IR 05000423/1987015

Insp Rept 50-423/87-15 on 870608-25.Violation & Deviation Noted.Major Areas Inspected:Allegation Involving Seismic Adequacy of Masonry Walls Around Battery Rooms in Control Bldg

ML20237H905
Person / Time
Site:	Millstone
Issue date:	08/17/1987
From:	Kamal Manoly, Strosnider J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
Shared Package
ML20237H889	List: IR 05000423/1987015 ML20237H888 ML20237H893 ML20237H897
References
50-423-87-15, NUDOCS 8708250193
Download: ML20237H905 (5)

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U.S. NUCLEAR REGULATORY COMMISSION

REGION I

Report N /87-15 Docket N License N NPF-49 Licensee: Northeast Nuclear Energy Company P.O. Box 270

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Hartford, Connecticut 06141-0279 Facility Name: Millstone Nuclear Power Station, Unit 3 Inspection Conducted: June 8-25, 1987 Inspector: .

i k 'N K. Manoly, Lead 4Mactor Engineer date 8!/7[87 '

Approved by: 8/7/87 Strosnider, Chief, Materials and date Processing Section, EB, DRS Inspection Summary: Inspection on June 8-25,1987 (Report No. 50-423/87-15)

Areas Inspected: Special inspection in the Region I office of an allegation involving the seismic adequacy of the masonry walls around the battery rooms in the control buildin Results: Some aspects of the allegation were substantiate One violation and one deviation were identified as a result of the NRC staff's revie Additional refined analysis performed by the licensee during the NRC investigation of the allegation indicated the adequacy of the above referenced battery room walls to the allowable limits set by the NRC's Standard Review Pla i l

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1. Allegation No. RI-_8_6-A-77 1.1 Allegation Description The Region I office was notified of an allegation involving the adequacy of the masonry walls around the battery rooms at elevation 4'-6" of the control building of Millstone Station Unit #3. The alleger expressed two concerns during a telephone discussion with the Region I staff on May 27, 1987. The first was related to the lack of performance of a slump test for the masonry block mortar during construction of the walls and the subsequent effect on the assumed design compressive strength of the mortar. The second concern related to the adequacy of the seismic qualification of the walls for battery rooms number 1, 2, 3 and 4. The alleger identified the walls for battery rooms number 1, 3 and 4 as bearing walls supporting a 3'-0" thick slab and for battery room number 2 as non-bearing wall .2 NRC Evaluation Slump Test The first concern expressed by the alleger, regarding the lack of performance of slump test for the masonry block mortar, was determined to be irrelevan The slump test is used in concrete construction for measuring of concrete mix consistency in accordance with ASTM C143. Such a requirement is neither applicable nor required for mortar. Determination of mortar strength was based on compression testing of mortar cubes. The Millstone specification No. C-991 for concrete masonry specified type S mortar. However, it was classified as type M which has a minimum specified compressive strength of 2500 ps Results of battery room block wall mortar tests indicated an average cube compressive strength of 4996 psi. The governing design allowable for hollow unit masonry walls subjected to out-of plane bending is that related to tension normal to bed join According to the Building Codes Requirements for Concrete Masanry Structures '(ACI 531-79), the above tension allowable under normal operator conditions should be the lesser of 0.5 (mg ) b or 25 psi where m g is the specified minimium compressive strength of mortar. The battery room design records indicate that the tension allowable was consistent with the above stated requirement. E 25 psi).

Based on the above, the staff concluded that the allegation regarding the requirement for slump test in determining mortar strength in the battery room walls was not substantiat Seismic Qualification To access the validity of the second concern regarding the seismic qualification of the masonry walls in the battery rooms, the staff reviewed applicable design calculation records, the masonry block wall design procedure and detailed construct'on drawings. The review J

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. 3 indicated that unreinforced masonry was used in the construction of partition walls in all five (5) battery rooms and the two electrical equipment rooms. A 7 " thick reinforced concrete slab provides the ceiling for all battery room Room numbers 1, 3 and 5 are located in the east side of the control building and room numbers 2 & 4 are located in the west side. In each side, the slab is supported vertically by the block walls and the control building outer reinforced concrete wall. The above described layout differed from the configuration stated by the alleger during the May 27, 1987 telephone conversation in two aspects:

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the slabs over the battery room walls are only 7 " thick and are not 3' - 0", and

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the slabs do not overhang beyond the battery rooms masonry wall boundar .

