05000446/LER-2015-001, Regarding Train B Safety Injection System Inoperable for Longer than Allowed by TS

Regarding Train B Safety Injection System Inoperable for Longer than Allowed by TS

ML15313A022
Person / Time
Site:	Comanche Peak
Issue date:	09/18/2015
From:	Flores R, Peters K Luminant Generation Co, Luminant Power
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CP- 201500862, TXX -15126 LER 15-001-00
Download: ML15313A022 (4)

LER-2015-001, Regarding Train B Safety Injection System Inoperable for Longer than Allowed by TS

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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 10 CFR 50.73(a)(2)(v), Loss of Safety Function
4462015001R00 - NRC Website

text

Rafael Flores Luminant Power Senior Vice President P 0 Box 1002

& Chief Nuclear Officer 6322 North FM 566 rafael~flores@Lurninant.com Glen Rose, TX 76043 Lum inant254 897 5550 CP-201500862 Ref. # 10CFR50.73(a) (2) (i) (B)

TXX -15126 September 18, 2015 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT (CPNPP)

DOCKET NO. 50-446 UNIT 2 TRAIN B SAFETY INJECTION SYSTEM INOPERABLE FOR LONGER THAN ALLOWED BY TS LICENSEE EVENT REPORT 446 / 15-001-00

Dear Sir or Madam:

Enclosed is Licensee Event Report (LER) 446/15-001-00, "Unit 2 Train B Safety Injection System Inoperable for Longer Than Allowed By TS," for Comanche Peak Nuclear Power Plant (CPNPP) Unit 2.

The Unit 2 Train B Safety Injection System was allowed to be inoperable for longer than the time allowed by the CPNPP Technical Specifications based on a request for enforcement discretion which was granted by NRC Region IV at 0920 on July 10, 2015.

This communication contains no new or revised commitments.

Should you have any questions, please contact R. A. Slough at (254) 897-5727.

Sincerely, Luminant Generation Company LLC Rafael Foe By:

Enclosure c -

Marc L. Dapas, Region IV B. K. Singal, NRR Resident Inspectors, Comanche Peak

N NRC F*ORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB NO. 3150-0104 EXPIRES:01/31/2017 (02-2014)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 05000 446 1 OF 3

4. TITLE Unit 2 Train B Safety In ection System Inoperable For Longer Than Allowed By TS

5. EVENT DATE

6. LER NUMBER I

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FALIYNMDOKTUBE

_NUMBER NO.I IFACILITY NAME DOCKET NUMBER

• 07 10 2015 2015 001 00 09 18 2015

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all/that apply) 1E 20.2201(d)

[]

20.2203(a)(3)(ii)

[1 50.73(a)(2)(ii)(C)

[]

50.73(a)(2)(viii)(

LI 20.2203(a)(1)

[]

20.2203(a)(4)

Lii 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(g)

_____________L 20.2203(a)(2)(i)

LII 50.36(c)(1)(i)(A)

LI 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)

10. POWER LEVEL

[]

20.2203(a)(2)(ii)

LII 50.36(c)(1)(ii)(A)

LII 50.73(a)(2)(iv)(A)

LI 50.73(a)(2)(x)

--I 20.2203(a)(2)(iii)

LI 50.36(c)(2)

LII 50.73(a)(2)(v)(A)

[]

73.71(a)(4) 100 20.2203(a)(2)(iv)

[]

50.46(a)(3)(ii)

[]

50.73(a)(2)(v)(B)

[]

73.71(a)(5)

LI20.2203(a)(2)(v)

Lj 50.73(a)(2)(i)(A)

LI 50.73(a)(2)(v)(C)

[]

OTHER LI 20.2203(a)(2)(vi) j]

50.73(a)(2)(i)(B)

[]

50.73(a)(2)(v)(D)

VOLUNTARY LER

12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)

