IR 05000338/1993028
| ML20059K359 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 10/29/1993 |
| From: | Belisle G, Mcwhorter R, Taylor D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20059K353 | List: |
| References | |
| 50-338-93-28, 50-339-93-28, NUDOCS 9311160017 | |
| Download: ML20059K359 (4) | |
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Report Nos.:
50-338/93-28 and 50-339/93-28 Licensee:
Virginia Electric & Power. Company 5000 Dominion Boulevard Glen Allen, VA 23060 Docket Nos.:
50-338 and 50-339
License Nos.: NPF-4 and NPF-7 Facility Name:
North Anna 1 and 2 Inspection Conducted-Oct ber 14 - October 20, 1993 Inspectors:
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R.D. M.cWhorter, Senior Reside'nt Inspector Date Signed b
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1, sa D.R. Taylor, Res~ident Inspector Date Signed
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Approved by:
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G. A. Belisle, Section Chief Date Sig~ned Division of Reactor Projects
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l SUMMARY l
I Scope:
This special inspection by the resident inspectors was performed to examine.
the circumstances surrounding the Unit 2 High Head Safety Injection subsystem not meeting the Technical Specfication (TS) minimum flow requirement on October 14, 1993.
Results:
An apparent violation was identified concerning the Unit 2 High Head Safety Injection subsystem failed to meet the TS 4.5.2.h.l.a Emergency Core Cooling-System minimum flow rate requirement. A non-cited violation. and a violation were issued in 1990 and 1992, respectively, for previous-failures to meet this TS.
9311260017 9333o3 DR ADOCK 05000338
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REPORT DETAILS
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1.
Persons Contacted
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Licensee Emplovees L. Edmonds, Superintendent, Nuclear Training
- R. Enfinger, Assistant Station Manager, Operations and Maintenance J. Hayes, Superintendent of Operations D. Heacock, Superintendent, Station Engineering
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- G. Kane, Station Manager
- P. Kemp, Supervisor, Licensing
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W. Matthews, Superintendent, Maintenance
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J. O'Hanlon, Vice President, Nuclear Operations D. Roberts, Supervisor, Station Nuclear Safety
- R. Saunders, Assistant Vice President, Nuclear Operations
D. Schappell, Superintendent, Site Services
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R. Shears, Superintendent, Outage and Planning l
- J. Smith, Manager, Quality Assurance A. Stafford, Superintendent, Radiological Protection
- J. Stall, Assistant Station Manager, Nuclear Safety and Licensing Other licensee employees contacted included engineers, technicians, operators, mechanics, security force members, and office personnel.
NRC Resident Inspectors
- R. McWhorter, Senior Resident Inspector
- D. Taylor, Resident Inspector
- Attended exit interview Acronyms and initialisms used throughout this report are listed in the last paragraph.
2.
Event Summary During testing on October 14, 1993, the sum of the HHSI line flow rates, excluding the highest flow rate, was found to be less than the value specified in TS 4.5.2.h.1.a.
TS 4.5.2.h.1.a required the sum to be equal to or greater than 359 gpm. The measured flow rate was 356 gpm.
The injection line throttle valves were re-adjusted to balance flow and corrective actions were taken to preclude valve movement.
3.
Event Description-On October 14, the inspectors observed performance of 2-PT-138.1, HHSI Flow Balance, revision 1-P2.
The purpose of the test was to verify that ECCS flow met TS 4.5.2.h requirements. TS 4.5.2.h.1.a required that the sum of the HHSI line ' flow rates, excluding the highest flow rate, be
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t greater than or equal to 359 gpm with a single pump running. The test l
was performed by establishing flow from one charging pump to the vessel
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through the three injection lines and verifying that the specified sum was greater than or equal to 373 gpm.
(The test procedure's acceptance value was based on the TS value plus allowances for instrument
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inaccuracy.) Flows through the individual branch lines were measured i
using high accuracy (11%) ultrasonic clamp on flow instruments.
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During the initial run for the cold leg flow rate verification, measured
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injection line flows were 166, 190, and 218 gpm.
