ML19257C013

LER 80-001/01T-0:on 800106,Unit 1 Caustic Addition Valves CA-1-2 & CA-1-4 Mistakenly Closed & Secure Cards Attached. Caused by Personnel Error & Procedural Inadequacies. Administrative Procedures Modified

ML19257C013
Person / Time
Site:	Prairie Island
Issue date:	01/18/1980
From:	Mayer L NORTHERN STATES POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19257C009	List: ML19257C008 ML19257C013
References
LER-80-001-01T, LER-80-1-1T, NUDOCS 8001220567
Download: ML19257C013 (3)

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, SUPPLEMENTAL INFORMATION FOR LER 80-1 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Description of Occurrence On January 6,1980 a check of the safeguard hold cards was being performed in accordance with SWI-0-3, Safeguards Hold Cards, and SP 1658, Monthly Safeguards Hold Verification. At approximately 0600, the operator perform-ing these checks found that two unit I caustic addition valves, CA-1-2 and CA-1-4, were closed with SECURE cards attached. Since the required position of these valves was open, the operator immediately reported the condition to the Unit 1 Shift Supervisor who directed the operator to immediately open CA-1-2 and CA-1-4.

Designation of the Apparent Cause of the Occurrence At about 2300 on January 3rd the unit 2 Lead Plant Equipment & Reactor Operator (LPE&RO) issued SECURE cards to be hung according to C1.3, Unit Shutdown procedure, Step 37b (Step 37b isolates caustic to the containment spray system on unit cooldown).

When these cards were filled out, the LPE&RO copied the unit I caustic addition valve numbers from the procedure, rather than unit 2 (numbers for both units are given in the procedure). The Plant Equipment and Reactor Operator 0?E&RO ) then placed the unit i valves in the position specified by the SECURE cards and attached the cards to the valves without realizing that he was isolating the caustic addition valves on the operating unit, rather than the shutdown unit. The basic cause of this occurrence is personnel error, with the procedure contributing.

Analysis of Occurrence The caustic addition system fulfills two purposes, neither of which is required to meet 10CFR100 release limits nor for immediate operation of engineered safety systems.

One of these functions is removal of iodine in the containment by the containment spray system. The analysis in the FSAR (Section 14) shows that 10CFR100 guidelines are not exceeded with or without taking credit for iodine removal. NRC calculations in the Prairie Island SER do assume some iodine removal. ilowever, these calculations allow only a little credit for this removal (only 11% from 24 minutes to 30 days, and higher values prior to 24 minutes). Taking no credit for caustic addition should not increase these doses much (11-20%) and should remain within the guidelines of 10CFR100.

The second function the caustic addition system fulfills is to provide pH control to inhibit stress corrosion cracking in a post accident environment.

The FSAR, section 6.4.3, shows that it is not credible for the chloride concentration in the recirculated post-LOCA fluid to reach the levels that might cause stress corrosion. Nevertheless, the caustic addition system provides a means of pH control to inhibit stress corrosion.

An even more conservative view is that the pH control might be required after the RHR system is placed in tervice for long term post-LOCA recircula-tion. Approximately 30 minutes would be available to manually initiate caustic addition before entering the recirculation mode.

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SUPPLEMENTAL INFORMATION FOR LER 80-1 (cont}

The re fo re , it is believed that the risk to the health and safety of the public as a result of this occurrence was minimal.

Corrective Action Administrative Controls have been strengthened in the following manner:

1. The requirement that " Safeguards Hold" tags be returned to the Shif t Supervisor (Ref SWI-0-3) has been re-emphasized. An exemption to logging requirements upon installation and removal of the tag has been deleted.

2. SWI-0-10 has been changed to require that, when using a procedure that can apply to either unit, a line be drawn through the numbers not applicable to the unit under consideration.

This occurrence and its significance has been discussed with the individuals involved.

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