05000445/LER-1997-001, :on 970124,identified Single Failure Outside of Design Basis.Caused by Failure to Identify Events as Credible Scenario During Design of Facility.Util Will Implement Design Mod on Each Unit
| ML20136C364 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 03/05/1997 |
| From: | Killgore M, Terry C TEXAS UTILITIES CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-97-001, LER-97-1, TXX-97050, NUDOCS 9703120055 | |
| Download: ML20136C364 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(e)(2) 10 CFR 50.73(e)(2)(x) 10 CFR 50.73(e)(2)(v) |
| 4451997001R00 - NRC Website | |
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.:d Log # TXX 97050 Z
Z File # 10200 7t/ELECTR/C-Ref. # 10CFR50.73(a)(2)(ii)(B)
March 5, 1997 C. Lance Terry Group Mce Presiden U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, D.C.
20555 i
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50 445 AND 50 446 CONDITION OlHSIDE OF DESIGN BASIS j
LICENSEE EVENT REPORT 445/97 001-00 Enclosed is Licensee Event Report (LER) 97-001-00 for Comanche Peak Steam Electric Station Units 1 and 2, " Identified Single Failure Outside of the Design Basis."
The condition described in the enclosed LER was identified on January 24, 1997.,
however it was not deemed reportable until February 3,1997.
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C. L. Terry RTB:rtb Enclosure cc:
Mr. J. E. Dyer, Region IV Mr. J. I. Tapia, Region IV Mr. T. J. Polich, NRR Resident Inspectors, CPSES V
d. ~V 9703120055 970305
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PDR ADOCK 05000445 s
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130026 P. O. Box 1002 Glen Rose Texas 76043
EnclosurQ to TXX-97050 I
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FCsddy Name (1)
Docket Numcor (2)
Page (3)
COMANCHE PEAK STEAM ELECTRIC STATION UNIT 1 05000445 01 0F 05 Title (4)
IENTIFIED SINGLE FAILURE OUTSIDE OF THE DESIGN BASIS i
Event Dale ((5)
LER Number (6)
Report Date (7)
Other Fechtee invo#ved (6)
Mo ith Day Year Year Sequential Revision Montn Day Year Facety Name
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CPSES UNIT 2 0
5 0
0 0
4 4
6 4
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3 0l5 9l7 N/A 0
5 0
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20 2201 (b) 20.2203 (e)(2)(v) 50 73 (e)(2)(i) 50.73 (e)(2)(ww)
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Specify bi Abstract below 5a73 (a)(2)(iv)
OTHER 20 2203 (e)(2)(Iv) 50.36 (c)(1) y 50 36 (c)(2) 50 73 (e)(2) fvii) or in =
SUMMARY OF THE EVENT, INCLUDING DATES AND APPR0XIMATE TIMES On January 24, 1997 at approximately 6:00 p.m. CST, after reviewing a similar condition reported by another operating nuclear power plant. TV Electric concluded that a potential scenario existed which had not previously been evaluated in the CPSES design basis. The event consisted of a FLB occurring on a Steam Generator (SG) which would be fed by the "A" Train Motor Driven Auxiliary Feedwater Pump (MDAFWP).
hereto referred to as an "A" Train SG coincident with the single failure of the "B" Train Solid State Protection System (SSPS). The "B" Train SSPS failure results in the failures of both the "B" Train MDAFWP to start and the "B" Train steam admission valve to the Turbine Driven Auxiliary Feedwater Pump (TDAFWP) to open. The "A" Train MDAFWP l
successfully starts but delivers its flow to the feedline break in the "A" SG. The TDAFWP successfully starts, but because its steam supply is i
from a depressurizing SG. an adequate steam supply to assure continual operation does not exist.
