done through additional interviews and document review along with Barrier Analysis, Change Analysis and STORM analysis. Broken barriers, conditions existing at the '

time of the inappropriate action and causes identified with these methods were then placed on the E&CF chart. Causes were 4

IIT 96-002 Page 59 of 78

1 reviewed to identify any programmatic causes and corrective actions were proposed.

Sources of Information:

Appendix "C" provides a list of documents reviewed by the llT, including procedures, WPs, lesson plans, NRC inspection reports, Quality Evaluation Surveillance Reports, Wolf Creek letters and inter-office correspondence, calculations, logs, drawings, temporary modifications, work histories and TSC/OCC documents.

Appendix "F" provides a list of personnel interviewed during the investigation. Efforts were made to interview allindividuals involved in l

an event or activity and to verify statements against procedures, I design documents or other interviews. I Event and Causal Factor Chart:

Appendix "E" provides a detailed sequence of activities and events ;

leading up to or occurring between January 30,1996, and February 2, 1996. The chart identifies those actions determined to be !

inappropriate for the given conditions. Inappropriate actions are shown separately on Appendix "E" along with related conditions, broken barriers and causes.

Barrier Analysis and Chanae Analysis:

Barrier analysis is the identification of barriers, physical or administrative in nature, that are intended to prevent an event from occurring. Often when an event occurs, one or more barriers have been broken. Appendix "E" identifies the barriers that should have been in place to prevent the inappropriate actions and why they were ineffective.

Change analysis is a review of activities that have been performed successfully in the past to determine what changes caused them to 1 be performed unsuccessfully. Although many of the activities occurring during this event had either not been performed in the past or were infrequently performed, change analysis did provide some insights and verification of potential causes of this event. Appendix "E" provides the results of this review. The questions contained in llT 96-002 Page 60 of 78

Appendix "E" are the standard set of. questions for change analysis that are contained in Al 28B-004.

STORM Analysis: ,

p I

. Once conditions or potential causal' factors that are likely contributors-F . to the event have been identified,' STORM ~ analysis can be applied to' identify areas' that needed further investigation. STORM stands for ;

Stimulus, Team, Operation, Response and Management and is a table "

of specific questions contained in Al 28B-004 that provides assistance j in identifying a root cause category. STORM is only for analyzing j human performance problems,'and therefore, was not applied to design issues identified during this investigation. Appendix "E" provides a summary of. the STORM analysis for the inappropriate- !

i actions involving human performance on the E&CF chart.

l Root Causes:

The ice blockage of the CW traveling screens and the ESW trash racks i are the primary events that were reviewed by this llT. Several other i events were also investigated, including the misalignment of the ESW j valves and the plant cooldown. not being completed in 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months as

. required by T/Ss. The following is a list of the main events, their root causes, primary contributing causes and proposed corrective actions. 1

.to prevent ' recurrence. Additional actions related to these events (immediate and enhancements) are contained in Sections VI through IX of this report.

Event: Ice buildup on the CW traveling screens resulting in plant I 3

shutdown.

Root Cause

Inadequate design. The design of the CW Intake Structure and e associated Traveling Screens was not adequate for the harsh environmental conditions imposed on them during the events of l January 30, 1996. The' design is inadequate for the following 4

reasons:

. When in " Auto" the traveling screens are susceptible to damage i by surface ice build-up. Such damage occurred during the first j several years of plant operation and was corrected in 1988 by i IIT 96-002

Page 61 of 78 1

changing how the traveling screens were operated. They were placed in " Manual slow" during the winter to prevent the build-up of surface ice.

. When in " Manual slow" the traveling screens are susceptible to ice build-up near the spray wash area and on the traveling screens themselves. The metal traveling screens are exposed to l cold air for approximately 7 minutes when they rotate out of the water during their 36-minute cycle. At one point during this 7 minutes, they are sprayed with SW that is at approximately lake temperature. During this event air temperature was approximately 7 F , winds were from the north at 10 - 25 mph and lake temperature was near 32.4 F. When the traveling screens leave the water under these conditions, they Cooldown i rapidly from near 32 F. When sprayed with approximately 33 F l water, icing conditions result. It is believed some inactive frazil j

ice may also have been present in the water, which could have I contributed to the ice build-up on the traveling screens. l Contributina Cause: 1 The failure of actions taken in 1988 to correct the design problem of surface ice around the traveling screens allowed an additional icing event to occur. A revision to STN GP-001 resulted in placing the traveling screens in manual slow to compensate for the design problem. This operational change compensated for one failure mode (surface ice) but caused another failure mode to become more likely to impact operations.

