IR 05000260/1989030
| ML20248E698 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/18/1989 |
| From: | Cheng T, Terao D Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20248E685 | List: |
| References | |
| 50-260-89-30, NUDOCS 8910050389 | |
| Download: ML20248E698 (18) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION
'0FFICE OF NUCLEAR REACTOR REGULATION TVA PROJECTS DIVISION Report No.:
50-260/89-30 Docket No.:
50-260 Licensee:
Tennessee Valley Authority 6N 38A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801 Facility Name:
Browns Ferry Nuclear Plant. Unit 2 Inspection At:
Tennessee Valley Authority Office Knoxville, Tennessee Inspection Conducted:
March-24, 1989 41/uf, /
f Inspector:
_ Thomas M. Cheng. Team eader Date
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Consultants:
A.
. Unsal, O. Mallon, Tom Tsai Approved By:
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TVA roject Divisio Office of huclear Reactor Regulation
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8910050389 890920 PDR ADOCK 05000260 Q
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SPECIAL INSPECTION RELATING TO ESSENTIAL DESIGN CALCULATIONS UNDER CIVIL CALCULATION REVIEW PROGRAM TENNESSEE VALLEY AUTHORITY (TVA)
BRDWNS FERRY NUCLEAR PLANT UNIT 2 (BFN-2)
DOCKET NO. 50-260
Introduction and Background The Tennessee Valley Authority ('s (TVA) quality assurance organizations, the Nuclear Regulatory Comcission NRC), and the Institute of Nuclear Power Operations conducted audits at.. Browns Ferry Nuclear Plant, Unit 2 (BFN-2).
During these audits, they found that the design basis for BFN-2 had not been
. adequately documented (e.g. documentation was missing, incomplete, not up-dated). This lack of documentation was first identified in the design for electrical systems and subsequently found in the design for mechanical, nuclear and civil systems and components. To resolve these audit findings and their generic implications, the Nuclear Engineering Division of TVA initiated a series of calculation. activities. As documented in the Browns Ferry Nuclear Performance Plan (BFNPP), Volume 3 these calculation activities, as part of the Design Baseline and Verification Program (DBVP),
were applied to all four engineering disciplines: electrical, mechanical, nuclear, and civil.
The civil calculation program is one of these calculation activities. The purpose of the civil calculation program is to complete and have available a set of technically adequate essential civil calculations.
The " Essential Calculations" are defined as calculations that address existinD plant structures, systems, and components whose failure could result:
(1)
in a loss of reactor coolant system integrity.
(2) in a loss of ability to achieve safe shutdown, or (3) in a release of radioactivity offsite in excess of the 10 CFR 100 guidelines.
The ultimate intent of this program is to ensure that this complete set of calculations meet the civil design basis and are maintained throughout the operating life of BFN-2. The scope of this program, as TVA. presented it to the staff on February 29,1988 (Reference 5.1), covers a total of 16 design areas: dynamic analysis, concrete structures, steel structures, primary containment, masonry walls, embedments, tanks and heat exchangers, seismic ground motions, soil and rock analysis, settlement and slope stability, piles
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.and foundations, buried structures, pipe rupture, tornado evaluations, heavy loads evaluations, and flooding. ~ 0n the basis of the status of their resolution and the results of other ongoing programs. TVA categorized these 16 design areas into 7 groups:
(1) The " Dynamic Analysis" issue was considered as part of the BFN-2 Seismic Design Program because of the nature of the issue and its interrelation with seismic design.
(2) The " Masonry Walls" issue was resolved under the NRC IE Bulletin 80-11 program.-
(3) The " Tanks and Heat Exchangers" issue will be resolved under the implementation of NRC Unresolved Safety Issue (USI) A-46.
(4) The " Seismic Ground Motions" issue was resolved by issuing a staff safety evaluation report (SER) and an inspection. The SER for the use of an artificial ground motion time history was issue,d on January 29, 1988 (Reference 5.2). The application of the ground motions (i.e., the El Centro ground motion time history and artificial ground motion time history to the seismic analysis of strucutures systems, and components)
was resolved during the February 20-24, 1989 staff inspection (Reference 5.3).
