IR 05000261/1991016
| ML14178A138 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 08/12/1991 |
| From: | Burnett P, Crlenjak R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML14178A137 | List: |
| References | |
| 50-261-91-16, NUDOCS 9108280090 | |
| Download: ML14178A138 (11) | |
Text
E1R REG& 4UNITED STATES o0 NUCLEAR REGULATORY COMMISSION f-REGION II 101 MARIETTA STREET, ATLANTA, GEORGIA 30323 Report No.:
50-261/91-16 Licensee:
Carolina Power And Light Company P. 0. Box 1551 Raleigh, NC 27602 Docket No.:
50-261 License No.:
DPR-23 Inspection Conducted:
June 24 -
28, 1991 T. Bu ett, Reactor Engineer Dat' Signed Approved by:
,
/__--__/_
Crlenja' Chief Da e Signed Operational Programs Section Operations Branch Division of Reactor Safety SUMMARY Scope:
This routine announced inspection was conducted in the areas of review of cycle 14 startup tests and followup of open item Results:
Cycle 14 startup tests were performed in an acceptable manner and all acceptance criteria were satisfied. Several areas in which procedural guidance should be enhanced and test methodology improved were identified and discussed with the licensee. The specifics of those discussions may be found in paragraph Two open licensee event reports and one open unresolved item were close No violations or deviations were identifie PDR ADOCK 05000261
REPORT DETAILS Persons Contacted Licensee Personnel:
- R. H.Chambers, Manager, Unit 2 Operations
- T. P. Cleary, Manager, Balance of Plant Systems/Reactor Engineering R. D. Crook, Senior Specialist, Regulatory Compliance
- C. R. Deitz, Manager, Robinson Nuclear Project W. T. Gainey, Jr., Manager, Plant Support
- W. S. Jackson, Technical Support/Reactor Engineering
- P. C. Jenny, Project Specialist, Regulatory Compliance
- W. T. King, Technical Support/Reactor Engineering
- J. D. Kloosterman, Director, Regulatory Compliance M. F. Page, Manager, Technical Support J. A. Padgett, Manager, E&RC
- J. J. Sheppard, Plant General Manager
- D. C. Stadler, Onsite Licensing Engineer, Nuclear Licensing
- G. A. Walters, Project Engineer, Regulatory Compliance Other licensee employees contacted included office personnel, engineers, and security personne NRC Resident Inspectors:
- L. W. Garner, Senior Resident Inspector K. R. Jury, Resident Inspector
- Attended exit interview on June 28, 199 Acronyms and initialisms used in this report are defined in the final paragrap.
Post-Refueling Startup Tests for Cycle 14 (72700, 61708, 61710) Precritical Tests The following completed, precritical test procedures were reviewed by the inspector:
(1) EST-049 (Revision 3), Rod Drive Mechanism Operation Testing (Refueling Outage), was performed with the RCS temperature less than 190 Degrees F on January 27, 1991, with satisfactory results. The test was repeated under similar RCS conditions on February 27, 199 (2) EST-048 (Revision 6), Control Rod Drop Test, Refueling Outage, was performed under cold conditions on January 29 and 30, 199 Forty-four of the rods gave satisfactory results, but one, C-07, exhibited an unusually long drop time ( seconds) and an abnormal trac C-07 was determined to be unlatche Following maintenance, which required removing the vessel head and replacing the rod guides in the upper internals package and the rod extension for C-07, the test was repeated for all rods, under cold conditions, on February 28, 199 The results were satisfactor The test was performed under hot conditions, RCS temperature at 547 Degrees F and three pumps running on March 5, 199 The results were satisfactory for all control rod It was noted that the SRNI count rates recorded in the procedures performed prior to and after February 27, 1991, were quite different for N3 Earlier count rates were ~150 cps vice latter rates of 20 cps, much like N3 The initial measurements had been performed with one active startup neutron source, which was closest to N3 During the removal of the upper internals for maintenance on rod C-07, the active source was inadvertently withdrawn and damaged. Subsequent measurements were without any active startup source in the core. Count rates from photoneu trons from the core were more than adequate to monitor core reactivit (3) EST-001 (Revision 0), Source Range Statistical Reliability Test, is performed prior to fuel handling in the core, prior to criticality with a new core, and prior to lowering vessel water leve The inspector reviewed the copy completed on March 4, 1991, prior to lowering vessel water level. Thirty observations were made of the countrate for each SRNI, and in both cases acceptable values of chi-squared were obtaine Low Power Tests Initial criticality and low power physics tests for cycle 14 were performed using EST-050 (Revision 10),
Refueling Startup Procedure, which included the following attachments:
8.1 Log of Boron Concentration Initial Criticality Data -
Rod Withdrawals Initial Criticality Data -