Event: Ice build-up on the ESW trash racks.

Root Cause:

Inadequate design. There was insufficient warming line flow for the actual warming line temperature to prevent the formation of frazil ice. A design calculation performed in 1976 assumed an ESW warming line temperature of 35 F. With this assumption, the calculation determined a flow of 4000 gpm was required. Later, a design calculation determined that actual flow would be 4413 gpm with the additional assumption that the pipes would be full of IIT 96-002 Page'62 of 78

k

. water. Both of the above assumptions were' incorrect. The actual warming line temperature on the morning of January 30,1996, was approximately 33 F. It was also discovered that_ the warming line-and the ESW to UHS return line piping _ diameters and elevations are.

such that portions'of these lines operate with partial pipe flows and' with the dry portions not vented. This condition was apparently not-foreseen by the piping designer, and 'makes the calculation methodology used for sizing the warming line invalid with resulting-non-conservative errors.- The warming line flow rate during an

~

accident line-up for the piping as-built configuration cannot_ be-readily calculated or measured with a high degree of certainty, but is estimated to have been about 2500 gpm.

Contributina Causes: .

The incorrect ESW valve line-up was a contributing cause to the ice build-up at the ESW trash racks. During the approximately six hour-period preceding the first time "A" ESW pump had to be secured due to the ice blockage, ESW return to SW return cross tie isolation valves were open and the ESW return to the UHS valve was '

throttled. -This caused some of the ESW return flow to be diverted from UHS through the normal SW discharge line. It is _ estimated that this caused warming line flow to be reduced to about two thirds of what it would have been, or about 1700 gpm.

Event: Incorrect Line-up of ESW System Valves Root Cause:

The root cause of this event was a failure to verify procedure requirements in a timely manner. Although the procedure was not used while doing the line-up, this was acceptable given the urgent conditions of the plant. Not using a procedure however, increases the risk a line-up will be done incorrectly. Because of this increased risk, effective communications become even more important.

Additionally, it is important to verify actions taken by performing a timely review of the applicable procedure. The six hour delay is not timely and did not meet management expectations regarding implementation of urgent action and subsequent procedure verification reviews.

IIT 96-002 Page 63 of 78

Contributina Causes:

There are three contributing causes to the incorrect valve line-up:

1. Contributing to the incorrect line-up were three examples of ineffective communication. When the Shift Supervisor instructed the RO to start the ESW Pumps, he did not fully communicate his expectations to isolate the ESW from the SW. When the RO's were walking the boards during shift turnover, the oncoming RO did not gain a full understanding from the on-shift RO as to why the abnormal ESW line-up existed. When the on-coming RO identified the abnormal line-up, he did not communicate it to his SO.

2. Some resources were not effectively used during the time period of this event. Rods were in manual and one RO was dedicated to monitoring Al to minimize any impact on the fuel during the power change. This left one RO to cariyout the rest of the RO's responsibilities. During a transient such as this, placing the rods in automatic would have allowed the RO to focus on higher priority issues. The Shift Supervisor and the SO are responsible for effective use of resources.

3. The Alarm procedure for SW Pressure Hi/ Low, ALR 00-008B, ;

instructed the operator to start the ESW Pumps in accordance !

with SYS EF-200. This caused some delay in performing l necessary immediate actions and, in this case, set the stage for immediate actions being performed without the aid of a procedure. Placing detailed actions in the alarm procedure (i.e., instructions to start the ESW Pumps and what valves to open and close), would have allowed the RO to perform the desired line-up in a timely manner.

Event: Failure to complete cooldown to MODE 4 in 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months as required by Technical Specification 3.7.1.2.

