IR 05000269/1978026
| ML15223A341 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 11/20/1978 |
| From: | Bettenhausen L, Burnett P, Julian C, Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML15223A338 | List: |
| References | |
| 50-269-78-26, 50-287-78-26, NUDOCS 7812130317 | |
| Download: ML15223A341 (5) | |
Text
REG,4 UNITED STATES NUCLEAR REGULATORY COMMISSION
REGION II
101 MARIETTA STREET, ATLANTA, GEORGIA 30303 Report No.:
50-269/78-26, 50-270/78-25, 50-287/78-26 Docket No.:
50-269, 50-270, 50-287 License No.:
DPR-38, DPR-47, DPR-55 Licensee:
Duke Power Company P. 0. Box 2178 422 South Church Street Charlotte, North Carolina 28242 Facility Name:
Oconee Units 1, 2, and 3 Inspection at:
Oconee Site, Seneca, South Carolina Inspection conducted:
October 23-27, 1978 Inspectors:
P. T. Burnett C. A. Julian L. H. Bett nhausen (Region I)
Reviewed by: _ _
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R. D. Ma'rtin, Chief D te Nuclear Support Section No. 1 Reactor Operations and Nuclear Support Branch Inspection Summary Inspection on October 23-27, 1978 (Report Nos. 50-269/78-26, 50-270/78-25, 50-287/78-26)
Areas Inspected: Routine, unannounced inspection including a review of past flow, power and power distribution anomalies; an inspection of the past refueling zero power physics tests, and inspection of power escalation tests conducted after the Unit 3 refueling for Cycle 4 during July 1978 and an inspection of the shutdown margin verifications and operation of Unit 2 at reduced power with one disabled control rod for a period beginning October 16, 1978, until the end of cycl Results:
During this inspection no items of noncompliance or deviations were identifie * RH Rpt. Nos. 50-269/78-26, 50-270/78-25-,
and 50-287/78-26 I-1 DETAILS I Prepared by:____4
.-. urnett, Reactor Inspector Date Nuclear Support Section No. 1 Reactor Operations and Nuclear Support Branch C. A. Julian, -eactor Inspector at Nuclear Support Section No. 1 Reactor Operations and Nuclear Support Branch L. H. Bettenhausen, Re rtor Inspector ate USNRC Region I King of Prussia, Pennsylvania Dates of Inspection:
9etober 23-27, 1978 Reviewed by :
D.
M h
f R. D. M~rrtin, Chief 5ate'
Nuclear Support Section No. 1 Reactor Operations and Nuclear Support Branch Persons Contacted
- J. E. Smith, Station Manager J. N. Pope, Superintendent of Operations
- R. M. Koehler, Superintendent of Technical Services
- T. S. Barr, Performance Engineer
- R. T. Bond, Licensing and Projects Engineer
- T. D. Curtis, Reactor Engineer
- D. J. Vito, Associate Engineer Various Station Operations and Engineering Personnel
- Denotes presence at Exit Intervie.
Licensee Action on Previous Inspection Findings Not addresse RII Rpt. Nos. 50-269/78-26, 50-270/78-25, and 50-287/78-26 I-2 New Unresolved Items Non.
Exit Interview The inspectors met with M J. E. Smith, Station Manager, and those others indicated by asterisks in paragraph 1 (above)
on October 27, 1978. The scope and findings of the inspection, as described in the following paragraphs, were presented and discusse.
