LIC-97-0122, Forwards Response to Supplemental RAI Re Resolution of USI A-46 for Fcs.Rev 1 to Calculation FC06313 & Rev 1 to Calculation FC06314,also Encl

Forwards Response to Supplemental RAI Re Resolution of USI A-46 for Fcs.Rev 1 to Calculation FC06313 & Rev 1 to Calculation FC06314,also Encl

ML20217H627
Person / Time
Site:	Fort Calhoun
Issue date:	08/04/1997
From:	Gambhir S OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20217H631	List: LIC-97-0122, Forwards Response to Supplemental RAI Re Resolution of USI A-46 for Fcs.Rev 1 to Calculation FC06313 & Rev 1 to Calculation FC06314,also Encl ML20217H633 ML20217H647
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR LIC-97-0122, LIC-97-122, TAC-M69447, NUDOCS 9708130154
Download: ML20217H627 (9)

Text

_ _ - _ - _ _ _ _ _ _ _ _ _ _ _ - _

s' o

% 998 Omaha Public PowerDistnct 444 South 16th Street Mall Omaha NE 68102-2247 August 4, 1997 LIC-97-0122 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Station: P1-137 Washington D.C. 20555

References:

1. Docket No. 50-285

2. Letter from OPPD (T. L. Patterson) to NRC (Document Control Desk) dated August 23, 1996 (LIC-96-0121)

3. Letter from NRC (L. R. Wharton) to OPPD (S. K. Gambhir) dated June 5, 1997

Subject:

Response to Supplemental Request for Additional Information on the l Resolution of Unresolved Safety Issue A 46 (TAC No. M69447)

Reference 3 transmitted a supplemental Request for Additional Information (RAI) on the resolution of Unresolved Safety Issue A-46 for Fort Calhoun Station. Enclosed is the Omaha Public Power District (OPPD) response to the supplemental RAI. This response reflects telephone discussions held with an NRC staff technical reviewer on July 10 and 11, 1997.

Please contact me if you have any questions.

Sincerely, g

hM S. K. Gambhir Division Manager Engineering & Operations Support TCM/tcm 7

Enclosures @e n r '".3

\

c: Winston & Strawn (w/o enclosures) / \

E. W. Merschoff. NRC Regional Administrator, Region IV , gf(/ ,

L. R. Wharton, NRC Project Manager '

W. C. Walker, NRC Senior Resident Inspector '

9708130134 970804 PDR llll111.1!!1.111'l2 !!11.1111.11111111 ADOCK 05000285 P PDR 45.5124 Errpoyment with Equal Opportunny s

LIC-97-0122 Enclosure 1 Page 1 Omaha Public Power District (OPPD)

Response to Supplemental Request for Additional Information (RAI) on Resolution of USI A 46 i

RAL0uestion_No_L In reference to Attachment 4 of your submittal LIC-96-0121. Calculation No. FC06313, please note the following:

1

a. The nominal allowable capacities of the cast in-place anchor bolts should be determined in accordance with Section C3 of the GlP, Appendix C, in the coriputation of allowable tension "P" for cast-in place anchor on sheet 14 of 37 (Calculation No, FC06313) an anchor is considered as a plain top rebar in a beam.

This representation is not conservative since a rebar most likely will be much l longer than an anchor and the end of the rebar is embedded in the compression V zone of the beam. Therefore, you are requested to provide a justification for the use of higher tensile allowables than those specified in Appendix C of the GIP for cast-in-place anchors, or revise your cocputation in conformance with the GIP provision.

OPPD_ Response l a Calculation FC06313 has been revised (as discussed below) and is attached to this response, The capacity of the J-bolts as specified in the GIP was based on the bond strength for plain rebars. See EPRI NP-5228-SL. " Seismic Verification of Nuclear Plant Equipment Anchorage (Revision 1). Volume 1. Development of Anchorage Guidelines," page 2-98. The only difference is that Calculation FC06313 used ACI 318-63 code while GIP ,

Appendix C followed the British code. There are, however, deviations between the ACI code and GIP. The calculation has been revised to follow the GIP provisions. The allowable pullout capacity for the J-bolt has been reduced to 15.16 kips from 18.3 kips.

b, The shear-tension interaction analysts on sheet 15 of 37 does not appear to be valid for the pedestal. which is under tension and shear. because under such condition, either the concrete or the shear reinforcement, not both can be considered to resist the shear. Therefore, your computation of allowable shear "V" should be just1fted or revised, as discussed in item 1.a above.

p s

'LIC-97-0122 Enclosure 1 Page 2 OPPD_ Response.l b Llt is a common practice to combine shear capacity of concrete and rebars. For' example, ACI 318 allows the combination of Vc and Vs in the design for beam shear. However. the cal _culation has been revised to use only the capacity of the rebars. The shear capacity of the anchor bolt has been reduced to 11.16_ kips from 13.35 kips. Since concrete does l not govern the failure.- the more conservative bilinear shear-tension interaction l equation is used_ for the A 46 outlier resolution.

l

c. As a result of revised allowable values of "P" and "V" your shear-tension interaction analysis on sheet 26 'and 32 of 37 should also be reassessed.