Root Cause:

The root cause of this event is the lack of procedure guidance for performing a rapid cooldown. The SO believed that he had to complete GEN 00-005, Appendix "A" prior to beginning a plant IIT 96-002 Page 64 of 78

cooldown. Several of the actions in the Appendix could have i been completed in parallel with the performance of GEN 00-006.

This would have expedited the start of plant cooldown.

Contributina Causes:

The SO had only been in his position for approximately 8 months, and had no prior experience or simulator training at completing the cooldown process within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . It should be noted that Wolf Creek as a plant has never experienced the pace of operations required to achieve Hot Shutdown in 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months .

Adherence to procedures is the expectation of Operations, which focused the SO on ensuring each step was completed prior to traveling on to the next.

The crew configuration had been changed that morning. The Shift i Supervisor was assigned to this crew when the regular Shift l Supervisor went home sick. This presented a condition where the l l

l crew was working in an environment where the individuals had not l had the opportunity to form a solid working relationship.

! Proarammatic Causes (Generic):

l l Of those root and contributing causes identified, some are l

considered programmatic weaknesses. The following is a list of those causes deemed programmatic in nature.

l . High level alarm procedures often reference other procedures as the immediate response requirements. This hinders timely implementation of these actions, at a time when prompt

response is important.

! . No formal administrative controls exist to ensure a procedure j gets verified when conditions necessitate actions without the use of a procedure.

These programmatic issues are being investigated as part of the corrective actions identified above.

i llT 96-002 l Page 65 of 78

1 VI. IMMEDIATE ACTIONS TAKEN:

Although there were numerous actions taken in response to the icing event of January 30,1996, the following is a brief summary of the key actions that were taken to mitigate the consequences of the event. A complete listing of all actions taken is contained at the end of this section of the report.

j Essential Service Water (ESW) System:

! Upon confirmation of a low "A" ESW pump fore bay level the

! operators immediately secured the "A" ESW pump. Personnel were l dispatched to the ESW Pumphouse to determine the cause and l implement actions to restore fore bay level.

l These subsequent actions included the erection of a tent (temporary shelter) over the fore bays to minimize conductive heat losses. The procurement and installation, on an interim basis, of portable space heaters and heater blowers to warm the air in the ESW Pumphouse and fore bays. The procurement and installation of portable air compressors, an air bubbler system, and portable i water boilers. These items were used to inject air and warm water

! into the fore bays of the ESW pumps to aid in the agitating / breakup and removal of the frazilice. WCNOC established a 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months watch of the temporary equipment installed at the ESW Pumphouse and fore bays to assure continuos proper operation of the equipment and to inform the Control Room of any equipment degradation.

Circulatina Water System (CW):

Upon receipt of the alarms associated with the CW pump traveling screens the Control Room immediately dispatched personnel to the CW Pumphouse to assess the alarms and to provide an equipment status report to the Control Room. Upon determination of severe icing of the CW traveling screens the Control Room immediately implemented actions to place the plant in a i configuration which minimized its reliance on CW and SW. These actions included a power reduction and subsequent reactor trip.

Further, the Control Room rotated the operating CW pumps and l SW pumps and subsequently tripped all CW pumps and placed the ESW System in service.

l l

LIT 96-002 Page 66 of 78

Subsequent actions included the erection; of a tent (temporary shelter) over the fore bay and traveling screens to minimize conductive heat losses. The procurement and installation, on an interim basis, of portable space heaters and heater blowers to warm the air in the fore bay. The procurement and installation of portable air compressors, an air bubbler system to inject air in front of the fore bays to the CWSH to aid in the agitating / breakup and removal of the ice.

Emeraency Response Proaram:

In response to the above discussed events WCNOC entered and implemented its Emergency Response Program. This consisted of the classification and declaration of two NUEs and the twenty four hour augmentation of plant staffing to aid the Control Room in responding to the above discussed events.

Appendix "E" consists of a complete chronological listing of the actions taken following the icing event.

Vll. ADDITIONAL ACTIONS TAKEN Letter WM 96-0014, from [name deleted] to [name deleted] documents:

The following contingency actions have been implemented and will be taken whenever lake temperature is 40 F or lower untillong term actions are implemented:

1. Air bubblers will be maintained in each outer bay. As a minimum, two air compressors are located at the ESW Pumphouse. A minimum of one air compressor is aligned for bubbling the outer bays with an additional compressor as a backup.