(5) The " Pipe Rupture" issue was resolved under the NRC DBVP inspection (Reference 5.4).
(6) The issues of " Settlement and Slope Stability," " Tornado Evaluations,"
" Heavy Loads Evaluations," and " Flooding" are to be resolved after the restart of BFN-2.
(7) The resolution of the design issues for the remaining seven areas are eitner complete or being prepared for NRC staff inspection (References 5.3 and 5.5).
Purpose and Scope The three purposes of this inspection were:
(1) to understand and become familiar with the approach and procedures that TVA used for completing the civil calculation review program, (2) to review TVA's justification for not completing their evaluation of the four design areas mentioned in Item 6 of Section 1 before the restart of BFN-2, and (3) to conduct an inspection of the results of TVA's review of the remaining seven design areas, which must be resolved before restart. For the design areas, such as dynamic analysis and tanks and heat exchangers, issues will be resolved by the staff under the seismic design program inspections.
Discussion of Inspection Findings During the weeks of March 13 through 24, 1989, the staff and its consultants conducted an inspection of TVA's civil calculation review program at TVA's Knoxville office, Knoxville, Tennessee. A list of those who attended the entrance meeting is provided in Enclosure 1.
As discussed in Section 2, three areas were covered by this inspection, namely, the overall program, the justifications for non-restart design areas, and the adequacy of the design-2-
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calculations for.'the seven design areas that must be resolved before the start-up of-BFN-2.
In addition to the civil calculation review program, two issues were also scheduled to be discussed during this inspection:
(1) the method for resolving the rod-hung aluminum conduit outliers, and (2) the themal growth effects on the steel platforms outside drywell for which TVA comitted to address (Reference 5.5).--
Over the two weeks of inspections, the staff and its consultants reviewed the
' documentation presented by TVA, the sample design calculations for all except one of the design areas in Group 7 (see Section 1 above), and other supporting materials provided by TVA. Because of the time constraint, the audit of calculations for the design of the primary containment was rescheduled for the next inspection of the program. Section 6 of this report provides a list of documentation and calculations reviewed by the staff and its consultants.
The inspectors identified a total of 14 concerns during this inspection, that is. CC-1 through CC-14. The staff review findings. TVA's responses to these findings, the detailed status of the resolution of e:ch of these 14 concerns, and the results of the discussion of the issues of thermal growth effects and rod-hung conduit systems are sumarized in the following sections. A sumary of. the status of the resolution for these 14 concerns is provided in Enclosure 3.
3.1 TVA Civil Calculation Review Program At the beginning of this inspection TVA presented a programmatic description of the ongoing calculation activities that comprise the calculation review program. Since many activities are involved in the calculation review effort.
-it is essential that a flow chart or check list be established for tracking this effort. The flow chart shown in Figure 3-1 of this report describes the method to be employed to ensure that all BFN-2 civil structural calculations do exist and are technically adequate.
Essentially, TVA's review effort is to be accomplished in six steps:
(1) Review all calculations and determine which calculations are essential (orsafetyrelated)andwhicharenon-essential.
(2) For those calculations determined to be essential, review the calculations to determine which ones are required for the restart of the plant. For those calculations that are detemined to be post-restart calculations, provide justification and documentation.
(3) Review the prerestart calculations, determine which calculations are covered by ongoing programs and review these calculations as part of the ongoing programs.
For those calculations that are not covered by ongoing programs, find out which calculations are retrievable and which are not retrievable.
(4) For those calculations that cannot be found or do not exist, produce
"new calculations based on the design criteria.
(5) Review the design input and design criteria for all existing calculations l
and review representative samples of the existing calculations for technical adequacy. Produce new calculations for those calculations that are not technically adequate.
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(6) Implement _ corrective actions if required before restart. Have the NRC staff and its consultants review the' program description, discuss with TVA how the program was conducted and its current status, and conclude that the overall program is reasonable and will fulfill its goal es
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comitted in the BFNPP. Volume 3, if the program is properly implemented.
