ML20148C218
| ML20148C218 | |
| Person / Time | |
|---|---|
| Site: | Washington Public Power Supply System |
| Issue date: | 01/24/1980 |
| From: | Renberger D WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20148C221 | List: |
| References | |
| GO1-80-47, NUDOCS 8001310285 | |
| Download: ML20148C218 (4) | |
Text
P P
W shington Public Power Supply System A JOINT OPERATING AGENCY S
P. O. Don 968 3000 Gro, WASHINGTON W AY RICML A N D. W A BMINGTON 99352 PHows (509) 375-5000 January 24, 1980 Docket Nos:
50-460 G01-80-47 50-513 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation V. S. Nuclear Regulatory Commission Washington, D. C.
20555
Dear Mr. Denton:
Subj ect: WPPSS Nuclear Projects Nos. 1 & 4 Loss of Main Feedwater Evaluation
Reference:
Letter, D. L. Renberger, WPPSS to Harold R. Denton, NRC, " Response to NRC 10 CFR 50.54 Letter of October 25, 1979," December 3, 1979.
In the reference letter we responded to the NRC's October 25, 1979 10 CFR 50.54 letter.
This response included, among other things, recommendations for studies and plant changes.
Our response did not c
address the subject of the Integrated Reliability Evaluation Program (IREP) as it may apply to WNP-1/4.
The subject of IREP was, of course, mentioned in your October 25, 1979 letter.
On January 22 we met with the staff and presented the reliability pro-gram described in the attachment to this letter. This program is based upon what we understand are the significant results of the Crystal River Unit 3 IREP study. That is, the loss of main feedwater coupled with loss of auxiliary feedwater and high pressure injection is a dominant sequence leading to system failure. At the January 22 meeting we received informal staff concurrence of this program as being a meaningful evaluation to be conducted at this time.
8001310 O N g
i Mr. H. R. Denton Page Two i
We will submit the results of this program to the staff by July 22, 1980. We want to review the status of this effort with the staff during the next six months and are open to suggestions as to the most effective means of doing this.
We point out that this effort is in addition to the secondary system reliability study we committed to in attachment f of the reference letter.
Very truly yours,
&k D. L. Renberge Assistant Director - Technology oe cc:
A. Bournia, Nuclear Regulatory Commission N. S. Reynolds, Debevoise & Liberman C. R. Bryant, Bonneville Power Administration A. McBride, Science Application Incorporated B. D. Redd, United Engineers & Constructors, Inc.
R. R. Steinke, Babcock & Wilcox
WNP-1/4 LOSS OF MAIN FEEDWATER EVALUATION Previous studies have indicated that a loss of main feedwater coupled with loss of auxiliary feedwater and high pressure injection is a dominant sequence leading to system failure.
This sequence will be studied for WNP-1/4.
The proposed evaluation will use the methodology and assumptions currently being used in the IREP studies. The subtasks to be included are:
1.
Event Tree Definition:
Event trees will be constructed to describe the possible result of loss of feedwater in terms of the success or failure of safety functions.
This task also will define success criteria for each safety function which will be based on the expected performance of the WNP-1/4 design.
2.
Safety Function Evaluation:
For each decision in the event tree the probability of function success will be estimated based on fault tree construction or on evaluation of histor-ical records as described below:
a.
Main Feedwater System:
Comparison of the design with historical records.
b.
Offsite A.C. Power:
Evaluation of historical records of the BPA power grid, c.
Onsite Emergency A.C. Power:
Evaluation of historical records of diesel-generator systems.
d.
D.C. Power:
Fault tree of the D.C. power system.
)
e.
Auxiliary Feedwater:
Fault tree of the auxiliary feed-water equipment including steam supply and water sources, f.
Instrumentation and Control:
Fault tree of the ECI and ESFAS Systems.
g.
Cooling Water and Ventilation: Evaluation of systems based on previous analyses.
h.
Reactor Scram: Evaluation of common mode failures of RPS, CRDCS and Control Rod Drives based on historical experience.
i.
High Pressure Injection:
Fault tree of the HPI/MU&P system including BWST supply.
j.
Operator Actions:
Evaluation of required actions and j
proposed procedural requirements.
1
'3.
Results Evaluation: The trees specified above will be evaluated using available component mean failure rates (primarily from WASH-1400 and values being developed from the IREP studies) to define sequence probabilities and identify critical loss of main feedwater sequence paths leading to system failure.