2. Tents will be maintained over the grating of the outer bay to provide additional freeze protection.

3. A dedicated cognizant individual will be stationed at the ESW Pumphouse 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months a day. This individual will: 1) monitor the air compressors 2) monitor the tents and 3) watch for formation of ice in the outer bays. The Control Room will be notified immediately upon compressor failure, tent degradation or ice formation in the outer bays.

IIT 96-002 Page 67 of 78

Letter WM 96-0014, from [name deleted] to [name deleted] documents:

Wolf Creek Nuclear Operating Corporation is taking the following additional actions to assure continued operability of the ESW System:

1. Cold weather preparations and equipment lineups in place prior to and during this event will be reviewed and incorporated into the appropriate operational procedures and training.

2. The lessons learned from the icing problems encountered at the CW Screenhouse will be captured and incorporated into the ;

appropriate operational procedures and training. l

3. Design adequacy of the ESW System for cold weather l operations will be reviewed and actions taken as appropriate. I

4. Design adequacy of the SW and CW System for cold weather operations will be reviewed and actions taken as appropriate.

WCNOC formed llT 96-002 to determine the cause of the icing event.

(PIR 96-0311) !

IIT 96-002 performed an evaluation of the initial engineering nonconformance evaluation on 2/2/96. The llT issued PIR 96-0367 l recommending revision of the evaluation and the proposed immediate l temporary actions.

Vill. RECOMMEND CORRECTIVE ACTION:

Essential Service Water intake Recommended Action Purpose Design change to ensure adequate To Correct Problem.

warming line flow. The purpose is not to only The hydraulics of the ESW discharge to correct the original design the UHS and Warming Line to the ESW flow deficiency, but to Pumphouse must be changed to establish the appropriate flow establish full pipe flow and distribute the rate to prevent ice blockage proper amount of flow to the ESW of the ESW Pumphouse trash Pumphouse Warming Line. Due to the racks due to a lower than low amount of heat (3/4~1 F) available expected temperature rise from the worst case safety train, a higher (3/4~1 F) across the worst flow rate than the original design (4,000 case ESW train. (PIRs 96-0316 gpm) may be required. The upper and 96-0334) bound for this warming line flow will be dictated by the UHS cooling IIT 96-002 Page 68 of 78

characteristics and the temperature range chosen for this mode of operation. To achieve the proper flow and full pipe conditions, back pressure on the ESW discharge to the UHS must l be raised downstream of the Warming Line tee. The back pressure orifices located upstream in the Powerblock ESW discharge lines will need to be re- i evaluated as to not increase the overall l back pressure on the ESW to an unacceptable level.

All documents referring to frazil ice at To eliminate incorrect !

ESW as not being a credible need to be information. (PIR 96-0377) revised or removed from records.

Recommended the deletion of T/S To eliminate incorrect Clarification 003-88, Rev. 2. information provided to operators on frazil formation at the ESW Pumphouse. (PIR 96-0366)

Maintenance activities including repairs To Correct Problem. (PIR 96-should be completed on volves EFV- 0483, WPs 102996, 103096, 0262,0263,0264 and 0265 prior to warm 106532, 100818, 104072, weather in order to accommodate the 100644; ARs 7587, 7681, 7823, corrective actions being developed to 10031, 11774, 5718, 5544, alter the ESW System hydraulic 8228) characteristics for satisfactory warm and cold weather operation.

Circulating Water Intake Recommended Action Purpose Enclose traveling screens with a To Correct the problem. (PIR structure that provides adequate heat 96-0316) and light.