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3.2 Justification for Post-Restart Design Areas In the. meeting with NRC on January 5, 1989, TVA proposed to postpone the review of calculations in the design areas of heavy load evaluations, settlements and slope stability, tornado (including missiles) evaluation, and flooding until after the restart of BFN-2 (Reference 5.6). A sumary of the staff's review of TVA's justification for postponing its review of these four design areas and the staff's findings follow:
(1) For the design heavy load evaluation. TVA provided a copy of NRC's safety evaluation reports (SER's) on the implementation of NUREG-0612. " Heavy Loads." The staff consultants reviewed these SER's and concluded that the justification provided by TVA was acceptable.
.(2) TVA also provided its justifications for postponing the review of sub-categories flooding, tornado and tornado missiles, and settlement and slope stability. Because of the time constraint, the staff will review these justifications during the next inspection. This item remains open.
(CC-1)
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?.3 Findings of Design Calculation Review To complete the civil calculation review program, TVA contracted with Stone &
Webster Engineering Corporation (SWEC) to review the original civil design calculations and to generate new calculations if necessary. The SWEC's findings were documented in a review report (B41 890308 001). The staff and its consultants reviewed samples of TVA's civil and structural design calcu-lations and the SWEC review report related to the seven prerestart design areas (i.e., concrete structures; steci structures; embedments; soil and rock analysis; tanks and heat exchangers; piles and foundations; an$ buried struc-tures, including buried piping), during this inspection. As 4. result, a total of 13 issues (i.e., CC-2 through CC-14) were identified and 8 of them remained open at the end of this inspection. A sumary of the staff's findings and conclusions follows.
3.3.1 Piles and Foundations In response to the staff's questions related to the design adecuacy of pile foundations and potential liquefaction of soil foundations, TVA provided a soil report for a low-level radwaste storage facility (CSB 80 0716 301) that documents the soil properties in the vicinity of the safety-related structures (equipment access lock and residual heat removal - emergency equipment cooling water (RHR-EECW) pipe tunnel) and the results of the liquefaction evaluation of the soil foundations. The staff consultant reviewed this report and found that the soils adjacent to these two safety-related structures are primarily clay. Therefore, the staff agreed with TVA's conclusion that the soil in the vicinity of the pile-supported structures is not subject to liquefaction.
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To address the concerns identified in the SWEC review report, TVA is presently revising the pile design calculations, including the anchor movements for piping evaluation. TVA agreed to provide these calculations for the staff review during the next civil calculation inspection. This issue remains open.
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(CC-2)
3.3.2 Soil and Rock Analysis
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All safety-related structures with the exception of the diesel generator (DG) building, standby gas treatment (SGT) building, and vacuum pipe (VP)
building are supported directly on rock or H-piles bearing on rock. The DG building is founded partly on compacted crushed stone and on an appendage to the reactor building. Both the SGT building and YP building are buried structures founded on compacted backfills. TVA's resolution to the problem, (Problem Identified Report CEB 8803) indicates that these three buildings will be seismically reanalyzed, using appropriate soil parameters.
TVA agreed to address the staff's concerns about the potential for differential settlement between the reactor and DG buildings and to complete the seismic reanalysis of these three buildings before the next inspection. This item remains open.
(CC-3)
f 3.3.3 Buried Structures During the inspection, TVA provided a list of safety-related buried structures and buried piping systems. The safety-related buried etructures include the equipment access lock (EAL), SGT building, off-gas treatment (OGT) building, VP building, RHR-EECW pipe tunnel, conduit banks, and cable tunnel. The safety-related buried piping systems include the containment atmospheric dilution system, the EECW system, the raw cooling water (RCW) system, the residual heat removal service water system and the SGT system.
