05000341/LER-1997-012, :on 970603,voluntary Rept Re Surveillance Testing of Recirculation Sys Overspeed Stops Was Performed. Caused by Conflict Re TS SR 4.4.1.1.2.MG Set Mechanical & Electric Stops Adjusted Downward within 4.4.1.1.2 Limits
| ML20141G608 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 07/03/1997 |
| From: | Peterson N DETROIT EDISON CO. |
| To: | |
| Shared Package | |
| ML20141G606 | List: |
| References | |
| LER-97-012, LER-97-12, NUDOCS 9707100048 | |
| Download: ML20141G608 (6) | |
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4 LICENSEE EVENT REPORT (LER)
FACIUTV NAME Op DOCKFiMMBFR@
PAGE (3p Fermi 2 0 l5 l010 l0 l3 l4 l1 1 l ' l6 Voluntary Report Regarding Surveillance Testing of Recirculation System Overspeed Stops twNT ruTe m teR *aWerR @
' RFPORT DATE (7 OTHER F ACILmES WVOLWD (81 MON DM VR VR 6EQUENf 6AL kWB(-R R
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X oTHER-Voluntary 0l9l3 (Specify 6n Abstract below and in text, NRC Form 366A)
ElCf hSEE CONT ACT FOR THa8 L ER D3)
EP**ONE MWBER Norm Peterson - Compliance Supervisor 313 586-4258 COMPLE1[ ONE UNE FOR EACH COMPONENT F AILURE DESCRIBED IN THIS REPORT (13)
CAUSE
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ABSTRACT (16)
Technical Specification Surveillance Requirement (SR) 4.4.1.1.2 requires demonstration every 18 months that each recirculation pump motor generator (MG) set scoop tube mechanical and electrical stop is OPERABLE with overspeed setpoints less than or equal to 110% and 107%, respectively, of rated core Dow. The surveillance procedure for testing these stops is divided into two sections, one for cold testing and one for testing at power. Detroit Edison believes that either of these methods is acceptable for satisfying SR 4.4.1.1.2.
Members of the NRC staff have taken the position that the cold testing does not meet the Surveillance Requirement; and therefore, SR 4.4.1.1.2 was not performed within its Technical Specification required frequency. This interpretation and the location of this SR within the Recirculation Loops specification created a con 0ict which could not be resolved within the framework of the Technical Specification Section 1.0 i
Definitions or Section 3/4.0 Applicability requirements. In order to resolve this situation, the Surveillance Procedure was revised, core Cow was reduced and the MG set stops were adjusted downward on June 4,1997 to demonstrate that the stops were set below the SR 4.4.1.1.2 limits. A License Amendment request has been submitted to relocate the SR 4.4.1.1.2 requirements from the Technical Specifications to the Updated Final Safety Analysis Report as discussed with NRC management on the afternoon of June 4,1997. Detroit Edison believes that performance of Section 6.1 of Surveillance Procedure 54.000.20 on April 17,1997 was sufficient to satisfy SR 4.4.1.1.2, and that no condition prohibited by Technical Specifications existed at any time.
Ilowever, due tc die degree of regulatory involvement, and to clarify details associated with this issue, a voluntary Licensee Event Report is being submitted.
