ML20086E300
| ML20086E300 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 09/21/1973 |
| From: | Walker R PUBLIC SERVICE CO. OF COLORADO |
| To: | Knuth D US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20086E297 | List: |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8312060450 | |
| Download: ML20086E300 (8) | |
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PUBLIC SERVICE COMPANY OF COLORADO
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[.k September 21, 1973 t -
i Dr. Donald Knuth I. 'A 2 '
Directorate Regulatory Operations
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Office of Regulation
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U. S. Atomic Energy Commission
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Washington, D.C.
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SUBJECT:
Deficiency Report h-AN[
Circulator Outlet
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Diffuser Valve
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Dear Mr. Knuth,
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Pursuant to the reporting requirements of 10 CFR 50, Part
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y 50.55, we are submitting herewith twenty (20) copies of the W;h h.h;. la tI subject report concerning diffuser valve spring f ailures.
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ir Final corrective action has been taken.
The attached pQT report is considered to be complete and fina).
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requirements of 10 CFR 50.
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Very truly yours,
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h f,W,Wdb hf'A R.F. Walker, Vice President p Engineering & Planning
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Facility: Fort St. Vrain Nuclear Generating Station l0... 1..G..
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Subject:
Helium Circulator Outlet Diffuser Valve m J.," -'
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Report Date: September 10, 1973
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- k..a,a Ei Incident: Nine (9) diffuser valve springs were found bro'ren.
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Upon completion of hot flow testing the DCRV internals were inspected.
It was noted that one of the springs installed in the diffuser section of the helium circuletor were broken.
The spring assembly as shown in Figure 1 attached, is installed in the diffuser section as shown in Figures 2 and 3, for the purpose of
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providing a positive return force for the diffuser flapper velve action.
Further inspection revealed that nine (0) of the sprines I
were broken.
The breek typically occurred at l owe r-c l osed-sh o r t-radius bend of the spring.
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_Couse of Incident i
T The cause of the breaks is still being investicated.
From all indications, however, i t would appear that the sprines failed in f atigue probably due to vibration of the spring and internal stresses at the short radius bend.
Action Taken All of the assemblies (16 in total) were removed.
The sprin?s were removed and a new design was initiated usino a new stop clip as sho' n in Figure 4 The new stop clip will keep the diffuser w
valve in a position'slightly more closed than with the previous spring design thereby ensuring a positive closing force by reverse flow.
Consequences of Tncident The broken sprinos did not result in any adverse effects durino the hot flow testing.
The circulators were started and shut down several times during the tests, and there was never rnv indication of failure of the diffuser valve to close.
It would be possible for broken spring parts to fail into the circulator which could s
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result in possible damage to the compressor blading.
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Although it is scademic, causes of the spring failure will a
be determined.
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Drawings are to be revised documenting design changes made.
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