ML19276H036
| ML19276H036 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 08/24/1979 |
| From: | Counsil W NORTHEAST UTILITIES |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| TAC-43142, NUDOCS 7908310502 | |
| Download: ML19276H036 (2) | |
Text
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August 24, 1979 Docket No. 50-336 Director of Nuclear Reactor Regulation Attn:
Mr. R. Reid, Chief Operating Reactors Branch #4 U. S. Nuclear Regulatory Commission Washington, D. C.
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Reference:
(1)
W. G. Counsil letter to R. Reid dated August 22, 1979.
Gentlemen:
Millstone Nuclear Power Station, Unit No. 2 Feedwater System Piping In Reference (1), Northeast Nuclear Energy Company (NNECO) provided the NRC Staff with a comprehensive justification for continued operation in light of the linear indications detected adjacent to four welds in the Millstone Unit No. 2 feedwater piping system.
Reference (1) further indicated that monitoring equipment would be installed on or adjacent to the safe-end to pipe weld on Steam Generator #2 prior to returning the unit to service, and that the details of the instrumentation package would be provided to the NRC Staff.
In fulfillment of that commitment, the following information is provided.
The instrumentation which is being provided in the vicinity of the safe-end to pipe weld (BC-G-1) on Steam Generator #2 consists of two basic types. The first is startup instrumentation which includes the following sensors:
(1) Thermocouples (2) Accelerometers (3)
Strain Gauges.
Because the details of the installation are being finalized at this time, only an approximate number of each type of sensor which will be provided can be specified.
Since the purpose of this instrumentation is to collect data, representative numbers are sufficient to explain and characterize the intent of the installation.
Approximately ten thermocouples will be installed.
Six will be located circum-ferentially in the vicinity of Weld BC-G-1.
Three will be located in the vicinity of the pipe to clbow weld, BC-C-2.
One will be located downstream of Weld BC-G-2 in the vertical run of piping.
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b t It is currently intended that three accelerometers will be installed on one triaxial mount downstream of Weld BC-C-2 in the vertical run of piping to obtain vibration data on the feedwater piping system.
Approximately sixteen strain gauges are being installed on the instrumented loop.
The purpose of the startup monitoring instrumentation is to obtain data to characterize the dynamic response and temperature distribution of the feedwater piping due to various operational modes of the feedwater system. As the data are accumulated, comparisons of the piping system behavior of other plants with similar instrumentation will be made.
The second type of instrumentation is the acoustic Jcak detection system which is being installed in the vicinity of Weld BC-G-1.
This three-channel (i.e., three independent transducers) redundant system in designed to detect leaks from the feedwater piping on the order of 0.5 gpm.
It is designed to alert plant personnel to a change in signal which would be indicative of a potential leak.
Should any one of the three redundant channels demonstrate that a leak exists, a visual inspection of the instrumented area will be conducted promptly. Corrective measures will be implemented as required.
In the unlikely event that all three redundant channels fail during plant operation, the existing leak detection system identified in Reference (1) would remain available. The sensitivity of the existing leak detection system has been demonstrated during operation to be adequate.
Because of the uniqueness of the instrumentation package to Millstone Unit No. 2, it is not possible to accurately determine what the normal signals from the various sensors will be.
Baseline data must be available and evaluated before sensor signals can be addressed with specificity. Therefore, NNECO's commitment regarding this instrumentation can be succinctly stated as follows: if a leak is detected, Millstone Unit No. 2 will initiate a controlled plant shutdown. Further, upon receipt of any abnormal instrumentation signals, the appropriate corrective action will be taken inmediately.
Data from this leak detection system will be monitored once per four hours. Fbre specific guidance as to the interpretation of the information will be provided as knowledge and interpretability of the data is acquired. These records will, of course, be available for the resident 16E inspector, and as such, further details of the instrumentation package are not planned to be docketed.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY I
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W. G. Counsil Vice President 2034 258