On February 3.1997. TV Electric engineering confirmed that the j
postulated condition identified earlier represented a credible event at CPSES. Upon engineering confirmation, it was determined that this j
accident scenario represents a condition that is outside of the design
l Enclosurs to TXX-97050 NRC FORM SI6A U S. NUCLEAR REGULATORY COMMISSION (4,06)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION l
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COMANCllE PEAK STEAM ELECTRIC STATION UNIT I 05000445 9
7 0
1 0
03 05 j
Text (f more space is rewred. une oddnional copies of NRC Form 366A) (17) i
. basis of the plant and therefore requires a 1 h6ur notification 4
pursuant to 10CFR50.72. At approximately 5:10 p.m. CST on February 3, 1997, the NRC was notified of the event via the Emergency Notificaticn System.
E.
THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE OR PROCEDURAL ERROR Following review of an NRC Daily Events Report on January 24. 1997, it was determined that a similar event to one that was reported had potential applicability at CPSES. Further engineering review concluded that a similar condition existed at CPSES.
II.
COMPONENT OR SYSTEM FAILURES A.
FAILURE MODE, MECHANISM, AND EFFECT OF EACH FAILED COMPONENT The identified failure mode is the postulation of any failure of the "B" Train SSPS to actuate. The mechanism of said failure is not identified. The effect of the failed component is that both the "B" Train MDAFWP fails to start and the "B" Train steam admission valve to the TDAFWP fails to open. These effects combine to create an event in which the "A" Train MDAFWP is feeding only the break and the TDAFWP has limited steam supply from the SG with a coincident FLB. The reverse situation, of a Train "A" SSPS failure coincident with a FLB to a "B" Train SG 1.s also a " valid failure" B.
CAUSE OF EACH COMP 0NENT OR SYSTEM FAILURE No failed components or systems contributed to this event.
C.
SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF COMP 0NENTS WITH MULTIPLE FUNCTIONS No failed components contributed to this event.
D.
FAILED COMP 0NEMf INFORMATION No failed components contributed to this event.
Enclosure to TXX-97050 N C FORM 366A U S. NUCLEAR REGUL#. TORY CGMMISSION LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION Fremy Name (1)
Docket y,
COMANCIIE PEAK STEAM ELECTRIC STATION UNIT 1 05000445 OF 9
7 0
0 1
0 0
04 05 Tint (# more space is requred, use addmonal copies of NRC Form 366A) (17)
III.
ANALYSIS OF THE EVENT
A.
SAFETY SYSTEM RESPONSES THAT OCCURRED No safety system responses occurred as a result of this event.
B.
DURATION OF SAFETY SYSTEM TRAIN IN0PERABILITY No safety system trains were inoperable as a result of this event.
C.
SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT TU Electric believes that the identified sequence of events is a more limiting failure than the current single failure scenario assumed in j
the licensing analysis. Analysis performed by TV Electric Engineering has shown that, via an independent event response sequence containing non-seismically qualified equipment which would occur in parallel with the new single failure scenario. sufficient auxiliary feedwater would be provided to the intact steam generators. These results demonstrate I
that all event acceptance criteria are satisfied and the Safety Analysis Report conclusions, presented in the Safety Analysis Report Section 15.2.8, remain valid for the Feedline Rupture Event. TV Electric concludes that the existing plant configuration provides protection for the Feedline Rupture Event and the occurrence of a FLB will not impact the health and safety of the public.
IV.
CAUSE OF THE EVENT
The cause of this condition was the failure to identify these events as a credible scenario during the design of the facility.
V.
CORRECTIVE ACTIONS
TV Electric will implement a design modification on each unit prior to entering the plant conditions which require the Turbine Driven Auxiliary Feedwater Pump to be OPERABLE following the completion of the next refueling outage for each unit.
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Enclosure to TXX-97050U.S NUCLEAR REGIM.ATORY COMMISSION
(+,es) 4 LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION
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VI.
PREVIOUS SIMILAR EVENTS
There have been no previous similar events related to the identification of more limiting single failures than those assumed in the licensing basis reported pursuant to 10CFR50.73.
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