Dilution 8.4 Reactivity Computer Testing 8.5 Boron Endpoint Measurement 8.6 Moderator Temperature Coefficient Measurement 8.7 Control Rod Reactivity Worth Measurement 8.8 Preparation of Reactivity Computer and X-Y Plotter for Startup Physics Test Surveillance Procedure Certification and Review For The completed procedure package included a test log for the procedure, which was also reviewed and discussed with the licensee. The inspector had no further questions following the discussion One particularly good feature of this procedure was the prerequisite step 3.9, which required that the high flux trips be set to <= 45 Degrees indicated power prior to initiating rod withdrawa Section 6.0, Acceptance Criteria, lacked specificity on satisfactory agreement between measured and predicted values of the parameters under test; however, pertinent steps of the procedure did require PNSC review if the agreement specified in the step was not satisfied. The licensee is considering revising the acceptance criteria section of the procedur In procedure steps 7.1.14 to 7.1.18, one decade of overlap between SRNIs and IRNIs is required before removing power to the SRNIs and it is assumed that P-6 will occur before criticality; which, according to test personnel, it did. Completing the approach to criticality on the IRNIs alone is not the best practice; since they, unlike the SRNIs, can not be confirmed to be responding to neutrons prior to beginning the startup. During the approach to criticality, the ICRR for both of the SRNIs reduced to 0.65 during rod withdrawal. The ICRRs were renormalized to 1.0 at the start of dilution. The ICRRs for the SRNIs reduced to 0.21 and 0.25 before the first IRNI started to respond. Thus there was little reactivity space to confirm proper operation of the IRNIs prior to criticality. The benefits of and possibilities for relocating the SRNI detectors to a lower flux region, which would allow the entire approach to criticality to be monitored by the SRNIs, were discussed with licensee personne The licensee's review of methods to achieve criticality in the source range will be tracked as inspector followup
item 50-261/91-16-0 In step 7.1.20, there is very little guidance on what parameters are to be observed to determine the onset of nuclear heating and, in subsequent steps, the upper limit for low power tests is set at the onset of observed heating without establishing any margin, which is common practice. The licensee is considering enhancing procedural guidance on identifying the onset of nuclear heating and establishing a margin between that point and the upper flux limit for low power test The procedure does not specifically require a comparison of predicted and measured differential boron worth, which is a test parameter described in Table A-1 of ANSI/ANS-19.6.1-1985, Reload Startup Physics Tests for Pressurized Water Reactors. This programmatic difference was brought to the attention of the license All of the attachments to this procedure were completed by the licensee and reviewed by the inspecto Specific comments on some of the completed attachments are given below: Initial Criticality Data -
Dilution included plots of ICRR for both SRNIs and IRNIs, once they came on scale, against CB, water added, and tim The latter did not appear to be particularly usefu The remaining SRNI plots did provide curves that could be easily extrapolated to a reasonable estimate of criticality. Because of the short time they were on scale and responding, the IRNI plots were precipitous and difficult to r
extrapolat The subsequent measurement of the ARO critical boron concentration of 1419 ppmB was in satisfactory agreement with the predicted concentration of 1425 ppm.4 Reactivity Computer Testing established a calibrated range from -57 pcm to +51 pcm with 5 percent or better agreement between reactimeter and stopwatch-inhour equation solutions. The procedure accepts differences of up to 10 percen That uncertainty coupled with the 10 percent tolerance allowed between predicted and measured rod worths, obtained using the reactimeter, challenges the acceptability of the assumption used in SDM calculations that the calculated rod
worth error is not greater than 10 percent. The licensee is considering requiring 5 percent agreement for the reactimeter calibration. Common industry practice is to require 4 to 5 percent agreement. The licensee is evaluating the acceptable tolerance for reactivity computer calibratio.6 Moderator Temperature Coefficient Measurement was performed for ARO only. The ITC measured during a 2.5 Degrees F heatup was -2.76 pcm/ Degrees F and the ITC obtained during a 3.3 Degrees F cooldown was -2.88 pcm/ Degrees F. Agreement between the two measurements was well within the 1 pcm/
Degrees F difference usually considered acceptable for such measurements. The MTC obtained from the average of the ITCs adjusted for the -1.46 pcm/
Degrees F DTC in the fuel was -1.36 pcm/ Degrees F, which was well below the TS 3.1.3.1 upper limit of +5 pcm/ Degrees The narrow temperature spans used in the test were appreciably less than the 5 Degrees F temperature change recommended in step 4.6 of this attachmen Furthermore, the chart recorder was not scaled to obtain a near full-span divergence for either the anticipated temperature or reactivity chang Consequently, the relationship between temperature and reactivity was not well resolved from the noise on the X-Y recorder chart, and slopes different from the ones reported as the ITCs were equally probable. However, no reasonable estimate of slope from the traces obtained leads to a violation of the TS or to even a positive MT Nevertheless, had the results been closer to the limits, this test would not be acceptable. The licensee is considering enhancing the procedure to better define the the slope of the temperature reactivity trac.7 Control Rod Reactivity Worth Measurement was performed for the sequential, no overlap, dilution of control banks D and C from full out to full i Since the measured total integral worth of banks C and D (1523 pcm and 564 pcm, respectively) agreed within 10 percent of the predicted total worth (1431 pcm and 569 pcm, respectively), no additional rod worth measurements were required to be performed by the procedure. The inspector independently analyzed the reactivity computer traces for the calibration of control bank C. No
