ML19317G855
| ML19317G855 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 09/02/1977 |
| From: | Reid R Office of Nuclear Reactor Regulation |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 8004010701 | |
| Download: ML19317G855 (4) | |
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DISTRLBUTION:
September 2, 1977 CDocket' t
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Docket Ho.:
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RIngram y (U) u d
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g EReeves Sacramento B:nicipal Utility District 0 ELD ATTH: ltr. J. J. l'attimore OI&E(3)
DEisenhut Assistant General Manager g
and Chief Engineer TBAbernathy JRBuchanan 6201 S Street P. O. Box 15830 ACRS(16)
Sacranento, California 95b13 TCarter file Gentlenen:
RE: RANCHO SECO h'JCLEAR GENERtTIMG STATION The I.RC staff continually reviews experience fron operating reactors to
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assure that an adequate level of safety is maintained at each individual i
nuclear plant and for the total population of nuclear plants. As new
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technical infemation and operatitG experience becones available, the URC evaluates whether such infomation coulo significantly alter the previously deternined levels of safety. In this regarc, we have noted that there have been about 50 reported v:ater hamrer events in light water reactors sone of which resulted in structural cacage to safety significant systens. Of those, approximately 20 water hammers have occurred due tc the rapid condensation of steau in feedvater lines in plants with Westinghouse and Co:bustion Engineering designed steam generators.
While for the nost part damage froa tnese events has ocen licited to piping supports, one event in the feadwater line of a pressurized water reactor did result in c significant piping failure. None of the events to date has resultec in an adverse inoact on the health ano safety of the public.
It is possinle, however, that rater hanners could lead to nore severe consequences; althouph it would be expected that the procadility of such events is very low.
Because of the continuing occurrence of water hanr.'er events, the IRC staff has been evaluating available operating experience, actively discussing ut th nuclear steac supply vendors and architect /cngineering firms ways of reducing the frecuency and consecuences of such events, and utilizing technical consultants to more definitely exaeine water hars:cr phenonena.
A copy of the report of our principal consultant, CREARE, is attached (Enclosure 1) for your information.
As a result of our erforts to date, ve believe that water hanners due to L{
the rapid conder.sation of stea?. in the feedwater lines of steam generators [IB represent a safety concern. Accordingly, licensees of facilities with 80040104 5
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Sacramento Municipal Utility
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Westingbouse or Combustion Engineering design steam generators are being requested to take further actions, including possible design
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nodifications, to assure an acceptably low risk to the health and safety of the public from such events. Your facility is not included
. ;;6 in this category since it utilizes B&W steam generators which have not exhibited a propensity for water hamners based on operating
[sg experience to date.
The staff will continue to monitor operating experience to assess
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the possible effects of water hatner on the safety of nuclear power pl ants. While existing Technical Specifi*:ations centain reporting requirements applicable to water hamners, the staff has developed E
additional guidance regarding the type of events to be reported.
Specifically, all dae: aging water harmer events occurring in safety-related syster.s, or occurring in other systens that affect safety-related systens, should be reported. A famat for the reports is E se F
enclosed. Danaging water hacner events are those events that result in:
(a) damage to pipe supports or pipe insulation, (b) pipe EE displacement, or (c) failure of pipes or cooponents.
9 Approved by GAO, B-180225 (R0072), clearance expires July 31,1980.
Approval was given under a blanket clearance specifically for identified generic probleas.
Sincerely, D
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Robert 3. Reid, Chief Operating Recctors Branch f4 Division of Operating Reactors
Enclosures:
1.
Report by CREARE on Vater }lanner Phenomena 2.
Fomat for Report cc w/o enclosures:
See next page 1
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cc: David S. Kaplan, Secretary and c:
Caneral Counsel 5
6201 S Street
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Post Office Box 15830
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s' Business and Municipal Department (w/enclosurel
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828 I Street
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Sacramento, California 95814
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-a ENCLOSURE N0. 2 s
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Report of Water Hantner P. 'D
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+2E Plant Nams and Unit No.
5' Operational Mode Date and Time of Occurrence Plant Systems Affected:
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Aux. Feedwater Reactor Coolant Containment Spray RHR b
Component Cooling ECCS
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Main Feedwater t.-F Other Systems
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Cause of Water Hammer
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Pump Start Rapid Condensatior.
Rapid Valve Motion 1
Voided Pipe m.
Water Entrainment Operator Error
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Other Instrument readings and other observations that indicate the probable cause and effects of the water hanraer:
Description of Damage:
- Corrective Action: