05000275/LER-2012-002, Regarding Failure to Comply with Technical Specification 3.0.3 Time Requirement
| ML12129A105 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/07/2012 |
| From: | Becker J Pacific Gas & Electric Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| DCL-12-043 LER 12-002-00 | |
| Download: ML12129A105 (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 |
| 2752012002R00 - NRC Website | |
text
Pacific Gas and Electric Company May 7,2012 PG&E Letter DCL-12-043 James R. Becker Site Vice President Diablo Canyon Power Plant Mail Code 104/6 P. O. Box 56 Avila Beach, CA 93424 805.545.3462 Internal: 691.3462 Fax: 805.545.6445 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 10 CFR 50.73 Docket No. 50-275, OL-DPR-80 Diablo Canyon Unit 1 Licensee Event Report 1-2012-002: Failure to Comply with Technical Specification 3.0.3 Time Requirement Dear Commissioners and Staff; Pacific Gas and Electric Company (PG&E) is submitting the enclosed Licensee Event Report, in accordance with 10 CFR 50.73(a)(2)(i)(B), for the failure to initiate actions, within the 1-hour time requirement of Technical Specification (TS) 3.0.3, to place Unit 1 in a Mode in which the Limiting Condition for Operation does not exist.
On March 2, 2012, Rosemount Nuclear Instruments, Inc. issued a 10 CFR Part 21 notification that negatively affected the existing setpoint margin for multiple steam generator water-level channels resulting in plant operators declaring them inoperable. PG&E implemented immediate corrective actions to re-establish setpoint margins; however, the evolution took 3 minutes longer than the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> that is allowed by TS 3.0.3.
PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this report.
This event did not adversely affect the health and safety of the public.
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James R. Becker wrl8/50465488 Enclosure cc/:
Diablo Distribution cc/enc:
Elmo E. Collins, NRC Region IV Michael S. Peck, NRC Senior Resident Inspector Joseph M. Sebrosky, NRR Project Manager INPO A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway. Comanche Peak. Diablo Canyon. Palo Verde. San Onofre. South Texas Project. Wolf Creek
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Diablo Canyon Power Plant 05000-275 1 OF 5
- 4. TITLE Failure to Comply with Technical Specification 3.0.3 Time Requirement
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 03 08 2012 2012. 002. 00 05 07 2012
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) o 20.2201 (b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii) 1 o 20.2201 (d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4) o 50.73(a)(2)(ii)(B) o 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i) o 50.36(c)(1)(i)(A) o 50.73(a)(2)(iii) o 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL o 20.2203(a)(2)(ii) o 50.36(c)(1)(ii)(A) o 50.73(a)(2)(iv)(A) o 50.73(a)(2)(x) o 20.2203(a)(2)(iii)
B 50.36(c)(2) o 50.73(a)(2)(v)(A) o 73.71(a)(4) 100 o 20.2203(a)(2)(iv) 50.46(a)(3)(ii) o 50.73(a)(2)(v)(B) o 73.71(a)(5) o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C) o OTHER o 20.2203(a)(2)(vi) o 50.73(a)(2)(i)(B) o 50.73(a)(2)(v)(D)
Specify in Abstract below or in LICENSEE EVENT REPORT (LER)U,S, NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET
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- 6. LER NUMBER I
SEQUENTIAL I NUMBER 2012 002 REV NO.
00 3
- 3. PAGE OF 5
and immediately began preparing for a safe and controlled shutdown by placing a second charging pump in service and briefing the control room crew for ramp down, while simultaneously working toward a resolution of the negative transmitter setpoint margin.
TS LCO 3.0.3 states: "When an LCO is not met and the associated actions are not met, an associated action is not provided, or if directed by the associated actions, the unit shall be placed in a mode or other specified condition in which the LCO is not applicable. Action shall be initiated within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to place the unit, as applicable, in mode... "
DCPP staff evaluated a memorandum from Christopher 1. Grimes, Chief, NRC TS Branch, "Use of Shutdown Times for Corrective Maintenance (TIA 92-08)," dated December 11, 1992. This memo supports the delay of initiating plant shutdown actions during a TS LCO 3.0.3 entry to avoid unnecessary plant transients as long as plant safety is better served by the delay. The memo states: "If a licensee responsibly concludes that plant shutdown be delayed or corrective action can be accomplished so that an unnecessary plant transient can be avoided, we believe that such a decision is permitted as long as the shutdown times specified by the TS are observed, including the "default" (3.0.3) provision, and no violation should be imposed."
DCPP completed adjustment ofLT-517 at 1922 PST, restoring the functionality of the LT. To avoid an unnecessary plant transient, DCPP did not initiate shutdown action directed by TS LCO 3.0.3 within one hour ofTS LCO 3.0.3 entry. Instead, DCPP adjusted the stearn generator low-low level setpoint to 17 percent to recover margin and incorporate the additional uncertainty identified in the 10 CFR Part 21 report issued by Rosemount, restoring channel L T -517 to operable 3 minutes beyond the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> allowed.
