05000237/LER-2013-009, Regarding HPCI Failed to Achieve Rated Flow Due to Failure of Stop Valve to Open

From kanterella
(Redirected from 05000237/LER-2013-009)
Jump to navigation Jump to search
Regarding HPCI Failed to Achieve Rated Flow Due to Failure of Stop Valve to Open
ML14043A118
Person / Time
Site: Dresden Constellation icon.png
Issue date: 01/29/2014
From: Marik S
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
SVPLTR 14-0008 LER 13-009-00
Download: ML14043A118 (7)


LER-2013-009, Regarding HPCI Failed to Achieve Rated Flow Due to Failure of Stop Valve to Open
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(v), Loss of Safety Function

10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications

10 CFR 50.73(a)(2)(i)

10 CFR 50.73(a)(2)(vii), Common Cause Inoperability

10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded

10 CFR 50.73(a)(2)

10 CFR 50.73(a)(2)(iii)

10 CFR 50.73(a)(2)(ix)(A)

10 CFR 50.73(a)(2)(x)

10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor

10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat

10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
2372013009R00 - NRC Website

text

oDresden Nuclear Power Station 6500 North Dresden Road Exelon Generation,,

Morris, IL 60450 815-942-2920 Telephone www.exeloncorp.com 10 CFR 50.73 SVPLTR # 14-0008 January 29, 2014 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station Unit 2 Renewed Facility Operating License No. DPR-1 9 NRC Docket No 50-237

Subject:

Licensee Event Report 237/2013-009-00, HPCI Failed to Achieve Rated Flow Due to Failure of Stop Valve to Open Enclosed is Licensee Event Report 237/2013-009-00, "HPCI Failed to Achieve Rated Flow Due to Failure of Stop Valve to Open." This event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(D), "any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident" and 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition prohibited by the plants Technical Specifications."

There are no regulatory commitments contained in this submittal.

Should you have any questions concerning this letter, please contact Mr. Glen Morrow at (815) 416-2800.

Respectfully, Shane M. Marik Site Vice President Dresden Nuclear Power Station Enclosure: Licensee Event Report 237/2013-009-00 cc:

Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 (01-2014)

Estimated burden per response to comply with this mandatory collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.

,~

~

Reported lessons learned are incorporated into the licensing process and fed back to industry.

Send comments regarding burden estimate to the FOIA, Prtvacy and Information Collections

(= "

Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001. or by Internet e-mail to *tn*oollocts.Resource@nr.gov, and to the Desk Officer, Office of tntormation and LICENSEE EVENT REPORT (IE.

J Regulatory Affairs, NEOB-10202, (3150-0104). Office of Management and Budget Washington, DC (See Page 2 for required number of 20503., f a means used to Impose an Information collection does not display a currently valid OMB for each block) contol number, the NRC may not conduct or sponsor, and a person is not required to respond to, dtgitstcharacters fthe information colection

3. PAGE Dresden Nuclear Power Station, Unit 2 05000237I 1 OF6
4. TITLE HPCI Failed to Achieve Rated Flow Due to Failure of Stop Valve to Open
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE S

AM

9. OTHER FACIUTIES INVOLVED SEU A I RE 1AILT NAM DOKET NUMBER MONTH DAY YEAR YEAR SEUMERNTIA RE MONTH DAY YEAR N/A 0 5000 j~AIIYNAEDCE NUMBERNOI I_

112013 2013 009 -

00 01 29 2014 N/A SELLi

9. OPERATING MODE

_11.

THIS REPORT iS hUBM1 5

1uArr TO E REQUIREMENTS OF 10 CFR§: (C W.kl1 OW aOW,)

o 20.2201(b) 0 20.2203(a)(3)(i)

C3 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii)

[] 20.2201(d) 03 20.2203(a)(3)(0i) 0 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(vfii)(A)

O3 20.2203(a)(1) 03 20.2203(a)(4) 03 50.73(a)(2)(i)(B) 03 50.73(a)(2)(vi')(B) 0 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)

10. POWER LEVEL 03 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2Xiv)(A)

E3 50.73(a)(2)(x)

O 20.2203(a)(2)(iii)

C0 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0 73.71(a)(4) 015 0 20.2203(a)(2)(iv) 03 50.46(a)(3)(1i) 03 50.73(a)(2)(v)(B)

[3 73.71(a)(5)

[3 20.2203(a)(2)(v) 03 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C)

[0 OTHER

ISpecify, in Abstract below or in P 20.2203(a)(2)(vI)

!0 50.73(a)(2)(i)(B) 7 1 50.73(a)(2)(v)(D)

NReC cannot open unless the control valves are closed because there will not be a buildup of pressure beneath the main valve.

