ML20125C759

Forwards Comments on Proposed ATWS Emergency Operating Procedures.Time Frame or Period,Plant Response & Concurrent Operator Action During Period Should Be Contained in Procedure

ML20125C759
Person / Time
Site:	Sequoyah
Issue date:	12/27/1979
From:	Rubenstein L Office of Nuclear Reactor Regulation
To:	Parris H TENNESSEE VALLEY AUTHORITY
References
FOIA-80-587 NUDOCS 8001110487
Download: ML20125C759 (6)

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NUCLEAR REGULATORY COMMISSION o

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'79 Docket Nos.: 50-327/328 Mr. H. G. Parris Manager of Power.

Tennessee Valley Authority 500A Chestnut Street Tower II Chattanooga, Tennessee 37401

SUBJECT:

ATWS PROCEDURES FOR SEQUOYAH Enclosed are cor.ents or. your proposed ATWS emergency operating procedures that were submitted on October 17,1979.. The procedure addresses ATWS in the TVA Abnormal Operating Instruction (A0I-1), Reactor Trip Procedure. AOI-l contains symptoms and automatic action which occur following a normal trip of the reactor.

The operator utilizes these conditions to diagnose the event and thereby classify the emergency. The. symptoms and automatic action for ATWS do not follow the nonnal trip sequence and therefore conflict with the procedure in its present form. Although A0I-l requires the operators to be alert for ATWS, it does not provide sufficient insight on reactor and plant response until the event is terminated. Manual actions outside the control room may be required. to terminate ATWS; therefore, the time frame or period, the plant response and concurrent operator action during this period, should be contained in the procedure.

We believe that including ATWS in the present form is contrary to Regulatory Guide 1.33, " Quality Assurance Program Requirements (Operational)," which includes a specific procedure for anticipated transients. Alsc, ANS 3.2, ANSI N18.7-1976, " Quality Assurance for Operational Phase of Nuclear Power Plants," addresses emergency procedures in Section 5.3.9 and recomends separate procedures for reactor transients and excursions.

Your response is requested by January 10, 1980.

Sincerely,

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. % >,.. b L. S. Rubenstein, Acting Chief Light Water Reactors Branch No. 4 Division of Project Management

Enclosure:

0,0022.10 As' stated cc w/ enclosure:

See next page.

800111.0487 p

1 Tennesse2. Valley Authority

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ces:

Herbert-S. Sanger, Jr. Esq.

General Counsel Tennessee Valley Authority 400 Comerce Avenue E 118 33 Knoxville, Tennessee 37902 Mr. E. G.'Beasley Tennessee Valley Authority g

W10C131 C 400 Comerce Avenue Knoxville, Tennessee 37902 Mr. Michael Harding Westinghouse Electric Corporation

'P.- 0. Box 355 Pittsburgh, Penn,sylvania 15230 Mr. David Lambert Tennessee Valley Authority 400 Che.stnut Street Tower II Chattanooga, Tennessee 37401

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l REVIEW OF ATWS PROCEDURES FOR SEQUOYAH PLANT A.

Symptomh l

The prockdura 1$ts the. 'arameters which cause the reactor to scran,

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p but does not describe the actual indications available to the operators in the control room which would make him aware that an g e' vent has occurred.

These ATWS symptoms would depend on initiating event and, therefore, they ought to be evaluated for at least the following three..

".d key events:

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Loss of Main Feedwater Loss.of Offsite Power Stuck Open PORY In making the evaluation it is important to show for each event what symptoms would indicate to the operator that scram action was called for but did not occur.

B.

Automatic Action 1.

This section does not address how the automatic actions relate to ATWS.

Some of.the automatic actions (e.g., turbine trip) may not even occur This should be specibed in more detail in the procedure.

after arr ATWS.

2.

Why.is automatic actuation of HPSI not included in this section of the procedure?

C.- Imediate Operator Action-1.

The procedure should specify critical indications available to the operator consistent with the initiating event and assumption that the reactor trip.has not occurred.

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2.

The. imediate actions that the operators have to take after ATWS has occurred and an attempt to manually sciim the reactor from the control room has failed should follow two para'iiel paths. While one operator should continue the operation of manualiy scraming the reactor by trip-ping the breakers powering.the control rod drive MG sets, the other operator should initiate the other actions leading to safe shutdown of the plant. The procedure should reflect that the actions described in sections A.2.b and A.2.c and those described in sections B.1 and B'.2 are to be performed simultaneously. Section B should require sequential actuation of turbine trip, all' auxiliarh feedwater pumps, and high pressure safety injection syster71.

(See Figure 1).

3.

Describe the actions taken by the operator when he discovers, during the verification of reactor coolant system status (section C), that the conditions are not within the prescribed limits.

What is the impact of loss of offsite power on availability of those signals to the operator.

What is the shutoff head of the HPSI pumps? What provisions are taken to prevent pump. damage when HPSI is operating against. the RCS pressure which is higher than the shutoff head of the punp?

D.

Subsequent Operator Action 1.

What is the time frame for these actions?

2.

What criteria are provided to verify that:

.a. The auxiliary feedwater system is providing the necessary flow to the i

stean generators,

b. The HpSI is providing necessary flow to RCS.

c. The containment heat removal is being accomplished, if the containment conditions are outside the normally specified valves.

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What additional procedure does the operator have to follow in order to bring the plant to and maintain in a cold shutdown condition after an ATWS7 For example, what boron concentration should be maintained in the RCS.

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SUBSEQtlENT ACTIONS Event & Action Transient Failure to Inmediate Opera-Verify RCS, Steam Long Tenn Sequence

' Initiated Scram tor Actions Generator, Contain-Shutdor.'n Symptoms Symptoms Two Operators ment Paraneters Values General time t,

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t Sequence Operator #1 Manual Scram If outside specified Describe special Attempts limits, describe the actions to bring operator actions, plant to a cold shutdown condi-Operator -f2 tion and main-

' Assure that tain th.it c ndition.

a) turbine tripped

.b) all AFWS provid-ing flow c) HPSI providing flow (shut off head) in that order.

What, if any, is the impact of stuck

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e open PORV.

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(J1 Figure 1.

Generalized Approach to be followed for writing ATWS procedure (s)

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