05000440/LER-2005-001, And LER 05-001-00 Perry Nuclear Power Plant Regarding Unplanned Automatic Oscillation Power Range Monitor Scram and Manual Reactor Scram Following Unexpected Reactor Recirculation Pump Trip
| ML050610021 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 02/21/2005 |
| From: | Richard Anderson FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PY-CEI/NRR-2863L LER 04-002-00, LER 05-001-00 | |
| Download: ML050610021 (13) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(iv), System Actuation |
| 4402005001R00 - NRC Website | |
text
FENOC FrstEnergy Nuclear Operating Company Perry Nuclear Power Plant 10 Center Road Perry, Ohio 44081 Richard Anderson Vice President-Nuclear 440-280-5579 Fax: 440-280-8029 February 21, 2005 PY-CEI/NRR-2863L United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Perry Nuclear Power Plant Docket No. 50-440 LER 2004-002-00 and 2005-001-00 Ladies and Gentlemen:
Attached are Licensee Event Reports (LER) 2004-002-00, "Unplanned Automatic Oscillation Power Range Monitor SCRAM" and 2005-001-00, 'Manual Reactor SCRAM Following Unexpected Reactor Recirculation Pump Trip." Any actions discussed within these LERs are described for information only and are not regulatory commitments.
If you have questions or require additional information, please contact Mr. Jeffrey J Lausberg, Manager - Regulatory Compliance, at (440) 280-5940.
Very truly yours, Attachments cc: NRC Project Manager NRC Resident Inspector NRC Region IlIl
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 6130/2007 (6-2004)
, the NRC may (See reverse for required number of not conduct or sponsor, and a person is not required to respond to. the digits/characters for each block)
Information collection.
- 3. PAGE Perry Nuclear Power Plant 05000440 1 OF 6
- 4. TITLE Unplanned Automatic Oscillation Power Range Monitor SCRAM
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE S. OTHER FACILITIES INVOLVED SE"LUENTIAL IREV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR 12 23 204 2004 002 -
00 02 21 2005 FACILITY NAME DOCKET NUMBER
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 0 20.2201(b)
[3 20.2203(aX3)(i) 0 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
Mode I 0 20.2201(d)
EJ 20.2203(aX3)(ii) 050.73(aX2)(iiXa)
D 50.73(a2)(2viii)(A)
Ea 20.2203(a)(1)
E 20.2203(a)(4)
E 50.73(a)(2)(iiXB)
El 50.73(aX2)(viii)(B) 0 20.2203(a)(2)(i)
El 50.36(c)(1)(iXA)
El 50.73(a)(2)(iii) 0l 50.73(aX2)(ix)(A)
- 10. POWER LEVEL 0 20.2203(a)(2)(ii)
[0 50.36(c)(1jXiiA) 0 50.73(a)(2)(iv)(A)
El 50.73(aX2)(x) 0l 20.2203(a)(2Xiii)
E] 50.36(c)(2) 0 50.73(a)(2)(v)(A)
El 73.71(aX4) 55 percent ED 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
E 50.73(a)(2)(v)(B) a 73.71(a)(5)
E0 20.2203(a)(2Xv) 0 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
Cl OTHER Specify in Abstract below 0E 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
E 50.73(a)(2)XvXD) orin NRC Forn 366A
- 12. LICENSEE CONTACT FOR THIS LER TELEPHONE NUMBER (Inducle Area Code)
Kenneth Russell, Compliance Engineer, Regulatory Compliance 1(440) 280- 5580CAUSE SYSTEM COMPONENT MANU-REPORTABLE
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- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR aYES (ifyes, complete EXPECTED SUBMISSION DATE).
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On December 23, 2004, at 2345 hours0.0271 days <br />0.651 hours <br />0.00388 weeks <br />8.922725e-4 months <br />, both reactor recirculation system (RRC) pumps at the Perry Nuclear Power Plant (PNPP) unexpectedly downshifted from fast to slow speed. At the time of RRC pump speed downshift, the plant was stable in Operational Condition I at 100 percent rated thermal power. Reactor power decreased to about 44 percent and then gradually increased to 55 percent rated thermal power. The power and flow reduction placed the plant in the immediate exit region of the power-flow map. At 2354 hours0.0272 days <br />0.654 hours <br />0.00389 weeks <br />8.95697e-4 months <br /> a reactor scram occurred due to core oscillations being detected by the oscillation power range monitor (OPRM). All control rods fully inserted.
The cause of the scram was determined to be a reactor protection system scram signal initiated from the OPRM per design and appropriate for the plant conditions. Troubleshooting of the RRC system pump speed downshift initially identified the probable cause to be a faulty card in the RRC pump control circuit.
However, following a subsequent similar RRC pump downshift on January 6, 2005, the cause was determined to be an optical isolator intermittent failure as a result of an inadequate surge suppression network in the control circuit for the RRC pumps (See PNPP LER 2005-001).
This event is being reported under requirements of 10 CFR 50.73(a)(2)(iv), any event or condition that resulted in manual or automatic actuation of any of the specified systems.
NRC FORM 366 (6-2004)
(if more space is required, use additional copies of NRC Forn 366A)
I. INTRODUCTION
On December 23, 2004, at 2345 hours0.0271 days <br />0.651 hours <br />0.00388 weeks <br />8.922725e-4 months <br />, both reactor recirculation system (RRC) pumps [AD]
at the Perry Nuclear Power Plant (PNPP) unexpectedly downshifted from fast to slow speed.