For the buried structures, the~ staff selected the SGT building and buried conduit banks as representative samples for review and the findings are as follows:
3.3.3.1 Standby Gas Treatment Building The SGT building is founded on compacted backfills and buried in soil.
For the purpose of clarification, the TVA contractor SWEC, generated a supplemental f
design calculation as part of the technical adequacy review of the original design calculations.
The review of the original design calculations (B22 880921 127 and CEB 830524 761) and supplemental design calculations showed that the design criteria, design method, loads and load combinations were consistent with the Final Safety Analysis Report (FSAR) and, therefore, acceptable. However, SWEC used ACI Code 318-71 and 318-77 in the supplemental design calculations which are more recent than those required by the FSAR. The use of more recent design codes (i.e., ACI Code 318-71 and 318-77) is incon-sistent with the FSAR which requires the use of ACI Code 318-63.
TVA agreed to ei'ther provide justification for using the more recent design codes or delete the references to them if the more recent design codes were never used in the calculations.
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3.3.3.2 Buried Conduit Banks The conduit banks are located adjacent to the reactor building and the diesel generator (DG) building and are buried in soil. The staff consultant reviewed TVA calculations B22 890109126. B22 881022199 and 890 880608 200 and found that the methods for computing the seismically induced axial and bending strains resulting from the seismic waves travelling along and perpendicular to the conduit banks axis are consistent with common industry practice and NRC's NUREG/CR-1361 (Reference 5.6) which formed the basis of the Standard Review Plan. Therefore, the use of these methods is acceptable. When the design adequacy of these conduit banks was reviewed, two concerns were identified:
(1) the basis for using 2.8 in/s as the maximum particle velocity of the ground and computing the seismic wave length based on a 0.3 s natural period of the soil deposit, and (2) the capacity of the expansion joints at the interface between the conduit banks and buildings to withstand the seismically induced relative structural movements.
TVA agreed to address these two concerns by the next civil calculation inspection.
Because of the open issues identified from the review of the sample structures, the staff expanded its sample size to cover the RHR pipe tunnel and the OGT Building.
In addition, the staff requested that TVA include the calculated seismic relative movement between the pipe tunnel and the reactor building in its RHR pipe tunnel calculations. TVA agreed to complete the calculations of these two buried structures by the next inspection. As for the buried safety-related piping systems. TVA committed to having(all calculations ready before the next inspection.
This item remains open.
CC-4)
3.3.4 Tanks and Heat Exchancers SWEC's review of this design area for the tanks and heat exchangers found that the design adequacy of the tanks and heat exchangers could not be demonstrated on the basis of the existing design calculations. TVA intended to make the design adequacy determination of these items after restart of the plant as part of the USI A-46 program.
The staff raised concerns about the following three issues:
(1) the integrity of nozzles, (2) the integrity of the tank shell, and (3) the integrity of support anchorages.
TVA stated that since the Browns Ferry Nuclear Plant is an A-46 plant, the qualification of tanks and heat exchangers will not be conducted until USI A-46 is implemented Therefore, the review of this design area is not considered as a prerestart item.
TVA also stated that the evaluation of nozzles will be performed as part of the IE Bulletin 79-14 program, since nozzle evaluations are not included in the USI A-46 program.
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The staff agreed with TVA's justification for the resolution of this design area and considers this item closed.
(CC-5)
3.3.5 Foundation Design Calculations (Reactor Building Base Slab)
I The review of the original reactor building design calculation (RIM No. B90 890208212) identified the following concerns:
(1) Torus uplift loads were not incorporated or referenced in the design.
(2) The analysis and design did not include loads associated with the maximum probable flood at elevation 752'5".
(3) The load distribution from the reactor building super structures was estimated instead of calculated.
(4) A dynamic stability analysis was not performed. This analysis should have been performed for the maximum design basis water at the reactor building and the loads associated with a safe shutdown earthquake (SSE) event.
(5) The SSE loads were not incorporated into the reactor building design.
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(6) The calculations did not include a check for shear stresses associated with hydrodynamic torus loads that could be caused by a loss-of-coolant accident and SSE loads.
