ML20141K274

Sser Supporting Util 850301 & 0716 Addl Info Re Compliance W/Ie Bulletin 80-11,Items 2(b) & 3 for safety-related Masonry Walls

ML20141K274
Person / Time
Site:	Fort Saint Vrain
Issue date:	01/15/1986
From:	NRC
To:
Shared Package
ML20141K273	List: ML20141K270 ML20141K274
References
IEB-80-11, TAC-42925, NUDOCS 8601220407
Download: ML20141K274 (4)

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ENCLOSURE SAFETY EVALUATION REPORT SUPPLEMENT MASONRY WALL DESIGN, IE BULLETIN 80-11 FORT ST. VRAIN NUCLEAR PLANT DOCKET N0.: 50-267 ,

In the Safety Evaluation Report (SER), the staff concluded that except for seventeen walls qualified by the licensee via the use of the horizontal joint reinforcing as structural elements to resist the tensile stresses, items 2(b) l and 3 of IE Bulletin 80-11 have been fully implemented at the Ft. St. Vrain facility for the remaining walls. The SER also included a staff position on the use of the joint reinforcing and stated that the implementation of this position was required to render the above seventeen walls acceptable to the staff.

By a letter dated November 8,1983, the licensee indicated its intention to reevaluate the above walls by taking no structural credit for the joint rein-forcement. Th'e licen:ee stated that these walls will be modified, as required, by reinforcing them with the metal bar straps to withstand the loading resulting from the safe shut-down seismic event. By a letter dated July 6, 1984, the licensee has informed the staff that the required reinforcements for these walls are complete. Based on this information, the staff concludes that the issue regarding the use of the joint reinforcement to qualify the masonry walls is now satisfactorily resolved as the joint reinforcement is no longer relied upon to resist design basis loads.

Subsequent to the issuance of the staff SER, during an inspection conducted

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,P under the Resident Inspection Program (Inspection Report 50-267/84-22), it was discovered that several different types of modifications had been made to the

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Ft. St. Vrain's masonry walls of which the staff had no knowledge. The staff findings reported in the SER were based on only one type of the modification scheme. The staff had reviewed this modification scheme and found it to be acceptable.

In order to evaluate the safety impact of the inspection finding, the staff conducted a site visit and meeting with the licensee on December 12-13, 1984.

As a result of this meeting and the subsequent conference call: on January 16, 1985, the licensee informed the staff of the following additional actions by a letter dated March 1, 1985.

• The licensee submitted a series of sketches indicating how the licensee reinforced each of the walls within the scope of IE Bulletin 80-11.

"The licensee committed to adding lateral restraints to the top,of turbine room walls #4, #6, #7, #8 and #9 to qualify the top boundaries as pinned joints (during the site visit the staff had questioned the appropriateness of the pinned end assumption).

• The licensee committed to remove one of the unmortared stacked block

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,' wall (wall #97) and mortared remaining five safety related walls of the similar construction such that they can withstand the seismic forces.

'The licensee committed to extend all bar straps (external bar straps are used to reinforce the walls)past the masonry-concrete boundary and anchor the straps to the concrete or install clip angles. Originally, these straps in some cases did not extend beyond the wall boundary.

All strap extensions, clip angles and anchors will be designed to resist seismic loads. ,

'The licensee committed to install a missing strap on wall #12. This discrepancy was discovered during the staff site visit. The licensee also reviewed the other similar situations to confirm that this i

discrepancy was an isolated incidence.  ;

i "The licensee analyzed the shear stress transferred from the masonry <

to the bolts and analyzed the compression stresses in the masonry resulting i from the bolt bearing. The results of these analyses demonstrated that actual masonry and steel stresses are within the allowables and the strap -

design is adequate as installed.

By a letter dated July 16, 1985, the licensee confirmed that all of the above r

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. 4 described wall modifications are designed to meet the staff acceptance criteria (Appendix A of the Attachment 1 to the staff SER). The litensee also indicated that all wall modifications will be complete by December 31, 1985 (the licensee had committed to complete most of the wall modifications by August 2, 1985 in a March 1, 1985 letter),

t In a July 16, 1985 letter, the licensee stated that the safety related masonry walls located in the newly constructed facility, Building 10, have been conservatively analyzed as unreinforced masonry walls, although in reality the walls are constructed of reinforced masonry. Based on this conservative analyses, it is shown that these walls comply with the staff acceptance criteria.

Based on the above findings and the licensee's committments, the staff concludes that the following issues are resolved: (1) the use of the joint rein-forcement to qualify the masonry walls; (2) the use of modification schemes other than that addressed in the staff SER; and (3) the staff findings during the site visit. Therefore, there is a reasonable assurance that all safety related masonry walls at the Ft. St. Vrain facility (including Building 10 walls) will withstand the specified design load conditions without impairment of wall integrity or the performance of the required safety function. Items 2(b) and 3 of IE Bulletin 80-11 are considered fully implemented at the Ft. St. Vrain facility. ,

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