ML18142A082

Forwards Addl Info Re IE Bulletin 80-11, Masonry Wall Design, in Response to 840828 Ltr.Technical Basis & Clarification of Fixity Condition Used in Block Wall Analysis Provided

ML18142A082
Person / Time
Site:	Surry
Issue date:	10/26/1984
From:	Stewant W, Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Harold Denton, Varga S Office of Nuclear Reactor Regulation
References
539, IEB-80-11, NUDOCS 8410310439
Download: ML18142A082 (4)

Text

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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 e

W. L. STEWART VxcE PRESIDENT NUCLEAR OPERATIONS October 26, 1984 Mr. Harold R. Denton, Director Serial No. 539 Office of Nuclear Reactor Regulation E&C/JFK/jdm:2005N Attn: Mr. Steven A. Varga, Chief Docket Nos. 50-280 Operating Reactors Branch No. 1 50-281 Division of Licensing License Nos. DPR-32 U.S. Nuclear Regulatory Commission DPR-37 Washington, DC 20555 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT NOS. 1 & 2 SUBMITTAL OF ADDITIONAL INFORMATION NRC IE BULLETIN 80-11 (MASONRY WALL DESIGN)

This letter provides the additional information regarding NRC IE Bulletin 80-11 {Masonry Wall Design) which was requested by your letter of August 28, 1984. Enclosure I to this letter provides the technical basis and clarification of the fixity condition used in the block wall analysis, as well as, summarizing how Vepco s activities regarding spent fuel pool block walls 1

satisfy the requirements of IE Bulletin 80-11.

Please contact us if you have any questions or require additional information.

Very truly yours, j

---.-k?J L6~~-Jt11 r W. L. Stewart Enclosure cc: Mr. James P. O'Reilly Regional Administrator Region II Mr. D. J. Burke NRC Resident Inspector Surry Power Station

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8410310439 841026 PPR ADOCK 05000280 G PDR

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• ENCLOSURE I e

Item 1 11 With respect to the boundary conditions used in the analysis, the- Licensee indicated in Reference J that fixity was assumed at the base of a b1ock wa 11 bui1t on a concrete slab. Also, at the perpendicular intersection of two block walls, fixity has been assumed in the corner joints formed by the alternating courses of the running bond. The licensee is requested to provide the technical basis for assuming fixed-end conditions for these cases. It is believed that without some clamping devices to prevent rotation at the wall boundary, the assumed boundary conditions may not be valid. 11 Answers:

In the context of the re-evaluation criteria used in the masonry wall analysis, it would be more appropriate to say that the boundary conditions where the wall might be assumed as fixed were as follows: 1) at the base of the masonry wall where block walls were constructed with a full bed joint, and 2) at the intersection of two block walls where the block walls were constructed with alternating courses of running bond and thus the block and joint interlock tied the walls together. Other types of joints were not considered adequate for the load transfer that would occur with the application of fixed boundary conditions.

The boundary conditions used in the analysis of a particular wall were dependent on the specific wall geometry, the relative stiffness of the adjoining structural elements (slab or wall), and the determination of how the wall would interact with these elements so that the load would be transferred in a manner consistent with the wall geometry specific to the wall being analyzed. In some instances, it was determined that the boundary conditions where fixity might be assumed were not consistent with the specific wall geometry and supporting elements, and in these cases the joints described above were considered as pinned.

The appropriate boundary conditions for each case were selected to be*

representative of the physical condition for both the calculations of dynamic response and in the distribution of the loads which resulted. The boundary conditions used in the dynamic analysis were consistent with those used in the distribution of loads in each case.

Re-evaluation of masonry block walls utilized conservative assumptions, simplified analysis techniques, conventional boundary conditions, and conservative acceptance criteria. Analysis employed conservative damping values and amplified response spectra. Conventional boundary conditions used were simple, fixed or pinned.

