ML20076L463
| ML20076L463 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 07/15/1983 |
| From: | Bradley E PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8307190197 | |
| Download: ML20076L463 (8) | |
Text
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6 PHILADELPHIA ELECTRIC COMPANY 23O1 MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 CDW ARD G. BAU ER, JR.
y
,4 No esses ak cousesso EUGENE J. BR ADLEY Q
assoctava eassanas cousessk DON ALD BLANKEN RUDOLPH A. CHILLEMI E. C. KI R K H ALL July 15, 1983 i
T. H. M AH ER CORN ELL PAUL AUERBACH assasvant asumma6 cousssak EDW ARD J. CULLEN. JR.
THOM AS H. MILLER, JR.
IRENE A. McK ENN A assistant counset Mr.
A.
Schwencer, Chief Licensing Branch No. 2 Division of Licensing U.
S.
Nuclear Regulatory Commission Washington, D.C.
20555
Subject:
Limerick Generating Station, Units !&2 Tornado Depressurisation Infornation for Me teorology and E f fluent Treatment and Structural and Geotechnical Engineering Branches Re fe rence :
Telephone Conversation among Meteorology and Effluent Treatment Branch, Structural and Geotechnical Engineering Branch and Philadelphia Electric Company on June 24, 1983 File:
GOVT l-1 (NRC)
Dear Mr. Schwencer:
The attached document is a draft revision to the response to FSAR Question 220.2 prepared as a result of the referenced telephone conversation.
The information contained in this draft FSAR change will be incorporated into the FSAR, exactly as it appears on the attachment, in the revision scheduled f or Augus t, 1983.
Sincerely l
8307190197 830715 PDR ADOCK 05000352
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A PDR u ene J.
radley JTR/gra/25 gj Attachment i
I Copy to:
See Attached Service List
c.-
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O cc: _ Judge Lawrence Brenner (w/o enclosure)
Judge Richard F. Cole (w/o enclosure)
Judge Peter A. Morris (w/o enclosure)
Troy B. Conner, Jr., Esq.
(w/o enclosure)
Ann P. Hodgdon (w/o enclosure)
Mr. Frank R. Romano (w/o enclosure)
Mr. Robert L. Anthony (w/o enclosure)
Mr. Marvin I. Lewis (w/o enclosure)
Judith A. Dorsey, Esq.
(w/o enclosure)
Charles W.-Elliott, Esq.
(w/o enclosure)
Jacqueline I. Ruttenberg (w/o enclosure)
Thomas Y. Au, Esq.
(w/o enclosure)
Mr. Thomas Gerusky (w/o enclosure)
Director, Pennsylvania Emergency Management Agency (w/o enclosure)
Mr. Steven P. Hershey (w/o enclosure)
Donald S. Bronstein, Esq.
(w/o enclosure)
Mr. Joseph H. White, III (w/o enclosure)
David Wersan, Esq.
(w/o enclosure)
Robert J. Sugarman, Esq.
(w/o enclosure)
Martha W. Bush, Esq.
(w/o enclosure)
Spence W. Perry, Esq.
(w/o enclosure)
Atomic Safety and Licensing Appeal Board (w/o enclosure)
Atomic Safety and Licensing Board Panel (w/o enclosure)
Docket and Service Section (w/o enclosure)
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LGS FSAR OUESTION 220.2 (Section 3.3.2.'1) i Section 3.3.2.1 of the LGS-FSAR states that the pressure transient caused by the design basis tornado is a 3 psi pressure drop at the rate of 1 psi /sec.
However, NRC R.G.
1.76, " Design Basis Tornado for Nuclear Power Plants" calls for a pressure drop of 3 psi at the rate of 2 psi /sec.
Discuss the effect on structures required to be tornado resistant of the faster rate of l
pressure drop.
RESPONSE
The increased depressurization rate of 2 psi /sec in Regulatory Guide 1.76 would have no effect on the external structural elements of tornado-resistant structures.
These structures are designed for the maximum pressure differential due to a tornado of 3 psi regardless of the rate of depressurization.
The increased depressurization rate would increase the maximum differential pressure for internal structural elements.
These elements were checked for the maximum differential pressure caused by the following design basis tornado pressurization profile: a 1 psi /sec pressure decrease for 3 seconds; a 2 second calm; a 1 psi /sec pressure increase for 3 seconds.
An analysis to determine the effects of the increased maximum differential pressures on the internal structural elements has.not been performed because the 1 psi /sec depressurization rate is considered to be conservative.
The design basis tornado pressurization profile used was committed to in the LGS PSAR, Appendix C, Section C.2.4, prior to the issuance of R.G.