OPPDlesponse_Lc The shear-tension Interaction for the J-bolt has been re evaluated on page-26 for the A-46_ condition. The interaction ratio is exactly 1,0 under the extreme conservative condition. The A-46 outlier issue is resolved. In the computation of HCLPF on pages 27 and 32, the interaction equation is not applied, Since the pullout failure is governed by the bond strength between the J bolt and concrete, but the shear failure is governed by the rebar yielding, the mechanisms are totally independent and apply to different materials. In light of the other conservative assumptions, the shear-tension interaction equation is not applied for the IPEEE evaluation.

d. The proposed modt fication as shown on sheet 37 of 37 (Calculation No, FC06313) .

1s not clear and the location of the modification in relation to the saddle and

' the tank as a whole, should be clearly ident1fied.

OPEDJesponse_Ld Page 37 has been re-drawn to illustrate the relative location of the tank to the saddle and the support.

RAL0uestion_No.1 In the computation-for A-46 Outlier Resolution for Heat Exchanger CH-7. you have not i followed Appendix C of the GIP to culculate the bolt capacities on the basis of the .;

embednent length check and edge distance check and have used the anchorage requirement i

.of a plain top rebar in _a beam to determine the bolt capacities. As indicated in 1.

above, such an approach results in overestimation of bolt capacities and is, therefore, unacceptable. We request a re-evaluation of bolt capabilities for this equipment using the approved methodology in Appendix C of the GIP.

.m

_.7 .-

LIC 97 0122 Enclosure 1 Page 3-

OPED_ Response _

-Calculation FC06314 has been revised (as discussed below) and is attached to this i

response. Similar to the response to Question No.1.- the capacity of the J bolts as specified in the GIP was based a the bond strength for _ plain rebars. See EPRI NP-5228 SL " Seismic Verification of Nuclear Plant Equipment Anchorage (Revision 1).

l Volume 1. Development of Anchorage Guidelines." page 2 98. The only difference is that Calculation FC06314 used ACI 318-63 code while GIP _ Appendix C followed the British code.

There are, however, deviations between the ACI code and GIP. The calculation has been revised to follow the GIP provisions. The allowable pullout capacity for_the J-bolt has been reduced to 12.14 kips from 17.0 kips The shear allowable has also been reduced by not combining Vc and Vs, However, the pullout of-the anchor is still governed by I

' the base plate yielding, and the shear capacity is still governed by the shear failure of the anchor bolt. The changes have no effect on the rest of the calculation.

RAI Question 3 has been broken into parts a. b. and c in order to enhance the clarity of_the response.

RAI_0uestion_3a i in the calculation for seismic qua11fication of the diesel fuel tanks, discussed in Calculation No. FC06011. the theoretical buckling stress is shown to be 76,150 psi which

'1s more than twice the yield stress of 30.000 pst of the steel used. Therefore. the L buckling is in the plastic range and hence, the analysis should be made on this basis.

OPP 0_ResponseJa

-Per Article 1600 of Code Case N-284, a decision on whether elastic or inelastic buckling is to be considered for a fabricated shell is based on the product of. the classical

buckling stress and the capacity reduction factor; it is not based on the classical buckling stress alone.

In the present case, classical buckling stress - 76.150 , psi (Page 27 of the calculation) capacity reduction factor - 0.31 (Page 26 of the calculation)

The product 76.150 x 0.31 - 23.607 ps1 i This product is less than the 30.000 psi y1 eld stress. Therefore, the buckling capacity does not require consideration of plasticity. l

.V A.

l

! LIC-97-0122'

- Enclosure 1---

Page 4 l:

i RA110uestfonJb

You calculated the buckling stress by using the formula in ASME Code Case 284.- In-accordance with Code Case 284, the formula you used is for local buckling of-unst1ffened or ring stiffened cylindrical shells under axial compression. Since the diesel fuel tank is buried, it is under both axial carpression and hoop corpression and the concern

- 1s general stability. Therefore, Code Case 2841s not applicable for the required 1 -evaluation.

