ML19207A267

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Forwards Addl Info Re PWR Feedwater Sys in Response to NRC 790525 Request.Details of Process Used to Make nozzle-to-pipe & pipe-to-sparger Welds Encl
ML19207A267
Person / Time
Site: Fort Calhoun Omaha Public Power District icon.png
Issue date: 08/10/1979
From: Short T
OMAHA PUBLIC POWER DISTRICT
To: Reid R
Office of Nuclear Reactor Regulation
References
NUDOCS 7908140394
Download: ML19207A267 (2)


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1623 HARNEY a OMAHA. NE5RASKA 68102 e TELEPHONE 536 4000 AREA CODE 402 August 10, 1979 Director of fluclear Reactor Regulation ATTN: Mr. Robert W. Reid, Chief Operating Reactors Branch tio. 4 U. S. Nuclear Regulatory Comission Washington, D. C. 20555

Reference:

Docket No. 50-285 Gentlemen:

The Omaha Public Power District herewith submits additional information in response to the Commission's letter of May 25, 1979, regarding PWR feed water systems. This information, together with our letter of June 18,1979, provides a complete response to the Commission's inquiry. ,

Sincerely, T. E. Short Assistant General Manager TES/KJM/BJH/sd xc: LeBoeuf, Lamb, Leiby & MacRae 1333 New Hanpshire Avenue, 3uite 1100 Washington, D. C. 20036

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DESIGN Ouestion 2 Provide the results of any stress or fatigue analyses which were performed for this system.

Response

The stress analysis (computer printouts) for the feedwater system, from the steam generator nozzles out to the containment penetrations, has been submitted to the Commission in a letter dated August 9,1979, from Mr. T. E. Short to Mr. K. V. Seyfrit.

Question 2 Provide the details of the welding processes used to make the nozzle-to-pipe, pipe-to-sparger, and piping welds. Include details of welding such as: preheat, jaint configuration (include with or without backing ring), and post weld treatmLnt, if any.

Response

The seal weld at the junction of the thermal expansion sleeve to the distribution (see figure 1) is internal to the steam generator and is not a structural weld. The steam generato nozzle-to-safe end welds were made during the manufacturing of the steam generators. The steam generators were fabricated in accordance with Section III of the ASME Boiler and Pressure Vessel Code in effect at the time of construction, 1966-1967. CE drawing E-232-485-5 previously provided in a letter to the Commission dated June 18, 1979, shows the joint configuration both before and after final machining which left a smooth bore even transition as shown in DETAIL "B" of the drawing. No backing rings were used in the nozzle-to-safe end welds. The welds were made using a shielded manual metal arc process. The components were preheated, 60 F minimum to 400 F maximum. The postweld heat treatment was performed with the initial temperature of the furnace at less than 600 F.

The heating rate at temperatures above 600 F was limited to 400 F per hour or 400 divided by the maximum shell or head plate thickness in inches, but was not required to be less than 100 F per hour. The postweld heat treatment was maintained at 1125 F 25 F for one hour minimum per inch of weld thick-ness but in no case less than one hour.

The maximam cooling rate was the lesser of 500 F per hour or 500 divided by the maximum shell or head thickness in inches, but was not required to be less than 100 F per hour. The weldments were permitted to be removed from the furnace when their temperature had fallen to 600 F.

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