05000317/LER-1981-002-03, /03L-0:on 810111,auxiliary Feedwater Flow to Steam Generators Found Set Below Normal Limit.Caused by Feed Regulating Valve Stroke Limitation Implemented Under Mods Required by NUREG-0578.Restriction Removed on 810122

/03L-0:on 810111,auxiliary Feedwater Flow to Steam Generators Found Set Below Normal Limit.Caused by Feed Regulating Valve Stroke Limitation Implemented Under Mods Required by NUREG-0578.Restriction Removed on 810122

ML19345F292
Person / Time
Site:	Calvert Cliffs
Issue date:	02/10/1981
From:	Tietjen K BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19345F291	List: 05000317/LER-1981-002, Forwards LER 81-002/03L-0 05000317/LER-1981-002-03, /03L-0:on 810111,auxiliary Feedwater Flow to Steam Generators Found Set Below Normal Limit.Caused by Feed Regulating Valve Stroke Limitation Implemented Under Mods Required by NUREG-0578.Restriction Removed on 810122
References
LER-81-002-03L, LER-81-2-3L, NUDOCS 8102170123
Download: ML19345F292 (3)

LER-1981-002, /03L-0:on 810111,auxiliary Feedwater Flow to Steam Generators Found Set Below Normal Limit.Caused by Feed Regulating Valve Stroke Limitation Implemented Under Mods Required by NUREG-0578.Restriction Removed on 810122

Event date:
Report date:
3171981002R03 - NRC Website

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' l o_ : 21 i At 2100 on 01-11-81, it was detennined that Auxiliary Feedwater flow l

i i o,2 i I (AFW) to the steam generators was only 480 GPM. The AFW regulating l

valves were reset to obtain a flow of 750 GPM at 1610,1-12-Gl. The l

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liioil A 75% AFW feed regulating i ilve stroke limit was implemented under modi _ _

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50-317 LICENSE NO. DPR-53 EVENT DATE 01-11-81 REPORT DATE 02-10-81 ATTACHMENT EVENT DESCRIPTION AND PROBABLE CONSECUENCES (CONT'D)

At 2100 on 1-11-81, while feeding Steam Generators with the Auxiliary Feedwater System, the operator observed that he could only obtain a total flow of 480 GPM to the Steam Generators (130 GPM to ill, 350 GPM to f12) using the valve position controllers on the main control boards.

This total flow was less than the value of design flow referenced in the T.S. Bases (700 GPM total).

It was determined that the maximum valve stroke limit was too restrictive to allow design flow conditions to be reached utilizing the valve controllers alone.

These valves were limited to 757. of full stroke under an approved design modification re-lating to the " Control Grade" AFW auto-start system (as required by NUREG0578). The Shift Supervisor initiated maintenance action to reset the maximum stroke limit so that a total flow rate of 750 GPM could be achieved. This corrective action was completed at 1610 on 1-12-81.

It was subsequently detemined that the system flow capability had not been tested upon implementation of approved design modifications re-lating to the " Safety Grade" AFW auto-start system (also required by NUREG0578). However, the required flow rate with the restriction of valve opening was only required to be 460 GPM total, as per the approved design changes, which is sufficient to remove decay heat on a loss of feedwater accident. The basis for the Technical Specification refers to the AFW system design flow rate of 700 GPM which provides for decay heat removal and the capability to cooldown the plant to less than 3000F.

In con-sideration of other design features (Manual Bypasses) of the AFW system, flow rates of at least 700 GPM were attainable throughout the period l,

of valve restriction and thus public health and safety were not affected.

This is not a repetitive occurrence.

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (CONT'D)

The cause of the reduced flow rates was determined to be the maximum open-ing setting of the AFW regulating valves. This restriction was implemented under special instructions relating to the " Control Grade" AFW auto-start system. The intent of this action was to limit the maximum flow rate of the APd system in order to prevent APA pump cav'itation on a loss of in-l strument air to the valves and to the AFW pump speed controller. The i

flow rate required to remove decay heat and maintain hot-standby con-ditions was determined to be 460 GPM. With the valve restrictions in effect, a total flow of 480 GPM was achieved. Under the specific condi-tions of this modification, no testing was required. Upon implementation of tne " Safety Grade" AFW auto-start modification, the special instructions for the " Control Grade" modification were continued in effeet.

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i The Technical Specification Bases refer to a flow requirement in excess of 700 GPM.

This number is based on the AFW system design capability to, not only remove decay heat in hot-standby, bug also additional flow capability to cooldown the plant to less than 300 F.

Only the capa-bility to remove decay heat is analyzed in the FSAR Safety Analysis.

The operators, believing the requirement to be 700 GPM, initiated cor-rect maintenance action to restore capability to greater than 700 GPM.

This action was not necessary since the actual requirement was 460 GPM l

and a flow rate of 480 GPM could be achieved. Also, the design of the AFW system includes manual bypass capabilities which could be used on cooldewn to attain the higher flow rates if required.

Calvert Cliffs Instructions refer to a requirement for verification test-ing of all safety-related modifications. Testing for non-safety related modifications is at the discretion of the responsible engineer or super-visor, and is accomplished on a as necessary basis. Since the flow restriction requirement was implemented as non-safety related, testing was not required at that time. However, on the subsequent upgrade to safety related, verification testing should have been performed, con-trary to existing instructions, the requirement was omitted and no veri-fication test was performed.

On subsequent review of this situation, it was decided to remove the 75%

restriction on AFW regulating valve stroke. This was based upon the l

installation of a safety related air supply to the subject valves which cbviates concern over loss of the normal air supply.

This corrective action has been implemented.

In addition, a memo was sent to the Engineering Department requesting that future modifications contain all special instructions necessary for implementation and that the use of cross referencing these instructions between different jobs be elimi-nated. This action provides increased assurances that a similar ccror will not occur again.

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