05000271/LER-1994-001, :on 940106,nonconservative TS Setpoint Range Applied to Calibr Procedure for Rod Block Monitor auto- Bypass Feature.Caused by Personnel Error.Setpoint Change Request Processed & OP 4304 Revised
| ML20064E313 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 02/03/1994 |
| From: | Wanczyk R VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-94-001, LER-94-1, NUDOCS 9403140246 | |
| Download: ML20064E313 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(x) |
| 2711994001R00 - NRC Website | |
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e VERMONT YANKEE NUCLEAR POWER CORPORATION i
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P.O. Box 157. Governor Hunt Road
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(802) 257-7711 y
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February 3, 1994 U.S.
Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555 REFERENCE: Operating License DPR-28 Docket No. 50-271 Reportable Occurrence No. LER 94-01
Dear Sirs:
As defined by 10 CFR 50.73, we are reporting the attached Reportable Occurrence as LER 94-01.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION Robert J anczyk Plant Manager cc:
Regional Administrator USNRC Region I 475 Allendale Road King of Prussia, PA 19406 i
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9403140246 940203 7 - --w; 40,I
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'NRC Form 366 U.S. NUCLEA3 REGULATOY COMMIS$10N APPROVED OMS NO. 3150 0104 (6 G9)
EXPIRES 4/30/92 ESTIMATED BCDEU PER RESPCSE TO CCHPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD CCNMENTS REGARDING BURDEN EST!KATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-350), U.S. NUCLEAR REGULATORY COMMIS$!ON, WASHINGTON DC 20555, AND To THE PAPERWORK R?. DUCT 10W PROJECT (3160 0104), OFFICE OF MANAGEMENT AND Bt.DGET, WASHINGTON, DC 20603.
FACILITY NAME (1)
DOCKET NO. (2)
PACE (3) l0l5l0l0l0l2l7l1 VERMONT YANKEE NUCLEAR POVER STAfl0N 0
1 0F 0
3 TITLE (4)
Non-Conservative Technical Specification Setpoint Range Applied to Calibration Procedere for Rod Block Monitor Auto-Bypass Feature Due to Personnel Error.
EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7)
OTHER FACILITIES INVOLVED (8)
MONTH DAY YEAR YEAR SEQ #
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MONTH DAY YEAR FACILITY NAMES DOCKET NO (S) 0 5
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5 0 0 0 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO REQ'MTS OF 10 CFR 1: CHECK ONE OR MORE (11)
MODE (9)
N 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)
POWER 20.405(a)(1)(i) 50.36(c)(1)
$0.73(a)(2)(v)
- 73. 71(c )
LEVEL (10) 1l0l0 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vil)
OTHER:
20.405(a)(1)(iii) x 50.73(a)(2)(i) 50.73(a)(2)(vi i i )( A) 20.405(a)(1)(iv)
X 50.73(a)(2)(li) 50.73(a)(2)(viii)(B) 20.405(a)(1)(v) 50.73(a)(2)(lii) 50.73(a)(2)(x)
LICENSEE CONTACT FOR THIS LER (12)
NAME TELEPHONE NO.
AREA CODE ROBERT J. WANCZYK, PLANT MANAGER 8l0l2 2l5}7l-l7l.'11{
COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRISED IN THIS REPORT (13)
CAUSE
SYST COMPONENT MFR REPORTABLE
CAUSE
SYST COMPONENT MrR REPORTABLE TO NDRDS TO NPROS l
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EXPECTED M0 DAY YR SUBMISSION DATE (15) l YES (If yes, conplete EXPECTED SUBMISSION DATE)
X NO ABSTRACT (Limit to 1400 spaces, i.e., approx. fifteen single-space typewritten lines) (16)
On 1/6/94 at 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br />, with the reactor operatin,) at 100% steady state power, it was identified that the setpoint for the Rod Block Monitor (RBM) Autu Bypass Logic was potentially set at a value which was slightly non-conservative relative to the specific value contained in Technical Specifications (TS). Following a review of the condition by plant personnel, it was confirmed that an error existed in the calibration procedure, that the setpoint was non-conservatively set, and a 1-hour NRC notification was made at 1524 hours0.0176 days <br />0.423 hours <br />0.00252 weeks <br />5.79882e-4 months <br /> on 1/7/94.
