05000260/LER-1979-011-01, /01T-0 on 790526:while Pulling Control Rods,First Rod 26-27 in Group 3 Was Inadvertently Withdrawn Three Notches.Caused by Unexplained Factors.Procedures Were Revised

/01T-0 on 790526:while Pulling Control Rods,First Rod 26-27 in Group 3 Was Inadvertently Withdrawn Three Notches.Caused by Unexplained Factors.Procedures Were Revised

ML18024A832
Person / Time
Site:	Browns Ferry
Issue date:	06/06/1979
From:	TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML18024A831	List: 05000260/LER-1979-011, Forwards LER 79-011/01T-0 05000260/LER-1979-011-01, /01T-0 on 790526:while Pulling Control Rods,First Rod 26-27 in Group 3 Was Inadvertently Withdrawn Three Notches.Caused by Unexplained Factors.Procedures Were Revised
References
LER-79-011-01T, LER-79-11-1T, NUDOCS 7906120330
Download: ML18024A832 (4)

LER-1979-011, /01T-0 on 790526:while Pulling Control Rods,First Rod 26-27 in Group 3 Was Inadvertently Withdrawn Three Notches.Caused by Unexplained Factors.Procedures Were Revised

Event date:
Report date:
2601979011R01 - NRC Website

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t4RC FORIFI 366 I7.77) "

LICENSEE EVENT REPORT CONTROL BLOCK:

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LICENSEE CODE 14 15 LICENSE NUMBER 25 26 LICENSE TYPE 30 57 CAT 58 CON'T soURcE ~LQB 0

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09 DOCKET NUMBER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES Q10

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While pulling control rods to achieve initial criticality for 'cycle 3, the first

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rod, 26-27 in rou 3 was inadvertentl withdrawn three notches.

The rod moved from

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L osition 02 to osition 08 rather than from osition 02 to 04 as rescribed in the

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rod move sheets.

The reactor scrammed on hi-hi IRM flux.

Based on evaluation of

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rocess neutron monitorin instrumentation no safet limit was exceeded but is

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re orted in accordance with T.

ST 6 ' '.a 4

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No hazard existed to the health and

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safet of the ublic.

Previous occurrence:

259/7901.

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CAUSE

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10 11 12 13 18 19 20 SEQUENTIAL OCCURRENCE REPORT REVISION LF RIRO EVENT YEAR REPORT NO.

CODE TYPE NO.

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ACTION FUTURE EFFECT SHUTDOWN ATl'ACHMENT NPROA PRIME COMP.

COMPONENT TAKEN ACTION ON PLANT METHOD HOURS Q22 SUBMITTED FORM SUB, SUPPLIER MANUFACTURER OIB ~Q9

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9 Q26 33 34 35 36 37 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS Q27 o

The withdrawal of the rod from position 02 to position 08 is unexplained.

Functional testing of the rod after the event revealed that the rod would not travel three positions when given a notch withdraw signal.

Prior to restartz

& review of the 3

event was conducted and no safety limits were exceeded.

A subsequent rod pull, using the same

sequence, resulted in a period of approximately 4'3 seconds.

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FACILITY STATUS

'YiPOWER OTHER STATUS Q I

6 B

28 0

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29 N/A METHOD OF DISCOVERY

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11 12 LOSS OF OR DAMAGETO FACIUTY Q43 TYPE

DESCRIPTION

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10 PUBLICITY ISSUED DESCRIPTION~

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8 N/A NAME OF PREPARER CC! LJO ~O ACTIVITY CONTENT RELE'ASED OF RELEASE AMOUNTOF ACTIVITYQS

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10 I I 44 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION Q39

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11 12 13 PERSONNEL INJURIES NUMBER OESCRIPTIONQ41

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Q44 DISCOVERY DESCRIPTION Q32 0 erator Observation LOCATIOTIOF RELEASE Q N/A NRC USE ONLY 68 69 PHONE:

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Tennessee Valley Authority Browns Ferry Nuclear Plant LER SUPPLEMENTAL INFORMATION Form BF-17 BF 15.2 1/10/79 BFRO 260 / 7911 Technical Specification Involved 6 7 2 a 4 Reported Under Technical Specification 6.7.2.a.4

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Identification and Descri tion of Occurrence:

BFNP unit 2 scrammed at 1928 on May 26, 1979,.while pulling control rod 26-27, l

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the first rod in RWM group 3, during an approach to critical,.

The cause of the scram was high neutron flux'on IRM's C, D, and F.

The reactor period was calculated to be 5.5 seconds.

Conditions 'Prior to Occurrence:

Normal startup procedure following the spring 1979 refueling 'outage.

This was the first approach to critical.

Action specified in the Technical Specification Surveillance Requirements met

'ue to ino erable e ui ment.

Describe.

N/A" A

arent Cause of Occurrence:

Movement of control rod 26-27 three positions.

Anal sis of Occurrence:

A reactivity insertion of approximately 0.287 percent delta K/K resulted when control rod 2o-27 was withdrawn from position 02 to position 08.

The resulting reactor period.by the SRH recorder was at3out one second.

Xt was calculated'o be 5.5 seconds.

Corrective Action

Prior to initial criticality follo<d.ng a.refueling outage, any control rod that has a single-notch worth wnich is capable of producing a period of equal to or less than 60 seconds, or any control rod that'has a double-notch worth capable of producing a period of equa'1 to or less than 30 seconds, will be wi<h-drawn"on a notch basis.

The nuclear engineer will be present in the control room during the period of time from initial rod pull until criticality is achieved.

During this period of time, he will confirm acceptable core behavior.

, Failure Data:

N/A

• Retention:

eriod - Lifetime; Responsibility - Administrative Supervisor

• Revision:

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