IR 05000413/1993012
| ML20036A157 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 04/28/1993 |
| From: | Burnett P, Crlenjak R, Curtis Rapp NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20036A153 | List: |
| References | |
| 50-413-93-12, 50-414-93-12, NUDOCS 9305100120 | |
| Download: ML20036A157 (7) | |
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UfdlTED ST ATES f6UCLEAR REGULATORY COMMISSION o
REGION 11
gy 101 MARIETTA STREET, N.W.
's ATLANTA, GEORGI A 30323
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Report Nos.: 50-413/93-12 and 50-414/93-12 Licensee: Duke Power Company 422 South Church Street Charlotte, NC 28242 Docket Nos.:
50-413 and 50-414 License Nos.:
NPF-35 and NPF-52 Facility Name: Catawba 1 and 2 Inspection Conducted: March 29 - April 2, 1993 Inspector:
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[MO K T. Burnett'
Date Signed
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Inspector:
J/lb/93 C. W. Rapp
D' ate Signed
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Approved y:
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R. V. Crle'njak, Chief
'Dhte signed j Operational Programs Section
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Operations Branch Division of Reactor Safety SUMMARY Scope:
This routine, announced inspection was conducted in the areas of witnessing and review of Unit 2, cycle 6 startup tests and close out of open items.
Results:
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All tests observed and reviewed were performed capably and satisfactorily.
There was good communication between testing and operating personnel.
One subject of concern was identified:
during dilution of the reactor coolant i
system, prior to the approach to criticality, the volume control tank was diluted to a boron concentration about 1000 ppm less than the target concen-
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tration for a period of over 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. A dilute volume control tank may be a precursor to a serious reactivity event (paragraph 2.c).
One previous violation was closed.
No, violations or deviations were identified.
9305100120 930428 PDR ADOCK 05000413 G
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1.
Persons Contacted
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Licensee Employees S. L. Abbey, Reactor Engineer
- T. E. Crawford, Systems Engineering Manager
- J. S. Forbes, Engineering Manager
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J. R. Fox, Reactor Engineer
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- R. C. Futrell, Regulatory Compliance Manager
- T. P. Harrall, Safety Assurance Manager M. W. Hawes, Reactor Engineer
- G. R. Horne, Reactor Engineering Supervisor
- J. L. Lowery, Regulatory Compliance Specialist
- W. R. McCollum,Jr., Station Manager M. S. Tuckman, Catawba Site Vice President D. A. Wellbaum, Reactor Engineer Other licensee employees contacted included engineers, operators, technicians, security force members, and office personnel.
l NRC Resident Inspectors P. Hopkins, Resident inspector
l W. Orders, Senior Resident Inspector
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- J. Zeiler, Resident Inspector
- Attended exit interview on April 1, 1993.
2.
Pre-Critical Tests The following tests, which were completed prior to the approach to criticality, were reviewed by the inspectors:
a.
IP/0/B/3220/01, Control Rod Drop Timing Test, was performed on
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March 29-30, 1993. The full-out control rod position was 231 steps.
l All four RCPs were operating with NC average temperature and pressure at 557*F and 2250 psig, respectively.
The slowest rod dropped to dashpot entry in 1.64 seconds, and the fastest time was 1.50 seconds.
The inspectors reviewed some of the timing traces, observed r,o anomalies in the traces reviewed, and arrived at drop times consistent with those obtained by the licensee.
i b.
PT/0/A/4600/05E, Preliminary NIS Calibration, was completed on March 29, 1993. This test uses ratios of predicted power distributions for the coming cycle to the measured power distributions of the previous cycle to estimate the leakage flux at the IRNIs and PRNIs and appropriate adjustments to trip setpoints. Those setpoints i
are used until an adequate plant calorimetric is obtained in mode 1 l
for nuclear instrument calibration. The fuel assembly locations
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!l chosen for the power distribution comparisons and the weighting given
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to each location are consistent with practice at other facilities and
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recommendations of the NSSS vendor. However, experience at another
facility has shown the method of predicting full power current for the IRNIs does not always lead to conservative interim trip setpoints -
The licensee was apprised of this experience.
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NOTE:
For the IRNIs, the first full power distribution of the previ-l ous cycle is used in the comparison, and the last measured
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distribution is used for the PRNIs.
