ML20027A628
| ML20027A628 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 10/20/1980 |
| From: | Lanik G NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Michelson C NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| Shared Package | |
| ML19295D771 | List: |
| References | |
| TASK-AE, TASK-E015, TASK-E15 801030, AEOD-E015, AEOD-E15, NUDOCS 8011060561 | |
| Download: ML20027A628 (3) | |
Text
.a ne:
UNITED STATES
[
g NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20666
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OCT 2 01960 This is an internal, pre-decisional document not necessarily representing a position of AE0D or NRC.
MEMORANDUM FOR: Carlyle Michelson, Director Office for Analysis and Evaluation of Operational Data FROM:
George Lanik Office for Analysis and Evaluation of Operational Data
SUBJECT:
JANUARY 3,1977 QUAD CITIES UNIT ONE LOSS OF AIR EVENT AND ITS EFFECTS ON SCRAM CAPABILITY The attachment to this memo discusses a loss of instrument air event at Quad Cities and its effect on scram capability.
The AE00 inter-pretation of the data in the Quad Cities event of January 3,1977 follows.
The data presented by Mr. Chrissatimos was compiled from the alam recorder and personnel interviews. We accept the accuracy of the data presented.
With respect to the analysis, we agree that the SIV alarm at 20 seconds following the scram (rather than 35 seconds evidenced in tests) indicates that water had accumulated in the SDV prior to the manual scram. Noting that the high level SIV alam at the Brown's Ferry Unit 3 event of June 28, 1980 occurred at 18 seconds shows that the condition of the SDV at Quad Cities was approaching the condition of the Brown's Ferry SDV during that event.
The analysis of the amount of water in the SDV as presented by Mr.
Chrissotimos may not be as conservative as he implies.
First of all, although leakage of the scram outlet valves associated with the 70 drifting rods is accounted for conservatively nothing is said of the remaining 107 rods which did not drift. However, it is likely that many of the remaining scram outlet valves associated with these CRDs were also leaking water to the SDY. That is, they were leaking at a lower rate insufficient to generate a 550 pound force across the CRD piston to move its associated control red or were associated with control rods which were already inserted when the event occur ed.
- Thus,
_ more than 210 gallons in 30 seconds (i.e. 420 gpm) could have leaked to the SDV. At this rate (without the possible contri-bution. from the other 107 CRDs), the time available for the operator to scram from the beginning of rod drift to before the SDV fills is t
dout 85 seconds (593 gal SDV capacity divided gpm).
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C. Michelson.
speculative to assume that adequate operator action can be consistently i
expected within this time frame, regardless of the available indications.
A second aspect of this analysis could also be non-conservative.
If the leakage rate from all scram outlet valves was insufficient to cause rod l
motion, the procedures in place at the time of Quad Cities event did not j
call for operator action to scram the plant. It could have been possible for there to be a lower level of leakage (say 200 gpm) to the SDV without 3
rod motion and with no action to scram the plant. Then within 3 minutes, the capability to scram the plant would have been lost.
I The Quad Cities sequence of events illustrates another aspect of the loss i
of air scenerio discussed in the AE0D Sept. 30 memo. Approximately four minutes passed from the time of receiving the low pressure alarm until the time of manual scram.
In contrast, rod drift began only 30 seconds prior to the manual scram.
The time of initiation of rod drift would probably cor~ espond closely with the time at which significant amounts of water began accumulating in the SDV.
In my judgement, this illustrates that reliance on a UT system indication of water in the SDV instead of t
I control air pressure reduction as a signal to the operator to scram the plant j
greatly reduces the already short time for operator diagnosis and action i
(in this case approximately 4 minutes is lost out of the few available).
It would seera prudent not to risk the shorter response time for the vital scram function.
i Thus, although I agree with both the facts of the Quad Cities event as presented in the attached memo and with the general methods used in the l
analysis, I believe that a truly conservative analysis of the data would indicate a very short operator response time. Thus I would conclude
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i that 'an immediate scram on the loss of CRD air header pressure should be j
required.
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i Georg anik Office for Analysis and Evaluation l
of Operational Data
Enclosure:
Memo dated 9/29/80 l
cc w/ enclosure:
E. L. Jordan P. S. Check W. Mills V. Panciera l
N. Chrissotimos E. G. Adensam i
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