Technical Specifications (TS) allow the RBM to be bypassed when reactor power is.<;. 30% rated.
Contrary to this requirement, the setpoint range listed in the calibration procedure was 30 to 32.5%. Following confirmation of the setpoint error, the calibration procedure was revised, and the RBM setpoint was recalibrated to the correct value. These actions were completed by 1630 on 1/7/94.
The root cause of this event is personnel error. The error was mado during the preparation of revision three to the calibration procedure (dated 4/2/73) which changed the setpoint from 30% to 2.30% power.
Corrective actions presently being implemented as a result of other recently identified TS non-compliance issues were reviewed and are considered appropriate to prevent recurrence of this event.
NRC Form 366 (6 89)APPROVED OMS NO. 3150 0104 (6 89)
EXPIRES 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THis INFORMATION COLLECTION REQUEST: 50.0 hrs. FORWARD LICENSEE EVENT REPORT (LER)
COMMENTS REGAR0 LNG BURDEN ESTIMATE TO THE RECORDS AND TEXT CONTINUAtl0N REPORTS MANAGEMENT BRANCH (P-350), U.s. NUCLEAR REGULATORY COMMISSION, WASHINGTON DC 20555, AND TO THE PAPERWORK REDUCT!oN PROJECT (3160-0104), OFFICE OF MANAGEMENT AND SUOGET, WASHINGTON, DC 20603.
FACILITY NAME (1)
DOCKET No (2)
LER NUMGCR (6)
PAGE (3)
YEAR SEQ #
REV #
VERMONT YANKEE NUCLEAR POWER CORPORATION 0l5l0l0l0l2l7l1 l2 l3 0
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a TEXT (if more space is required, use additional NRC Form 366A) (17) i
DESCRIPTION OF EVENT
On 1/6/94 at 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br />, with the reactor operating at 100% steady state power, it was identified that the setpoint for the Rod Block Monitor (RBM) Auto Bypass logic was potentially set at a value which was slightly non-conservative relative to the specific value contained in Technical Specifications (TS). Following a review of the condition by Engineering, Instrument & Control, and Reactor Engineering personnel, it was confirmed that an error existed in the calibration procedure, that the setpoint was non conservatively set, and the 1-hour NRC notification was made at 1524 hours0.0176 days <br />0.423 hours <br />0.00252 weeks <br />5.79882e-4 months <br /> on 1/7/94.
Technical Specifications Section 3.2.5, Note 7 allows the RBM to be bypassed when reactor power is i 30% rated. Contrary to this requirement, the setpoint range listed in calibration procedure OP4304 " Rod Block Monitor Functional / Calibration Test" was 30 to 32.5%. The erroneous setpoint was identified as a result of a review of the Instrumentation and Control Department calibration procedure by a department engineer.
Per TS Section 3.2 Bases, the Rod Block Monitor System is considered an aid to the reactor operator. The RBM System monitors control rod withdrawal actions of the reactor operator. The RBM System compares localized reactor core power levels around a selected control rod to the core wide Average Power Range Monitor (APRM)(Ells =JE) power levels. When local core power levels exceed preset limits, the RBM System supplies a block signal to the Reactor Manual Control System (Ells = AA) and prevents further control rod withdrawal. The primary purpose of the RBM is to prevent localized fuel damage as a result of the accidental withdrawal of a high worth control rod and to avoid conditions that would require Reactor Protection System (RPS)(Ells =JE) action if allowed to proceed. if any of these conditions are present during control rod withdrawal operations, the RBM p oduces the block. signal. The RBM system auto-bypass logic bypasses its rod block output when reactor power is oss th'.n 30%.
Vermont Yankee Technical Specifications Section 3.2.5, Note 7 states that the RBM trip logic for the rod block mc qitor Jpscale and downscale alarms may be bypassed when reactor power is 130% power. The portion of the RBM c:rcuitry that provides the reactor power reference signal (APRM) to the logic has been set at or slightly above 30% power since 1973. The potential result of this condition is that had a valid RBM block signal been generated in the past, with the reactor operating between 30 to 32.5% power, the RBM block output signal may have been bypassed by the RBM auto-bypass logic.
