05000457/LER-2004-001, Regarding Pressurizer Backup Heater Groups a and D Identified to Be Inoperable Greater than Required Technical Specification Allowed Outage Time
| ML043410085 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 11/24/2004 |
| From: | Joyce T Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BW0400106 LER 04-001-00 | |
| Download: ML043410085 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 4572004001R00 - NRC Website | |
text
Exelkuns.
Exelon Generation Company, LLC Braidwood Station 35100 South Rt 53, Suite 84 Braceville, IL 60407-9619 Tel. 815-417-2000 www.exeloncorp.com Nuclear November 24, 2004 BW0400106 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Unit 2 Facility Operating License No. NPF-77 NRC Docket No. STN 50-457
Subject:
Submittal of Licensee Event Report Number 2004-001 -00, "Unit 2 Pressurizer backup heater groups A and D identified to be inoperable greater than required Technical Specification Allowed Outage Time" The enclosed Licensee Event Report (LER) is being submitted in accordance with 10 CFR 50.73, "Licensee event report system", paragraph (a)(2)(i)(B). 10 CFR 50.73(a) requires an LER to be submitted within 60 days after discovery of the event; therefore, this report is being submitted by Nove nber 24, 2004.
Should you have any questions concerning this submittal, please contact Dale Ambler, Regulatory Assurance Manager, at (815) 417-2800.
Respectfully, T. P. Joyce Site Vice President Braidwood Station
Enclosure:
LER Number 2004-001-00 cc:
Regional Administrator - Region IlIl NRC Braidwood Senior Resident Inspector
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/3012007 Estimated burden per response to comply with this mandatory collection request 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Reported lessons learned are Incorporated Into the licensing process and fed back to Industry. Send comments regarding burden estimate to the Records and FOIA/Privacy Service Branch (T-5 F52). U.S.
LICENSEE EVENT REPORT (LER)
Nuclear Regulatory Commission, Washington, DC 20555-0001, or by Internet e-mail to Infollects~nrc. ov, and to the Desk Officer, Office of Information and Regulatory Affairs, NE B-10202, (3150-0104), Office of Management and Budget. Washington. DC 20503. If a means used to Impose an Information (See reverse for required number of collection does not display a currently valid OMB contro number, the NRC may di ts/h t s for each block) not conduct or sponsor, and a person Is not required to respond to. the igits/charaters f)informtinnr rnili.tinn.
- 3. PAGE Braidwood, Unit 205000457 1
of 3
- 4. TITLE Unit 2 Pressurizer backup heater groups A and D identified to be inoperable greater than required Technical Specification Allowed Outage Time
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIALIY REV LXCK1ZIJNUMBER-MONTH DAY YEAR YEAR SENUMBER I NO.
MONTH DAY YEAR N/A N/A FAU.LI Y NAME UUCRET NUMBER 09 25 2004 2004 -
001 -
00 11 24 2004 N/A N/A
- 9. OPEEATING ODE 11 IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) o 20.2201(b) 0 20.2203(a)(3X))
0 50.73(a)(2XiXC) 0 50.73(aX2)(vii) 1 Q 20.2201(d) 0 20.2203(a)(3Xii) 0 50.73(a)(2Xii)(A)
D 50.73(aX2)(viiiXA) o 20.2203(aXl) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(aX2)(viii)(B) 0 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A)
Q 50.73(a)(2Xiii) 0 50.73(aX2)(ix)(A)
- 10. POWER LEVEL 0 20.2203(a)(2)(ii) 0 50.36(c)(1 Xii)(A)
D 50.73(a)(2Xiv)(A) 0 50.73(aX2)(x) o 20.2203(aX2)iii) 50.36(c)(2)
D 50.73(a)(2Xv)(A) 0 73.71(aX4) 100 0 20.2203(aX2)(iv) 0 50.46(a)(3Xii) 50.73(a)(2Xv)(B) 5 73.71(a)(5) o 20.2203(aX2)(v) 0 50.73(a)(2XiXA) 5 50.73(a)(2)(v)(C) 5 OTHER O 20.2203(aX2)(vi) 0 50.73(a)(2XiXB) 5 50.73(a)(2)(v)(D)
Specify In Abstract below or In (If more space Is required, use additional copies of NRC Form 366A) (17) the armature in relation to the operating shaft and reduces axial movement. The absence of the lock washers on the 2A occurred, once again, because of the lack of instructions for this maintenance activity. There is no detail on either local or vendor drawings that provide the details for installation of lock washers.
The corrective action to prevent recurrence is to develop a maintenance procedure for this type contactor assembly.
This procedure will provide the appropriate torque requirements for the armature mounting screws, and instructions for washer installation and armature centering.
Safety Consequences
In Modes 1, 2, and 3, the LCO requirement for a steam bubble is reflected implicitly in the accident analyses.
Safety analyses performed for lower Modes are not limiting. All analyses performed from a critical reactor condition assume the existence of a steam bubble and saturated conditions in the pressurizer. In making this assumption, the analyses neglect the small fraction of non-condensible gases normally present.
Safety analyses presented in the Updated Final Safety Analysis Report does not take credit for pressurizer heater operation; however, an implicit initial condition assumption of the safety analyses is that the RCS is operating at normal pressure.
The maximum pressurizer water level limit, which ensures that a steam bubble exists in the pressurizer, satisfies Criterion 2 of 10 CFR 50.36(c)(2)(ii). Although the heaters are not specifically used in accident analysis, they provide the capability to maintain sub-cooling in the long term during loss of offsite power, as indicated in NUREG-0737, reference 2, and thus, satisfy Criterion 4 of 10 CFR 50.36(c)(2)(ii).
A risk assessment classified this event as being of very low risk significance. The primary purpose of the pressurizer heaters is to maintain the assumption in the safety analysis and probabilistic risk assessment that all accidents start with a steam bubble and saturated conditions in the pressurizer. As these conditions were maintained during the event, there was no impact on either the safety analysis or probabilistic risk assessment.
This event did not result in a safety system functional failure.
Corrective Actions
Develop a maintenance procedure to standardize and provide an additional level of detail for the replacement of the coils and/or inspection/maintenance of the contactor assembly. These instructions will include torque specification requirements for the armature mounting fasteners, the clearance (gap) for the armature to side-plates, and inspection for, or installation of, locking washer onto the armature mounting fasteners.
F. Previous Occurrences
There have been no similar Licensee Event Report events at Braidwood Station.
In 1988, the Braidwood 2D back-up heaters failed to operate due to armature misalignment, and repairs completed on 2/4/1988.
G. Component Failure Data
Manufacturer Nomenclature Model Mfg. Part Number N/A N/A N/A N/A