Prior to the RRC pump speed downshift, the plant was stable in Operational Condition 1 at 100 percent rated thermal power. The reactor pressure vessel (RPV) was at 1020 psig and saturated conditions. Following the downshift, at 2354 hours0.0272 days <br />0.654 hours <br />0.00389 weeks <br />8.95697e-4 months <br /> a reactor scram occurred due to core oscillations being detected by the Oscillation Power Range Monitor (OPRM)[JC]. At the time of the scram, the plant was at approximately 55 percent rated thermal power. All control rods fully inserted as a result of the scram signal.
The primary purpose of the RRC system is to provide forced circulation through the reactor core to achieve full power operation and permit variations in power level without control rod movement. Control interlocks are provided for RRC pumps to automatically downshift the pump from fast to slow speed. These controls are provided to prevent cavitation in RRC system components and mitigate the effects of various operational transients on reactor water level and reactivity. The OPRMs are designed to detect reactor core power oscillations and suppress the oscillations by providing a trip signal to the reactor protection system, which results in a reactor scram.
On December 24, 2004, at 0307 hours0.00355 days <br />0.0853 hours <br />5.076058e-4 weeks <br />1.168135e-4 months <br />, the required non-emergency four-hour notification was made to the NRC pursuant to the requirements of 1 OCFR50.72(b)(2)(iv)(B), reactor protection system actuation while critical (NRC Event 41290). This event is being reported under the requirements of 1 OCFR50.73(a)(2)(iv), any event or condition that resulted in manual or automatic actuation of any of the specified systems.
II. EVENT DESCRIPTION
At 2345 hours0.0271 days <br />0.651 hours <br />0.00388 weeks <br />8.922725e-4 months <br /> on December 23, 2004, both RRC pumps A and B unexpectedly transferred from fast to slow speed. At the time of RRC pump speed downshift, the plant was stable in Operational Condition 1 at 100 percent rated thermal power. After the downshift, reactor power stabilized at about 44 percent and then gradually increased to about 55 percent rated thermal power. The power and flow reduction placed the plant in the immediate exit region of the power-flow map. In this region, the reactor core is susceptible to power oscillations. At 2346 hours0.0272 days <br />0.652 hours <br />0.00388 weeks <br />8.92653e-4 months <br />, off-normal instruction, "Unplanned Change in Reactor Power or Reactivity," was entered. At 2348 hours0.0272 days <br />0.652 hours <br />0.00388 weeks <br />8.93414e-4 months <br /> the first OPRM alarm was annunciated and subsequently cleared.
The magnitude of the core power oscillations detected by the OPRM instrumentation was not observable to operators monitoring reactor power on the control room instrumentation. The OPRM alarm came in three additional times at 2351, 2352 and 2354 hours0.0272 days <br />0.654 hours <br />0.00389 weeks <br />8.95697e-4 months <br /> also with no observable power oscillations.
At 2354 hours0.0272 days <br />0.654 hours <br />0.00389 weeks <br />8.95697e-4 months <br /> a reactor scram occurred due to OPRM trip signals. All control rods fully inserted. The operators properly entered, off-normal instruction, "Reactor SCRAM". The operators also correctly entered plant emergency instruction, "Reactor Pressure Vessel Control" when the reactor vessel level momentarily decreased as expected below Level 3 (178 inches above the top of active fuel) due to void collapse. Level was restored by the (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (if more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (if more space is required, use additional copies of NRC Form 366A)
VI. PREVIOUS SIMILAR EVENTS
Manual Scram due to unexpected Reactor Recirculation Pump downshift, LER 1993-015.
This manual scram was initiated in accordance with procedures in effect at that time when entering the power-to-flow region of core instability. The cause of the downshift was a failure of both RRC pump suction resistance thermal detectors, which is not similar to the January 6, 2005 event. Optical isolators were specifically evaluated as not being the cause.
Manual Scram due to unexpected Reactor Recirculation Pump downshift, LER 1994-002.
This manual scram was initiated in accordance with procedures in effect at that time when entering the power-to-flow region of core instability. The cause of the downshift was a failure of a K1 relay on an alarm card, which is not similar to the January 6, 2005 event.
Automatic Scram following unexpected Reactor Recirculation Pump downshift, LER 2001-005. This automatic scram occurred following a high reactor pressure vessel water level that was initiated by a RRC pump downshift. The cause of the downshift was a failure of a feedwater system level summer card, which is not similar to the January 6, 2005 event.
The corrective actions from the above events would not have precluded occurrence of this event.
Automatic Scram following unexpected Reactor Recirculation Pump downshift, LER 2004-002. This automatic scram occurred due to an oscillation power range monitor (OPRM ) actuation. The cause of the downshift was thought to be a failed low feedwater flow or low reactor water level sensing card. The subsequent pump downshift, which occurred on January 6, 2005, was determined to be due to a failed optical isolator, which was also subsequently determined to be the cause for the prior pump downshift on December 23, 2004.
Although the cause of the downshift was the same, the corrective actions for the OPRM scram were judged effective since the correct operator actions were in progress to exit the immediate exit region of the power to flow map. No OPRM alarms were received indicating that an automatic scram was unlikely to have reoccurred. The RRC pump tripped to off, causing the control room crew to manually scram the reactor in this event.
Energy Industry Identification System Codes are identified in the text as [XX].