Following confirmation of the setpoint error, the calibration procedure was revised, and the RBM setuoint was recalibrated to the correct value. These actions were completed by 1630 on 1/7/94.
CAUSE OF EVENT
The root cause of this event is personnel error. Revie N of the Rod Block Monitor Functional / Calibration Test procedure history indicates that in the early 1970's the RBM auto-bypass setpoint was to be set at 30%
power. It appears that a cognitive error was made during preparation of revision three to the calibration procedure (dated 4/2/73) which changed the setpoint from 30% to 130% power. In 1978, the procedure setpoint was revised to include a calibration range. The range of 30 to 32.5% was instituted at this time.
ANALYSIS OF EVENT
The primary purpose of the RBM is to prevent localized fuel damage as a result of the accidental withdrawal of a high worth control rod and to avoid conditions that would require RPS action if allowed to proceed (ie: APRM Rod Block, APRM Hi-Flux Scram). At the time that this event was discovered, the plant was operating at 100% power and the bypass was not in effect.
NRC Form 366 (6-89)
RRc Form 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMS NO. 3150-0104 (6 89)
EXPIRES 4/30/92 ESTIMATED BUROCN PER RESPONSE TO COMPLY t3lTH THis INFORMATION COLLECTION REQuEsit 50.0 HRS. FORWARD LICENSEE EVENT REPORT.(LER)
COMMENTS REGARDING BURDEN ESTIMA1E TO THE RECORDS AND TEXT CONTINUATION REPORTS MANAGEMENT BRANCH (P-350), u.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON DC 20555, AND To THE PAPERWORK REDUCTION PROJECT 13160-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHlkGTON, DC 20603.
FACILITY NAME.1)
DOCKET NO (2)
LER NUMBER (6)
PAGE (3)
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VERMONT YANKEE NUc'. EAR POWER CcRPORATION TEXT (if more space is required, use additional NRC F0rm 366A) (17)
This event is significant in that the procedure did not provide correct implementation of the TS parameter, however there is no safety Wynificance of this event relative to the health and safety of the public. The setpoints for the rod block monitoring system are chosen so that rod motion is halted well before local fuel damage can occur. The Technical Specification setpoint of 130% rated power and the potential non-conservative setting of-32.5% is not significant relative to the large reactivity changes necessary ta cause fuel damage.
The RBM Rod Block is the first of several design features in place to limit the affects of a control rod withdrawal error and to limit fuel damage due to large localized reactivity increases. The APRM Rod Block is set to trip at a slightly higher value, approximately 42%, biased to account for recirculation flow conditions. The APRM High Flux Scram Occurs at approximately 52% power.
CORRE. _TIVE ACTIONS C
Short Term:
1.
A Setpoint Change Request was processed and OP 4304 was revised to implement a new setpoint range of 28 +/-1% rated power. The RBM Average Power Range Monitor (APRM) Reference Downscale setpoint was reset to the new value.
2.
Although Vermont Yankee is currently in the process of performing a comprehensive review of Technical Specifications to insure compliance, a separate review team was immediately tasked with focusing on Technical Specifications notes to determine if other similar discrepancies existed. No other similar 4
conditions were identified. The results of the this review effort have been factored into the Main Task Force review.
Long Term:
4 1
Corrective actions presently being implemented as a result of other recently identified Technical Specification non-compliance issues were reviewed and are considered appropriate to prevent recurrence of this j
event. This particular condition was identified during the self assessment of a calibration procedure by the responsible department engineer.
Other long term corrective actions previously implemented include:
1.
A Task Force was formed to perform a comprehensive review of the Technical Specifications with a focus on compliance methods via plant procedures / policies, this review is expected to be completed by 4/1/94.
2.
Plant departments have been instructed to perform self assessments of plant procedures that satisfy Technical Specification requirements to reverify compliance.
3.
Department Supervisors are responsible for review of surveillance test data for Technical Specification equipment.
i
ADDITIONAL INFORMATION
Similar events have been reported to the Commission in LERs 91-04, 93-04, 93-09, and 93-10. These l
events were similar because they involved a procedure that did not adequately satisfy a testing requirement listed in TS.
NRC Form 366 (6-89) l