As a result of reviewing the supplementing calculations by TVA and SWEC, the staff found:
(a) concerns 1 and 5 were satisfactorily addressed in SWEC's supplemental calculations, (b) concerns 2, 4 and 6 were reasonably addressed in
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TVA's supplemental calculations, and (c) TVA agreed to provide its justification for addressing the third concern during the next civil calculation inspection.
This item remains open.
(CC-6)
3.3.6 Soil Amplification The purpose of this review is to ensure that proper soil-amplification factors were used to calculate the input ground motion for the analyses of soil-supported safety-related structures.
The review of soil amplification for the DG building, SGT building, RHR service water tunnel. EAL and OGT building was conducted and closed during the December 19-22, 1988, inspection of the seismic design program (IR 50-260/88-39).
During this inspection, the staff consultant reviewed TVA's calculation of soil amplification factors for the concrete cable tunnel and found it accep-table on the basis of the theories and results of the review documented in IR 50-260/89-39. Therefore, this item is considered closed.
(CC-7)
3.3.7 Embedments/ Anchorages TVA intended to demonstrate the design adequacy of embedments and anchorages by j
evaluating them with associated ongoing programs such as heating, ventilation, and air conditioning (HVAC), conduit systems, miscellaneous steel frames, and IE Bulletin 79-14. All embedments and anchorages related to these programs would be evaluated for the interface loads to seismic loads, dead weights, etc. The-7-
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. staff's review of this item covered both embedded and surface-mounted steel base plates (including anchorages). During the review of the sample embedment calculations relating to miscellaneous steel frames and conduit supports, the staff found that the design of base plates and anchor bolts followed TVA Civil Design Standard DS-C1.7.1, which is consistent with AISC Steel Manual and standard industry practice. Therefore, the staff concluded that these calcu-lations were acceptable. However, the embedment calculations related to HVAC and piping systems were not available for review because of the ongoing HVAC and IE Bulletin 79-14 procrams. TVA agreed to complete the remaining calcu-lations before the next civil calculation inspection. This item remains open.
(CC-8)
3.3.8 Foundation Design Calculations - Intake Structure The staff consultant reviewed the calculations for the water supply pump station foundation (RIM B22 881211 124) and had the following concerns:
(1) The maximum probable flood water elevation 572'6" was not considered in the design of structure and equipment.
(2) SSE loads were not combined with normal resevoir water level (i.e.,
elevations 56'0").
In response to concern (1) in this section TVA advised that flood protection was installed in the area of the RHR service water pumps in resolving ECN C-23, and this protection was shown on TVA drawing 31 N 209, dated September 20, 1972.
This drawing also showed that all essential electrical equipment was protected in the equipment room in which the opening was properly sealed.
In addition, TVA performed calculations (CD-QO303-884856) to demonstrate that the intake structure is stable under the load condition of the maximum probable flood plus wave runup. The staff found this response acceptable.
In response to concern (2) in this section. TVA stated that the load combi-nation of the SSE plus the loads associated with the normal resevoir water level are not part of the licensing design basis for the plant (Table 12.2-27 of the FSAR).
To satisfy the staff's concern, TVA performed a study calcu-lation which showed that the intake structure is stable for this loading condition. The staff considers this issue closed.
(CC-9)
3.3.9 Reactor Building Corner Room Floor Framing
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The staff consultant reviewed sample calculations to deternlne the design i
adequacy of the structural steel framing at BFN-2. One of the calculations reviewed was TVA Calculation B22 880829 149 related to the reactor building floor framing at elevation 541'6".
From this review, the staff had the following concerns:
(1) Seismic loads were not considered.
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(2) Equipment acceleration loading was not included.
(3) Attachment loads were not considered.
(4) Equipment weights were assumed without verification.
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(5) As stated in the calculation, there was a discrepancy in beam sizes between the calculation and the drawing.
(6) The design of attachments to concrete was not included in the calculations.
(?) The design of connections was not explicitly addressed in the calculations.