This is appropriate since
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the IRNIs are calibrated against heat balance only-during the beginning of the cycle. TS Table 4.3-1 requires only refueling interval calibration of the IRNIs. The PRNIs are
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calibrated against secondary side heat balance daily, when
operating. This licensee makes a practice of. continuously monitoring heat balance on the plant computer, and PRNI calibrations are performed more often than daily if necessary.
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c.
PT/0/A/4150/19A, NCS Dilution with Shutdown Banks Inserted, was performed and completed on March 30, 1993. The target C, was 1655 ppm B, and the concentration obtained was 1656 ppm B.
The predicted reduction in ICRR during dilution was.from 1.0 to 0.6.
The final ICRR
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was 0.55 and 0.57 on N31 and N31, respectively.
ICRR was plotted for every 1000 gallons of dilution water added, and the plotted ICRR stayed within the limits of the prediction throughout the addition of nearly 14,792 gallons of primary grade water.
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The inspectors observed the initial dilution of the NCS and reviewed and independently verified that the calculations performed in' the controlling procedure were correct. A mini-hydro was performed concurrently with the dilution to verify no pressure boundary leakage i
existed before containment integrity was established. While the mini-hydro did not negatively impact the dilution, the inspector:. noted two issues that could impede initial criticality.
First, due to the higher NC system pressure required for the mini-hydro, the pressurizer could not be mixed while the dilution was in progress.
Second, only a single 75 gpm letdown orifice could be used at the higher pressure to establish a letdown-charging balance. Both of these issues resulted in additional mixing time to establish NC system equilibrium boron concentration. The inspectors concluded that no additional hazard existed when performing the initial dilution and mini-hydro concurrently.
The dilution was performed in the ' alternate dilute mode of operation.
The charging rate was greater than the dilution rate, and the valve from the boric acid blender to the VCT spray was closed. These actions had been believed sufficient to prevent over-dilution of the VCT during extended dilution operations.
For this facility, these actions were insufficient to prevent greatly reducing the boron i
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concentration in the VCT below the desired concentration in the NCS.
Miniflow lines installed to prevent dead-heading the charging pumps returned charging flow directly to the VCT. As shown in the table below, the boron concentration in the VCT was much less than the equilibrium concentration for which the SDM was calculated, for a period of over 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
BORON CONCENTRATIONS (ppm) DURING DILUTION I
Tine VCT NCS 0600 1005 2037 0705 507 1876
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0805 493 1745 0900 1430 1670
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1125 1645 1656
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FOREIGN EXPERIENCE REGARDING BORON l
l DILUTION (September 6, 1991) describes a sequence of events, which might lead to core damage. One precursor to such an event is a VCT significantly more dilute than the NCS. Once reminded of th.s-concern, the licensee agreed to re-evaluate their current procedures l
to obtain better control of the dilution of the VCT.
They also agreed to remind McGuire Station personnel of the concern. This issue will be tracked as IFI 50-413 and 50-414/93-12-01:
Improve control of VCT boron concentration during extended dilution operations.
3.
Post-Refueling Startup Tests (72700)
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PT/0/A/4150/01, Controlling Procedure for Startup Physics Testing, established the prerequisite conditions for and scheduled the tests discussed below. This procedure also provides the acceptance criteria for these tests.
The inspectors observed the pre-job briefing, for this procedure, provided to the control room operators by reactor engineering personnel.
a.
Initial Criticality for Unit 2 Cycle 6 PT/0/A/4150/19,1/M Approach to Criticality, was performed on March 30, 1993. The inspectors attended the pre-job briefing for control room operators and witnessed the test activities as they were directed from the reactor engineering work station and conducted in i
the control room. Subsequent to obtaining criticality, one decade of overlap between the SRNIs and IRNIs was confirmed. Next, sensible heat was determined to be at 6.6x10'7 amps on picoammeter used with the DRC. The upper limit for ZPPTs was set at 3.3x10~ 7 amps. The DRC was checked out against reactivity determined from periods determined from stop watch measurements. The maximum difference between measure-ments was 2.3% for reactivities ranging from -36 pcm to +45 pcm.
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B b.
Zero Power Physics Tests
(1) PT/0/A/4150/10, Boron Endpoint Measurement (for all rods out),
was completed on March 31, 1993.