This effectively removes the CW Traveling Screens from the environment that promotes ice formation and also provides an environment that accommodates personnel to perform IIT 96-002 Page 69 of 78

l l 4 l surveillance and maintenance activities l l on the Traveling Screens. 1 l Misalignment of ESW System :

Recommended Action Purpose A method for tracking urgent actions This action is being l and subsequent verification of implemented to provide the acceptability of these actions will be operating crews with the !

developed. This methodology should necessary tools to prevent provide a simple tool to the operating recurrence of this type of an crews to log, track, and resolve urgent event. (PIRs 96-0338 and 96- l actions. 0373) l Communication training will be This action is being enhanced for the operating crews. The implemented to assure all ;

training will add emphases to stressing operating crew members !

use of clear concise instructions, and not have a clear understanding taking the watch until the relieving of management's !

individual has a full understanding of all expectations in this area, l abnormal conditions. The need to bring (PIRs 96-0338 and 96-0374) abnormal conditions to the attention of i supervision will be reinforced. l The alarm procedure for the top-level This will eliminate the need to I alarms will be reviewed and revised, as have operation personnel use l needed. These revisions willincorporate a secondary procedure to I all expected operator actions into the implement immediate alarm I applicable alarm procedure. procedure response requirements. (PIRs 96-0338 and 96-0375)

Delayed Cooldown Recommended Action Purpose l Procedures GEN 00-005 and GEN 00-006 This action is being will be revised to provide guidance on implemented to remove un- I which steps are mandatory and which necessary programmatic steps may be delayed in an obstacles for the accelerated shutdown condition. performance of an accelerated cooldown.

(PIRs 96-0264, 96-0369, and 96-0480) l Simulator Training will be developed to This action is being IIT 96-002 Page 70 of 78

4 provide the operating crews with the implemented to provide the 1 opportunity to operate under conditions operators with an t

which require a forced cooldown in 6 understanding of the actions !

hours. and time frames to 1 accomplish the action for a rapid forced cooldown. !

(PIRs 96-0264 and 96-0370) 1 Management's expectations will be This action will be reviewed regarding procedure implemented to assure

adherence as they relate to rapid adequate guidance has i cooldown events, been provided to the I

operating crews. (PIRs 96- l

0264 and 96-0372) 1 The need for a method / strategy for This action is being l

addressing heightened awareness to implemented to assure the communication techniques and operating crews have been command and control issues in the given the necessary tools to Control Room when an operating crew perform their assign duties in

, makes configuration changes will be an effective manner under 4

evaluated. these conditions. (PIRs 96-0264 and 96-0371)

IX. RECOMMENDED ENHANCEMENTS:

Essential Service Water Intake Recommended Action Purpose Provide an accurate lake water Monitoring for frazil temperature indication. conditions.

The potential for frazil ice is significant Accurate temperature when bulk lake water temperature is at monitoring of the lake water 33 F and decreasing. Very small conditions can be used to changes in temperature when the water initiate additional measures is in the 32 F range can trigger frazil to detect and mitigate frazil production. Lake water temperature ice blockage. (PIR 96-0316) indication with a high degree of accuracy (+/-0.2 F) at the inlet to the ESW Pumphouse can provide the most reliable means to detect the conditions llT 96-002 Page 71 of 78

conducive to produce frazil ice.

Provide an air bubbler (broom) to Compensatory Measure sweep frazilice off of the trash rocks. It is envisioned that air Once the lake has reached the critical bubbler tube manifolds be environmental conditions to produce used as a compensatory frazil ice and the ESW Pumps suction measure, with air begins pulling frazil ice-laden water into compressors, hoses and the Pumphouse inlet, Air bubblers can manifolds being brought in provide a brooming or sweeping effect and utilized in a temporary upward across the trash rack to keep off fashion. (PIR 96-0316) or break off frazil ice accumulation. Air bubbling also creates a high circulation ratio of the bulk fluid, thus promoting mixing and heat transfer.

Enclose and heat the ESW trash rack Compensatory Measure enclosure. Supplemental heating As the lake is the prime should be considered in the ESW source that produces frazil Traveling Screen Bay area as well. ice, enclosing the trash rack Observations made during the ESW area does not prevent frazil freezing incident indicated that limited ingress. It does, however, amounts of ice washed off of the provide a suitable traveling screens and that this limited environment for personnel to amount did not affect traveling screen monitor the trash rack fore operation, bay and perform ice removal work activities, if necessary.