Timothy A. Hope, Manager, Regulatory Affairs 254-897-6370______

CAUSE

SYSTEM ICOMPONENT MANU-REPORTABLE mlCAUSE SYSTEM ICOMPONENT MANU-REPORTABLE IFACTURER TO EPIX 1

FACTURER TO EPIX

14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YA SUBMISSION L..J YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

I_]NO DATE ABSTRACT (Limit to 1400 spaces, iLe., approximately 15 single-spaced typewritten lines)

On July 10, 2015 at 1304 Comanche Peak Nuclear Power Plant, Unit 2 exceeded a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> limiting condition for operation (LCO), after being granted a period of enforcement discretion, due to a through-wall leak found on the "B" train of the Safety Injection (SI) system piping at the 3/4" socket weld coupling to valve 2SI-0055. The flaw resulted in declaring the "B" train of SI inoperable. This event was reportable under 10 CFR 50.73(a)(2)(i)(B) as an operation or condition which was prohibited by the plant's Technical Specifications. A Notification of Enforcement Discretion (NOED) was granted by the NRC at 0920 on July 10, 2015. The repair process issues leading to the NOED request were the requirement to apply a freeze seal to allow installation of a new vent valve to allow adequate static refill of the system and complete dye penetrant testing of the weld, ultrasonic examination of the suction piping to verify the system full of water, and pump testing to establish operability of the system. The most probable cause of the through-wall leak was determined to be an original weld defect which resulted in a stress concentration that allowed otherwise acceptable tensile loads to cause propagation of a through-wall crack. The corrective action was to grind out the weld and repair (re-weld).

This event had no adverse effect upon the health and safety of the public.

All times in this report are approximate and Central Daylight Time unless noted otherwise.

NRC FORM 386A 102-20141 PRINTED ON RECYCLED PAPER (If more space is required, use additional copies of SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES:

While performing a quarterly system walkdown on 7/7/2015, the SI System Engineer discovered a boric acid accumulation coming out of the insulation on pipe segment SI-2-070 beneath 2SI-0055 and accumulating on the floor. The insulation was removed within an hour of identifying the accumulation. Upon removal, a through wall leak was discovered in the socket weld beneath test vent 2SI-0055. T.S. LCO 3.5.2 Condition B was entered immediately upon discovery of the through wall leak on 7/7/2015 at 1304. The socket weld was reworked as an emergent activity under WO-5087339. An enhanced weld design was implemented to improve the fatigue life of the socket weld by using a 2:1 weld leg ratio. Repairs took a total of 82 hours9.490741e-4 days <br />0.0228 hours <br />1.35582e-4 weeks <br />3.1201e-5 months <br /> and 56 minutes. A Notification of Enforcement Discretion (NOED) was approved which allowed Unit 2 to remain at power despite exceeding the allowed LCO time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for Condition B.1 plus 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for Condition Cl.1 E.

THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE, OR PROCEDURAL PERSONNEL ERROR While performing a quarterly system walkdown on 7/7/2015, the SI system Engineer discovered a boric acid accumulation coming out of the insulation on pipe segment SI-2-070 beneath 2SI-0055 and accumulating on the floor. Upon removal of the piping insulation, a through wall leak was discovered in the socket weld beneath test vent 2S1-0055.

I1. COMPONENT OR SYSTEM FAILURES A. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE An original weld defect resulted in a stress concentration that allowed otherwise acceptable tensile loads to cause propagation of a through-wall crack.

B. FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED COMPONENT Cracking of the socket weld beneath 2SI-0055 allowed system fluid to leak through the resulting weld fracture. Cracking was evident by visual inspection which indicated that the failure was brittle in nature since there was a lack of deformation in the failed socket weld.