The measured C, at ARO was 1747 ppm B, which was in acceptable agreement with the predicted concentration of 1715 ppm B.
(2)
PT/0/A/4150/12A, Isothermal Temperature Coefficient of Reactivity Measurement, was completed on March 31, 1993. The inspectors observed the performance of the procedure. A single cooldown and heatup was required to measure the ITC.
A cooldown of 4*F was established using steam dumps. A heatup of 5'F was used as NC
temperature recovered. The measured ITCs for was 0.66 pcm/*F and 0.71 pcm/*F for the cooldown and heatup respectively.
Corret. ting i
the measured values to conditions assumed in CNEI-0400-30, the l
ITCs were determined to be 0.37 pcm/*F and 0.47 pcm/*F for an
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average ITC of 0.42 pcm/*F.
The inspectors independently reviend the data collected and the slopes used to determine the ITC and did not find any deficiencies.
The predicted value for ITC was 0.77 pcm/*F. The average ITC was within the acceptance criteria of 12 pcm/*F.
Using the averaged ITC value, the MTC was calculated to be +1.81 pcm/*F. This value was within the acceptance criterion of 13 pcm/*F of the predicted value of +2.16 pcm/*F.
The calculated MTC was within the Technical Specification limit of +7 pcm/*F.
During their review PT/0/A/4150/12A, the inspectors noted that a 5*F temperature change was desired. However, the procedure re-i quired a minimum temperature change of only 3*F.
The inspectors questioned the adequacy of the minimum 3*F temperature change to determine the slope with confidence. Because the ITC measurement i
is endpoint dependent, the larger temperature change would give more confidence to the result. The licensee noted the inspectors' concern.
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PT/0/A/4150/11A, Control Rod Worth Measurement by Boration/Dil-ution, was completed on March 31, 1993.
The measured reactivity worth of shutdown bank B (the reference bank) was 975 pcm, which was in good agreement with the predicted reactivity worth of 988 pcm. The inspectors witnessed the test in progress and j
independently analyzed the DRC reactivity traces.
The inspectors' results, which are plotted in the figure below, were in agreement with those reported by the licensee.
(4) PT/0/A/4150/10, Boron Endpoint Measurement (for reference bank in), was completed on March 31, 1993. Two measurements gave identical results of 1628 ppm B.
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(5) PT/0/A/4150/11B, Control Rod Worth Measurement by Rod Swap, was completed on April 1, 1993.
The inspectors witnessed portions of the test. All acceptance criteria were satisfied.
Catawba Unit 2 Cycle 6
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Reference Bank (Shutdown Bank B)
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75 100 125 150 175 200 225 Rod Position (steps)
3.
Followup of Previous Violation 92702)
(Closed) Violation 50-414/92-26-01:
Required procedure steps were not completed for the surveillance of Unit 2 core power distribution performed on June 16, 1992, at 168 EFPD.
The procedure steps were completed as soon as the inspector orally identified the error to the licensee on October 22, 1992. The results of
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the completed steps confirmed that no further action in power distribution monitoring was required. The licensee conducted training, for all affected personnel, on Review of Verification Requirements. That training was completed on October 28, 1992.
4.
Exit Interview (30730)
The inspection scope and findings were summarized on April 1, 1993, with those persons indicated in paragraph 1 above.
The inspectors described
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the areas inspected and discussed in detail the inspection findings. No dissenting comments were received from the licensee.
Proprietary
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information was reviewed in the course of this inspection, but is not t
included in this report.
The item listed below was discussed.
IFI 50-413 and 50-414/93-12-01:
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concentration during extended dilution operations (paragraph 2.c).
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Acronyms and Initialisms Used in This Report Ce boron concentration in the NCS DRC digital reactivity computer EFPD effective full power days i
ICRR inverse countrate ratio
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IRNI intermediate range nuclear instrument ITC isothermal temperature coefficient MTC moderator temperature coefficient NIS nuclear instrument system
NC(S)
nuclear coolant system
NSSS nuclear steam supply system pcm percent millirho PRNI power range nuclear instrument PT periodic test SDM shutdown margin RCP reactor ~ coolant pump VCT volume control tank ZPPT zero power physics test j
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