(PIR 96-0316)

Surveillance on ESW warming lines to Monitoring for ESW Warming ensure appropriate warming line flow. Line flow. (PIR 96-0316)

Provisions for a flow metering device should be included in the design change development to determine the actual warming line flow. This would also assist in future ESW and EA system flow balance determinations and detection of flow degradation.

Local ESW Bay level indication for each Monitoring for trash of the traveling screen bays and trash rack / screen blockage. (PIR rack bays. 96-0316 and 96-0329)

IIT 96-002 Page 72 of 78

Local ESW Bay level indication would provide the means for site watch personnel to clearly determine existing bay levels and the margin in regard to the minimum expected lake level and ESW Pump net. positive suction head.

Level Indication could simply be an attached tape or painted elevations to the ESW Bays.

Manual Rake Available Compensatory Measure (PIR '

Based upon. the recommendation of 96-0316) the Army Corp of Engineers, the use of a )

" Rake" to manually remove frazil ice is successfully used by other power plants.

Provide adequate lighting in the bay Monitoring for frazil ice. (PIR and trash rack area. 96-0316)

This should be integrated with the design i efforts. I Discharge path for the ESW traveling Need to. assess / identify screen and strainer backwash became methodology of keeping restricted due to the buildup of ice. path free of ice. To prevent flooding of the ESW )

Pumphouse. (PIR 96-0396) !

Provide Computer based tools for Assist in correcting problem. I modeling ESW System hydraulics. (PIR 96-0316)

System Engineering will reevaluate the To assure that correct operability call associated with Work guidance is provided to the Request 5134-93 and Valve EFV-0263. operating crews on warming line flow with the valve stuck in the 50% open position. (PIR 96-0430)

Determine and correct cause of erratic To assure accurate ESW Bay operation of EF LIT-0027. Level indication is available.

WP 109205 was generated I and STN IC-265 will be performed. (PIR 960-0365) -

IIT 96-002 Page 73 of 78

-= . -_ - . . . - . . .

i Circulating Water intake Recommended Action Purpose l CW Traveling Screen Operation To rnonitor for degradation. I Procedure Change (PIRs 96-0398, 96-0316, and l

Procedure STN GP-001 will be revised to 96-0482) i require controlotron setup and zero adjustment prior to opening the CW I j Warming Line valve. l Procedure SYS SW-121 will be revised to provide guidance on the use of air bubblers to assist in breaking up surface j ice. '

Revise ALR 00-006C CWSH Fast Wash, To prevent the buildup of ice ,

should be revised to place the traveling on the traveling screens. (PIR )

screens wash local mode switch to OFF 96-0399) l when icing conditions are apparent.

Provide an air bubbler (broom) for Compensatory measure.

inactive bays (and all bays) during It is envisioned that air shutdown mode to mitigate effect of bubbler tube manifolds be surface ice. used as a compensatory The CW Warming Line was found to be measure, with air

, adequate in providing heat to the CW compressors, hoses and Screenhouse, thus preventing frazil ice manifolds being brought in accumulation on the trash racks. and utilized in a temporary However, when CW pumps are secured fashion. (PIR 96-0316) or Condenser vacuum is broken, CW warming either becomes unavailable or has a much lower heating content.

Procedure SYS SW-121 will be revised to To eliminate the spraying of delete the requirement to operate the cold (near or at freezing traveling screens continuously in slow temperature) water on the manual during cold weather or unusual screens. This will eliminate the icing conditions. ice buildup on the traveling screens which occurred during the January 30, 1996, icing event. (PIR 96-0376 and l 96-0482)

IIT 96-002 Page 74 of 78

Procedure SYS SW-121 will be revised to This actions will provide the l direct operators to use air sparging in operators with a tool for situations, where icing can occur. breaking up surface ice that may inhibit traveling screen )

operation. (PIR 96-0316 and 96-0482)

Emergency Plan Recommend Action Purpose PAR Charts require clarification to make To align WCNOC's .

allowances for not evacuating JRR for Emergency Plan Program with l non-radiological events. the State and County l Programs / Desires. (PIR 96-0405) {

On 2/8/96 the Manager Emergency To provide better tools to the Planing drafted several changes to the operating crews. (PIRs 96-EALs. These changes were drafted 0418 and 96-0432) based on the recent icing event.