TVA responded that a new calculation that would address these seven concerns clas being performed and would be available for the staff to review during the next inspection. At the staff's request, TVA also agreed to complete the revised calculations for the RRR heat exchanger support frame before the next inspection. As for generic implications of the staff's concern for steel platforms TVA provided a listing of the platfonns that have been or are being evaluated by TVA. The listing contains 19 platforms that represent a cross-section of platforms and types of platforms at Browns Ferry. When the evaluations of all these platform; are completed, it would represent the total population of the platforms at Browns Ferry. Therefore, the evaluation >
performed by TVA for generic implications is acceptable to the staff.
This concern is open pending the review of the calculations to be developed by TVA for the reactor building floor framing (at elevation 541'6" and the support framing for the RHR heat exchanger.
CC-10)
3.3.10 Baseplate Prying During the review of TVA's calculations, the staff found that prying action was not considered in'the evaluation of expansion anchors.
In response to the staff's concerns, TVA provided the following information for review:
f (1) Cyclic Test Report, (2) Load deflection curves for SSD and WB anchors, (3) Finite element analysis of a 2-bolt baseplate, (4) Previous TVA response to NRC on anchor stiffness and prying, (5) Example of industry responses on prying, (6) Additional load deflection curves for 3/4" self-drilling anchors, and (7) Base plate II finite element analysis of 2-bolt baseplate.
TVA's evaluation showed that prying action does not exist for the case of expansion anchors since the deformation of the bolt is larger than that of the base plate. As a result, the deformation of the expansion anchors for typical base plates generally results in separation between the base plate and the concrete. Therefore, the prying forces are small. The concept of base plate / concrete separation and the property of the supporting materials are
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being reviewed by the staff. This item remains open.
(CC-11)
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3.3.11 Concrete Structures The staff consultant reviewed sample calculations for the reinforced concrete chimney and reactor building concrete. A summary of each review finding
follows:
Reinforced Concrete Chimney According to the FSAR, the reinforced concrete chimney should be designed for a 300 mph tornado wind load, resonant wind load, and seismic loads (OBE and SSE)
in combination with the dead load and apr.licable live load. When subject to the 300 mph tornado wind load, which is the governing load case, the location of the chimney at 280 feet from the base will form a weak point and the top 320 feet of the chimney tends to break away. The design methods and codes required by the FSAR are:
-(1) working stress method per ACI Chimney Code 307-69 for the 100 mph wind,
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(2) working stress method per ACI Code 318-63 for both the seismic and resonant wind conditions, and (3) ultimate strength method per Section 1503 of ACI Code 318-63 for the tornado wind condition, with the use of a load factor of 1.1 and 0.55 for the lower 280 feet and upper 320 feet of the chimney, respectively.
In order to ensure that the analysis and design documented in the original calculations were adequate, TVA performed a supplemental calculation which showed that the original design is valid and the failure of the top 320 feet of the chimney will not affect the function of required safety-related structures, systems, and components.
The staff consultant reviewed both the original design calculation (B22 880923 102) and supplemental design calculations performed by SWEC and found that the design of the reinforced concrete chimney complied with the FSAR requirements and that results are acceptable.
Reactor Building The staff consultant reviewed sample calculations of the reactor pressure vessel support pedestal (B22 881123 120, B22 881123 121. B22 881123 119, CEB 800619 006 and the SWEC supplemental calculation for the RPV pedestal),
columns and walls (B22 880921 121 and the SWEC supplemental calculation for columns), and drywell concrete structures (B22 881211 147 and the SWEC supple-mental calculation for the biological shield wall) and identified the following concerns:
(1) For the pedestal design, confim the use of:
(a) the proper jet load-induced base moment, (b) the shear / moment owing to the jet, and (c) the 3et and seismic loads for the design of the ring guider anchor bolts.
(2) For the design of concrete columns, justify the use of ACI codes 318-71 and 318-77 in the supplemental calculations because the licensee committed to using ACI Code 318-63 in the FSAR.
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(3) For the design of walls, clarify how the seismic load generated from the seismic analysis were used in'the design.
