05000260/LER-2009-006, Automatic Reactor Protection System Scram While Shutdown

Automatic Reactor Protection System Scram While Shutdown

ML093030282
Person / Time
Site:	Browns Ferry
Issue date:	10/27/2009
From:	West R Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 09-006-00
Download: ML093030282 (6)

LER-2009-006, Automatic Reactor Protection System Scram While Shutdown

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), 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
2602009006R00 - NRC Website

text

Tennessee Valley Authority, Post Office Box 2000, Decatur, Aiabama 35609-2000 October 27, 2009 10 CFR 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Browns Ferry Nuclear Plant Unit 2 Facility Operating License No. DPR-52 NRC Docket No. 50-260

Subject:

Licensee Event Report (LER) 50-260/2009-006 The enclosed Licensee Event Report (LER) provides details of an automatic Reactor Protection System scram while shutdown. At the time of the event Operations personnel believed the event to not be reportable due to the understanding of guidance provided in NUREG-1022, Event Reporting Guidelines 10 CFR 50.72 and 50.73. Station management reviewed the event and initially agreed with operations personnel that the event was not reportable. Subsequent to further review, TVA concluded that this event should have been reported. This resulted in the LER being submitted late. TVA is reporting this in accordance with 10 CFR 50.73(a)(2)(iv)(A), as an event that resulted in a manual or automatic actuation of the systems listed in paragraph 10 CFR 50.73(a)(2)(iv)(B) (i.e, Reactor Protection System including reactor scram or trip).

There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact F. R. Godwin, Site Licensing and Industry Affairs Manager, at (256) 729-2636.

R estfully, R. G. West Vice President cc: See page 2

\\JIaR

U.S. Nuclear Regulatory Commission Page 2 October 27, 2009 Enclosure cc (Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 08/31/2010 (9-2007)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE Browns Ferry Unit 2 05000260 1 of 4

4. TITLE: Automatic Reactor Protection System Scram While Shutdown

6. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED TR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER SEQNUMBER NO.

None N/A FACILITY NAME DOCKET NUMBER 05 25 2009 2009 006 00 10 27 2009 None N/A

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 0J 20.2201(b)

L0 20.2203(a)(3)(i)

L0 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii) 5i 20.2201(d) 0i 20.2203(a)(3)(ii) 0i 50.73(a)(2)(ii)(A)

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

EL 20.2203(a)(1)

Di 20.2203(a)(4) 0i 50.73(a)(2)(ii)(B) 0i 50.73(a)(2)(viii)(B) 0_ 20.2203(a)(2)(i) 0i 50.36(c)(1)(i)(A) 0i 50.73(a)(2)(iii)

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

10. POWER LEVEL 0i 20.2203(a)(2)(ii) 0i 50.36(c)(1)(ii)(A)

[

50,73(a)(2)(iv)(A) 0i 50.73(a)(2)(x) 0i 20.2203(a)(2)(iii) 0i 50.36(c)(2)

Li 50.73(a)(2)(v)(A)

[1 73.71 (a)(4) o 20.2203(a)(2)(iv) 0L 50.46(a)(3)(ii)

Li 50.73(a)(2)(v)(B) 0i 73.71(a)(5) 0 0

20.2203(a)(2)(v) 0i 50.73(a)(2)(i)(A) 0i 50.73(a)(2)(v)(C)

L OTHER Specify in Abstract belew er in NRC Li 20.2203(a)(2)(vi)

Li 50.73(a)(2)(i)(B)

Li 50.73(a)(2)(v)(D)

Fpein Ab

12. LICENSEE CONTACT FOR THIS LER NAME TELEPHONE NUMBER (Include Area Code)

Deborah Bentzinger, Licensing Engineer 256-729-7533CAUSE SYSTEM COMPONENT MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX

14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEAR SUBMISSION El YES (Ifyes, complete 15. EXPECTED SUBMISSION DATE)

NO DATE N/A N/A N/A ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On May 24, 2009, with Unit 2 in a refueling outage and all rods fully inserted, at approximately 0232 hours0.00269 days <br />0.0644 hours <br />3.835979e-4 weeks <br />8.8276e-5 months <br /> Central Daylight Time (CDT), Operations personnel inserted a "B" channel half scram to support a contactor maintenance work activity. At approximately 0247 hours0.00286 days <br />0.0686 hours <br />4.083995e-4 weeks <br />9.39835e-5 months <br /> CDT, Operations received an "A" channel half scram and a Reactor Protection System (RPS) actuation (full scram). The RPS actuation occurred when a fuse was removed from the circuit that supplied power to the contact that bypassed a high level scram signal from the scram discharge volume (SDV). At the time of the occurrence, the SDV had been isolated and was full due to an in-progress surveillance. As a result, with the bypass removed, a reactor scram signal was generated, which lead to an RPS actuation (full scram).

NRC FORM 366 (6-2004)

I. PLANT CONDITION(S)

Prior to the event, Unit 2 was shutdown in Mode 5 and in a refueling outage and Units 1 and 3 were in operating in Mode 1 at 100 percent thermal power (approximately 3458 megawatts thermal).

Units 1 and 3 were unaffected by the event.

