ML18219C127
| ML18219C127 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 04/14/1975 |
| From: | Dolan J American Electric Power Service Corp |
| To: | Kniel K Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18219C127 (10) | |
Text
- REPORT OF ABNORMAL OCCVRREiNCE AÃ)/OR INCIDENT NRC DISTRI ION FOR PART 50 DOCKET MAT AL (TEMPORARY FORM)
CONTROL NO:
FILE INCIDENT REPORT FILE F ROM: American Electric Power DATE OF DOC Service Corp.
New York, N.Y.
100 II.
J 4-14-75 DATE REC'D 4 LTR TWX RPT OTHER TO:
Mr. Karl Knie9t CLASS UNCLASS PROP INFO XXX ORIG 1
1 si ned INPUT CC OTHER NO CYS REC'D 1
SENT LOCALPDR DOCKET NO:
50-315 DESCRIPTION: Ltr reporting a deficiency which involves the containment isolation membrane barrier for the non<<essential service water system...
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ENCLOSURES:
PLANT NAME: Donald C. Cook Unit 1 FOR ACTION/INFORMATION BUTLFR (L)
W/ Copies CLARK (L)
W/ Copies PARR (L)
W/ Copies 4fCNI~ (L) copies SCHWENCER (L)
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W/ Copies VASSALLO (L)
W/ Copies PURPLE (L)
'W/ Copies ZIEMANN(L)
W/ Copies DICKER (E)
W/ Copies KNIGHTON (E)
W/ Copies YOUNGBLQQD (E)
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W/ Copies LEAR (L)
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BRAITMAN SALTZMAN MELTZ
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get,ulatorg De'li: File ANERICAN ELECTRIC POVfER Service Corporafi on 2 Broadway, New York, N. Y. 10004 (2121 422.4800 Docket No.
$0-315 License No.
DPR No.
58
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Dear Mr. Kniel:
This is to inform you of a deficiency which currently exists at the Donald C.
Cook Nuclear Plant Unit No. 1 operating under Facility Operating License DPR-58.
The deficiency involves the containment isolation membrane barrier for the non-essential service water system.
The membrane barrier is comprised of the tubes of the containment ventilation units and the portion of the non-essential service water piping inside the contain-ment up to the containment penetration.
Mr. Karl Kniel, Chief Pressurized Mater Reacto Branch No.
2 Directorate of Licensing U. 8. Nuclear Regulatory Mashington, D. C. 20555 It was recently discovered that this membrane barrier has not been qualified as Seismic Class I.
The Donald C.
Cook Nuclear Plant Final Safety Analysis Report page 5.4-2, Item 5 states, "All isolation valves and equipment are designed to operate as Class I seismic equipment".
The current status of this equipment is that the casings and the tubes of the ventilation units have been qualified to Seismic Class 2 (e.g. for the operating basis earthquake).
The non-essential service water piping and Incoming and outgoing lines to the ventilation units each have an appropriate Class C isolation valve outside the containment and therefore they meet the isolation valve criterion.
The isolation valves are Seismic Class 1 and in a piping section which is Seismic Class 1 from the valve up to the containment and including the containment penetration.
This meets the FBAR requirement that, "all isolation valves are designed to operate as Class 1 seismic equipment".
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Nr. Karl Knick April 14, 19'75 welds between the containment penetration and these units are Seismic Class 2, but they do not have the additional quality control associated with Seismic Class 1 equipment.
VFe have made a safety evaluation of this deficiency as described in Item a, b and c below.
a ~
The possibility exists that the membrane barriers inside the containment would fail in the design basis earth-quake.
In this case,,the resultant water flooding would be detected by the cooling coil catch basin, flow meters on the incoming and outgoing lines, sump level or humidity detection, and the operator can close the isolation valves and shutdown the unit.
In the event of a failure of an isolation valve to close, all headers have hand valves which can be manually closed.
Adequate isolation protection exists if a single active failure did not occur.
Adequate protection exists even with a single active failure because the failure would be detected and hand valves would be closed.
Because no radioactivity is created as a result of the earthquake, the isolation can be made without radiation release to the environment.*
b.
No mechanism exists for failure of the membrane barriers in a loss-of-coolant accident.
All ventilation units are behind the missile barrier wall.
The non-essential service water pipes to the ventilation units are adequately separated from missile -sources in the lower containment.
The membrane barriers can withstand the external pressure and environment without loss of isolation function.(they withstood the integrated leak rate test pressure).
In the event of a single failure of an isolation valve to close, the membrane barrier will therefore form the.
isolation barrier.
Therefore, adequate protection exists in a loss-of-coolant accident.
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For conservative containment design purposes, the reactor containment structure is designed for simultaneous loss-of-coolant accident and earthquake loads to assure that its isolation function is maintained.
The ventilation unit tubes and non-essential service water piping between these tubes and the containment isolation valves are a part of the containment isolation barrier.
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hfr. Karl Kniel April 14, 1975 For the isolation function in a loss-of-coolant accident plus design basis earthquake, without Class-I seismic qualification of the membrane barrier, we depend on the isolation valve in each penetration line to close.
A single active failure of a valve to close would 'then create a leakage path.
In a loss-of-coolant accident signals are generated to automatically close these valves.
They are also designed to fail in the closed position on loss of control air.
The solenoids on these valves are such that if the coil burns out or loss of power occurs, they fail such that the isolation valve goes closed..
Although this situation of loss-of-coolant accident plus earthquake plus sin'gle active failure is improbable, we believe that the FSAR, although not explicit, does recognize it as a design condition (PSAR Chapter 5).
For the. situation of loss-of-coolant accident plus earthquake, the operator can take the same action of manually closing hand valves as in Item (a) above.
However, in the case of loss-of-coolant accident plus earthquake, a radioactive source is assumed to exist in the containment and some of this could be released in the time period before the hand valve is closed.
n Ne have underway a design study to add an additional isolation valve on each of the incoming and outgoing lines in the non-essential service water system to the containment venti-lation units -- a total of 20 additional valves.
These additional valves will upgrade the isolation from Class C to Class A for those units.
We intend to perform the necessary modifications at future unit outages of long enough duration to allow this work to be done and as material availability allows.
As an interim corrective
- measure, we have instructed the plant operating personnel to increase the surveillance of the""existing isolation valves on the non-essential service water lines to the containment ventilation units from once every 90 days to once every 30 days (See Technical Specification 4.6.3.1.1.)
This will give increased assurance that they will close if called upon to do so
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The existing design presents a safety problem only in the compounded event of LOCA, plus design basis earthquake, plus single active failure of the valve to close.
Such an event is remote.
Because of the temporary corrective action we are taking, and the fact that the ventilation units and non-essential service water system piping are designed to
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Mr. Karl Kniel ib
~April 14., l9'75 withstand the operating basis earthquake, and the remote possibility of the series of events which must occur to create a safety hazard, it is concluded that the health and safety of the public and operating personnel will not be affected.
Very truly yours, P.
I JED: mla Exe ohn E. Dolan ive Vice President CC ~
Engineering and Construction G. Charnoff, Esq.
Richard 'Malsh, Esq.
Robert J. Vollen, Esq.
Robert C. Callen, Esq.
Peter M. Steketee, Esq.
R. S. Hunter R. M. Jurgensen
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