ML19340A270
| ML19340A270 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 04/26/1979 |
| From: | Frahm R Office of Nuclear Reactor Regulation |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8002110628 | |
| Download: ML19340A270 (2) | |
Text
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NUCLEAR REGULATORY COMMisslON y*
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WASHINGTON. D. C. 20555 3
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MEMORANDUM FOR:
R. L. Tedesco, Assistant Director for Reactor Safety, DSS
.FROM:
R.
Fr hm, Reactor Systems Branch, DSS
SUBJECT:
OCONEE SMALL BREAK ANALYSI$
I I have performed a cursory review of the Duke Power submittal (W. Parker to H. Denton, dated April 21,1979) on small break LOCA's for Oconee.
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The analysis assumes a small break and failure of emergency feedwater i
system (EFWS). No ECCS failure is assumed concurrently with failure of-the non-ECC EFWS. Operator action is assumed at 20 minutes to manually i
l establish EFWS for. those small LOCA's that will not depressurize the primary. system to the high pressure injection set point. The limiting break was the largest size for the depressurization of the primary system to just above the HPI actuation set point before the system repressur,2ed.
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The analysis only used a blowdown code because the 50.46 criteria were considered to be met if no core uncovery occurred. Therefore, no heatup l
analyses were performed.
L There are some basic questions that must be answered before the subject I
transmitted can be reviewed and accepted.
It does not appear that the L
analysis took into account any inventory loss when the PORV set point is exceeded. This probably will cause inventory loss without significant f
l depressurization toward the HPI actuation pressure.
If a manual action is taken at 20 minutes to initiate the EFWS, what operator actuations are needed to terminate or control EFWS and HPI for the long-term cooling mode?
These may occur in a very short time interval.
It is not clear that Oconee has the proper instrumentation available to an operator so'he can issess the l
need for a manual action in 20 minutes and the conditions for controlled I.
long-term cooling. Since the pressures are close to HPI initiation and PORY actuation pressures, sensitivity studies on break area and ECCS single failures are needed. The actuation or initiation set points of 1
reactor trip. ECCS, SRV's including initial conditions and other L
assumptions used.in the analysis are needed; as well as criteria t
used and operator actions needed, for long-term cooling. A discussion of natural circulation is also needed.
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Contact:
Ronald Frahm, NRR-492-7341 i
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- S 1 8 1979 R. L. Tedesco
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I suggest we have a meeting with Oconee to get these-answers.
Ronald K. Frahm Reactor Systems Branch Division of Systems Safety cc:
Z. Rosztoczy T. flavak S. Israel G. Matetis B. Sheron O..Ross ~'.
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