Upon review of the original calculations performed in January 1983 for the seismic qualification of the battery room wall and slab systems, two findings were note . The licensee's response to question No. Q220.38 in the NRC letter of May 3, 1983 regarding safety related walls at Millstone unit

1. 3 was documented in section 3.8.4.8 of the FSAR. The response stated that masonry walls in safety related areas in the plant comply with the requirements in Appendix A to the Standard Review Plan (SRP) Section 3. Revision 0, July 1981, of Appendix A to SRP section 3.8.4 does not permit the use of unreinforced masonry walls in newly constructed plants. It also does not permit the increase in allowable tensile stresses beyond the limits of ACI 531-79 in lead combinations involving Operating Basis Earthquake (OBE). However, it permits the increase of these allowables by 50% and 30%, respectively, for tension parallel and normal to the bed joint in load combinations involving Safe Shut Down Earthquake (SSE).

The criteria used for the evaluation of the battery room walls were documented in SDM 80-14 titled " Analysis Procedure for l Masonry Slock Walls". Section 4.8 of the procedure addressed stress combinations and allowable stresses. The criteria permit the increase of allowable stresses above those specified in the i ACI 531-79 by 33% for the Dead Weight (DW) plus Operating Basis Earthquake (OBE) condition and by 67% for the DW plus Safe Shutdown 4 Earthquake (SSE) condition. In both wall panels evaluated in j the original calculation and the supplementary submittal to the j NRC of June 15, 1987, the maximum calculated stress for tension )

l normal to the bed joint exceeded the specified 1.3 increase, j permitted by the SRP for the DW plus the SEE loading condition !

by approximately 17%.

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10 CFR 50.34(g) requires that applications for nuclear power plant operating licenses, docketed after May 7, 1982, include an evaluation of the facility against the Standard Review Plan (SRP), in effect. It also requires that the evaluation includes an identification and description of all differences in design features, analytical techniques, and procedural measures proposed i for the facility and those corresponding features, techniques l

and measures given in the SRP criteria. It further requires that, where such a difference exists, the evaluation addresses how the alternative proposed provides an acceptable method for complying with those rules or regulations that underlie the corresponding SRP acceptance criteri The licensee did not evaluate the above stated differences and an NRC review was not performed as a result of the licensee's response to question No. Q 220.38 in the NRC letter of May 3, 1983 which stated that the SRP criteria were satisfie These differences constitute a deviation from FSAR commitment (423/87-15-01) Evaluation of battery room walls for out-of plane stresses was done for one wall only (Calculation No. 12179-NS(B)-108). The designation of the selected wall was not correlated to the floor layout drawing. Further, the area of the wall was significantly smaller than other battery room walls. The calculation did not provide the engineering rationale or justification for the selection of what was intended as the governing wall (i.e. boundary conditions, penetrations, wall attachments, etc.).

Several other deficiencies were noted regarding the lack of consideration and documentation of major structural design aspects which required evaluation and conformance to applicable design code These included:

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Evaluation of shear stresses along the boundary of governing wall (or walls)

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Transfer mechanism of slab's seismic inertia loads in the vertical, north-south, and east-west direction Evaluation of the slab's connections and anchoring mechanisms to the outer concrete walls as a result of dead weight and seismic load Revision Nos. O and 1 of the wall calculations referenced above were signed as completed and independently reviewe The failure of the design control measures to verify the adequacy of the battery room walls is a violation of section 3.2.4 of the Quality Assurance Program Topical Report and Criterion III of Appendix B to 10 CFR 50. (423/87-15-02).

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l As indicated above, the staff requested further information pertaining to the deficiencies noted in the original calculation and other design related assumption The licensee's response of June 15, 1987 included supplementary calculations addressing these design deficiencies and provided the basis for continued operation of the facility. These calculations were discussed in a telephone conversation on July 16, 1987 between the Region I Materials and Processes Section Chief and the Chief of the Structural Engineering Branch, NRR, and it was agreed that based on the calculations submitted to and reviewed by Region 1, the subject walls were acceptable for continued operatio .3 Conclusion Based on the above evaluation, the s'aff concluded that some aspects of the allegation which related to the adequacy of the seismic qualification of battery room walls were substantiated. The noted deviation from the FSAR commitment needs to be resolved with the Office of Nuclear Reactor Regulation. However, the licensee's latest defined analysis documented that the wall stresses met the Standard Review Plan allowable value J

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