1.76.
This pressurization profile was based on the technical paper
" Nuclear Power Plant Tornado Design Considerations" by J.A.
Dunlop and K. Wiedner in the Journal of the Power Division, Proceedings of the American Society of Civil Engineers, March 1971.
Previous documents used as the design basis for tornado effects were Bechtel Power Corporation's topical report " Design Criteria for Nuclear Power Plants Against Tornadoes", B-TOP-3, dated March 12,.1970, and Bechtel Power Corporation's July 1969 report " Tornado Criteria for Nuclear Plants." Actual tornado parameters were developed by studies of the tornado damage,
. eyewitness accounts of the maximum tornado depressurization on L
barometric instruments, and analysis of films of actual tornadoes.
The depressurization effects defined in the ASCE paper and the Bechtel reports substantiate the conser/atism of
' the 1 psi /see_depressurization rate because they exceed the observed effects of actual tornadoes.
IAM 220.2-1 Rev. 7, 06/82
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Per R.G.
1.76, Limerick is in zone I, a region which encompasses a wide vari. tion of tornado risks; from high tornado riskiareas such as the4J4idweste to low risk areas such as New England.
_ g, $ enspecific tornado risk data base is used to determine O.e_.,_Da:Jgn coc.16Tomc6659P"'l*-
l Tornado data was obtained from the National Severe storms' Forecast Center for th ars 1950 through 1981 in lusive for an area 125 nautical mile r.dius centered on Pottstown, PA.
During this time period there were 322 tornadoes, or 10.1 tornadces per year.
The probability that a tornado will strike a particular area is given by WASH-1300 as:
Ps = n (a/A) where Ps.is the tornado strike probability, n is the average number of tornadoes per year, a is the average individual tornado area, and A is the land area within 125 nm of Pottstown.
From the tornado data, tornado areas were calculated for 307 ternadoes (data was not available for 15 tornadoes).
The average area was 0.24 square miles.
The land area within 125 nm of Pottstown is approximately 53,500 square miles.
Therefore, the average proba-bility of a tornado strike is:
4
= 4.6 x 10-5/ year s*
3,50 In accordance with WASH-1300, the probability of occurrencg of a tornado that exceeds the DBT should be on the order of 10 ' per
-year to adequately protect public health and safety.
Therefore:
e Ps.Pi.g 10-7 whcre Pi is the acceptable intensity probability.
- Thus, Pi = 10-7/4.6 x 10-5 = 2.2 x 10-3 per year =.22%
Each tornado in the tornado data base has been classified according t.o a.windspeed scale (the Fujita parameters).
The'distributi n of
' tc rnadoes with respect to. windspeed is given in Table 3 The cumu-l'ative distribution from Table,, is plotted in Figure $
Using Figure 1, the maximum windspeed corresponding to a prcbability Pi of-0.22% is 280 mph.
9 Q 2lLO. 7_-l 9 Q 720 2.- l.
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4h-g g*ild} ff9" s_E To determine the rotational and translational components of the maxi-mum windspeed, the values obtained from Table 4 of WASH-1300 are used for interpolation.
The values thus obtained are:
translational wind-speed of 56.5 mph and rotational windspeed of 223.5 mph.
The depressurization rate is calculated by WASH-1300 as follows:
DV
=
m where p is the pressure t is time T is the translational windspeed Vm is the rotational windspeed p is the density of air rm is the radius of-maximum rotational windspeed From Table 4 and Table 5 of WASH-1300, the parameters for a Region I DBT are:
T = 70 mph Vm = 290 mph ff=2 psi /sec Thcrefore, by ratio 2
dp2 dpi T2 Vm dt-dt
= 2.0 x 56.5 x (223.5)2 V,2 70 x (290)2 T1
= 0.96 psi /sec These site specific tornado parameters are less limiting than the values used for the DBT in FSAR Section 2.3.1.
F.,a rg=P s4 s.
khu _ E mte Q uo.t -l Windspeed and Cumulative Windspeed Distribution for Tornadoes within 125 nm of Pottstown, PA
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No of Percent Cumulative Windspeed Classification Tornadoes of Total Percentaga F5 (261 - 308 mph) 0 0.0 0.0 F4 (207 - 2fG mph) 0 0.0 0.0 F3 (158 - 206 mph) 15 4.9 4.9 F2 (113 - 157 mph) 93 30.2 35.2 F1 (73 - 112 mph) 154 50.2 85.3 F0 (4 0 - 72 mph) 43 14.0 99.3 F-1 (<40 mph) 2 0.7 100.0 4
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