IR 05000237/1986012
| ML17199F801 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/11/1986 |
| From: | Dupont S, Ring M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML17199F800 | List: |
| References | |
| 50-237-86-12, NUDOCS 8606180298 | |
| Download: ML17199F801 (4) | |
Text
U.S. NUCLEAR REGULATORY COMMISSION
REGION III
Report No. 50-237/86012 Docket N ~0~237 License N DPR~19 Licensee:
Common~ealth Edison Company Post Office Box*767 Chicago, IL 60690 Facility Name:
Dresden Nuclear Power Station, Unit 2 Insp~ction At:
Morris, IL Inspection Conducted:
April 30 through May 1, 1986
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Inspecto~ S. G. Dufont
Approv~d *B~Chief
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Test*Programs Section
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Inspection Summary
~;{J/!c Date Ins ection on A ril 30 throu h Ma 1 1986 (Re ort NbJ 50-237/86012 DRS))
Areas Inspected:
Licensee Event Report ~q. 86--0Q4 927-00.
Results:
No violations were identifi~ * *
DETAILS Persons Contacted
- D. J. Scott, Station Manager
- R. Flessner, Service Superintendent
- R; Sto 11 s, Qua 1 ity Assurance Engineer
- J. Brunner, Assistant Superintendent, Technical Services
- J. Achterberg, Technical Staff Supervisor The inspector also interviewed other licensee employees, including members of the technical staff, instrument mechanics and nuclear engineer *Denotes personnel in attendance at the May 1, 1986 exit meetin.
Licensee Event Report (LER) Review LER No.86-004, Unit 2, Summary On February 7 through 20, 1986, Unit 2 _operated above the license thermal power limit of 2527 megawatts while at 100 percent powe The maximum power overshoo.t was 1.52%.- The licensee attributed th power overshoot to a masked input signal to the process computer from the 2C Reactor Feedwater Flow transmitter. * The error of indicated the~mal power was a result pf changing the reactor feedwater pump combination from pumps 11A 11 and 118 11 to 11A 11 and 11C
after a seal 1 eak developed on pump uau.. This made the 2C -Reactor Feedwater Flow transmitter an foput to the process compute Since the transmitter signal was in ~rror, the computer-provided thermal power indication was indicating less than actual *thermal power, allowing elettric output and thermal power to be increased to the 11 indicated 11 limi However, when.the electric output was increased to 834 megawatts-electric and thermal power to 2527 megawatts-the.rmal, the a~tual thermal power.was.2563 megawatts-thermal or an error of 36 megawatts..,.ttierma The* transnii tter was discovered to be i out of calibration on Felfruary 24, 1986..The out-of-calibration condition was attributed to the transmitter being jarred during the Unit 1 outage (additional information is provided in Paragraph 2.b).
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The inspector reviewed the event and discovered that the f611o~ing information contributed to the event and masked the error from the licensee:
(1) Prior to the event the licensee was researching a decrease in the unit effici~ncy from the previous yea Norma1*1y, the unit produces approximately 830 to 840 megawatts-electr,ic at 2527
.megawatts-thermal with similar circulating water inlet temperature However, recently the unit has been somewhat less efficient with approximately 820 megawatts-electric outpu *
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After the reactor feedwater pump combination had been changed, the unit was able to increase the electric output to approximately 830 megawatts-electric without exceeding the indicated thermal limi Because of this concern with
. efficiency and the actions which* were being taken to improve efficiency, the licensee did not associate the increase in electric output after changing the reactor feedwater pump combination with a possible error in indicated thermal powe (2)
The licensee had established an alarm to alert the operator to take corrective action whenever power level exceeds 100.5%.
However, the tripping signal for the alarm is provided by the process computer which is the same signal that provides indicated thermal powe Since the erroneous indicated power level had not exceeded 100.5% the alarm did not annunciat *Review of Instrument Calibration
'Required The inspector reviewed the calibration documents for the 2c Reactor Feedwater Flow Transmitter, model GEMAC 553, and found that prior to the January 1986 calibration, the instrument had demonstrated good stability requiring only slight recalibratio Listed below is a table of calibration data showing the rapid change in the instrument in 1986, compared to previous calibrations:
May 1983 August 1983 January 1986 February__ 24 2 As As As As As As As As 1986 set~oint(ma) Found Left( ma) Found Left( ma) Found Left( ma) Found Left( ma}
1.0 1.1 10. l
- 11. 5 1 *.0 lL6 -
11. 6 11. 6 11. 7 1 *1. 5
- . 7 1.4 1.5 1 *1.3
- 1.4 2 *2.4 2.5
- 2.4
- 2.5 3.7 3 *3.6
- 3.5
- 3.7 5.1 5.1 5 *5.9
- 4.1 Note: *Points of calibration that did not meet the acceptance criteria of +/-0.2 m Additional review of data collected in 1985 revealed the same findings as the data collected in 198 From the above data, the inspector concluded that the change in calibration since January 1986, was not from gradual agin The inspector also reviewed the calibration procedure DIP 600-1, 11 Feedwater Control Calibration and Maintenance,
Revision 2 (dated 1984), and determined that the procedure and practices used to calibrate the instrument were adequat Licensee personnel informed the inspector that they believed the change in the
- instrument characteristics was due to an acute physical shock during the recent Unit 1 outag The inspector visually verified that the instrument appeared to have received a shock from a physical impact since both sensing lines had been ben In conclusion, the licensee determined that the instrument had been slightly damaged and will be replace Licensee's Corrective Action (1)
Reactor Feedwater Flow Transmitte All transmitters are scheduled to be replaced due to lack of sufficient speed and accuracy to adequately interface with computer In addition, to provide protection from future jarring of the transmitters that may produce erroneous inputs, the licensee installed a barrier around the instrument The inspector finds this to be sufficient to prevent further recurrenc ( 2)
Program The licensee revised operating surveillance procedure DOS 500-18, "Operators 1 Flow Control Line and Average Core Thermal Power Surveillance," to notify a qualified Nuclear Engineer after a feedwater pump combination alteration. The Nuclear Engineer will verify core thermal power before and after the feedwate changeove The inspector finds that this should identify any transmitter calibration problem Cone 1 us ions Even though the core power exceeded the license thermal limit by 1.52%, the inspector verified, by document review, that no safety limits or fuel related limits (102%) of the Technical Specifications were exceede However, during the review, the inspector noted that thermal power did exceed the license thermal limit by 1% continuously for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and 59 minutes on February 18, 198 This issue is not being considered a violation in that it appears to meet the tests of 10 CFR 2, Appendix C, Section V.A:
1) it was identified by the licensee, 2) it would have been considered a Severity Level IV or V violation since the Safety Limit of 102% was not exceeded, 3) it was reported by the licensee, and 4) it was corrected within a reasonable time to prevent recurrenc The inspector has no further concern.
Unresolved Items Unresolved items are matters about which more information is required in order to ascertain whether they are acceptable items, items of violation or deviation An unresolved item disclosed during the inspection is discussed in Paragraph.
Exit Interview The inspector met with the licensee representatives (denoted in Paragraph 1)
on May 1, 198 The inspector summarized the scope and findings of the inspection. The inspector also discussed the likely informational content of the inspection report with regard to documents or processes reviewed by the inspecto The licensee did not identify any such documents or processes as proprietary. The licensee acknowledged the statements made by the inspector with respect to the finding