05000302/LER-1978-016-01, /01T-0:on 780310,in Mode 5 Operation,Unplanned Reactivity Insertion of 4.3% of Delta K/K.Caused by Dilution of RCS Upon Draining.Rcs Boron Sampling Surveillance Increased

/01T-0:on 780310,in Mode 5 Operation,Unplanned Reactivity Insertion of 4.3% of Delta K/K.Caused by Dilution of RCS Upon Draining.Rcs Boron Sampling Surveillance Increased

ML19308D551
Person / Time
Site:	Crystal River
Issue date:	03/17/1978
From:	Cooper J FLORIDA POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19308D542	List: 05000302/LER-1978-016, Forwards LER 78-016/01T-0 05000302/LER-1978-016-01, /01T-0:on 780310,in Mode 5 Operation,Unplanned Reactivity Insertion of 4.3% of Delta K/K.Caused by Dilution of RCS Upon Draining.Rcs Boron Sampling Surveillance Increased
References
LER-78-016-01T, LER-78-16-1T, NUDOCS 8002280983
Download: ML19308D551 (2)

LER-1978-016, /01T-0:on 780310,in Mode 5 Operation,Unplanned Reactivity Insertion of 4.3% of Delta K/K.Caused by Dilution of RCS Upon Draining.Rcs Boron Sampling Surveillance Increased

Event date:
Report date:
3021978016R01 - NRC Website

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No safety hazard as the shutdeva margin was greater than 10%

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Redundancy NA.

Secend occurrence of an event of this type, refer to LER 77-08.

The diluted RCS returned to 2024 ??MB at,

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,' SUPilEMENTARY Di!ORMATION Report No.*:

50-302 /78-016/01T-0 Facili g:

Crystal River Unic #3 3.

Report Date:

17 March 1978 4

Occurrence Date:

10 March 1978 5.

Identification of Occurrence:

Unplanned reactivity insertion of more than.5% Delta I/K contrary to Technical Specification 6.9.1.8.d.

6.

Conditions Prior to Occurrence

• Mode 5.

7.

Description of Occurrence:

rtplanned reactivig insertien of 4.3% Delta K/K At 0900 it was determined that an had occurred during the period between 1015 en 9 March 1978 and 0520 on 10 March 1978.

The Reactor Coolant System had initially been drained to the 132 ft. level to facilitate

• the opening of "3 " Once Through Steam Generator for inspection en 7 March 1978. The f

boren concentration of the RCS at that ti== vas 1042 ppm.

The RCS samples are all taken at the Decay Heat ? ump discharge while the RCS is on the Decay Heat Syscam.

After entry into "3" OTSG, the detercation was nade that the Reactor Vessel Head would have t.o be removed and boren cencentration brought up to Ji925 ppm.

To facilitate

}

Reactor Vessel Head removal and boration of the RCS, the level was brought up to the

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145 ft. level, using water from the Scrated Water Storage Tank, via the EH Systen.

v After reaching the 145 ft. level, the RCS boren cencentration was 1430 pps en 3 March 1978. At this time, approx 1=ately 2200 gallens of cencentrated boric acid were added to the RCS via the EH System. After parking the Axial ?cuer Shaping Rods in the RV head, the RCS was again drained to the 129 ft. 6 inch level. The "A" OTSG not being directly in ene RCS flev path while on the DH System, the boren concentratica in "A" OTSG was less than the RCS.

Consequently, upon final draining to the 129 ft. 6 inch leve:,

the water from the "A" OTSG drained back into the Reactor Vessel, causing a dilution of the RCS, creating a reactivity addition of 4.3% Delta K/K.

S.

Designation of Apparent Cause:

The apparent cause of this event has been deter =ined to be insufficient sa=pling frequene:

while draining the Raactor Coolant System.

9.

Analysis of Oc*urtence:

There was no safety hatard to the plant or general public as shutdown =argin remained greater than 10% Delta K/K.

'O*

Corrective Action

The Procedure for Draining & Nitrogen 31anketing of the Reactor Ceolant Systen (0?-203) has been revised to add increased sa=pling frequency during RC draining.

Failure Data:

This is the second occurrence of an event of this type, refer to LR2 77-08 of 26 January 1978.