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9707100048 970703 PDR ADOCK 05000341 8
PDR l
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1 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION j
F ACluTY 8eAME (tj DOCKET NUMBER G)
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2 l 'l 6 Fermi 2 0 l5 l0 l0l0 l3l4l1 97 0-1 2 ww, Lnitial Plant Condition.;
i Operational Condition:
1 (Power Operation)
Reactor Power:
93 Percent Reactor Pressure:
1018 psig Reactor Temperature:
540 degrees Fahrenheit Description of the Event:
Technical Specification Surveillance Requirement (SR) 4.4.1.1.2 requires demonstration every 18 months that each recirculation pump motor generator (MG) set scoop tube mechanical and electrical i
stop is OPERABLE with overspeed setpoints less than or equal to 110% and 107%. respectively, of rated core flow. The Fermi 2 plant entered a 53 day scheduled refueling outage on September 26, 1996.. SR 4.4.1.1.2 had been performed satisfactorily on July 6,1995, and would not have been considered to be beyond its Technical Specification required periodicity until May 24,1997 (critical completion date), based upon the 18 month surveillance Frequency plus 25% extension allowed by SR 4.0.2. Therefore, it was not necessary to perform this surveillance prior to shutdown for the refueling outage. The refueling outage was extended beyond the originally scheduled 53 days for unforeseen f
reasons, until January 3,1997 when the unit was synchronized to the grid. This still allowed l
approximately four months in which to perform this SR. The SR was scheduled to be performed during the plant startup when the appropriate conditions could be achieved. The unit was tripped on
' January 6,1997, prior to achieving these conditions, to add balance weights to the turbine. Successive attempts to restart the plant were unsuccessful, and culminated on January 17,1997 with a turbine generator failure which kept the plant shut down until_ May 2,1997.
Surveillance Procedure 54.000.20," Reactor Recirculation System MG Set Scoop Tube Positioner Operability Test," contains two sections,6.1 and 6.2, either of which can be used to satisfy SR 4.4.1.1.2. Section 6.1," Setting and Verification of Recirculation MG Set Scoop Tube Positioner Stops with MG Set Shutdown" is used to verify and, if required, set the stops when the recirculation MG set is shutdown. Section 6.1 is performed when maintenance has been performed on the stops and retesting is required, or when the surveillance interval is expiring and Section 6.2 cannot be performed due to plant conditions (i.e., the plant is in other than Operational Condition 1 at near rated flow).
i Section 6.1 demonstrat:s OPERABILITY of the stops by verifying that the physical settings have not changed from the previous surveillance. The surveillance provides margin for uncertainty between the l
settings and their limits. Section 6.2," Setting and Verification of MG Set Scoop Tube Positioner l
Stops with MG Set Near Rated Speed," is considered the primary method for demonstrating that the stops are set correctly, and is performed when the appropriate plant conditions are achieved following performance of Section 6.1.
Section 6.1 of this procedure was performed on April 17,1997 prior ta entry into Operational I
Condition 2 following the maintenance outage, because it was not known at that time whether the j
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l'l6 TEAT 04 plant would be at the rated flow conditions necessary to perform Section 6.2 by the critical completion date. Section 6.2 was scheduled to be performed when the appropriate plant conditions could be achieved during the startup. Section 6.2 of this procedure requires core flow to be established at i
between 102% and 103% of Rated Core Flow, and thus can not be performed prior to entry into Operational Condition 1. The conditions for performance of Section 6.2 had not been achieved as of June 3,1997, when members of the NRC staffinformed Detroit Edison that they did not consider Section 6.1 to be sufficient to satisfy SR 4.4.1.1.2, and that they considered the plant to be operating in
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i violation of the Technical Specifications. The associated Limiting Condition for Operation (LCO) i 3.4.1.1 requires two reactor coolant system recirculation loops to be in operation, and both loops were I
in operation.
SR 4.4.1.1.2 contains no exception to Technical Specification 3.0.4 and is not associated with a specific OPERABILITY requirement or ACTION statement. Interpretation of SR 4.4.1.1.2 to require demonstration of the relationship of the stop settings with core flow at near rated flow conditions in Operational Condition 1 as a requirement for LCO 3.4.1.1 would prevent plant startups, because there would be no way to complete the surveillance should it expire while shutdown.
In order to resolve this situation, Surveillance Procedure 54.000.20 was revised to include a section for verifying the stop settings at below rated flow conditions, core flow was reduced and the MG set stops were adjusted downward on June 4,1997 to demonstrate that the stops were set below the SR 4.4.1.1.2 4
limits. A License Amendment request has been submitted to relocate the SR 4.4.1.1.2 requirements 4
from the Technical Specifications to the Updated Final Safety Analysis Report as discussed with NRC 4
management on the aftemoon of June 4,1997. Once relocated, the SR can be clarified to provide for its performance as necessary to ensure the settings are appropriate.