In addition the evaluation should include a review of the evacuation of the ESW Bay, i Need to revise EPP 01-4.1 to ensure that To remove ambiguity from the minimum staffing requirements for the procedure and to assure !

the TSC/OSC activation are clear, correct staffing prior to i concise, and consistent with the RERP. activation of the facility. (PIR 96-0428) l Need to evaluate a revision to the To provide enhanced l Emergency Program at WCNOC. This response to non-radiological revision should provide a mechanism for emergencies which require accounting for personnel who are the activation of the responding to a non-radiological event, Emergency Program. (PIRs the need to establish a assembly point 96-0424 and 96-0427) outside of the exclusion area and the need for an assembly point inside the I exclusion area. I Need to develop a non-emergency To provide the operating callout method for the TSC/OSC/ERO crews with a simple and fast j Personnel. tool for obtaining the necessary assistance to ;

IIT 96-002 j Page 75 of 78

W respond to a non-radiological emergency (PIR 96-0428)

During the icing event pagers were To eliminate confusion and to activated but the ADS Machines assure personnel respond l indicated that an emergency was not when needed. (PIR 96-0260) l declared. Need to change message on l ADS Machine to eliminate confusion during an event where the TSC is being l staffed but an emergency has not been l declared.

During the icing event security failed to To ensure all personnel are ,

make the NUE announcement for the informed of an emergency l buildings not covered by Gatronics. (PIR 96-0261) l Review announcement methodology to l assure proper tools are made available to assure announcements are made in a I timely manner. l During the icing event two NUEs were To eliminate confusion which ;

declared. It has been determined that occurred during the icing l the procedure do not provide event. (PIR 96-0296) !

adequate guidance on how to terminate an event. Revise procedures to provide adequate event termination guidance.

During the icing event WCNOC made To provide greater assurance several emergency notifications. A forms are completed !

review of the notification revealed minor correctly. (PIR 96-0346) l form completion inconsistencies.

Perform a review to determine if action is warranted.

Misalignment of ESW System Recommended Action Purpose Management will reiterate expectations To assure procedure use and that plant personnel will obtain and adherence in accordance utilize the applicable procedures when with management performing a task. Under special expectations. (PIR 96-0541) conditions the Shift Supervisor may llT 96-002 Page 76 of 78

F direct Control Room personnel to l conduct activities without the aid of procedures provided that a verification of actions taken per the approved procedure is conducted in a timely manner.

Delayed Cooldown Recommended Action Purpose Perform a review to determine if Reactor To eliminate confusion and 1 Engineering / Management has provide delays in performing a rapid l adequate guidance on when and how cooldown. (PIR 96-0362) i it is appropriate to implement actions to )

control Al.

Need to enhance Shutdown Margin The program did not Calculation Program to address plant encompass this operating coastdown practices. aspect and as a result did not I function correctly during the 1/30/96 reactor trip event. l (PIR 96-0406) !

Need to consider including Reactor To provide the operating Engineering personnel in selected crews and the reactor simulator training scenarios. engineers with the opportunity to practice interface activities under stress conditions and to give the reactor engineer a perspective on maneuvering the plant and a sense of urgency with regard to operational concerns during these periods. (PIR 96-0416)

Probabilistic Safety Assessment Recommended Action Purpose PAS models for ESW and SW did not To correctly model all possible model warming lines in the fault tree. system faults. (PIR 96-0412)

The models will need to be revised.

l llT 96-002 l Page 77 of 78

y; Frazil ice Training Recommended Action Purpose The llT recommended that frazil ice To provide the operating formation and contingencies for its crews with enhanced formation be included in applicable knowledge of frazil ice and training material. the methodologies of retraveling it. (PIR 96-0415)

Auxiliary Boller Recommended Action Purpose During the recent icing event the boiler To prevent un-need tripped several times. Perform an distraction to the operating evaluation to determine the adequacy crew and to prevent of this component's operation and the equipment damage. (PIR 96-need for improved performance 0417)

X. APPENDICES:

l LIT 96-002 Page 78 of 78

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