05000254/LER-2006-004, For Quad Cities, Unit 1, Regarding Through-wall Leak in Standby Liquid Control Tank Due to the Original Construction Use of Grout with Leachable Halogens
| ML063530355 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/11/2006 |
| From: | Tulon T Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVP-06-114 LER 06-004-00 | |
| Download: ML063530355 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 2542006004R00 - NRC Website | |
text
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Exelon Generation Company, LLC www.exeloncorp.com Nuclear Ouad Cities Nuclear Power Station
\\Y 22710 206th Avenue North Cordova, IL 61242-9740 December 11, 2006 SVP-06-114 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Quad Cities Nuclear Power Station, Unit 1 Renewed Facility Operating License No. DPR-29 NRC Docket No. 50-254
Subject:
Licensee Event Report 254/06-004, "Through-wall Leak in Standby Liquid Control Tank Due to the Original Construction Use of Grout with Leachable Halogens" Enclosed is Licensee Event Report (LER) 254/06-004, "Through-wall Leak in Standby Liquid Control Tank Due to the Original Construction Use of Grout with Leachable Halogens," for Quad Cities Nuclear Power Station, Unit 1.
This report is submitted in accordance with the requirements of the Code of Federal Regulations, Title 10, Part 50.73(a)(2)(i)(B), which requires the reporting of any operation or condition prohibited by Technical Specifications, and Part 50.73(a)(2)(vii), which requires the reporting of any event where a single condition caused two independent trains to become inoperable in a single system designed to shut down the reactor and maintain it in a safe shutdown condition.
There are no regulatory commitments contained in this letter.
Should you have any questions concerning this report, please contact Mr. W. J. Beck at (309) 227-2800.
Respectfully, Timothy J. Tulon Site Vice President Quad Cities Nuclear Power Station cc:
Regional Administrator-NRC Region III NRC Senior Resident Inspector - Quad Cities Nuclear Power Station
Abstract
On October 12,
- 2006, at 2236 hours0.0259 days <br />0.621 hours <br />0.0037 weeks <br />8.50798e-4 months <br />, the Unit 1 Standby Liquid Control (SLC) system was declared inoperable due to a through-wall leak in the SLC tank.
Although the SLC tank is exposed to atmospheric pressure, it is an ASME Code Section XI Class 2 boundary.
The SLC tank leak was originally identified on May 27, 2004, but the ASME Code Class of the SLC tank was not identified, and the SLC tank was incorrectly determined to be operable at that time.
On October 13, 2006, the NRC approved a Notice of Enforcement Discretion to extend the Allowed Outage Time for the inoperable SLC system.
On October 15,
- 2006, following draining, repair, refilling and testing of the tank, the SLC system was declared operable.
The SLC tank leak was due to the use of grout material containing leachable halogens during original installation of the SLC tank supports, resulting in an environment that supported stress corrosion cracking in the stainless steel tank where it was in contact with the grout.
The safety significance of the event was minimal.
The leak was-extremely small and did not affect the capability of the SLC tank to perform its safety function.
Corrective actions include development of issue review guidance, redesign of the SLC tank supports, and review of systems for the use of grout.U.S. NUCLEAR REGULATORY COMMISSION (7-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION Quad Cities Nuclear Power Station Unit 1 05000254 NUMBER NUMBER 2006 004 00 2 of 4 (If more space is required, use additional copies of NRC Form 366A)(1 7)
PLANT ANDSYSTEM IDENTIFICATION General Electric
- - Boiling Water Reactor, 2957 Megawatts Thermal Rated Core Power Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
EVENT IDENTIFICATION Through-wall Leak in Standby Liquid Control Tank Due to the Original Construction Use of Grout with Leachable Halogens A.
CONDITION PRIOR TO EVENT
Unit: 1 Event Date: October 12, 2006 Event Time: 2236 hours0.0259 days <br />0.621 hours <br />0.0037 weeks <br />8.50798e-4 months <br /> Reactor Mode:
1 Mode Name: Power Operation Power Level: 100%
B.
DESCRIPTION OF EVENT
On October 12, 2006, at 2236 hours0.0259 days <br />0.621 hours <br />0.0037 weeks <br />8.50798e-4 months <br />, the Operations Shift Manager declared the Unit 1 Standby Liquid Control (SLC)
[BR] system inoperable due to a through-wall leak in the SLC tank [TK].
Although the SLC tank is exposed to atmospheric pressure, it is an ASME Code Section XI Class 2 boundary.
Quad Cities.Unit 1 entered Technical Specification (TS) Limiting Condition for Operation (LCO)
Section 3.1.7, Condition B, for both SLC subsystems and declared the SLC system inoperable.
This action was in response to Engineering identifying the ASME Code Class of the SLC tank.
The Unit 1 SLC tank through-wall leak was originally identified on May 27,
- 2004, documented *in an Issue Report by the SLC System Engineer, and reviewed by System Engineering supervision, Design Engineering Mechanical supervision, and the Operations Shift Manager on May 28, 2004.
The ASME Code Class of the SLC tank was
- not identified during the origination or review of the Issue Report.
Consequently, the Unit 1 SLC tank was incorrectly determined to be operable by the Operations Shift Manager on May 28, 2004.
The Issue Report generated on October 12,
- 2006, was generated as a result of discussions with a SLC system engineer from another plant concerning repair options for the through-wall leak and the information that the SLC tank was a Code boundary.
In parallel with maintenance activities, including further analysis of the through-wall leak, Quad Cities Station requested a Notice of Enforcement Discretion (NOED) on October 13, 2006.