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Detroit Edison believes that performance of Section 6.1 of this surveillance procedure on April 17, 1997 was sufficient to satisfy SR 4.4.1.1.2, and that no condition prohibited by Technical Specifications existed at any time. Detroit Edison also believes that the methodology employed in Surveillance Procedure 54.000.20 is consistent with industry practice. However, due to the degree of l
regulatory involvement, and to clarify details associated with this issue, a voluntary Licensee Event
. Report is being submitted.
Cause of the Event
SR 4.4.1.1.2 was originally intended as a Minimum Critical Power Ratio (MCPR) related surveillance
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which was included in the Recirculation System / Recirculation Loops specifica: ion in the Standard Technical Specifications from which the Fermi 2 Technical Specifications were derived. With the implementation of the Average Power Range Monitor (APRM) Rod Block Monitor Technical i
Specification (ARTS) Improvement Program /MEOD modification in Cycle 3, SR 4.4.1.1.2 also became an Average Planar Linear Heat Generation Rate related surveillance. The location of this SR j
in the Recirculation Loops specification created conflicts which could not be resolved within the framework of the Technical Specification Section 1.0 Definitions or Section 3/4.0 Applicability j
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0 1 2 TEXTOF) requirements, and which could have led to a plant shutdown for two separate and equally unjustified reasons. The first conflict is that this SR determines the OPERABILITY of the MG set overspeed stops; however, the LCO has no OPERABILITY requirements itself as described above in the Event
Description
' Thus, even with the MG sets administratively declared inoperable, the Recirculation Loops LCO requires only that two recirculation loops be in operation; and therefore, the LCO would continue to be satisfied. The second conflict involves the general use of the undefined terms
" demonstrate" and " verify"in the Technical Specifications. SR 4.4.1.1.2 requires " demonstration";
however, the method that the NRC considers acceptable to " demonstrate" this SR (Section 6.2 of procedure 54.000.20) could not be utilized because the plant conditions necessary to perform Section 6.2 (near rated flow conditions) could not be established. This dilemma is recognized in procedure 54.000.20, which provides a two step process (Section 6.1 for cold set verification and Section 6.2 for at power verification) to ensure that the stops are set correctly, given the plant conditions available at the time each is performed. This was also the process used and accepted during the initial startup test program to demonstrate that these stops were set correctly. Reliance on Section 6.2 as the only method for demonstrating. OPERABILITY establishes a conflict in that once the plant is shutdown for an extended period of time (i.e., beyond the required periodicity of the SR), it could never be restarted because the plant conditions necessary to perform Section 6.2 could not be achieved without an LCO 3.0.4 exception.
These two conflicts are recognized and have been resolved in the Improved Standard Technical Specifications (ISTS), NUREG 1433, Revision 1. OPERABILITY related Surveillance Requirements have been removed from specifications whose LCOs have no OPERABILITY requirements, such as this specification. The problem with determining the intent of the terms " demonstrate" and " verify" is resolved in the ISTS by eliminating the use of the term " demonstrate" and using only " verify". The ISTS Bases describe the intent of any specific use of the term " verify" for each Surveillance Requirement. In the particular case of LCO 3.4.1," Recirculation Loops - Operating", NUREG 1433, Revision 1 specifies that two recirculation loops with matched flows shall be in operation, or...(single loop criteria).
