ML19317F114
| ML19317F114 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 03/14/1974 |
| From: | Peltier I US ATOMIC ENERGY COMMISSION (AEC) |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8001080805 | |
| Download: ML19317F114 (2) | |
Text
[
- r, MAR 1 4 1974 j
Docket Nos.60-269
'0-270 and 50-287 y te to Files:
OCONEE FLUX / FLOW TRIP INSTRUMENTATION I held a conference call with Duke Power (Canady) and B&W (Straub)
- regarding the discovery at Oconee that the time constant of the' flux /
flow sensing string "as-built" is different than assumed in the FSAR safety analysis.
According to B&W, the "as-built" sensing string time constant was checked
' during the start-up program in Oconee 1 by comparing it to an essentially "zero" time constant parallel test string. The time constant was discovered to be 1.4 seconds with the appropriate snubbers installed to provide adequate instrument damping. The value assumed in the safety analysis was 0.65 seconds.
Since the "as-built" value is in the non-conservative direction, B&W reanalyzed the two pump trip condition to assure that
-the flux / flow trip setting of 1.08 is still conservative and adequate to meet the hot channel DNBR criteria of 1.3.
The reanalysis confirmed that the 1.08 value is still conservative and adequate and consequently a change in the Technical Specifications is not required. However, in the reanalysis B&W used the B&W-2 CHF correlation instead of the W-3 CHF correlation. JThe B&W-2 correlation shows about 1 second longer to DNBR of 1.3 than the W-3 correlation which more than off-sets the increase The staff has accepted the B&W-2 correlation.
in time constant. _
Furthermore the design value of 4 pump flow was used in the calculation but in fact the actual flow is about 8% higher than the design value consequently the analysis is conservative in this respect. I have made an additional inquiry of the applicant regarding the analysis of the locked-rotor accident.
l By Technical Specification an " unusual event" is, among other things,
" Discovery of any substantial errors in the transient or accident analyses or in the methods _used for such analyses, as described in the Safety Analysis Report or in the bases for the Technical Specifications."
"Any substantial variance from performance specification contained in
-the Technical Specifications or the Safety Analysis Report."
1 Therefore, the question as to why Duke did not report this discovery as an " unusual event" can be raised.
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, ggg g 4 gy, According to B&W the real time constant for the sensing string is not
. checked until the plant is well into its start-up program. Then a study is performed to determine if the "as-built" value is within the required ban or range. Since Oconee 1 started up a year ago, the only conceivable logic for not reporting the discovery as an " unusual event" lies in the interpretation of the word " substantial" in the definition of an " unusual event".-
The Part 50 (10 CFR) Section 50.59 says that the licensee may make changes that do not involve changes to the Technical Specifications or an unreviewed safety question. It does not specifically address discovery of "as-built" performance different from FSAR described or assumed performance.
Section 50.36 " Technical Specifications", subsection 11, says that automatic protective system settings must be such as to prevent exceeding safety limits.
It would appear that a discovery of this nature could be judged to be either " substantial" or "not substantial" depending upon whether or not it leads to the conclusion that a Safety Limit could have been exceeded as a consequence of an improper setting of the protective system.
I have discussed this situation with R0 Region II and it is in the process of looking into the matter further to determine if there has or has not been a " violation" in Duke's handling of the matter.
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d I. A. Peltier, Project Manager Light Water Reactors Branch No. 2-3 Directorate of Licensing ces:
A. Schwencer V. A. Moore J. G. Davis, RO F. Jape, RO:II l
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