ML19256B176

Responds to NRC Request for Addl Info Re Tornado Missile Protection of Main Steam Lines.Info Deals W/Analysis of Automobile Impact on Main Steam Line Piping & Calculation of Restraint Barrier Stiffness

ML19256B176
Person / Time
Site:	05000580, 05000581
Issue date:	01/08/1979
From:	Mcwhorter R OHIO EDISON CO.
To:	Boyd R Office of Nuclear Reactor Regulation
References
NUDOCS 7901240202
Download: ML19256B176 (7)

Text

a

• s s O OHIO EDISON COMPANY 76 SOUTH MAIN STREET, AKRON, OHIO 44308 216-384-5918

""'"[/;,",l1",""" January 8, 1979 Mr. Roger S. Boyd, Director Division of Project Management U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Subject:

Erie Nuclear Plant, Units 1 & 2 USNRC Docket Nos. STN50-580 and STN50-581 Additional Information for SER Supplement

Dear Mr. Boyd:

In a letter from Lynn Firestone to you dated September 14, 1978, information was submitted to address SER Outstanding Issue 2 concerning tornado missile protection of the main steam lines. After reviewing the above information, the NRC staff requested further clarification in order to complete their review.

The requested information is enclosed and deals with two topics. The first topic is an analysis of the automobile impact on the main steam line piping. The second topic is a calculation of the restraint barrier stiffness. Details are provided to substantiate the stiffness values transmitted previously.

It is our understanding that the submittal of the enclosed information resolves all outstanding issues which have delayed iscuance of the Safety Evaluation Report. If this 4 3 incorrect, please advise.

Very truly yours,

/c//c , hW lWvtW RJM/ROR:jmm Enclosure cc: See Attached Distribution List

• b 790124 02.02. 'b $

6

A, [ [ I, p, A.,,11 T, STATE OF OHIO )

SS.

SUMMIT COUNTY On January 8, 1979, before me, a Notary Public in and for the State and County aforesaid, personally appeared Robert J. McWhorter, who after being sworn according to law, deposed and said that he is Vice President and an Officer of Ohio Edison Company, an Ohio corporation, that in such capacities he is authorized to make this Affidavit; and that the foregoing is true and correct to the best of his knowledge, informa-tion, and belief.

/Pr/r # h 31 T (( S M Robert J. McWhorter Sworn to and subscribed before me the day and year aforesaid.

f Notary Public JOSEPHINE M. ftELROY I'OTAiY PU3LIC - STATE OF CH!O RES! DENT OF SUI.!TAl! COUtiTY fly Commisdon Expires Au217,1932

Distribution List ec: DWHayes (USNRC OIE:III)

RThoma (Oak Ridge National Lab)

HKohn (OPSC)

JAckerman (Ohio Dept. of Health)

PGasteier (Erie County Commissioner)

RLMuctard (USEPA, Chicago)

Librarian /ThermalReactorsGroup (Brookhaven National Lab)

Atomic Industrial Forum GCharnoff (SPPT)

EStebbins RTufts

Overall Structural Response of Pioing Due to Automobile Impact The automobile is the largest tornado missile and contains the most kinetic energy. However since much of the energy is lost in the de-formation of the automobile upon impact with the piping, the overall structural damage is less severe thar. that of the 12" pipe, in fact the elastic limits of the pipe material are not even exceeded. A time history dynamic analysis is presented here to show this.

The applied force time history for the automobile crash is taken from a topical report " Design of Structures for 14issile Impact", BC-TOP-9A, Rev. 2, Sept. ,1974. Subsection 5.1 of that report gives a force time history as follows (with Erie Nuclear values for the automobile inserted):

F(t) = 485.0 sin 20t (Kips) O s t s 0.0785 sec.

F(t) = 0 - 0.0785 sec < t where: F(t) is the force on the target and t is the time from the instant of initial contact.

The automobile impacts directly upon the main steam line piping which in turn transmits the load through the adjacent pipe restraint barrier to the Auxiliary Building. The main steam line piping and adjacent barrier are considered as a single degree of freedom system with stiffness, K, and effective mass, M . The system is the same as that used in the energy balance method

• however only the elastic portion of the system is needed since the yield point of the pipe material is not exceeded.