significant differences in reactivity increments were identified. The traces were generally indicative of a constant and reasonable dilution rate with little reactivity undershoot or overshoot at the endpoints. There was some ripple in the traces, but it was judged not to interfere with the interpretation of the trace The licensee has considered using rod swap methodology to measure the worths of all of the control rod banks, but has identified no compelling reason to go to the extra expense involved in supporting such measurement The licensee's activities to enhance procedure EST-050 to increase guidance on identifying the onset of nuclear heating and establishing a margin between that point and the upper flux limit for low power tests; to define the acceptable tolerance for reactivity computer calibration; and to better define the the slope of the temperature-reactivity trace will be tracked as inspector followup item 50-261/91-16-0 Power Escalation Tests The following completed power escalation tests were reviewed by the inspector:
(1) EST-105 (Revision 0), Post-Refueling Power Escalation Procedure, was performed over the period from March 8 to March 21, 1991. The process of maintaining a conservative high flux trip setpoint, initiated in EST-050, was continued by this procedure. After completing the tests required for the 30 percent RTP plateau, the high flux trip setpoints were successively increased to 70 percent RTP, 85 percent RTP, and 108 percent RTP as the successive plateau test requirements were satisfied. RTP was attained on March 16, 199 The tests performed at the test plateaus, as required by this procedure, are described belo (2) EST-051 (Revision 5), Operational Alignment of Nuclear Instrumentation (Refueling Interval),
scheduled or initiated performance of other instrument surveillance procedures. Plots of PRNI total currents showed good linearity with powe (3) EST-052 (Revision 7), Operational Alignment of Process Temperature Instrumentation (Refueling Startup),
tracks the performance of RCS RTDs
throughout power escalation. This procedure assures (step 7.1.6) that full power delta T is spanned to 57.5 Degrees F to be consistent with the calibrations of overpower and over temperature delta T trip setpoints. Plots of average and differential temperature against calorimetric power showed good linearity over the entire operating rang (4) EST-053 (Revision 6), Thermal Power Measurement Refueling Interval, is an essentially sound procedure for performing a secondary side heat balance. Two minor discrepancies were noted in the procedure or in its performance. In attachment 8.1 the data collection table indicates that blowdown flow is to be recorded in units of lbm/hr. Review of the completed procedures showed that units of gpm or inches of HO were recorded and later converted to mass flow rate. The constant for converting blowdown flow from gpm to lbm/hr uses a density of 8.347 lbm/gal, which is greater than the density at 68 Degrees F, the usual calibration temperature for dP cells used in flow measurements. These discrepancies were brought to the attention of the licensee staf (5) EST-054 (Revision 3), Power Distribution Maps (Refueling Startup), was performed at 30 percent, 70 percent, 89 percent, and 99.7 percent RTP, during power escalation. In every case both and FdH were within limits to allow escalation to the next planned power plateau. Files at the plant do not contain the complete INCORE power distribution analysis. According to plant personnel, power distribution analysis is performed at the corporate offices, and only a summary of the results is sent to the plan Consequently, the inspector was not able to review the comparisons of measured and predicted relative power on a bundle-by-bundle basi (6) EST-003 (Revision 4), F(delta I) Correlation, was first performed for cycle 14 at a nominal 70 percent RTP. The inspector analyzed the raw current data using a linear correlation to deter mine the constants of the equation I(AO) = 10 + b * A where I(AO) is the current from a PRNI chamber at RTP and axial offset A Io is the current at AO = 0, b is the slope of the correlation of I(AO) and A The correlation was poor for the top chambers (correlation coefficient less than 0.9) at 70 percent RTP. Acceptable results were obtained when the surveillance was repeated above 90 percent RTP. The licensee uses a bilinear regression for the correlation, which should be superior to the method discussed abov With the exceptions noted, the licensee's program for post refueling startup tests conformed to ANSI/ANS-19.6.1-1985, Reload Startup Physics Tests for Pressurized Water Reactor No violations or deviations were identifie.