(If more space is required, use additional copies of (If more space is required, use additional copies of SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES:

While performing a quarterly system walkdown on 7/7/2015, the SI System Engineer discovered a boric acid accumulation coming out of the insulation on pipe segment SI-2-070 beneath 2SI-0055 and accumulating on the floor. The insulation was removed within an hour of identifying the accumulation. Upon removal, a through wall leak was discovered in the socket weld beneath test vent 2SI-0055. T.S. LCO 3.5.2 Condition B was entered immediately upon discovery of the through wall leak on 7/7/2015 at 1304. The socket weld was reworked as an emergent activity under WO-5087339. An enhanced weld design was implemented to improve the fatigue life of the socket weld by using a 2:1 weld leg ratio. Repairs took a total of 82 hours9.490741e-4 days <br />0.0228 hours <br />1.35582e-4 weeks <br />3.1201e-5 months <br /> and 56 minutes. A Notification of Enforcement Discretion (NOED) was approved which allowed Unit 2 to remain at power despite exceeding the allowed LCO time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for Condition B.1 plus 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for Condition Cl.1 E.

THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE, OR PROCEDURAL PERSONNEL ERROR While performing a quarterly system walkdown on 7/7/2015, the SI system Engineer discovered a boric acid accumulation coming out of the insulation on pipe segment SI-2-070 beneath 2SI-0055 and accumulating on the floor. Upon removal of the piping insulation, a through wall leak was discovered in the socket weld beneath test vent 2S1-0055.

I1. COMPONENT OR SYSTEM FAILURES A. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE An original weld defect resulted in a stress concentration that allowed otherwise acceptable tensile loads to cause propagation of a through-wall crack.

B. FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED COMPONENT Cracking of the socket weld beneath 2SI-0055 allowed system fluid to leak through the resulting weld fracture. Cracking was evident by visual inspection which indicated that the failure was brittle in nature since there was a lack of deformation in the failed socket weld.

(If more space is required, use additional copies of NRC Form 366A) (17)

C. SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF COMPONENTS WITH MULTIPLE FUNCTIONS The sole safety function of the socket weld was pressure boundary integrity in support of the train B ECCS. No other safety functions or components with multiple safety functions were affected.

D. FAILED COMPONENT INFORMATION

Through-wall crack of the socket weld beneath 2SI-0055, a cantilever connected, 3/4" vent valve near the Unit 2, Train B Safety Injection pump suction.

III. ANALYSIS OF THE EVENT

A.

SAFETY SYSTEM RESPONSES THAT OCCURRED Not applicable - No safety system responses occurred as a result of this event.

B. DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY Unit 2, Train B Safety Injection System was declared inoperable at 1304 Central Time on July 7, 2015 and was restored to operable at 0000 Central Time on July 11, 2015. The total time Unit 2, Train B Safety Injection System was inoperable was 82 hours9.490741e-4 days <br />0.0228 hours <br />1.35582e-4 weeks <br />3.1201e-5 months <br /> and 56 minutes.

C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT During the time the Unit 2, Train B Safety Injection system was inoperable, the Unit 2 Train A Safety Injection system was operable and fully capable of performing the intended safety functions of the Safety Injection system. Prior to discovery, Train A SI had been operable since completion of the pre-summer cleaning of the 2-01 CCWISSW heat exchanger on June 20, 2015 at 0233. Since the Train A Safety Injection system was capable of performing the intended function during the period of inoperability, there was no impact to public health and safety.

IV. CAUSE OF THE EVENT

An original weld defect added a stress concentration which allowed otherwise acceptable tensile loads to cause propagation of a through-wall crack.

V. CORRECTIVE ACTIONS

The failed socket weld was replaced with an improved 2:1 weld leg ratio. As a part of the CPNPP Corrective Action Program, Engineering has reviewed the extent of condition for this event and plans to perform dye penetrant testing and volumetric inspections, capable of detecting subsurface indications, of the process pipe to vent and drain pipe socket welds for other potential locations where the condition may exist.

VI. PREVIOUS SIMILAR EVENTS

There have been no previous similar reportable events at Comanche Peak Nuclear Power Plant (CPNPP) in the last three years.PRINTED ON RECYCLED PAPER