Excluding the highest
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flow rate, the sum of the remaining injection line flow rates e e 356 t
gpm. Thus, for the cold leg injection lines, the specified sum failed
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to meet the TS requirements. The failure to meet the TS required flow
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is identified as an apparent violation: 50-339/93-28-01, failure To Meet TS ECCS Flow Requirements.
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Throttle valves, 2-51-89, 2-SI-97, and 2-SI-103, were repositioned as necessary and the test was completed satisfactorily.
On October 19, 1993, a thread sealant, Thread Locker 290, was applied around the valve
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stems to prevent valve movement induced by vibration and/or thermal and i
hydraulic conditions.
Preliminary investigation by the licensee attributed the event to i
throttle valve movement.
This conclusion was bastd on operators'
recollection of the ease with which these valves operate, the small
amount of movement required for a relative large flow rate change, and
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the elimination of other probable causes. Radiography was used to eliminate stem-disk partial disengagement as a probable cause.
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reviews revealed no evolutions which would have re-positioned the valves. As discussed below, inadvertent valve movement was precluded by the locked valve caps.
In addition pump performance data indicated no degradation that would account for the reduced flow rate. The mechanism i
that caused the valves to not remain in their as-left positions could
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not be definitively determined.
I The inspectors reviewed the past history for the test and noted this was the third successive failure to meet TS requirements.
During the two l
previous failures, TS 4.5.2.h.l.a required a flow of at least 384 gpm.
l The past two failures were:
On October 20, 1990, the required flow rate was found to be j
347 gpm. The failure to meet the TS requirement was
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attributed to a combination of preoperational test
inaccuracies and imprecise methods for positioning throttle valves. As a result of the failure, NCV 50-339/90-28-01,.
Inadequate and Unbalanced Safety Injection Flow Rates, was issued.
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On April 10, 1992, the required flow rate was again found to l
Ise 347 gpm.
Improper control of throttle valve position was
again postulated as the cause.
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violation, 50-339/92-10-04, Fr.ilure to Meet TS Flow Requirements For ECCS, was issued.
Corrective actions for violation 92-10-04 included measuring the stem height of the throttle valves using a micrometer; caps were installed on the valves; the caps were locked; and, the locks were destructively jammed.
In addition to the controls placed on the valves, the licensee initiated a TS change.
Th'e licensee proposed that the minimum branch line flow requirement be changed from 384 gpm to 359 gpm. On August 4, 1993, this TS change was approved by the NRC.
The licensee determined that Unit I was not susceptible to this problem.
This was based on previously acceptable test performances and operators'
observations that the applicable Unit 1 throttle valves demonstrated more resistance to operation than those on Unit 2, and were not as susceptible to movement from vibration.
At the end of the report period, the licensee was evaluating possible long term corrective actions.
Included among these were potential valve replacement with a type more suitable fer the application.
5.
Safety Significance of Event At the time of the events, Unit 2 was shut down for a refueling outages.
The licensee evaluated the potential safety implications of the reduced flow rates during the preceding operating cycles. They determined that the safety signficance of the events were minimal. Their evaluations concluded that with the measured flow rates, allowable PCT limits would not have been exceeded under design basis accident conditions.
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6.
Exit (30703)
The inspection scope and findings were summarized on October 20, 1993,.
with those persons indicated in paragraph 1.
The inspectors described
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the areas inspected and discussed in detail the inspection results i
listed below. The licensee did not identify as proprietary any of the j
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material provided to or reviewed by the inspectors during this
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inspection.
Dissenting comments were not received from the licensee.
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Item Number Description and Reference 50-339/93-28-01 (Apparent Violation) Failure To Meet TS ECCS
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j Flow Requirements (paragraph 3).
7.
Acronyms and Initialisms ECCS Emergency Core Cooling System
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GPM Gallons Per Minute
HHSI High Head Safety Injection NRC Nuclear Regulatory Commission PCT Peak Centerline Temperature SI Safety Injection
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