05000416/LER-2011-001, Re High Pressure Core Spray (HPCS) Failure Due to Failed Test Equipment
| ML111320547 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 05/12/2011 |
| From: | Perino C Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GNRO-2011/00028 LER 11-001-00 | |
| Download: ML111320547 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2) |
| 4162011001R00 - NRC Website | |
text
~Entergy GNRO-2011/00028 May 12, 2011 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555-0001
SUBJECT:
LER 2011-001-00 High Pressure Core Spray (HPCS)
Inoperability - Failure Due To Failed Test Equipment Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 License No. NPF-29
Dear Sir or Madam:
Attached is Licensee Event Report (LER) 2011-001-00 which is a final report. This report is submitted in accordance with 10 CFR 73(a)(2)(v)(D).
This letter does not contain any commitments. Should you have any questions regarding the attached report, please call Christina L. Perino at 601-437-6299.
Respectfully, CLP/JAS Attachments:
1.
Licensee Event Report (LER) 2011-001-00
cc:
NRC Resident Insoec~tor Grand Gulf Nuclear Station Port Gibson, MS 39150 U. S. Nuclear Regulatory Commission ATTN: Mr. A. B. Wang, NRR/DORL (w/2)
ATTN: ADDRESSEE ONLY ATTN: Courier Delivery Only Mail Stop OWFN/8 B1 11 Rockville Pike Rockville, MD 20852-2378 cc:
NRC Resident Insoec~tor Grand Gulf Nuclear Station Port Gibson, MS 39150 U. S. Nuclear Regulatory Commission ATTN: Mr. A. B. Wang, NRR/DORL (w/2)
ATTN: ADDRESSEE ONLY ATTN: Courier Delivery Only Mail Stop OWFN/8 B1 11 Rockville Pike Rockville, MD 20852-2378
Attachment To GNRO-2011/00028 Licensee Event Report (LER) 2011-001-00
- 1. FACILITY NAME Grand Gulf Nuclear Station, Unit 1 LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
NRC FORM 366 (10-2010)
U.S. NUCLEAR REGULATORY COMMISSION
- 2. DOCKET NUMBER 05000416
- 3. PAGE 1 OF 4
- 4. TITLE High Pressure Core Spray (HPCS) Failure Due To Failed Test Equipment
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED NUMBER DOCKET N/A N/A all that apply) 50.73(a)(2)(vii) o 50.73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) 50.73(a)(2)(ix)(A) 50.73(a)(2)(x) 73.71 (a)(4) 73.71(a)(5)
OTHER Specify in Abstract below or in D.
Cause of Occurrence
- 2. DOCKET 05000416
- 6. LER NUMBER YEAR I SEQUENTIAL I NUMBER 2011 001 00 REV.
NO.
- 3. PAGE 30F4 The repeated cycling of the valve open and closed and the resulting surge currents created excessive heat in the circuit breaker instantaneous trip and overload circuits. The condition caused the failure of the motor overload relay circuit to trip and also resulted in breaker setpoint drift. This resulted in the single train system being inoperable.
The root cause of the failure was a power failure in the current calibrator test equipment used in performance of the HPCS System Flow Rate Low (Bypass) Functional Test. The loss of power was due to exhaustion of the batteries powering the unit.
The contributing factor was the lack of procedural guidance requiring new batteries or use of the AC power source.
Corrective Actions
Immediate Actions 1)
A replacement breaker was obtained, tested and installed.
2)
Valve 1E22F012 was retested after breaker replacement.
The corrective actions for the contributing cause are:
Procedure 06-IC-1 E22-Q-0004 was revised to require either use of new batteries or AlC power when using the current calibrators Clarify what value of milliamp direct current (madc) to input when using the current calibrator The corrective actions were completed as required by the GGNS Corrective Action Program under CR-GGN-2011-1902.
E.
Safety Assessment
According to the GGNS Technical Specification Bases, the High Pressure Core Spray (HPCS) is part of the Emergency Core Cooling Systems (ECCS). The ECCS is designed, in conjunction with the primary and secondary containment, to limit the release of radioactive materials to the environment following a loss of coolant accident (LOCA). The ECCS uses two independent methods (flooding and spraying) to cool the core during a LOCA. The ECCS network is composed of the High Pressure Core Spray (HPCS) System, the Low Pressure Core Spray (LPCS) System, and the low pressure coolant injection (LPCI) mode of the Residual Heat Removal (RHR) System.
The ECCS also consists of the Automatic Depressurization System (ADS). The suppression pool provides the required source of water for the ECCS. The design basis of the HPCS System is to provide core cooling over a wide range of RPV pressures (0 psid to 1177 psid, vessel to suction source). Upon receipt of an initiation signal, the HPCS pump automatically starts approximately 10 seconds after AC power is available and valves in the flow path begin to open. Since the HPCS System is designed to operate over the full range of expected RPV pressures, HPCS flow begins as soon as the necessary valves are open. The TS Bases also states that the ECCS System satisfies Criterion 3 of the NRC Policy Statement. This means that it is considered to be a part of the primary success path which functions to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier.
F.2. DOCKET 05000416
- 6. LER NUMBER YEAR I SEQUENTIAL I NUMBER 2011 -- 001 00 REV.
NO.
- 3. PAGE 40F 4 The HPCS t:>yt:>ll:::lll was inoperable and incapable of performing its design function for approximately 15.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. The GGNS UFSAR states that in the event of a HPCS system failure such that HPCS cannot maintain the reactor water level, the automatic depressurization system, which is independent of any other ECCS, reduces the reactor pressure so that flow from LPCI and LPCS systems enters the reactor vessel in time to cool the core and limit fuel cladding temperature.
Additionally, high pressure makeup was available from the reactor core isolation cooling (RCIC) system. Two of three divisions of emergency core cooling systems (ECCS) are required for the GGNS loss of coolant accident"'::::::.:y::;~::;. While HPCS was out of service, Division 1 and Division 2 ECCS t:>yt:>ll:::lllt:> and the automatic depressurization system were operable, and would have met the ECCS performance criteria of 10CFR50.46. The out of service time was maintained within the limits of GGNS technical specifications, thereby minimizing any safety significance of this event.
G.
Additionallnformation Previous Occurrences - There has not been any occurrence of an HPCS event or condition in the past two years at Grand Gulf Nuclear Station involving reportability under 10CFR50.73(a)(2)(D) or involving these same conditions.
The corrective action response addressed the extent of the cause of this event. HPCS is a single train system.