II. DESCRIPTION OF EVENT

A. Event:

On May 24, 2009, with Unit 2 in a refueling outage and all rods fully inserted, at approximately 0232 hours0.00269 days <br />0.0644 hours <br />3.835979e-4 weeks <br />8.8276e-5 months <br /> Central Daylight Time (CDT), Operations personnel inserted a "B" channel half scram to support a maintenance work activity on the Reactor Protection System Contactor Relay. At approximately 0247 hours0.00286 days <br />0.0686 hours <br />4.083995e-4 weeks <br />9.39835e-5 months <br /> CDT, Operations received an "A" channel half scram and a Reactor Protection System (RPS) [JC] actuation (full scram). A previous clearance was placed to support work on hydrolazing the Scram Discharge Volume header which had a caution order placed on the SDV hi level bypass switch to keep the switch in bypass with a warning that unbypassing would result in a full reactor scram. Restoration of the clearance supporting the SDV hydrolazing only removed the caution order from the by pass switch and did not reposition the switch. When the fuse was removed from the circuit that supplied power to the contact that bypassed the high level scram signal, a reactor scram signal was generated, which initiated an RPS actuation (full scram).

Operations reset the reactor scram per procedure 2-01-99, Reactor Protection System, Section 6.1 by 0253 hours0.00293 days <br />0.0703 hours <br />4.183201e-4 weeks <br />9.62665e-5 months <br /> CDT.

Submission of this LER is late because at the time of the event Operations personnel believed the event to not be reportable due to the understanding of guidance provided in NUREG-1022, Event Reporting Guidelines 10 CFR 50.72 and 50.73.

TVA is submitting this report in accordance with 10 CFR 50.73(a)(2)(iv)(A). An event that resulted in a manual or automatic actuation of the systems listed in paragraph 10 CFR 50.73(a)(2)(iv)(B) (i.e., reactor protection system including reactor scram or trip).

B. Inoperable Structures. Components. or Systems that Contributed to the Event:

None.

C. Dates and Arwroximate Times of Maior Occurrences:

May 24, 2009 0232 hours0.00269 days <br />0.0644 hours <br />3.835979e-4 weeks <br />8.8276e-5 months <br /> CDT Operations personnel inserted a Unit 2 "B" channel half scram.

May 24, 2009 0247 hours0.00286 days <br />0.0686 hours <br />4.083995e-4 weeks <br />9.39835e-5 months <br /> CDT Unit 2 reactor automatically scrammed.

May 24, 2009 0253 hours0.00293 days <br />0.0703 hours <br />4.183201e-4 weeks <br />9.62665e-5 months <br /> CDT Operations personnel reset Unit 2 scram.

D. Other Systems or Secondary Functions Affected

None.

E. Method of Discovery

The operations crew received main control room annunciators Reactor Channel "A" scram and Reactor Channel "B" scram.

F. Operator Actions

Operators responded in accordance with the alarm response procedures. Since the reactor was already in Mode 5 with all control rods inserted, no plant parameters were changed.

G. Safety System Responses The RPS logic responded to the reactor scram. Since the reactor was already in Mode 5 with all control rods inserted, no reactor parameters were changed.

Ill. CAUSE OF THE EVENT A.

Immediate Cause The immediate cause for the event was due to pulling a fuse, associated with bypassing an SDV high level scram signal, in combination with a half scram that had been inserted earlier in support of work on the Reactor Protection System Contactor Relay.

B. Root Cause The root cause of this event was lack of awareness of the SDV system configuration. The control room operators were not cognizant of the fact that the SDV was isolated and full of water in combination with the associated SDV high level scram signal being bypassed.

C. Contributincq Factors Contributing causes were ineffective communication and ineffective pre-job brief.

IV. ANALYSIS OF THE EVENT

Prior to the event, an outage activity to hydrolaze the SDV Instrument Tank and Headers had been completed. The associated clearance had a caution order on the SDV High Level Bypass switch to keep the switch in "BYPASS" with a warning that taking the switch out of "BYPASS" would result in an RPS actuation (full scram). The hydrolazing was completed several days before this event, but the restoration of the clearance for that activity was only partially completed and had only removed the caution order from the "BYPASS" switch and did not return the switch to its "NORMAL" (un-bypassed) position.

Operations had inserted a "B" RPS Channel half-scram to support placement of a clearance to support RPS Channel "B" scram contactor maintenance. When fuse 2-FU 1-99-5A/K27B was pulled a full scram signal was generated. The cause of the scram was the fact that the SDV vents and drains were closed and the volume had filled above the scram setpoint. Even though the High Level Scram signal for the SDV was in bypass, the pulling of the fuse also opened a contact in the "A" scram circuit. The SDV High Level Scram signal, in conjunction with the open contact, negated the key lock bypass contact and resulted in the receipt of a RPS actuation (full scram).

V. ASSESSMENT OF SAFETY CONSEQUENCES

The safety consequences of this event were not significant. Since the reactor was already in Mode 5 with all control rods inserted, no reactor parameters were changed. The reactor scram was not complicated. TVA concludes that the event did not affect the health and safety of the public.

VI. CORRECTIVE ACTIONS

A.

Immediate Corrective Actions

Immediate corrective action was to reset the scram per procedure 2-01-99. A stand-down was held in the Unit 2 Main Control Room, which included the entire control room, Work Control Center, and Outage Control Center staff, to discuss all ongoing activities and unit conditions.

B.

Corrective Actions to Prevent Recurrence - The corrective actions are being managed by the Browns Ferry Nuclear Plant corrective action program.

Corrective actions include a training needs analysis of the event for possible inclusion into Licensed Operator Requalification training.

VII.

ADDITIONAL INFORMATION

A.

Failed Components None.

B.

Previous LERs on Similar Events None.

C.

Additional Information

Corrective action documents PER 172053, PER 178146 and SR 84741.

D.

Safety System Functional Failure Consideration:

This event is not a safety system functional failure in accordance with NEI 99-02.

E.

Scram with Complications Consideration:

This event was not a complicated scram according to NEI 99-02.

VIII.

COMMITMENTS

None.