ML17244A604
| ML17244A604 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 07/06/1979 |
| From: | White L ROCHESTER GAS & ELECTRIC CORP. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7907130250 | |
| Download: ML17244A604 (28) | |
Text
REGULATORY INFORMATION DISTRIBUTION SYS N (RIDS)
ACCESS ION NBR: 7907130250,DOC.
DATE: 79/07/06 NOTAR 1 ZED:
NO FACIL:50-244 Robert Emmet Ginna Nuclear Pl'anti Unit ii Rochester G
AUTH. MANE AUTHOR AFFlLIATION NHITEiL. D.
Rochester Gas 5 Electric Corp.
REC IP. NANE RECIPIENT AFFILIATION ZIENANNiD. L.
Operating Reactors Branch 2
SUBJECT:
Forwards addi info re pressure shielding steel diaphragmi
=
in response to questions raised during review of 790517 submittal.
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ROCHESTER GAS AND ELECTRIC CORPORATION D
89 EAST AVENUE, ROCHESTER, N.Y. 14649 LEON D. WHITE, JR.
VICE PRESIDENT TEI.EPHONE AREA CODE Tld 546-2700 July 6, 1979 Director of Nuclear Reactor Regulation Attention:
Mr. Dennis L. Ziemann, Chief Operating Reactors Branch No.
2 U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Pressure Shielding Steel Diaphragm R.E. Ginna Nuclear Power Plant Docket No. 50-244
Dear Mr. Ziemann:
This letter is in response to questions raised by members of your Staff during the course of their review of our submittal dated May 17, 1979.
The questions and responses are provided below.
In our May 17 letter, the pressure transients resulting from pipe breaks in the turbine building were discussed.
The assump-tions employed in the a'nalysis were summarized and the plots of pressures as a function of time for the transients resulting in the peak pressures were presented.
In response to a request for the plots for the remaining (non-limiting) cases, we have pro-vided in Enclosure I to this letter the plots of pressure as a
function of time for both nodes for the five cases reported in our May 17 submittal.
A question was raised as to whether credit was taken for cold condensing surfaces in the turbine building.
Since the duration of the transient. is short.,
no credit was claimed for any condensing surfaces in any of the calculations.
A question was raised concerning the use of the Moody correla-tion with subcooled liquid.
Our analysis shows that the fluid immediately upstream of the feedwater line break reaches saturation pressure within 4 msec.
Thus, determination of break flow using the Moody correlation without a multiplier is valid.
Members of your Staff requested that. we investigate the con-sequences of an instantaneous double-ended guillotine break in either the 24" or the 36" main steam lines in the turbine building.
This request was made recognizing that. such breaks are precluded by the augmented inservice inspection program which has previously oor'9I>>>>04 ~
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ROCHESTER GAS AND ELECTRIC CORP.
oATE July 6 g 1979 To Mr. Dennis L. Ziemann SHEET NO.
been reviewed and approved by the NRC Staff.
Nonetheless, the two breaks have been analyzed.
The peak pressures on the mezzanine and operating levels from a 24" steam line break on the operating level are 0.507 psid and 0.589 psid respectively.
The results for the 36" main steam line break on the mezzanine level for the mezzanine and operating levels are 1.264 psid and 0.742 psid, respectively.
Curves of pressure vs. time for these two breaks are provided in Enclosure II to this letter.
In the calculation of the pressure transient following a 24" steam line break, credit.
was taken for failure of a section of block wall as described and justified in our letter of May 17, 1979.
In the calculation of the pressure transient resulting from a 36" steam line break, credit was taken for failure of the block wall and for failure of the building exterior siding.
The exterior siding will fail at a pressure of 0.93 psi.
This failure pressure is based on consideration of the siding design and method of attachment to the building and is set as the ultimate capacity of the aluminum panels in tension.
A total of 2166 ft on the mezzanine/basement elevations is assumed to fail.
Since the pressure on the operating level for the 36" steam line break does not reach 0.93 psi, the siding at that elevation is assumed to remain in place.