Clamping devices were not used as a means of preventing rotation at fixed boundaries because there was no assurance that such a device would behave as designed to transmit loads without damaging the masonary walls. In lieu of clamping devices and where moment fixity was included as a boundary condition the stresses associated with the resulting boundary moment were transmitted to supporting structures within acceptable stress limits.

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'o Item 2

• e 11 Summarize your activities regarding the block walls around the spent fuel pool and provide the basis for which these actions satisfy the requirements of I.E.

Bulletin 80-11. 11 Answer:

1.r: Bulletin 80-11 required that Vepco analyze all block walls at Surry Power Station. Vepco performed the required analysis and issued several clarifying letters and reports to the NRC. As described in the I.E. Bulletin 80-11, Masonry Wall Design Final Report for Surry Power Station Units 1 and 2, the seven walls located in the fuel building could not be proven acceptable under the re-evaluation criteria. Vepco notified the NRC that these walls were being removed from the I.E. Bulletin 80-11 reanalysis effort via our final report and would henceforth be addressed under Licensee Event Report No. 81-020/03L-O.

This LER identified the problem with these fuel building walls and provided the corrective action Vepco was taking. Subsequently these walls have been removed and replaced with metal siding as presented in the LER.

In a recent telephone conversation between the NRC and Vepco on October 9, 1984, the extent of question number 2 was expanded to request additional clarifications similar to those provided for North Anna Power Station via Vepco response to questions 1, 2 and 3 in our letter to the NRC Serial No. 450D dated April 10, 1984 and Vepco s response to question B.3 in our letter to the NRC 1

Serial No. 456 dated September 13, 1983. The situation at Surry Power Station concerning the fuel building block wall problem and corrective action is similar to that of Vepco's North Anna Power Station. The following questions and answers provide a response specific to Surry Power Station comparable to that provided for North Anna Power Station in the previously cited letters.

Question 1 Are the new walls going to be Seismic Category I?

Answer:

The fuel building block walls have been replaced with metal siding similar to the siding on the walls of the rest of the fuel building. The existing fuel building structural steel and the girt system on which the siding is attached are designed to be Category I. The metal siding is not Category I.

Question 2 Verify, in the event of a tornado, that the new walls could not damage stored spent fuel, the spent fuel pool cooling system, or other safety-related equipment.

Answer:

As discussed in the answer to questions 1 above~ the only part of the new portion of the fuel building walls that it not designed to be Category I is the siding. The siding consists of sheet metal, rigid insulation (styrofoam), and sub girts screwed together as a unit.* The l~rgest panel has been postulated to fall from elevation 90 1 -2 11

• This wall panel was conservatively considered to 72-JFK-2042B-2

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e e fall on edge with its shortest side entering the water first. Since the density of the panel is less than water, the panel will float subsequent to initial submergence in water. Calculational results indicate that spent fuel pool water drag and buoyancy effects reduce the kinetic energy of the falling panel such that impact with the spent fuel racks is prevented.

The fuel pool cooling system is missile protected for horizontal m1ssiles as discussed in Section 15.2 of the UFSAR.

Question 3 Verify that the new walls provide adequate protection against tornados and tornado missiles for stored spent fuel, the fuel pool cooling system, and other safety-related equipment.

Answer:

No credit for missile protection was taken in the UFSAR for the block walls and no credit for missile protection is taken for the siding which will replace the block walls. The missile criteria and safety analysis for the fuel pool is discussed in Section 15.2 of the Surry UFSAR.

Question B.3 Verify that the solution to the concerns of Multiplant Action .Item B.24 is applicable to the spent fuel storage facility as modified to permit storage of 1737 fuel assemblies.

Answer:

The installation of new spent fuel racks to accommodate 1737 fuel assemblies is not applicable to Surry Power Station. However, the seven (7) masonry block walls which are located in the fuel building have been removed and replaced with metal siding like that which is on the rest of the fuel building superstructure. The plan in regard to block wall removal and replacement is described in LER 81-020103L-O which was previously transmitted to the NRC. A copy of t~is LER is attached.

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