ML19260C881
| ML19260C881 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 01/25/1980 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8002060336 | |
| Download: ML19260C881 (2) | |
Text
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SACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 s street, Box 15830, sacramento, California 95813; (916) 452-3211 January 25, 1980 Director of Nuclear Reactor Regulation Attention: Mr. Robert W. Reid, Chief Operating Reactor, Branch 4 U.S. Nuclear Regulatory Comission Washington, D.C.
20555 Docket No. 50-312 Rancho Seco Nuclear Generating Station, Unit No. I
Dear Mr. Reid:
Your letter of November 21, 1979, requested small break analysis information. The District's letter of December 19, 1979, provided that portion of the infomation related to reactor coolant pump seals. The attachment to this letter provides the information concerning the mechanical effects of slug flow on steam generator tubes.
This submittal completes the District's response to your November 21, 1979 letter.
Sincerely, htUT M
' John Mattimoe Assistant General Manager and Chief Engineer Attachment 1933 077 bol 5
30 0 2 06 0 3 3c f/j
6UEST10H1 Transitions from solid natural circulation to reflux boiling and back to solid natural circulatioin may cause slug flow in the hot leg piping.
By use of analysis and/or experiment address the mechanical effects of the induced slug. flow on steam generator tubes.
RESPONSE
The loads imposed on the tubes of the OTSG during the postulated " slug flow" have been conservatively evaluated and found to be acceptable.
Based on very conservative assumptions, the end loading on each tube will be 21.5 lbf compared to a theoretical buckling load of about 700 lb.
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It was assumed for this analysis that a water level has been established in the hot leg piping and inside the tubes of OTSG.
The transient consists of a " front" of solid water impinging on the primary face of the upper tubesheet.
The flow was assumed to be equal to full 100% power flow (about 70,000,000 lb/hr).
The load is assumed to be a suddenly - applied load.
The upper tubesheet is conservatively assumed to offer no resistar.ce to the lcad and the lower tubesheet is assumed to be fixed so that the entire load is absorbed by tubes directly under the primary inlet nozzle.
The flow is assumed to not follow the diffuser so that the. velocity impinging on the tubesheet is the same as the velocity in the 36-inch nozzle.
Hot leg temperature is assumed to be 6050F.
The velocity in the 36-inch pipe would be 64.4 f t/sec.
By use of the momentum equation, the steady-state force on the upper tubesheet due tc the velocity would be 16,020 lb. Assuming a suddenly-applied load. the f
comentary force would be 32,160 ibr.
There are about 1500 tubes in a 36-inch diar.eter circle.
Thus the 32,160 lbf will resul t in 21.5 lbf per tube.
Since the cross-secticnal area of each tube is 0.070 in, the acmentary axial compressive stress in these tubes would be 307 psi.
e 1933 078
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