ML19210B366

Addendum 4,Rept on Containment Bldg Ring Girder Const & Repair.

ML19210B366
Person / Time
Site:	Three Mile Island
Issue date:	09/22/1972
From:	METROPOLITAN EDISON CO.
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ML19210B365	List: ML19210B364 ML19210B366
References
NUDOCS 7911070691
Download: ML19210B366 (8)

Text

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ADDENDUM h FIFORT ON CONTAINMENT BUILDING RING GIPIER CCNSTRUCTION MID FIFAIR THREE MILE ISLAND NUCLEAR STATICH UNIT NO. 1 METROPOLITAN EDISON CO:GANY September 22, 1972 -

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Addendun h INTRODUCTION On December 3,1971 Metropolitan Edison Cenpany filed with the AEC a document entitled " Report en the Containment Building Ring Girder Constructica and Repair."

Addenda 1, 2, and 3 to that report have subsequently been filed with AEC. The information included herein as Addendu= b is ec= piled in response to questions raised by DRL during the meeting held en September 7, 1972 in Bethesda, Maryland.

These questions were raised to clarify Addendu 3 which was written in response to Docket No. 50-289 TEXT The hori: ental ring girder construction joints at elevatiens hh3 ft-0 in. and hh6 ft-9 in, have been investigated for transfer of shear under lead cc=binations including normal operation, initial prestress , accident , pressure test , seismic, vind, and aircraft impact. As originally constructed, the joints at these elevations extended hori:Ontally across the entire ring girder section. Visual examinatien and core-borings as documented in Addendu= 2 indicated that part of the joint extending in frc= the outside face of the ring beam was questionable for lead transfer. The questionable areas of the joint have been ec=pletely excavated as shown in Fisures 1, 2, and 3 s

Visual and core-bore examinations confirm that the remainder of these horizontal joints left as originally placed is sound. The construction joints required for the replacement of concrete in the excavated areas (see Figures 1, 2, and 3), will be carefully prepared by green-cutting and other suitable methods to ensure that a sound construction exists prior to cencrete placement. The repaired ring bea=

will perfor= its structural function as part of the reacter containment building as intended in the original design.

Due to the specialized nature of the proble= discussed in Addendum 2 where bcnd at the joint is questionable, shear transfer is conservatively assumed to occur solely by friction under a normal ec=pressive force. The effect of the diagonal reinforcing steel across the joint is disregarded for the analysis. The joints in the repaired ar'ea's , as well as the part of the original joints that were not excavated, are deemed to be completely adequate for transferring ec=pressive forces. In Addenda 2 and 3, it has been shown that the net me=brane cc=pression for all lead conditions is sufficient to transfer the shear across the joints cy friction assuming an allevable coefficient of friction, u=1.

A conservative minimum factor of safety for shear transfer at elevaticns hh3 ft-0 in, and hh6 ft-9 in, for all load ce=binations except the aircraft impact lead is tve.

The greatest coefficient of friction required for either elevation is p=0.686.

This cccurs at elevation kh6 ft-9 in. for the Accident Lead Cc=bination (see Table 2 in Addendu 2). A coefficient of friction p=1.0 was allowed for the joints. This coefficient of friction is used in conventional shear friction theory. Based on the evaluatica of the remainder of these joints left in the ring beam a: eer the concrete re=cval and en the expected effectiveness of the repair, an ultimate coefficient of friction of 1.h is reascnable. Tvc times the greatest required.ccefficient of friction, 0.686, is less than 1.h. Therefore , tvc is considered as the mini =u= factor of safety for shear transfer at these tvc horitental joints.

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Addendu: 3 should be clarified to reflect that the effect of Aircraft Impact Loading on the entire ring beam is generally small for the majority of the ring beam. Figures k and 5 indicate the required coefficients of friction to transfer shear at elevations hh3 ft-0 in. and hh6 ft-9 in. due to Normal Operation plus Aircraft Impact. The coefficients are conservatively derived using the greater of the in-plane shear or radial shear along with the normal force in the conventional friction equation F=pN.

From Figures h and 5 the required coefficients of friction are seen to be less than or equal to the allowable value of one. For the majority of the ring team, the minimum factor of safety is still two under this load. However, for part of the ring beam where the required coefficient of friction is greater than 0.7 (the ultimate coefficient of friction 1.h divided by a factor of safety 2 is equal to 0.7), the minimum factor of safety will be less than 2.

The lowest factor of safety will be 1.h in the area around ih0c shown en Figure 5 At that location the required coefficient of friction is p=1.00. A factor of safety cf 1.h is derived by dividing the assumed ultimate coefficent of friction 1.h by the required value of p=1.00. Since it has been conservatively assumed that the shear is carried across the joint only by friction under a normal compressive stress, a minimum factor of safety of 1.h for a limited portion of the ring beam is considered adequate under the Aircraft Impact Loading.

Except for the local area of the aircraft impact where the factor of safety at the joint elevations kh3 ft-0 in, and hh6 ft-9 in. is 1.6h minimum (l.h/0.855=1.6h),

the rest of the ring beam at these two joints has a minimum factor of safety of 2.

The immediate area of aircraft impact is considered lto be less than h0 0 of the perimeter or smaller than 11.2 percent of the entire perimeter. A minimum factor of safety of 1.6h is considered adequate for this limited portion of the ring beam for the Aircraft Impact Leading.

The " Report on Containment Building Ring Girder Construction and Repair" dated Dece=ter 1,1971 and subsequent Addenda allow for various options in the repair of the ring girder. For example repair of the reinforcing bars may be made by splicing, cadwelding, or with the approval of the Engineer butt-velding. All efforts are made to eliminate the use of the butt-velding procedure. In two sections of the North 180 ; eight butt-veld repairs were used. These vere removed and replaced with cadvelds or a full length bar at a later date. The final tabulation of the North 18C O shows that no butt-velds were used in the repair.

The same effort to eliminate the use of butt-velds vill be made in the repair of the South 1800 . At the present time, it is impossible to say that the butt-velding technique vill be eliminated entirely.

Complete records of the repair are being kept by United Engineers and Ccnstructors Incorporated Quality Control group at the job site.

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