Analysis of the Event
i The purpose of the MG set scoop tube mechanical stop is to terminate a postulated reactor recirculation pump slow flow runout transient which is not terminated by a reactor scram (the design basis event for the Maximum Extended Operating Domain (MEOD) analysis documented in GE l
Nuclear Energy," Maximum Extended Operating Domain Analysis for Detroit Edison Company i
Enrico Fermi Energy Center Unit 2," NEDC-31843P, July 1990.). This event stabilizes at a new core power level, corresponding to the maximum possible core flow along the Maximum Extended Load Line Limit (MELLL) rod line, as limited by the MG set scoop tube mechanical stop setting. The intended function of the MG set scoop tube electrical stop is similar to that of the mechanical stop; however, the electrical stop is not credited for mitigating any accident or transient event, nor is it considered to be redundant to the mechanical stop. The mechanical stop protects the fuel cladding by limiting the reactor power increase which would result from a postulated increase in recirculation flow,
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\\"l 6 0 1 2 TEXT (17) such that neither the 1% plastic strain limit nor the Minimum Critical Power Ratio Safety Limit ere j
violated. This analysis assumes that the core is being operated within the flow dependent limits for Average Planar Linear Heat Generation Rate (MAPLHGRr) and Minimum Critical Power Ratio (MCPRr), which are also dependent on the MG set scoop tube mechanical stop setting. These limits are specified in the Core Operating Limits Report (COLR) in terms of core flow and correspond to an assumed MG set mechanical stop setting of 110% core flow for Cycle 6.
During the course of any given fuel cycle, the performance of the Reactor Recirculation System can be observed ta slightly degrade over time due to such factors as impeller wear and corrosion product buildup. This reduction in system performance manifests itselfin a gradual decrease in flowrate 3
delivered by the recirculation pumps for any given pump speed. Thus, the speed required for the recirculation pumps to reach the mechanical and electrical stop setpoints of 110% and 107% core flow, respectively, is expected to gradually increase from the beginning to the end of a given fuel cycle. It is therefore reasonable to assume that the MG set stops positioned in accordance with Section 6.2 of i
Surveillance Procedure 54.000.20 for Cycle N-1 will be set very close, if not conservative, with i
respect to the required stop settings for Cycle N. This is the rationale for Section 6.1 of Surveillance I
Procedure 54.000.20, which verifies that the MG set stops are still set at the positions determined during the previous cycle.
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Review of the as-found readings from the performances of Section 6.2 of Surveillance Procedure 54.000.20 for Cycles 3 through 5 (MEOD was not implemented for Cycles 1 or 2) confirmed that the mechanical and electrical stops were indeed set conservatively to their Technical Specification required limits, taking into account the differences between the test rod lines and the MELLL rod line assumed in the analysis. Tims, it can be concluded that performance of Section 6.1 of Surveillance Procedure 54.000.20 is adequate to ensure that the stops are set properly until plant conditions can be achieved to support performance of Section 6.2 of Surveillance Procedure 54.000.20.
Surveillance Procedure 54.000.20 provides additional margin to the Technical Specification setpoints l
for the mechanical and electrical MG set stops of 110% and 107% of rated core flow, respectively, by l
setting these stops conservatively at the pump speeds which are pro.;ected to produce 108% and 106%
of rated core flow, respectively, at a test rod line which is lower than the MELLL rod line. This conservative margin is intended to accommodate uncertainties in the methodology for setting the
' stops, and any potential non-conservativisms associated with carrying the stop settings from Cycle N-1 over to the beginning of Cycle N until Section 6.2 of 54.000.20 can once again be performed.
l Mditionally, the recirculation pumps slow flow runout transient event assumes that the plant is l
- - initially operating at both the MCPR and the APLHGR thermal limits. The reactor was actually determined to be operating with a greater than 15% margin to the MCPR operating limit and a greater than 20% margin to the APLIIGR limit on June 4,1997, thereby providing substantial margin to accommodate any potential non-conservativisms associated with the delay in performing Section 6.2 of Surveillance Procedure 54.000.20 for Cycle 6. Therefore, there was no threat to the public health or safety as a result of this condition.
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Corrective Actions
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l A.
Immediate Actions The MG set mechanical and electric' stops were adjusted downward on June 4,1997 to ensure that they were well within the SR 4.4.1.1.2 limits.
B.
Corrective Actions to Prevent Recurrence A License Amendment request was submitted on June 19,1997 to relocate SR 4.4.1.1.2 from the I
Technical Specifications to the UFSAR, and thus, to remove this conflict.
l AdditionalInformation:
A.
Failed Components None B.
Previous LERs on Similar Problems J
l None l