(4) For the drywell concrete structure, address the thermal restraint load
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. produced from walls framing into the biological wall.= Explain."Restr" p-
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'(5)' Provide the generic implication of Item (2) above.
-The results of the reactor building base slot design calculations is discussed in Section 3.3.5 of this report.
(CC-6)
In sumary, the design calculations for the concrete chimney are acceptable.
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-TVA agreed to address the staff's five concerns related to reactor building concrete structures during the next inspection. This item remains open..
-(CC-12)
j 3.3.12' Control Bay Ficor Steel j
In response to SWEC's concerns raised in the. review report ef the contrsl bay floor steel framing calculations. TVA performed a finile elecent compuer
analysis of this steel frame. The results were documerced in TVA calculation
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B68 890320 001. The staff consultant reviewed these calculattens and found that there was.a discrepancy in the live load used for the platfom analysis.
'Also, TVA did not calculate the maximum compressive stresses in the flange of the supporting beam to detemine whether the stresses were below those allowed.
During the inspection. TVA issued a revision of this calculation (B90 890322 202) to address the two concerns mentioned in the previous paragraph. The staff reviewed this revised calculation and found it to be acceptable. There-fore,.the staff considers this item closed.
(CC-13)
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3.3.13 Diesel Generator Base Slab (Unit 2)
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The staff consultant reviewed TVA original design calculation B30 880523 200-for the diesel generator base slab. The base slab is a reinforced concrete mat with the diesel fuel storage tanks embedded in the mat. The staff has the-following concerns about the design of this base slab:
I (1) The calculation did not include the analysis of the base slab, considering the FSAR load combinations.
(2) Minimum flexural reinforcing was used without justification.
l (3) The embedment of the 12 tanks in the base slab was not considered in the load distribution to the slab.
It is believed that stress concentrations may exist because of openings caused by the embedment of the tanks.
(4) The high pressure coolant injection (HPCI) room extends under the DG building base mat creating a hard spot in the soil.
Differential settlement of the foundation of the DG building owing the presence of the HPCI room was not considered in the design of the base mat.
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(5). The soil pressures calculated under the base mat might not envelop all
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the load combinations as stated in the FSAR. The maximum soil pressure was not checked to determine whether it was below the allowable soil
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(6) Factors.of safety against overturning and sliding were not calculated.
(7) Shear was not checked in the base slab design.
(8) Because the diesel fuel storage tanks are an integral part of the base-
- slab, the stresses / displacements of the base slab should be checked to ensure that the integrity of _the tanks is not jeopardized.
TVA agreed to re-review the original design calculations and address these eight concerns as well as to evaluate the generic implication of this item during the next inspection. The staff considers this item opene (CC-14)
3.4 Review of Miscellaneous Items In addition to the 16 design areas discussed above, the staff extended its review to cover three miscellaneous items. These three items are the (1) adequacy of cable tray and supports (2) rod-hung conduit supports, and (3) thermal growth of steel platforms. The results of the staff's review are summarized in Sections 3.4.1, 3.4.2, and 3.4.3.
3.4.1 Adequacy of' Cable Tray and Supports The review of the NRC staff safety evaluation for the restart evaluation of BFN-2 cable tray and supports, dated February 5, 1987 (Reference 5.7) showed that NRC has reviewed TVA's restart criteria and calculations and accepted TVA's evaluation results. The staff agreed with the' conclusions drawn and presented in Reference 5.7.
Therefore, this issue is considered closed.
3.4.2 Rod-Hung Conduit Supports This issue was originally identified in NRC Inspection Report 50-260/88-38.
In response to the staff's concerns, TVA selected five sample outliers based on the worst cases relating to rod-hung conduit supports for confirmatory evaluation. The staff consultant reviewed the calculations for these outliers and found that three of the five outliers were about 3 percent over the stress allowable set for interim operability criteria. The staff considers this acceptable.
As for the remaining two outliers, TVA agreed to provide additional calcu-lations for staff review by the next Seismic Design Program audit. This
. issue is open pending the staff's review of these additional calculations.
