05000410/LER-2013-004, Regarding Manual Reactor Protection System Actuation Due to Loss of Reactor Recirculation Flow
| ML14043A091 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 01/31/2014 |
| From: | John Stanley Constellation Energy Nuclear Group, EDF Group, Nine Mile Point |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 13-004-00 | |
| Download: ML14043A091 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 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)(B), System Actuation |
| 4102013004R00 - NRC Website | |
text
James J. Stanley Plant General Manager Office: 315-349-5205 Fax: 315-349-1321 E-mail: James.Stanley@cengllc.com CENG.
a joint venture of ConsteDation 64,% tnf Energy ON NINE MILE POINT.
NUCLEAR STATION January 31, 2014 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION:
SUBJECT:
Document Control Desk Nine Mile Point Nuclear Station Unit 2 Renewed Facility Operating License No. NPF-69 Docket No. 50-4 10 Licensee Event Report 2013-004, Manual Reactor Protection System Actuation due to Loss of Reactor Recirculation Flow In accordance with 10 CFR 50.73(a)(2)(iv)(A), please find attached Licensee Event Report 2013-004, Manual Reactor Protection System Actuation due to Loss of Reactor Recirculation Flow.
There are no regulatory commitments in this submittal.
Should you have questions regarding the information in this submittal., please contact Everett (Chip)
Perkins, Director Licensing, at (315) 349-5219.
Sincerely, JJS/KJK
Attachment:
Licensee Event Report 2013-004, Manual Reactor Protection System Actuation due to Loss of Reactor Recirculation Flow cc:
NRC Project Manager NRC Resident Inspector NRC Regional Administrator Nine Mile Point Nuclear Station, LLC P.O. Box 63, Lycoming, NY 13093 66
ATTACHMENT LICENSEE EVENT REPORT 2013-004 MANUAL REACTOR PROTECTION SYSTEM ACTUATION DUE TO LOSS OF REACTOR RECIRCULATION FLOW Nine Mile Point Nuclear Station, LLC January 31, 2014
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010i
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 13. PAGE Nine Mile Point Unit 2 05000410(
1 OF 5
- 4. TITLE Manual Reactor Protection System Actuation due to Loss of Reactor Recirculation Flow
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR NA NA NUMBER NO.
NA NA FACILITY NAME DOCKET NUMBER 12 2
2013 2013 004 00 1
31 2014 NA NA
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
El 20.2201(b)
[I 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii)
El 20.2201(d)
[I 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
[I 50.73(a)(2)(viii)(A)
[I 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
[I 50.73(a)(2)(viii)(B)
- 10. POWER LEVEL I] 20.2203(a)(2)(i)
[I 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
El 20.2203(a)(2)(ii)
[I 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4) 025 El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in 0904 A manual reactor scram is initiated when the recirculation pumps did not restart and the loss of recirculation flow condition was not corrected.
1046 One recirculation pump restarted in slow speed.
1048 Second recirculation pump restarted in slow speed.
E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
There were no other systems or secondary functions affected.
F.
METHOD OF DISCOVERY
This event was discovered when operators observed the loss of recirculation flow condition in the control room.
G. MAJOR OPERATOR ACTION:
Upon discovery of the loss of recirculation flow condition, operators attempted to restart the LFMGs manually. The LFMGs were able to be started manually, but the output breakers did not close and the recirculation system pumps did not start in slow speed due to the required speed of the recirculation system pumps being too low. The reactor was manually scrammed in accordance with plant procedures.
H. SAFETY SYSTEM RESPONSES:
Following initiation of the manual scram, all control rods fully inserted. No other operational conditions requiring the response of safety systems occurred as a result of this event.
II. CAUSE OF EVENT
Both reactor recirculation pumps failed to downshift due to high resistance connection(s) in the auto transfer circuits, associated with switches SOIA and SI01B. This caused the auto transfer relays K121A and K 121B to not actuate during the reactor recirculation high to low speed transfer.
The industry guidance is that hand switches are exempt from the AP-913 process as defects could be found during routine surveillance and rotation of equipment activities and the equipment repaired without generating scrams or adversely impacting plant operations. Oxidation of contacts that occurs naturally over time would be addressed by the periodic cycling of the switches (luring surveillance and equipment rotation activities as well. This assumption should not have been applied in the case of reactor recirculation switches SOIA and S I01B as they are only cycled during plant startup, power ascension, and down-power activities to less than 40% which may only occur once every two years.
