ML19260D052
| ML19260D052 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 01/30/1980 |
| From: | Davison D CLEVELAND ELECTRIC ILLUMINATING CO. |
| To: | |
| References | |
| NUDOCS 8002070302 | |
| Download: ML19260D052 (7) | |
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ILLUMINArtNG BLOG. e PUBLIC SCUA At e CLE. ELAND ; m 0
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- C. Son 3:00 Dafwyn R. Davidson TcE *RES CENT s s7E"ENsweeams 4No ccNstauct' "
January 30, 1980' Mr. James G. Keppler Director, Pegion III Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 799 Rcosevelt Road 1938 105 Glen Ellyn, IL 60137 Re:
Perry Nuclear Power Plant Final Report on Natural Gas
Dear Mr. Keppler:
Pipeline Break Analvsis On October 3,1979, a letter describi'ig a potential significant deficiency concerning the analysis of the ef feet of a postulated 5 eak of the natural gas pipeline on the structural integrity of plant buildings was sent to your office. An interim report was included for your information and files.
Deficiency Description As described in the October 3,1979, letter, the 16-inch natural gas (99':
methane) line originally existing near the site was moved to a distance of 3,200 ft. from the nearest plaa: structure, as a result of the P5A.1 eraluation of the design basis accident (DBA). The D3A consisted of a guillotine break of the pipe with subsequent detonation of the resulting uncontained plume.
The design limit on the pressure wave was 1.2 psig of overpressure at the plant structures.
During the modification of moving the pipeline, it was also increased in size to 20 inches.
Re-evaluation of the DBA with the increased pipu size resulted in a possible overpressure exceeding the desizn linit of !.2 psig.
~his avaluation precipitated our le: tar of ?ct
- 3, 1979 Resolution Discussion with the East Ohio Gas Company and investigation by the NUS Corpore. tion revealed that recent studies and tests have proved that detonation of an unconfined methane plume is not possible.
A new DBA was defined which involvu a flammable concentration of methane adjacent to the air intakes of plant structures.
The design limit is that no fla==able gas mixture be adjacent to plant intakes.
The NUS Corporation has performed an analyais of this event. The results cf their analysis indicated that accidents involving the release of natural ga:
from existing pipeline do not pose a hazard to the plant, as the concentrati n 30/ 7 of the natural gas at all plant air intakes would be well below the fl=mable gg limit. The enclosed report is a ecpy of our proposed FSAR submittal on this
- item, ff 8002 07 0 SO A 3
{r. James G. Keppler Janua ry 20, 1930 As a result of this analysis, the patential significant deficiency na longer exis t s.
Please feel free to call if you have any questions or require additional information pertainittg to this matter.
Very truly yours,
- f... '..,i:, )
l
, sit Dalwyn R. Davidson Vice' President System Engineering and Construction
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DRD/WEC:pb 19/M/2 Enclosure ec:
1938 106
PERRY NUCLEAR POWER PLANT Accidents Involving Natural Gas Pipelines Potential accidents involving the release of natural gas from existing pipelines described in FSAR Section 2.2.2.3 do not pose a hazard to the plant. As shown below, in the event of an accident the concentration of gas at all plant air intakes is well below the lower flammable limit. Also detonation of an unconfined natural gas-air mixture is not considered to be a credible event (1,2,3,4).
Each of the existing pipelines was analyzed to determine the most limit-ing potential accident condition; the results of this analysis indicated that the most limiting release of natural gas would involve a break in the closest 4-inch natural gas pipeline. The analysis of this accident was performed using the following conservative assumptions:
1 A break in the pipeline occurs at the point of nearest approach to the plant (3200 feet for 20-inch pipe and 2000 feet for 4-inch pipe).
2 Gas is released by a constant enthalpy process yielding a gas temperature for' dispersion calculations of 240F (for a 400F initial gas temperature) due to the Joule-Thompson effect.
3 The flow rate out the break is ranged from the maximum transient 3
flow rate to a minimum flow rate of im /sec.
4.
Atmospheric dispersion is for class G stability using Regulatory Guide 1.78 dispersion parameters and a virtual source distance correction to account for initial finite source size.
1938 107 1
PERRY NUCLEAR POWER PIANT a substantially lower pressure at the end of the blowdown, the energy gain from (2) above and the energy transformation indicated in (1) above must be present in the form of heat. Therefore, the slowed down natural gas in the atmosphere would be at a slightly higher temperature than the original temperature. The blowdown is therefore, in essence, a throttling or isenthalpic process. Since natural gas is a real gas, not a perfect gas, the Toule-Thompson Effect will cause the natural gas to be about 16F below that expected for a perfect gas after blowdown.
The above description process indicates that there is a tendency for a perfect gas after the blowdown and mixing phase to be at a slightly higher temperature than the original temperature. However, with real gases, this temperature increase is lessened or, perhaps, reversed slightly. Therefore, extra conservatism is introduced into the plume rise analysis by assuming that the natural gas does not mix thermally with air and is cooled tsenthalpi-cally 16F below the temperature it pcssessed prior to the break.
The plume rise calculations conservatively assumed the gas is released at zero momentum flux at the point of the break. In reality, because the pipe is below grade, the gas would be expected to have a significant vertical velocity compcnent. This would tend to carry the plume higher than calculated.
Class G stability results in the smallest plume rise and the largest centerline concentration. These combine to give the highest concentration at the air intake and the smallest distance from the air intake to the icwer flammable limit. Using Class G stability is therefore conservative.
3 3
A range of flow rate from 1 m /see to 1800 m /sec, which covers up to the maximum break flow from the 20-inch pipe, were studied. While the larger 1938 108 3
PERRY NUCLEAR POWER PIANT References 1
Foster, J.C., Jr., et al, "Detonatability of Some Natural Gas-Air Mixtures," Air Force Armament Laboratory, AFATE-TR-74-80, November 1970 2
Kogarko, o.M., et al, "An Investigation of Spherical Detonations of Gas Mixture," International Chemical Engineering, Vol. 6, No. 3, July 1966 3
Loesch, F. C., " Thermal Radiation and Overpressure from Instantaneouu LNG Release into the Atmosphere," TRW Report No. TRW-08072-4, April 26,1968 4.
" Safety Evaluation Report, Tennessee Valley Authority, Hartsville Nuclear Plants A and B," U.S. Nuclear Regulatory Commission, NUREG-0014, Apd18,1976 5.
Briggs, G. A., " Plume Rise," TID 25075, Equations 4.19c, 4.32 and 5.7, November 1969 1938 109 5
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