Review of Flow, Power and Power Distribution Anomalies During previous cycles, Unit 3 had experienced some power oscillations at power levels of less than 100 percen These small oscillations of power were determined by analysis to originate from the feed-water flow distribution through the downcomer of the steam generato The NSSS vendor recommended changing the orificing in that region, and that modification was accomplished during the recent refueling outag Operating experience on Unit 3 to-date has been favorabl The magnitude of the fluctuations has been reduced, and the power span over which they occur narrowed. Since the threshold for these fluctuations and the magnitude are dependent upon primary system moderator temperature coefficient, the final judgment on the efficacy of these modifications is being deferred until the end of the current cycle, during which time more experience with more negative moderator coefficients will be gaine The licensee has contracted with an outside engineering firm to consult both analytically and through testing on their observed problems on Unit 3 of variable primary system flow, and oscillating quadrant power tilts in three pump operation The consultant has performed extensive analytical evaluation of the hydrodynamics of the primary system as well as performing neutron and mechanical noise analyse Their report,
"Investigation of Flow Anomalies at Oconee Unit 3" (R-8010),
by J. Mott and J. C. Robinson, Technology for Energy Corporation, October 5, 1978 (Revisions through October 17, 1978),
had been received on-site only shortly before the onset of this inspectio The inspectors reviewed this report and discussed it with licensee engineering personne The consultant analyzed the situation of total flow variations during four pump operations. The analysis did not identify the source of flow variations. It was concluded that the "flow anomalie" is not caused by a change in reactor geometry (i.e., blockage or broken component),
and that there is no significant reduction in core flo They concluded that the lowest flow observed lies between 100 and 107 percent of rated flow, with 105 percent being the most probable valu RII Rpt. No /78-26, 50-270/78-25, and 50-287/78-26 1-3 The consultant analyzed the reactor coolant system in three-pump operation, and described a very complex assymetric flow distribution in the downcomer, lower plenum and through the cor Both analysis aid test results (neutron noise measurements)
support the argument that in three pump flow a vent valve can open slowly, not creating any mechanical noise, and change the flow distribution, mixing hot water through jet-pump action with downcomer flo The vent valve is not strongly held in either position, open or closed, and a small variation in flow can initiate a change in valve position and, through that, a change in the quadrant power tilt. Such changes have been observed, both in routine three-pump operation and in special operations performed to support this test progra Direct measurements of in-core neutron detectors and thermocouples indicate that the tilts occur or change in about five second In discussions with licensee personnel, they stated that they have not established an upper limit to the three-pump oscillating quadrant-power tilt by analysi The experience to-date has been that the tilts rarely exceed the technical specification limit for full-power operation, and then only briefl The consultant collected noise monitoring data for cycle 3 and compared them with data collected by others during cycles I and They identified three areas of interest: The CSB beam-mode vibration from which they have ascertained no trends over plant life from cycle to cycle has a total associated motion of about 0.5 to 0.7 thousandths of an inch. They judge that variation to be neither unusual nor of concer Power spectral density values were observed to increase over core life and from cycle to cycl This has been identified as fuel element vibration, and, over the lifetime of the facility, the frequency has decreased from 3.4 to 2.8 to 2.5 hz. This is judged to result from the loosening of grid spacers in the fuel bundle Because the core is near equilibrium, this effect is not expected to change or increase much in the futur The source of a 6.2 hz resonance has not been identifie The consultant in the report speculated that this was a reactivity effect, possibly from the orifice rod assemblie Its magnitude has increased with core life and from cycle to cycl This speculation, of course, preceeded operation of Unit 3 with the orifice rod assemblies removed. Discussions with plant personnel indicate that this resonant frequency still exists without the orifice rod assemblies. Thus, the source of this resonance at this time is unassigne RII Rpt. Nos. 50-269/78-26, 50-270/78-25, and 50-287/78-26 I-4 The licensee was asked what distribution was going to be given their consultant's report and whether they intended to summarize and distribute their own report on the subjec Their response was that other than providing the report to their NSSS vendor, they had no further dissemination planned; since none have been requeste At this time, neither the licensee, its NSSS vendor nor the consultant have identified a need for new tests or additional testin.
Zero Power Physics Tests The zero power physics tests results for Unit 3, cycle 4, as prescribed by procedure TT/3/A/711/4, were reviewe Tests included the measurement of the all rods out critical boron concentration; measurement of the temperature coefficient of reactivity for all rods out and partial rod insertion; control rod worth measurements for group 5, 6 and 7 and measurement of the pseudo-ejected-rod wort All test results met the numerical acceptance criteria identified by the license Following discussions of these tests with plant staff, the inspectors had no further question.
Power Escalation Tests The results of the physics tests conducted during power escalation on Unit 3, cycle 4 in accordance with procedure TT/3/A/811/4 were reviewed and discussed with plant personnel. Tests included the measurement of the moderator temperature and power coefficients of reactivity; reactor heat balance, and core power distributio All tests met the numerical acceptance criteria specified in the procedur.
Shutdown Margin Verification and Operation with One Disabled Rod Ref:
RO-270/78-20 Due to electrical failure of a control rod drive mechanism stator coil, one control rod was declared inoperableduring cycle 3 operation of Unit 2. As a result, Unit 2 will operate from October 18, 1978, until the end of cycle 3 in early November 1978, with one control rod inoperable and fully inserte Reactor power is limited to 55 percent by the license The circumstances of this operating mode were reviewe Procedure PT/2/A/600/1 for Periodic Instrument Surveillance on Unit 2 was temporarily modified to incorporate a more conservative control rod insertion limit curve than that prescribed by the technical specifi cations and to require increased surveillance frequency on control rod position. Following discussions with operations and performance personnel, the inspector had no further questions. This action completes review of Reportable Occurrence Report RO-270/78-10.