1

The equation of motion for the main steam line piping is ME + Kx = F(t) where: M is the combined mass of the automobile, main steam line piping and restraint barrier, K is the stiffness of the main steam line piping and restraint barrier, and F(t) is the force as defined above.

Boundary conditions are x = x = 0 at t=0 The solution to this equation for t 10.0785 sec. is, x= 485.0 1 E

" 2 (sin 20 t

• sin wt) w -400 where w =

The solution to the equation for t >0.0785 sec. is, x = A sin (wt + B) where A = 485.0 M 2 1

3 _ m40 sin 40E + 400 g- 400 2 w

~

mu '20 B = arccos sin 40 - w 40 nw 400 1-o sin 40 + g 2

The maximum deflection of the system is 6

max

A Consider the case of the automobile impacting the main steam line in the middle of a 6.5 foot span. The stiffness of the pipe is 456,000 Kip /ft and the stiffness of the barrier is 110,000 Kip /ft giving a combined Kip /ft. The effective mass of the pipe and barrier stiffnessof89,00g/ft are20.0960 Kip sec and the mass of the automobile is 0.125 Kip sec /ft. The natural frequency of the combined system is e = VK/M

634.60 rad /sec. The maximum deflection is:

6 max

= 0.005528 ft.

2

This deflection produces a stress which is within the yield limit of the material and shows that the impact of the automobile do,1 not stress the main steam line piping and restraint barrier beyond the elastic region.

This is because most of the initial kinetic energy of the automobile is lost in its own crushing on impact. Therefore the automobile missile is much less severe than the 12" pipe, the worst non-deformable missile.

As discussed.in the September 14, 1978 letter, additional conservative effects not considered in this analysis include: (1) the reduction in the missile velocity when the missile perforates the protective enclosures for the pipe, (2) the 1.5 inch gap between the pipe and the barrier which allows the pipe to absorb energy over long spans, (3) the 30 percent reduction in missile velocity for missiles striking from the vertical direction, and (4) the initial stress in the pipe due to internal steam pressure. The consideration of these effects will tend to reduce the damage to the main steam lines.

Calculation of Barrier Stiffness The information requested on barrier stiffness is of such detail that it would not normally be supplied in an SAR. The following is a summary of the analysis necessary to calculate stiffness. Drawings of the barrier have not been finalized at this date and therefore are not transmitted.

In addition, standard techniques to calculate beam stiffness and cc.nbined stiffness are not given in detail.

1. Vertical segment of pipe The stiffest segment of barrier adjacent to the vertical pipe is near the header at the bottom of the vertical run. In this region the pipe runs parallel to a vertical beam which is supported at 15 feet intervals.

Shims are placed over this beam at 8 foot intervals at the location of the horizontal crcss beams. When the pipe impacts the barrier these shims are the points of contact. The pipe and barrier are sketched below.

Barrier bean - W24X162 2'

Shim

( N 8' r ss beans 4-1 Pipe

~

o 5'

Points assumed rigid 3

Stiffness of the beam at the upper cross beam is 600,000 Kip /ft.

Stiffness of the beam at the lower cross beam is 85,000 Kip /ft.

The stiffness of a point midway between the two cross beams is approximately 300,000 Kip /ft.

Therefore if the pipe is loaded midway between cross beams the net stiffness is the stiffness of the pipe, 245,000 Kips /ft, combined with the stiffness of the barrier, 300,000 Kip /ft. The net stiffness is 135,000 Kips /f t.

2. Horizontal segment of pipe Over the Auxiliary Building roof the main steam lines are perpendicular to cross beams spaced at 7.0 foot or 6.5 foot intervals. When the pipe contacts and loads the barrier these cross beams are loaded at a point either 5 feet or 10.5 feet from an end depending on which pipe is hit.

10.5'

6. 5 '__ _ 5 '__

Pipe Barrier beam L!24X162 Points assumed rigid The stiffness of the beam under the pipe 5' from the end is 55,000 Kip /ft which is the stiffer of the two locations.

The net stiffness of the barrier is the sum of two cross beams acting together which is 110,000 Cip/ft. When the pipe is loaded midway between cross beams the stiffness of the system is the combination of the pipe stiffness, 456,000 Kip /ft and the barrier stiffness, 110,000 Kip /ft.

This net stiffness is 89,000 Kip /ft.

4