(GSG-32)
3.4.3' Thermal Growth of Steel platfoms Outside Drywell TVA committed to the resolution of this issue as discussed in Section 111.14.3, of BFNPP, Volume 3.
During the meeting's discussion, TVA presented its concept and evaluation approach for the following three areas:
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'(1) self-relieving behavior of thermal loading, (2). ductibility ratios recommended by ANSI Code for impact. loads, and (3) enveloping calculations for thermal growth effect.
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' The staff. agreed to review the documentation and calculations presented by TVA at this meeting.
The staff also stated that a ductility factor higher than 3 would not be' acceptable because this is the limiting value that has previously been accepted by NRC, on a case-by-case basis. This item remains open.
(CSG-34)
Conclusion As discussed in Section 3 of this report,10 of 14 civil items and 2 of 3 miscellaneous items reviewed during this inspection remain open.
In order for the' staff to complete its review of the civil calculation review program and the items discussed for BFN-2 in BFNPP Volume 3, TVA is requested to respond to all of the open items and to complete its evaluation of them before the next inspection.
References 5.1 Summary of meeting on February 29, 1988 - Browns Ferry Overall Civil Program and Identification of Design Programs Requiring NRC Approval (" Criteria Meeting"), dated March 4, 1988 5.2 Letter from G. G. Zech (NRC) to S. A. White (TVA), " Alternate Input for Seisraic System Analysis - Artificial Time History," dated January 25, 1988 5.3 NRC Inspection Report 50-260/89-29
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5.4 NRC Inspection Report 50-260/89-07 5.5 Summary of Meeting Held on January 5,1989. " Civil / Seismic Issues Review - BFN-2," dated March 22, 1989 5.6 NUREG/CR-1161, "Recomended Revisions to Nuclear Regulatory Commission -
Seismic Design Criteria," dated May 1990 5.7 Letter from D. R. Muller (NRC) to S. A. White (TVA), dated February 5, 1987
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ENCLOSURE 1 Civil Calculation Audit
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Entrance Meeting March 13, 1989 Wayne.A. Massie BFN Site Licensing Ruben O. Hernandez NE-CEB Tom C. Tsai NRC Consultant John A. Ellis NE-Civil
'Ahmet 1. Unsal-NRC Consultant Owen Mallon NRC Consultant Thomas M. Cheng NRC/NRR/TVAPD
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ENCLOSURE 2 Civil Calculation Audit
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Exit Meeting i
March 24, 1989-Wayne A. Massie BFN Site Licensing Ruben 0. Hernandez NE-CEB Don L. Williams NLRA Tom C. Tsai NRC Consultant John A. Ellis NE-Civil Ahmet I. Unsal NRC Consultant David Terao NRC/NRR/TVAPD Owen Mallon NRC Consultant Thomas M. Cheng NRC/NRR/TVAPD John McCall TVA/CEB l
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ENCLOSURE 3 Status Civil Calculation Review Program Open Items
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-Concerns
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Section Identified Status Subject No.
CC-1 (0 pen)
Justification for Post-Restart 3.2-CC-2 (0 pen)
Piles and Foundations 3.3.1 CC-3 (0 pen)
Soil and Rock Analysis 3.3.2 CC-4 (0 pen)
Buried Structures 3.3.3
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CC-5 (Closed)
Tanks and Heat Exchangers 3.3.4 CC-6 (0 pen)
Foundation Design Calculations 3.3.5 CC-7 (Closed)
Soil Amplification 3.3.6 CC-8 (0 pen)
Embedments/ Anchorages 3.3.7 CC-9 (Closed)
Foundation Design Calculations-3.3.8 Intake Structure CC-10 (0 pen)
Reactor Building Corner Room 3.3.9 CC-11 (0 pen)
Baseplate Prying 3.3.10 CC-12 (0 pen)
Concrete Structures 3.3.11 CC-13 (Closed)
Control Bay Floor Steel 3.3.12 CC-14 (0 pen)
Diesel Generator Base Slab 3.3.13
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