The NOED would extend the time that Unit 1 could be operated with the SLC system inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
At 0636 hours0.00736 days <br />0.177 hours <br />0.00105 weeks <br />2.41998e-4 months <br /> on October 13,
- 2006, Quad Cities Unit 1 entered TS LCO Section 3.1.7, Condition C, which requires the unit to be in hot shutdown in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
At 1034 hours0.012 days <br />0.287 hours <br />0.00171 weeks <br />3.93437e-4 months <br />, power was decreased on Quad Cities Unit 1 in preparation for shutting down the unit.
At 1046 hours0.0121 days <br />0.291 hours <br />0.00173 weeks <br />3.98003e-4 months <br />, an ENS notification was made in accordance with 10 CFR '50.72(b) (2) (i) due to initiation of a reactor shutdown required by Technical Specifications.
At 1138 hours0.0132 days <br />0.316 hours <br />0.00188 weeks <br />4.33009e-4 months <br />, the NRC approved the NOED request, and Unit 1 was returned to full power.
At 2312 hours0.0268 days <br />0.642 hours <br />0.00382 weeks <br />8.79716e-4 months <br /> onU.S. NUCLEAR REGULATORY COMMISSION (7-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION Quad Cities Nuclear Power Station Unit 1 05000254 NUMBER NUMBER 2006.
004 00 3 of 4 (If more space is required, use additional copies of NRC Form 366A)(17)
October 13, 2006, the station began draining the SLC tank to facilitate repair of the through-wall leak.
At 0204 hours0.00236 days <br />0.0567 hours <br />3.373016e-4 weeks <br />7.7622e-5 months <br /> on October 14, 2006, the SLC tank was drained.
At 0413 hours0.00478 days <br />0.115 hours <br />6.828704e-4 weeks <br />1.571465e-4 months <br /> on October 15, 2006, the SLC tank was refilled, and at 1122 hours0.013 days <br />0.312 hours <br />0.00186 weeks <br />4.26921e-4 months <br />, following successful testing, the SLC system was declared operable.
C. CAUSE OF EVENT
The programmatic root cause for the incorrect operability determination of the Unit 1 SLC Tank was an incomplete application of technical rigor resulting in incorrect assumptions regarding the ASME Code applicability to the Ul SLC tank.
These incorrect assumptions were not adequately challenged during the condition identification and review process.
The technical root cause of the Unit 1 SLC tank leak is the use of.grout material containing leachable halogens during original installation of SLC tank supports during original plant construction.
When the grout is wetted, Stress Corrosion Cracking can develop at the grout/tank interface.
In this case, the source of moisture was occasional condensation from above when the SLC tank lid was removed.
D.
SAFETY ANALYSIS
The safety significance of this event was minimal.
During the time frame from development of the through-wall leak in 2004 until draining of the SLC tank on October 13, 2006, the SLC tank was fully functional and capable of providing the required boron solution during an accident.
Although the leak was through-wall, the leakage was extremely small and was identifiable only by the formation over time of boron crystals.
There was no effect. on the level of the tank or the concentration of the boron solution.
During the 29 hours3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br /> that the SLC tank was drained, all control rods were operable, and all surveillances were current.
There were no TS "slow" control rods on Unit 1 and no performance issues existed that could impact the scram function of any individual control rod.
The Alternate Rod Insertion (ARI) system was available as a separate means for reactor shutdown in the event that the normal scram path could not be initiated by the Reactor Protection System (RPS).
The ARI system is diverse and independent from RPS.
Additionally, as compensatory actions during the NOED timeframe, both Automatic Transient Without Scram Recirculation Pump Trip Systems and the RPS were protected, mitigating the need for SLC; and production risk activities were prohibited, minimizing the likelihood of initiation events (i.e., plant transients).
- Also, Boric Acid was staged for alternate injection if required during the repair.
This LER is being submitted in accordance with 10 CFR 50.73 (a) (2) (i) (B),
which requires reporting of any operation or condition which was prohibited by the plant's Technical specifications, and Part 50.73(a) (2) (vii), which requires the reporting of any event where a single condition caused two independent trains to become inoperable in a single system designed to shut down the reactor and maintain in a safe shutdown condition.U.S. NUCLEAR REGULATORY COMMISSION (7-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION Quad Cities Nuclear Power Station Unit 1 05000254 NUMBER NUMBER 2006 004 00 4 of 4 (If more space is required, use additional copies of NRC Form 366A)(17)
E.
CORRECTIVE ACTIONS
Guidance will be developed and implemented concerning the initial review process for Issue Reports with potential system operability challenges.
The existing Unit 1 and Unit 2 SLC tank supports will be redesigned to remove the Stress Corrosion Cracking environment.
A review of systems will be made to identify instances of stainless steel in contact with grout.
F.
PREVIOUS OCCURRENCES
No previous incidents involving through-wall leakage on a SLC system Code boundary were identified.
There were 28 instances of SLC system leaks documented since October 2004, but they were from mechanical connections, and did not cause the system to be inoperable.
A Finding involving inadequate documentation for the basis of operability determinations performed by the Operation Shift Managers was identified in NRC Inspection Report 254(265)/2006003.
Corrective actions included presenting the issue as a lessons-learned to the Shift Managers.
Because this occurred after the 2004 determination of operability for the SLC tank, it did not affect this event.
No instances of an incorrect prompt operability determination were identified.
G.
COMPONENT FAILURE DATA
The SLC tank is a 5,000 gallon non-insulated tank manufactured by Bethlehem Steel from Type 304 stainless steel and vented to atmosphere.