05000313/LER-2010-001, Regarding Main Steam Safety Valves Not within Limits Due to Seat Bonding and Transient-Induced Drift Resulting in a Condition Prohibited by Technical Specifications
| ML101370245 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/14/2010 |
| From: | David Bice Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 1CAN051001 LER 10-001-00 | |
| Download: ML101370245 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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)(iv)(A), System Actuation 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 |
| 3132010001R00 - NRC Website | |
text
1CAN051001 May 14, 2010 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
Subject:
Licensee Event Report 2010-001-00 Arkansas Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51
Dear Sir or Madam:
In accordance with 10 CFR 50.73(a)(2)(i)(B), attached is the subject report concerning main steam safety valve testing.
There are no new commitments contained in this submittal. If you have any questions or require additional information, please contact me.
Sincerely, DBB/nbm Enclosure Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR 72802 Tel 479-858-4710 David B. Bice Acting Manager, Licensing Arkansas Nuclear One
1CAN051001 Page 2 of 2 cc:
Elmo Collins Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339-5957 LEREvents@inpo.org
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
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- 3. PAGE Arkansas Nuclear One, Unit 1 05000313 1
OF 4
- 4. TITLE Multiple Main Steam Safety Valves not within Limits due to Seat Bonding and Transient-Induced Drift resulting in a Condition Prohibited by Technical Specifications
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 03 18 2010 2010 - 001 - 00 05 14 2010
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 1 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C) 100 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
OTHER-Specify in Abstract below or in
E. Safety Significance
The secondary side pressurization analyses assume a full-power turbine trip coincident with loss of the condensate heat sink to establish the required MSSV relief capacity. The design basis of the MSSVs is to limit secondary system pressure to <110% of design pressure. The setpoint of the normally highest set MSSVs, including the +3% tolerance, is 1133 psig. Only one of the setpoints found during the testing was above this allowable setpoint, that being the as-found setpoint of PSV-2691. Since TS 3.7.1 requires only seven of the eight MSSVs on each main steam line to be operable, this condition would not prevent the MSSVs from performing the associated specified safety function of overpressure protection.
In addition to secondary side pressurization analyses, the MSSVs are credited in the safety analysis report (SAR). The Chapter 14 SAR events that assume availability of the MSSVs are those characterized by decreased heat removal events and include loss of load, loss of all alternating current (AC) power, steam generator tube rupture (SGTR), and small-break loss-of-coolant accident (SBLOCA). These safety analysis events could be negatively impacted, if a MSSV lift setpoint drifts greater than -3% from its nominal setpoint; therefore, the MSSV lift setpoints found to be outside of the
- - 3% tolerance during testing were evaluated for impact on these safety analyses.
The loss of load transient assumes that steam is relieved from the MSSVs and through the condenser via turbine bypass. After turbine runback, excess steam is relieved to the atmosphere via the MSSVs until the once-through steam generator [SG] (OTSG) pressure drops below the setpoint of the lowest set MSSV. In the loss of all AC power transient described in the SAR, the plant trips, the condenser is lost, and the operator utilizes the atmospheric dump valves as a method of heat removal. Excess steam is also released via the MSSVs until pressure is reduced below the lowest setpoint utilizing the atmospheric dump valves. The SGTR assumes release of secondary inventory through the MSSVs until the ruptured OTSG is depressurized below the lowest set MSSV and is isolated. The SBLOCA analysis assumes that the OTSGs are removing heat from the core at a saturation pressure consistent with the MSSV having the lowest lift setting.
The safety analyses have a common input in that the setpoint of the MSSV with the lowest lift setting is limiting; therefore, the two MSSVs having an as-found setpoint greater than +3% of their nominal setpoint have no impact on these safety analyses. None of the setpoints identified during the testing were below the allowable setpoint of the MSSV having the lowest setpoint; therefore, these valves additionally had no impact on the subject analyses. Therefore, the loss of load, loss of all AC power, SGTR, and SBLOCA results remained valid for the given condition.
Based on the above, the MSSVs would have performed their specified safety function and would have operated accordingly such that no safety analysis bases would have been invalidated.
F. Basis for Reportability The affected MSSVs discovered OOT is reportable under 10CFR50.73(a)(2)(i)(B) as a condition prohibited by TS that existed during plant operation. Guidance provided in NUREG-1022 states that the existence of similar discrepancies in multiple valves is an indication that the discrepancies may well have arisen over a period of time; therefore, the condition existed during plant operation and the event is reportable under 10CFR50.73(a)(2)(i)(B) as operation prohibited by TS.
G. Additional Information
There was one other previous similar event reported as LER-2002-001-00 for ANO-1 in which the lift settings of eight of the 16 MSSVs were OOT. Potential failure modes were spring relaxation, seat bonding, excessive spindle run out, a change to a different type of test device, and steam header pressure oscillations during the testing.
Energy Industry Identification System (EIIS) codes are identified in the text as [xx].