ML19211C552
| ML19211C552 | |
| Person / Time | |
|---|---|
| Issue date: | 12/15/1979 |
| From: | Thadani A Office of Nuclear Reactor Regulation |
| To: | Stahle C Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML18025B195 | List:
|
| References | |
| FOIA-80-587, REF-GTECI-A-09, REF-GTECI-SY, TASK-A-09, TASK-A-9, TASK-OR NUDOCS 8001110668 | |
| Download: ML19211C552 (5) | |
Text
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- pa ancyg'o, UNITED STATES 3 s.( [ j NUCLEAR REGULATORY COMMISSION E
WASHINGTON, D. C. 20555 b.
p La 1572 NOTE T0:
C. Stable FROM:
Ashok Thadani We have reviewed the ATWS emergency operating procedure submitted by TVA on October 17, 1979. The enclosed coments on this procedure are written in such a manner as to minimize the TVA effort required to develop accep-table ATWS procedure (s).
I recomend that you request the Operator Licens-ing Branch to review the proposed TVA precedure and our comments.
If requested, we will be pleased to discuss these coments with TVA.
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Ashok Thadani Reactor Systems Branch Division of Systems Safety cc: ATWS Task Force S Hanauer Speis S. Varga 1740 034 soonie df f
REVIEW 0F A_TWS_ PROCEDURES FOR SEQUOYAH PLANT A.
b iors
.1 The procedure lists the parameters which cause tre reactor to scram, but does not describe the actual indications av611able to the operators in the control room which would make him aware that an g event has occurred.
These ATWS symptoms would depend on initiating event and, therefore, they ought to be evaluated for at least the following three key events:
Loss of Main Feedwater Loss of Offsite Power Stuck Open PORV In making the evaluation it is important to show for each event what s;cptoms would indicate to the operator that scram actici 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 after an ATWS. This should be specified in more detail in the procedure.
2.
Why is automatic actuation of HPSI not included in this section of the procedure?
C.
Immediate 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.
1740 035
2.
The imediate actions that the operators have to take after ATWS has occurred and an attempt to manually scram the reactor from the e.ontrol room has failed should follow two parallel paths.
While one operator should continue the operation of manually 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 auxiliary feedwater pumps, and high pressure safety injection system.
(See Figure 1).
3.
Describe the actions taken by the operator 1:Sen 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 1 css 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 pump?
0.
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 steam generators.
- c. The containment heat removal is being accomplished, if the containment conditions are outside the normally specified valves.
1740 036
3.
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 ATWS? For example, what boron concentration should be maintained in the RCS.
174O 037
SUBSEQUErlT ACTIONS Event & Action Transient Failure to Innnediate Opera-Verify RCS, Steam Long T. na g
Sequence Ini tiated Scram tor Actions Generator, Contain-Shutdown y
Symptoms Symptoms Two Operators ment Parameters Valies a
O wr is General time t
t t
t t
o j
2 3
4 Sequence Operator #1 Manual Scram If outside specified ih ; ribe special Attempts limits, describe the r-tions to bring operator actions.
plant to a cold shutdown condi-Operator #2 tion and main-Assure that tain that condi tion, 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 open PORV.
Figure 1.
Generalized Approach to be followed for writing ATWS procedure (s)
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