ML19345E117
| ML19345E117 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/17/1980 |
| From: | Cross J TENNESSEE VALLEY AUTHORITY |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8012230158 | |
| Download: ML19345E117 (5) | |
Text
TENNESSEE VALLEY AUTHORITY CH AT TANOOG A. TENNESSEE: 37401 500A Chestnut Street Tower II Decemtser 17, 1900 Mr. Ecbert L. Tedesco Assistant Director for Licensing Divisien of Licensing U.S. Nuclear ReEulatory Cocsission Washington, DC 20555 Lear Mr. Tedesco:
In the Matter of
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Docket Nc. 50-327 Tennessee Valley Authority
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In response to your letter to H. G. Parris dated December 9,1980, enclosed is the additional information requested cencerning items 2 and 5 of your letter. Enclosure 1 is the basis for the local detonation pressure profile, and Enclosure 2 is the information on the analysis of the surviv--
ability of the air return fan system. The item concerning a temperature profile for equipment survivability was submitted in my letter to you dated December 11, 1980.
Items 3 and 4 concerning additional cLASIX code cal-culations will be presented to the lac during the TVA/NRC meeting of December 18, 1980, and they will be documented by December 19, 1980.
Very truly yours, YENNESSEE VALLEY AUTHORITY f
1 J. L. Cross-Executive Assistant to the Manager of Power i
Enclosures l
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ENCLOSURE 1 LOCAL DETONATION PRESSURE PROFILE (Basis for P'ulse Shape and Magnitude-)
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Our review of the Sequoyah Nuclear Plant. geometry and analyses to date have found no significant buildup of hydrogen which could lead to pockets of hydrogen in the detonable range. This is also the conclusion of the consultants Lewis and Karlovitz, who have reviewed the Sequoyah contain=ent.
Since the potential for a local detonation has not been identified, the December 1, 1980, submittal provided information on a best-esti= ate pressure spike. This information was based on a review of various areas within the contain=ent to arrive at a typical size for a cloud of gas. A typical space would have a width of around six feet and thus a six-foot dia=eter cloud was selected.
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Wavre speeds for hydrogen-air =ixtures are generally given in the range fro: 6500 to 9000 ft/sec. For points on the edge of the cloud, a pulse from the shock wave and gas pressure behind the shock front-would have a duration less than 0.5 millisec based on the time required for the wave to traverse the radius of the cloud after the shock wave arrives at the point (i.e., when the rarefaction wave arrives).
The pressure pulse peak given in the Dece=ber 1 sub=ittal was on the order of 100 psi.
This best estimate is based on the previoitsly A
described s=all gas volu=e',a,d is not greatly dependent on gas concentration within the detonable range. In s=all clouds, the wave or shock front does not have ti=e to properly form and thus will not ordinarily reach the maxi =um detonation presures predicted in strong explosions. Maximum peak overpressure for hydrogen in air is given by the Naval WeaponsCenter in technical paper.NWC TP 6089, " Peak Overpressures for Internal Blast," as 12.5 bar of 181 psi. This conservative value would represent the largest peak overpressure outside the detonable mixture. For s=all clouds, this theoretical peak (shown in the figure) would be the largest pressure expected.
The wave fro dthe explosion will obey similarity laws as it traverses the contain'Ed atmosphere proportionally to (rg/r)3.and the peak overpressure will be reduced Thus, within two cloud radii (rs) the peak overpressure should be below containment capability. Studies with this i= pulse loading (see figure) are being performed to estimate the contain=ent capability to local detonation.
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AIR RETURN FAN SURVIVABILITY i
The effa"
'f hydrogen deflagration on the air return fan system has been examin=J. CLASIX results for upper co=partment burns which result in high temperature gases entering the air return. fan inlet plenu: have been reviewed and indicate the temperature histories are within the capabilities of the gystem. The air return fan motor is designed to wi-thstand up to 300 F for four hours in e:ergency conditions.
Burns in the upper compartment result in te=peratures a
l generally below 300 F with only two exceptions (as summarized in Appendix U, Volume II of the Sequoyah Nuclear PlantDegraded Core i
Program Report). fhe first exception is characterized by a temperature of 480 F which lasts only a fer seconds. The other exception is a high temperature upper compartment burn which assumed total fan failure prior to the burn. Hence, this case would certainly not be a rational one for fan temperature qualification.
1 In addition, a continuous burn of 12 percent hgdrogen in a skim =er i
system duct.only results in approximately a 30 F temperature rise in the air at the fan ence mixed with the 40,000 cfm of cooler air entering the inlet plenum from the upper co=partment. An ignition within the fan is not expected since igniters located above each of the fan inlets within the upper compartment would have ignited any fla==able mixture $n the upper compartment volume before entering the fan area. Any high temperature mixture or ignition within the fan volu=c would have caly a short residence time due to the high flow velocity in the fan throat. The fan motor asse=bly is_ constructed of cast iron with a total motor weight of over 1000 pounds. The' system therefore possesses significant thermal inertia to withstand briefly resident high temperatures.
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