The design of the spare cover plate (Figure 1) is a combination of an interference fit and a seal weld (Figures 2) to hold it into place. The interference fit is the primary mechanism that holds the spare cover plate in place. The seal weld is not a structural weld and its main purpose is to prevent bypass steam flow. When heat is applied to the valve the expansive forces of the spare cover plate and compressive forces of the turbine casing should hold the spare cover plate in place even without the seal weld intact.

The following indications were observed during the failed start:

  • The Stop Valve showed closed and the green light (LS-9) remained on. Video from within the room also indicated minimal valve travel.
  • The OPEN, red light (LS-1) did not illuminate.

Flow of -3200 gpm from the HPCI Main Pump was achieved (>5000 gpm required; -5600 gpm expected).

The HPCI Turbine reached a speed of -2000 rpm (-3500-3600 rpm expected).

  • The Motor Speed Changer (MSC) remained on the low speed stop (verified through video) and the Main Control Room (MCR) indication for the low speed stop remained lit.

HPCI Turbine Exhaust Pressure reached 24 psig (-30-40 psig expected at rated conditions).

HPCI Achieved a discharge pressure of 3671bs (Via Computer Data Point)

This event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(D), "any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident" and 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition prohibited by the plants Technical Specifications."

C.

Cause of Event

The apparent cause of the Unit 2 HPCI system failing to reach rated flow was a failure of a spare cover plate within the control valve manifold. A failure analysis was provided to Dresden which attributed the failure to a 360 degree circumferential fracture (Figure 3) due to thermal fatigue cracking. The failed control valve spare cover plate was original plant equipment that had been in-service for over 40 years and over 350 system startups.

During each system startup, steam is admitted into the control valve manifold which causes a significant temperature gradient to form across the spare cover plate, and it leads to different rates of thermal expansion between the small spare cover plate and the relatively large turbine casing. These thermal stresses, during system startup, led to fatigue cracking, and allowed for the eventual dislodging of the spare cover plate.

A review of operation and work history shows that there were two potential times the spare cover plate could have been dislodged:

1. Following the securing of steam to the turbine during the last quarterly run, or
2. During outage related activities of D2R23 The run on September 26, 2013, was observed by the system manager and no related abnormalities were noted prior to, during or after the conclusion of the surveillance. Therefore, the most probable time of failure, based upon the available information, is during D2R23 outage activities (i.e., during control valve stroking without steam).

During D2R23, significant maintenance was performed on the HPC1 system, including a full overhaul of the front standard which included several post maintenance strokes of the control valve in the absence of steam. Based upon information provided by GE after the event, "Tripping the valves from full-open position could cause damage to the Stellite coated valve seating surfaces, thus this type of testing should be performed a minimal number of times to insure the proper function of the system."

Additionally, GE stated "Stroking the HPCI valves through the entire range of motion without steam applied is a typical post-outage/pre-startup test."

D.

Safety Analysis

The safety significance of this condition is low. The Automatic Depressurization and Low Pressure Emergency Core Cooling Systems [BO] [BM] were available to provide makeup to the reactor vessel inventory in the event of an accident or transient. Additionally, the respective Isolation Condenser [BL]

systems and other High Pressure Injection Systems (i.e., Feedwater System [SKI and Control Rod Drive System [AA]) were available for reactor vessel pressure control and injection, if required.

Therefore, health and safety of the public were not compromised as a result of this condition.

E.

Correctliy Actions:

As a result of this event, the station has completed or is planning to complete the following:

1. The Unit 2 HPCI Failed Control Valve Spare Cover Plate was replaced.
2. The station is planning an appropriate inspection of the Unit 3 control valve spare cover durng D3R23.
3. The station has created an action to revise the scope of future control valve inspections to include NDE on the seal weld and associated lip for the spare cover plate.

F.

Previous Occurrences

A review of DNPS Licensee Event Reports for the last three years revealed the following reportable conditions related to HPCI inoperabilities:

0 0

0 LER 237/2012-002, "Inlet Steam Drain Pot Drain Une Leaks Result in HPCI Inoperabilities" LER 237/2011-002, "Steam Leak Results in HPCI Inoperability" LER 249/2010-003, *Steam Leak Results in HPCI Inoperability" The corrective actions from the above Licensee Event Reports would not have prevented the current HPCI event.

G.

Comg)onent Failure Data:

Manufacturer Model SIN Type General Electric (GE) 7TDRV231 R1 122610 Turbine Figure 1: H Spare Cover Plate 00% CeNnA~A -A

Figure 2: HPCI Turbine Casing Figure 3: Failed Spare Cover Plate flrns r..tn,,, c.un ~V SCS~*~

i*

rvnm

  • tv l
  • iql