Followup of Open Items (92701) (Closed) Unresolved item 50-261/90-23-02:
Review investigation results associated with incorrect application of TS Figure 3.10- The licensee's review of operating cycles 10 through 13, the only cycles of vulnerability, revealed no instances of operation outside of the allowed regime of axial flux difference and reactor powe Conformance to this TS requirement is tracked by the NSSS subsystem of the ERFIS/SPDS compute New software for power distribution analysis and control was installed at the start of operating cycle 1 The new software, PDC-III, replaces the earlier PDC-II package. The inspector reviewed the calculation changes, in the program modules, which were made to correct the earlier error. The changes are documented in SOFTWARE UPDATE SUP 91-0001, ATTACHMENT 2, PROGRAM LISTINGS. Based upon review of those software changes and discussions of the documentation with licensee personnel, the inspector concluded that the installed software does have the capability to assure operation within the limits of TS Figure 3.10-5 and to generate the appropriate alarms when the limits are approache The licensee monitors the integrity of the software by performance of EST-070 (Revision 8), Power Distribution Control Code Verification, Bi-Weekly. The procedure was last performed on June 24, 199 That surveillance confirmed that the correct constants were in the program and that computed values of target band, target warning band, operating band, for each PRNI chamber,
agreed with calculated value This item is close (Closed) Licensee Event Report 50-261/90-14:
Misapplication of Technical Specification for Allowable Deviation from Target Flux Differenc This report addresses the issue raised in item a.,
above, and is closed by that revie (Closed) Licensee Event Report 50-261/89-07:
Potential for Nonconservative Delta Temperature Setpoint Spanning of delta temperature inputs to trip circuits is now controlled by EST-052, which is discussed in paragraph 2.c.3, above. This item is close.
Exit Interview The inspection scope and findings were summarized on June 28, 1991, with those persons indicated in paragraph 1 above. The inspector described the areas inspected and discussed in detail the inspection findings. No dissenting comments were received from the licensee. Proprietary information was reviewed in the course of this inspection, but is not included in this repor On August 12, 1991, licensee personnel were informed by telephone that some of the activities they planned to perform or consider as a result of the inspection would be tracked more formally as inspector followup items. The licensee agreed that the descriptions of the items were consistent with their intentions. The items are listed below:
Inspector followup item 50-261/91-16-01:
The licensee is reviewing methods to achieve criticality in the source range (paragraph 2.b).
Inspector followup item 50-261/91-16-02:
The licensee is reviewing enhancements to procedure EST-050 to increase guidance on identifying the onset of nuclear heating and establishing a margin between that point and the upper flux limit for low power tests; to define the acceptable toler ance for reactivity computer calibration; and to better define the the slope of the temperature-reactivity trace (paragraph 2.b).
10 Acronyms and Initialisms Used in This Report ANS American Nuclear Society ANSI American National Standards Institute AO Axial offset (measured incore)
ARO All rods out CB Boron concentration in the RCS cps Counts per second dP Differential pressure DTC Doppler temperature coefficient ERFIS Emergency response facility information system EST Engineering surveillance test FdH Enthalpy rise hot channel factor FO Heat flux hot channel factor gpm Gallons per minute ICRR Inverse countrate ratio IRNI Intermediate range nuclear instrument ITC Isothermal temperature coefficient lbm/hr Pounds mass per hour MTC Moderator temperature coefficient NSSS Uuclear steam supply system pcm Percent millirho PNSC Plant Nuclear Safety Committee ppmB Parts per million boron PRNI Power range nuclear instrument RCS Reactor coolant system RTD Resistance temperature detector RTP Rated thermal power SDM Shutdown margin SPDS Safety parameter display system SRNI Source range nuclear instrument TS Technical Specifications