05000528/LER-2006-006, Re Reactor Trip Due to Core Protection Calculator Generated Low Departure from Nuclear Boiling Ratio (DNBR) Trip Signal

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Re Reactor Trip Due to Core Protection Calculator Generated Low Departure from Nuclear Boiling Ratio (DNBR) Trip Signal
ML063610346
Person / Time
Site: Palo Verde Arizona Public Service icon.png
Issue date: 12/18/2006
From: Eubanks C
Arizona Public Service Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
105-05612-CE/SAB/DJS LER 06-006-00
Download: ML063610346 (6)


LER-2006-006, Re Reactor Trip Due to Core Protection Calculator Generated Low Departure from Nuclear Boiling Ratio (DNBR) Trip Signal
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)(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

10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
5282006006R00 - NRC Website

text

10 CFR 50.73 L A LM A

subsidiary of Pinnacle West Capital Corporation Cliff Eubanks Mail Station 7602 Palo Verde Nuclear Vice President Tel (623) 393-6116 PO Box 52034 Generating Station Nuclear Operations Fax (623) 393-6077 Phoenix, Arizona 85072-2034 102-05612-C E/SAB/DJS December 18, 2006 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Dear Sirs:

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit I Docket No. STN 50-528 License No. NPF 41 Licensee Event Report 2006-006-00 Attached please find Licensee Event Report (LER) 50-528/2006-006-00 prepared and submitted pursuant to 10 CFR 50.73. This LER is being submitted to report a reactor protection system (RPS) initiated reactor trip which occurred on October 21, 2006 at approximately 15:49 Mountain Standard Time (MST).

In accordance with 10 CFR 50.73(d), copies of this LER are being forwarded to the NRC Regional Office, NRC Region IV and the PVNGS Senior Resident Inspector. If you have questions regarding this submittal, please contact James A. Proctor, Section Leader, Regulatory Affairs, at (623) 393-5730. Arizona Public Service Company makes no commitments in this letter.

Sincerely, CE/SAB/DJS/gt Attachment cc:

B. S. Mallett NRC Region IV Regional Administrator M. B. Fields NRC NRR Project Manager G. G. Warnick NRC Senior Resident Inspector for PVNGS A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway e Comanche Peak

  • Diablo Canyon e

Palo Verde South Texas Project

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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007

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, the NRC may sfor each block) not conduct or sponsor, and a person is not required to respond to, the digits/characters finformation collection.

13. PAGE Palo Verde Nuclear Generating Station (PVNGS) Unit 1 05000528 1 OF 5
4. TITLE Reactor trip due to Core Protection Calculator generated Low Departure from Nuclear Boiling Ratio (DNBR) trip signal
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE 1
8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FAITYNMDOKTUBE NUMBER NO.

05000 FACILITY NAME DOCKET NUMBER 10 21 2006 2006

- 006 -

00 12 18 2006 05000 D. OPERATING MODE

11. THIS REPORT IS SUBMITrED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)

El 20.2201(b)

El 20.2203(a)(3)(i)

El 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii)

El 20.2201(d)

El 20.2203(a)(3)(ii)

[I 50.73(a)(2)(ii)(A)

El 50.73(a)(2)(viii)(A)

[I 20.2203(a)(1)

El 20.2203(a)(4)

[I 50.73(a)(2)(ii)(B)

El 50.73(a)(2)(viii)(B)

El 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)

10. POWER LEVEL

[] 20.2203(a)(2)(ii)

[E 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)

El 50.73(a)(2)(x)

[I 20.2203(a)(2)(iii)

El 50.36(c)(2) 0l 50.73(a)(2)(v)(A)

El 73.71(a)(4)

El 20.2203(a)(2)(iv)

El 50.46(a)(3)(ii)

El 50.73(a)(2)(v)(B)

El 73.71(a)(5) 100 [E 20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A)

El 50.73(a)(2)(v)(C)

E] OTHER El 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B)

[E 50.73(a)(2)(v)(D)

Specify in Abstract below or in (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)

Procedure (ARP) in use by the control room (CR) staff. The section for response to the Cross Channel Comparison Failure was very limited in its guidance, directing the CR staff to seek assistance from the Operations Computer Systems (OCS) technicians when an invalid alarm was identified. The section for response to a CEA deviation contained insufficient guidance for action to take for an invalid CEA deviation. The CR staff then waited for OCS to validate the alarm indication before taking action to remove the affected CEAC from service.

7.

CORRECTIVE ACTIONS

A CEA #29 cable connector was disconnected, visually inspected and re-connected. The problem cleared.

A night order was written for licensed operators to ensure that they are familiar with the guidance of the procedures required to facilitate prompt removal of a CEAC from service when a faulty input is identified.

The plant procedure (72AO-9SB01 CEAC INOPERABLE) was revised to provide guidance for Units with the upgraded CPCs, Palo Verde Units 1 and 2.

Any additional corrective actions taken as a result of this event will be implemented in accordance with Palo Verde's corrective action program.

8.

PREVIOUS SIMILAR EVENTS

In the past three years, Palo Verde reported one similar trip event.

Licensee Event Report (LER) 50-530/2006-002-00 reported an automatic Unit 3 Reactor Protection System (RPS) actuation (Reactor Trip) on Low DNBR due to Control Element Assembly Calculator (CEAC) # 1 penalty factor receiving an invalid input signal. The direct cause of the reactor trip was an erroneous position indication signal for CEA #60 as sensed by CEAC #1 due to a faulty CEA Positional Isolation Amplifier (CPIA) board. The probable cause of the CPIA board failure was a "random electronic failure" of the U6 operational amplifier. Corrective actions for this Unit 3 event would not have prevented the reactor trip in Unit 1.