A question was raised concerning the vent area between the basement and the mezzanine levels of the turbine building.
The total free vent arey between the basement and the mezzanine levels is at least 3800 ft A discussion of the distribution of the vent areas is presented in Enclosure III to this letter.
Members of your Staff reguested some additional discussion of the depressurization which occurs for a short period of time immediately following a feedwater line break.
Information is provided in Enclosure IV.
Very truly yours, Enclosures p
I L. D. White, Jr.
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Enclosure I This enclosure provides the plots of pressure as a function of time for the pipe break events reported in our submittal of Nay 17, 1979.
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Enclosure II This enclosure provides the plots of pressure as a function of time for the two'nodes for a 24" steam line break on the operating floor and a 36" steam line break on the mezzanine level.
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Enclosure III The turbine building at Ginna Station is a three story structure with large openings between the three floors.
These openings are shown in FSAR Figures 1.2-3 and 1.2-4.
The total open arey between the operating floor and the lower levels is 1160 ft.
The major opening is an open access hatch (52.5 feet by 19 feet) which is located on the north side of the floor.
The balance of the open area is comprised of three stairwells.
As noted in our May 17 submittal, the analyses assume one nope for the mezzanine and basement levels.
An open area of 3800 ft,exists between the mezzanine and the basement levels.
The largest opening is an open hatch and grated area (69.5 feet by 39 feet) which is located on the north side of the mezzanine floor directly below the operating level open access hatch.
A second major open area is located in the western portion of the mezzanine floor.
This area (33'4" by 14'8") is in the immediate vicinity of the main steam and feedwater lines.
Additional area is avail-able from the condensate pump withdrawal hatch, the heater drain pump withdrawal hatch, open and grating space around the moisture separators, and three stairwells.
For breaks on the mezzanine level, significant open areas between the mezzanine and basement levels are found in the immediate vicinity of the major steam and feedwater lines.
The additional openings elsewhere in the building make further contributions to maintaining pressure equalization between the two levels.
It should be noted that the large openings between floors and the relatively unrestricted area around the major piping make these analyses substantially different from pressurization analyses typically performed for major pipe breaks in containment.
Limited opening between floors in containment and compartmentalization of the reactor coolant system increase the need for more detailed treatment of the containment volume.
The design of the turbine
- building, as described above and as depicted in the FSAR, is seen to be substantially less restricted.
For breaks located on the operating level, an important factor in minimizing the pressure differential between the mezza-nine and basement floors is the location of the floor openings.
As can be seen from the figures, there are larger openings in the mezzanine floor below each opening in the operating floor.
This facilitates steam flow from the operating level to both of the lower levels.
Enclosure IV Whenever subcooled water or a two-phase mixture is introduced into an environment at less than 100% relative humidity, a short-term depressurization transient will occur until the atmosphere becomes saturated.
The phenomena occurs for breaks such as a
feedwater line or a primary system rupture.
The magnitude and duration of the depressurization is dependent on the energy of the water and the volume considered.
More specifically, the short-term depressurization phase after a postulated subcooled water or two-phase line pipe rupture is due to evaporative cooling or the process of adiabatic satura-tion.
The fluid leaving the ruptured line separates into steam and water fractions depending on fluid enthalpy and environmental conditions.
If the atmosphere is not saturated, the water will evaporate into the atmosphere.
This mass transfer process, or mass diffusion, is due to the vapor mass concentration difference between the water surface and the environment (Fick's law).
The water vapor will diffuse from the water surface to the lower concentration point in the atmosphere at a rate determined by the interfacial area, mass transfer coefficient, and the driving force due to the concentration difference.
This process is analogous to the heat transfer process which is driven by tempera-ture differences.
This change in phase from liquid to vapor requires the addition of latent heat to the liquid which must be supplied by the air.
Thus, the energy of the air, and consequently, the temperature and pressure, decrease.
This process continues until the atmosphere becomes saturated or the water'nventory is evaporated.