ML20084C958

Forwards Supplemental Info to Special Rept 13 Re Core Spray Water Hammer Incident

ML20084C958
Person / Time
Site:	Dresden
Issue date:	06/24/1971
From:	Brian Lee COMMONWEALTH EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084C956	List: ML20084C958 ML20084D064
References
13400, NUDOCS 8304080391
Download: ML20084C958 (5)

Text

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. s-Commonweahh Edison Company

1. ONE FIRST NATOONAL PLAZA

• C H I C A G O. ILLINOIS h A6ereen Repip ee-b POST OfflCt 802 747

• C H IC A C O. It LINOIS 4049 0 i e -

Jtane 24,1971 ' '

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', Dr. Peter A. Morris, Director

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Division of Reactor Licensing -

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U.S. Atostic Energy Cossaission [ [

'/ Washington, D.C. 20545 _

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Subject:

Additional Information concerning_the \. _

[ eseration of Dresden' nit 3r' s

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Dear Dr. Morris:

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On April 24,19717 we substitted to you' Dresden Special

{ Report Nos. 10 through 13. Report No. 13 of that series 4,iss . ,

j cussed the core spray water hasumer problast., Tbja report has s 2

been reviewed by members of your staff and additional infor'antion

! concerningtheappliedforcesandfatiguelife,oftheaserge}fk:y l Core Cooling Systest piping was requested.

1 Attached hereto is a report entitled "Supplessental Information to special Report #13 Core Spray Water Hausser Incident". We believe that this inforusation answers the questions raised by asabers of your staff.

In addition to three signed originals, 19 copies of this additional inforenation are also subsaitted.

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$50 qo h CJJL

/)g pg Syr Lee, Jr. V Assistant to the President SUBSCRIBED and to before y thim,2 '/ day of _

_ Lh / _ , 1971. -

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cN J W-Notary Public Yb

. J1TI 8304080391 710401 i PDR ADOCK 05000237 G . PDR

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O-SUPPLEMENTAL INFORMATION TO SPECIAL s' REPORT # 13 CORE SPRAY WATER IIAPJ45R I.NCIDENT

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i There are two questions concerning the stress analysis included in Special Raport No. 13, Dresden 2 Core Spray Water Hammer Incident, dated April 21, 1971 which are as follows: 's 1 - Each of the loading cases presented consists of a momentum force applied at a sipgle location within' the system. Would it not be more realistic to account for the ov,erlap that would actually occur and therefore apply force 'at more than one location for each case?

s 2 - No mention is made in the report of how many stress' cycles occurred nor is any assessment made of the cumulatize fatigue

. damage that might have~ occurred due to the rather large stret.s of 115,078 psi calculated in run No. 5 at point 70. What is the calculated fatigue damage, and does enough fatigue life remain to prcvide for the operational loads the piping ~will be '

subsequently subjected to?

In answer to the above, the following information is presented:

?

Special Report No'. 13 covered water hammer incidents for

' both the 2A and 2C core spray discharge lines, but only in'cluded w l ,

stress calculations for the .2A lin't.. The 2C analysis was not

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t included because the calculat, inns were not complete at the time 4 s + s

• t g report was'i ued.' k. .

As stated in the report, the statl , loading analysis made for the 2A .s piping yields gross overestimates of' piping stresses and -

deflections. For this reason a , realistic fatigue damage could not be estimated from the results. Furthermore,,an estimate of fatigue damage requires knowledge of the number of stress cycles applied.

The static, analysis does not provide in' formation from which to estimate number of cycles. Had momentum forces been applied at '

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T Q(m C) k-more than one location for each of the loading cases analyzed, the calculated deflections would have been even more exaggerated and inconsistent with the physical evidence. Clearly, the only useful purpose of the analysis was to establish areas of relative high stress so that those portions of the system could be more closely e investigated by appropriate non-destructive examination techn: ,uer Since Report No. 13 was issued, the analysis of the 2C piping has been completed. The 2C analysis is more reatlistic in that a dynamic method was used; i.e., time varying momentum forces were applied at all points within the system. Calculated stresses and deflections were much smaller than the values obtained from the static method and calculated deflections were in better agreement with the physical evidence. The results of this more refined analysis supports our position that the 2A piping static analysis was very conservative.

Attached is a calculation showing the estimated fatigue damage due to calculated stresses in the 2C piping. The maximum calculated usage factor of 0.02 shows the fatigue life of the piping was only slightly degraded. Since the cyclic operating loads for the core piping discharge outside the drywell consists primarily of internal pressure, the remaining fatigue life of the piping is more than adequate to provide the intended design life.

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2 No formal fatigue damage estimate has been made for the 2A discharge since we still have only a static loading analysis i for that piping. However, because of physical similarities between the 2A and 2C piping, the 2C calculation can be considered as 1 representative for both systems, i

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