The infrequent operation of these switches led to buildup of oxidation or other non-conductive material on the contacts resulting in a latent failure of the switches. Preventive maintenance on control switches SlO0A and SIO0B, be it regularly cycling the switch or cleaning the contacts, is not possible due to the plant impact and physical location of the switch.
NRC FORM 366 (10-2010)
The root cause of this event is a failure to identify that the control switches for the reactor recirculation pump IA and pump 1B motor breaker control (switches S101A and S101B respectively) are single point vulnerable (SPV) components because they were exempted from the AP-913 classification process. Since the switches were not classified as SPV components no mitigation strategies were developed. The complex design in place for the reactor recirculation pumps control circuitry combined with the application of industry guidance associated with hand switches resulted in a failure to identify the switches as SPV components.
This event has been entered into the Nine Mile Point Nuclear Station corrective action program as condition report number CR-2013-009735.
III. ANALYSIS OF THE EVENT
There were no actual nuclear safety consequences associated with this event. This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in manual or automatic actuation of any of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). The Reactor Protection System is listed in 10 CFR 50.73(a)(2)(iv)(B).
The plant transient that occurred is similar to the Trip of Two Reactor Recirculation Pumps transient described in Updated Safety Analysis Report (USAR), Chapter 15, Section 15.3, "Decrease in Reactor Coolant System Flow Rate." The December 2, 2013 recirculation pump transient was bounded by the USAR described transient assumed to occur at more limiting high power conditions. The transient described in the USAR is terminated by the Reactor Pressure Vessel (RPV) level 8 (L8) trip and subsequent turbine trip resulting in a reactor scram. In the actual transient, operator action was taken prior to any adverse trends in reactor water level being noted. During this event the Mode Switch was placed in shutdown in accordance with procedure N2-SOP-29, "Sudden Reduction in Core Flow." The USAR described transient describes reactor vessel water level control through the use of High Pressure Core Spray (HPCS) or Reactor Core Isolation Cooling (RCIC) systems. Reactor vessel water level was controlled by the operators by lowering pressure and using the condensate booster pumps. The use of HPCS or RCIC was not required. During the transient, a subsequent reactor scram signal was received on low reactor water level (L3). This is an expected signal due to water level shrink. One recirculation pump was restarted in slow speed at 1046, 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 43 minutes after the loss of recirculation flow, and the second recirculation pump was restarted at 1048. These actions are more conservative than those covered in the USAR; therefore this transient is fully bounded by the event analysis per USAR section 15.3.
Based on the above discussion, it is concluded that the safety significance of this event is low and the event did not pose a threat to the health and safety of the public or plant personnel.
This event affects the NRC Regulatory Oversight Process (ROP) Index for Unplanned Scrams. Due to this scram, the Unplanned Scrams Index value will be 0.8 compared to the Green-to-White threshold value of greater than 3. This reduction will not result in entry into the Increased Regulatory (White)
Response Band.
NRC FORM 366 (10-2010)
IV. CORRECTIVE ACTIONS
A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:
I.
Cleaned the contacts on the control switch.
B.
ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
- 1.
Revised the operating procedure to start the LFMG sets using their respective control switches prior to initiating the reactor recirculation downshift logic, and to install a temporary jumper to defeat the automatic transfer relay from preventing the high-speed to low-speed transfer.
- 2.
Revise the operating procedure, to include guidance to cycle the 5101A and/or S101B switches if LFMG transfer does not immediately occur.
V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
There were no other failed components that contributed to this event.
B. PREVIOUS LERs ON SIMILAR EVENTS:
There have been no previous similar LERs for NMP2.
C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:
COMPONENT IEEE 803 FUNCTION IDENTIFIER IEEE 805 SYSTEM IDENTIFICATION SBM Type Control Switch Low Frequency Motor Generator Reactor Recirculation Pump Automatic Transfer Relay Reactor Recirculation System High Pressure Core Spray System Reactor Core Isolation Cooling System D. SPECIAL COMMENTS:
None HS MG P
83 NA NA NA AD AD AD AD AD BG BN NRC FORM 366 (10-2010)