05000353/LER-2002-001, Manual Scram Due to Failure of Main Condenser Air Removal System
| ML022680021 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 09/18/2002 |
| From: | Levis W Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 02-001-00 | |
| Download: ML022680021 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3532002001R00 - NRC Website | |
text
ExekIcen SM Exelon Nuclear Limerick Generating Station PO Box 2300 Sanatoga, PA 19464 wwwexeloncorp com Nuclear 1 OCFR50.73 September 18, 2002 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Unit 2 Facility Operating License Nos. NPF-85 NRC Docket Nos. 50-353
Subject:
LER 2-02-001, Unit 2 Scram due to Degraded Main Condenser Vacuum This Licensee Event Report (LER) addresses a Unit 2 unplanned manual scram due to a degraded main condenser vacuum condition as a result of a failure of the air removal system.
Report Number:
Revision:
Event Date:
Discovered Date:
Report Date:
2-02-001 00 July 23, 2002 July 23, 2002 September 18, 2002 This LER is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(iv)(A).
If you have any questions or require additional information, please do not hesitate to contact us.
Sincerely, William Levis Vice President - Limerick cc: H. J. Miller, Administrator Region I, USNRC A. L. Burritt, USNRC Senior Resident Inspector, LGS
- - I--6~O
NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 EXPIRES 6-30-2001 (1-2001)
COMMISSION Estimated burden per response to comply wth this mandatory information 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 Management Branch (T-E6, S Nclar eglatryComision. Washingtn, DC 20555-0001,or by internet LCENSEE EVENTmal to bis nr go and to the Desk OicerOffice Information and Regulatory Affairs, NEO-1002(310-104, Ofie o Mnagement and Budget, Washington, DC203If a (See reverse for required number of meansuseodtto impose Inform nc tiondoe display a currently valid OMB control digits/characters for each block) numberShe NRC may not conduct orsponsor, and a person is not required to respond to,the information collection FACILITY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
Limerick Generating Station, Unit 205000 353 1 OF 3
TITLE (4)
Manual Scram due to Failure of Main Condenser Air Removal System l
EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7)
OTHER FACILITIES INVOLVED (8)
S FACILITY NAME DOCKET NUMBER MO DAY YEAR YEA NUMBER IQNO MO DAY YEAR 05000
_FACILITY NAME DOCKET NUMBER 7
23 2002 2002 001 00 9
18 2002 05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 Cl R (Check all that apply) (11)
MODE (9) 1
__20 2201 b_
20 2203(a)(3)(11) 50 73(a)(2)(D)(B) 50 73(a)(2)(K)(A)
POWER 20 2201 (d)
_ 20 2203(a)(4)
_ 50 73(a)(2)(m) 50 73(a)(2)(x)
LEVEL (10) 100 20 2203(a)(1) 50 36(c)(1)(i)(A) x 50 73(a)(2)(iv)(A) 73 71 (a)(4) 20 2203(a)(2)(I)
I 50 36(c)(1 )(i)(A) 50 73(a)(2)(v)(A) 73 71 (a)(5) 20 2203(a)(2)(ii) 50 36(c)(2)
_ 50 73(a)(2)(v)(B)
OTHER Specify In Abstract below or In 20 2203(a)(2)(mii) 50 46(a)(3)(n) 50 73(a)(2)(v)(C)
(If more space is required, use addibonal copies of (If more space is required, use addibonal copies of NRC Forn 366A) (17)
Analysis of the Event
There were no actual safety consequences associated with this event. The potential safety consequences of this event were also minimal. The degrading main condenser vacuum resulted in a manual main turbine trip and manual reactor scram. Reactor critical parameters were monitored and controlled by Operations.
Main turbine retrofit projects were completed on Unit 1 in 1998 and on Unit 2 in 1999. The new turbines are able to function at higher backpressures, thus higher condensate temperatures would also be expected. Post event analysis indicated that the higher condensate temperatures were not properly evaluated for effects on the condenser air removal system at the time of the retrofit.
Because of this, plant operating limits allowed SJAE (EIIS:EJR) system temperatures to exceed design limitations.
On the day of the transient outside air temperature increased to 95 deg F with very high humidity in the late afternoon. The high ambient temperature caused an increase in main condenser backpressure that resulted in higher than normal condensate temperature. The elevated condensate temperature caused insufficient cooling in the SJAE inter-condenser resulting in a "stalling" condition on the first stage SJAE. This stall condition caused a drop in condenser off-gas flow and further increased the main condenser backpressure. As non-condensables accumulated in the main condenser, the tube bundles became "air blanketed" reducing overall heat transfer, increasing backpressure, and rapidly increasing condensate temperature. The reactor power reduction performed was not effective in recovering condenser vacuum.
Cause of the Event
The cause of the event is that the impact of elevated condensate temperatures on the design limitations of the condenser air removal system was not addressed during the turbine retrofit project and was not adequately documented in plant design documents. Because the effect of condensate temperatures on SJAE performance was not fully realized, changes to plant-operating limits were implemented based solely on condensate demineralizer resin considerations. This allowed full power operation to continue at temperatures exceeding SJAE system design limits.
Corrective Action Completed Operating procedures and basis documents have been revised to reflect the proper operating conditions for SJAE condenser temperature and condenser backpressure.
Previous Similar Occurrences There were no previous occurrences of degraded condenser capacity that resulted in unit shutdown.
Component:
Cond (Steam Jet Air Ejector Condenser)
Manufacturer:
F175 (Foster Wheeler Corp)
Model:
261-KA