C. Status of Inoperable Structures, Systems, or Components that Contributed to the Event None.
D. Other Systems or Secondary Functions Affected
This notification applied to various SG level transmitters on both Units 1 and 2; however, only Unit 1 SG 1-1 had two affected transmitters on one SG requiring entry into TS LCO 3.0.3.
E. Method of Discovery
Rosemount issued a 10 CFR Part 21 report (NRC EN 47693), announcing the potential 1154 Series H pressure transmitter safety hazards caused by incorrect transmitter accuracy specifications.
F. Operator Actions
Operators entered TS LCO 3.0.3 because the required actions ofTS LCOs 3.3.l and 3.3.2 did not apply to SG 1-1 as two of the three SG NR water level channels were affected by the Part 21 notification. Operators prepared for plant shutdown by organizing the necessary procedures, placing a second charging pump in service, and briefmg the Unit 1 control room crew on OP L-4, "Normal Operation at Power," which includes instructions for decreasing power.
LICENSEE EVENT REPORT (LER) u.s. NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET
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Operators took every action necessary to prepare for a safe and controlled shutdown at the completion of the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> allowed by TS LCO 3.0.3.
G. Safety System Responses None.
III. Cause of Problem Rosemount conducted a thorough investigation regarding the out-of-tolerance condition and determined that it was a result of the magnitude of a resistance change made to the transmitter temperature compensation circuitry during a final factory acceptance test.
IV. Assessment of Safety Consequences
DCPP concluded that the information presented in Rosemount's 10 CFR Part 21 report would not have prevented the SG low-low level signal from tripping the reactor as credited in the design-basis FLB accident analysis in FSARU Section 15.4.2.2.
The FLB, as analyzed in FSARU 15.4.2.2, is the limiting design-basis accident with respect to crediting the SG low-low level reactor trip function and evaluating the potential environmental error associated with the Rosemount Part 21 issue. The SG low-low level trip is designed to actuate early enough to ensure there is adequate remaining secondary side liquid inventory which in combination with the auxiliary feed water system provides adequate decay heat removal to maintain reactor coolant system and nuclear fuel integrity.
The FLB sequence of events in FSARU Table 15.4-8, "Time Sequence of Events for Major Secondary System Pipe Ruptures," shows that the SG low-low level reactor trip is actuated within 12 seconds after the FLB occurs. Design Calculation STA-237, "LOCA/MSLB Containment EG Envelope PIT Curves for RSGs," compiles the limiting pressure/temperature profile for a Main Steam Line Break (MSLB) inside containment (which bounds the FLB event) for environmental qualification (EQ) effects. The results in STA-237 Table 5, "EQ Envelope Pressure and Temperature Profiles," show that the containment air temperature could be as high as 317 degrees F in the first 10 to 20 seconds after the break occurs.
The design of the Rosemount transmitter housing would significantly delay the thermal heat-up of the internal components.
This was confirmed by review of the thermal lag evaluation performed for a Rosemount 1153H pressure transmitter as documented in STA-232. This calculation used the Generation of Thermal-Hydraulic Information for Containments (GOTHIC) computer code to evaluate the Rosemount transmitter heat-up when exposed to the limiting MSLB cases outside containment which due to superheated steam effects generates a more severe temperature profile than that inside containment. STA-232 Table 8-3 shows that at 30 seconds after the break, while the air temperature is at 319 degrees F, the Rosemount cover is only 203 degrees F and the air temperature inside the housing is only 148 degrees F. This confirms that the SG low-low level trip would already have actuated for the design basis FLB accident before the environmental temperature error effects could occur as identified in the Rosemount Part 21 report.
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In conclusion, the Rosemount Part 21 environmental error issue would not have prevented the SG low-low level signal from tripping the reactor as described in the FSARU.
V. Corrective Actions
DCPP concludes that no corrective actions are warranted for exceeding the I-hour time frame, as plant operators made a conscious decision to delay plant shutdown to avoid an unnecessary plant transient as described in NRC TIA 92-08.
Also, plant staffrecalibrated the transmitters within the I-hour time frame allowed by TS LCO 3.0.3, but operators needed additional time to complete necessary reviews and perform closeout actions to declare the transmitter channels operable. In response to the Rosemount Part 21 Issue, DCPP replaced the level transmitters for Unit 1 and intends to replace the level transmitters for Unit 2 at the next available outage of sufficient duration.
VI. Additional Information
A. Failed Components None.
B. Previous Similar Events
On August 17,2009, Pacific Gas and Electric Company submitted DCL-09-059, "Licensee Event Report 2-2009-001-00, Technical Specification 3.0.3 One Hour Exceeded Due to Failure of Group Step Counters," to the NRC in accordance with 10 CFR 50.73(a)(2)(i)(B). The cause of this event was inappropriate maintenance schedule and priority to replace the group demand counter batteries prior to failure. The corrective actions for this event were not relevant to the TS 3.0.3 entry reported in this Licensee Event Report.
C. Industry Reports None