ML19309A247
| ML19309A247 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/19/1974 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| Shared Package | |
| ML19309A245 | List: |
| References | |
| NUDOCS 8003260944 | |
| Download: ML19309A247 (2) | |
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3ACRAML*.iTO M!!NICIPAL UTILD e DISTRICT C 6201 S Street. Box 15830. Sawamento California 95813: (916) 452-3211 fm l
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.. June 19, 1974 Mr. R. R.' Engelken Directorate of Regulatory Operations Region V U. S. Atomic Energy Commission Post Office Box 1515 Berkeley, California 94701 Rancho Seco Nuclear Generating Station No. 1 Report on Feedwater Line to Steam Generator
Dear Mr. Engelken:
During the early phases of the hot functional test program at Rancho Seco Nuclear Generating Station No. 1, a water hammer was experienced in the feedwater piping which caused damage to a Class I seismic support.
In accordance with our Quality Assurance pro-cedures, this nonconformance has been reviewed and has been determined to be a reportable "significant deficiency" as defined by 10CFR50.55(e).
Debeription of Deficiency:.The water hammer occurred during an operating sequence tba was specifically developed to maintain the stringent water chemist.ry requirements established for the secondary water.
The valve lineup used to obtain the desired water chemistry also opened up a path for water in the steam generatdr to flow down the feedwater inlet line, into the feedwater cleanup line, and then flash into the condenser. With this particular valve lineup, a water hammer was experienced when the operator reduced the flow by thrott-ling the startup pneumatically operated feedwater flow control valve.
This reduced the pressure in the feedwater inlet lines to a value less than that in the steam generator and caused a flashing, reverse flow in these lines.
An inspection following this water hammer revealed that one of the 14" feedwater inlet lines to the steam generator had a loose seismic support. This support is a floor mounted sliding ring type of support with the centerline of the pipe about a foot and a half above the grade floor elevation in the reactor building just as the line passes through the secondary shield wall. This seismic o
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Mr..R. H.,Engalken June 19, 1974 V
restrain ring was fastened to the grade slab with four 3/4" anchor bolts, and these bolts had pulled loose-from the floor as a result of the water banener.
Corrective Action: A recheck of the seismic calculations showed that the original design was conservatively designed for the-postulated earthquake loading. However, these seismic restraints have been repaired using eight 1" anchors to provide additional con-servatism.
The stress engineer for this system has also analyzed the stresses imposed on this piping by the water hammer in addition to performing NDT on the pipe welds in the affected area.
No damage occurred in the involved piping.
To prevent any future water hammer in these lines, the District has added two new feedwater cleanup lines. These lines take off upstream of existing feedwater line check valves, take off up-stream of the feedvster flow control valves and route the cleanup feedwater flow back to the main condenser. Under these conditions, i
the existing check valves will prevent any backflow out of the steam generator and eliminate the type of water hammer experienced during hot functional testing.
The District's Standard Operating Procedures have been rewritten to require the use of these new cleanup lines whenever the O
startup requires simultaneous feedwater cleanup flow and mini-feed
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this type of water hammer on future startups.
Should any additional information be needed on this problem or if we can be of further assistance, do not hesitate to call.
Sincerely yours, 1
. Mattimoe Assistant General Manager and Chief Engineer 9
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