OEPD Response _3b

.It is true that the buried diesel fuel tank is under both axial compression and hoop compression. :The evaluation performed also considered this combined effect: it did not consider axial compression alone, Article-1712 of the Code Case states,

- 1712.1 gives equations for ' determining -the classical buckling stresses of unstiffened shells or the parels between: stiffeners of stiffened shells;

- 1712.2 gives equations for determining the theoretical stringer buckling and general instability stresses for stiffened shells."

-- Accordingly, since the diesel- fuel tank is an unstiffened cylindrical shell, evaluation of the tank under combined axial-and hoop compression was made using axial. and external pressure loading cases of Section 1712.1 and the interaction equation of Article 1713.

(Refer to Pages 27 and 28 of the calculation.)

For. ~an unstiffened shell with large radius to thickness ratio and small length to diameter ratio under axial loading, which is the case with the diesel fuel tank, overall

-buckling is not expected to control, i.e.. local buckling governs. Also, since uniform hoop compression is being considered, there is no_ clear distinction between local and overall' buckling, Therefore, use of Section 1712.1 and Article 1713 of the Code Case

_( as used) is appropriate.

RAL0uestion_3c The ' basic allowable buckling stress values should be established on the basis of

.NE-3131(b), NE-3133 and NE-3222 or other applicable criteria.

On the basis of the above observation, we request- a re-evaluation of the seismic

capability of the diesel fuel tanks.

v o E

LIC-97-0122

-Enclosure 1-Page 4 RAL0uestlofL3b

- You calculated the buckling stress by using the formula in ASME Code Case 284. In

. accordance with Code Case 284, the fomula you used is for local buckling of unst1ffened

l. or ring stiffened cylindrical shells under axial compression, Since the diesel fuel

[ tank is buried - it is under both axial cmpression and hoop cmpression and the concern l 1s general; stab 111ty. Therefore Code Case 284 Is not applicable for the required evaluation, OPED_ Response _3b h-L l It is true that the buried diesel fuel tank is under both axial compression and hoop compression. The evaluation performed also considered this combined effect: it did not consider axial compression alone.

Article 1712 of the Code Case states.

~

- 1712;1- gives equations for determining the classical buckling stresses of unstiffened shells or the panels between st1ffeners of stiffened shells.

- 1712.2 gives equations for determining the theoretical stringer buckling and I general instability stresses for stiffened shells."

L Accordingly, since the diesel fuel tank is an unst1ffened cylindrical shell, evaluation of the tank under ccmbined axial and hoop compression was made using axial and external pressure loading cases of Section 1712.1 and the1nteraction equation of Article 1713.

-(Refer to Pages 27 and 28 of the calculation.)

For an unstiffened shell with large radius- to thickness ratio and small length to

-diameter ratio under axial loading, which is the case with the diesel fuel tank, overall buckling 1s not expected to control, i.e., local buckling governs. Also, since uniform hoop compression 1s being considered, there is no clear distinction between local and overall buckling. .Therefore, use of Section 1712.1 and Article 1713 of the Code Case (as used) is wpropriate.

RAL0uestionlc The basic allowable buckling stress values should be established on the basis of

-NE-3131(b), NE-3133 and NE-3222 or other applicable criteria. '

On the basis of the above observation, we request a re-evaluation of the seismic capability of the diesel fuel tanks. '

J

s .

LIC-97 0122 Enclosure 1 Page 5-OPP 0lesponse_3c Based on Responses 3a and 3b, re-evaluation of the diesel fuel tank is not ccnsidered i necessary. However, to provide additional information to the NRC staff technical reviewer, a tank evaluation is enclosed using ASME, subtection NE, as requested. This evaluation shows that the subject diesel fuel tank is seismically -qualified.

L Additionally l, as discussed with the reviewer on July 11, 1997, a re-evaluation of the tank has been made in the enclosed calculation asing a factor of safety of 2.0 for the SSE loading with the code case N 284 equations, instead of the 1.34 factor of safety

. used originally. The calculated interaction co-efficient is 1.023. This slight exceedance over 1.0 is acceptable based on the conservatisms listed at the end of the attached calculation.

RAL0uestjon A In the evaluation of the seismic resistance of concrete block walls. you have idealized the portion of the wall between Wall No.10 and row line Q as one way slab with single

~

-span and sitiple support in the hcrizontal direction. On the basis of such an idealization, you have calculated the seismic bending moment and the corresponding bending stress (21.2 psi) which can be tensile or cmpressive. This stress is caripared.

to the allowable value (f3 which is taken as 50 ps1. According to Table 10.1 in ACI 531-79 code, the allowable stress for tension normal-to-bed joints 1s 25 psi. With the idealization of the layer of block wall as a beam, the flexural tension force is normal to the vertical bed joint. A close examination of your calculation for the moment of inertia of the idealized beam section kould indicate the calculated moment of inertia to be for a section of a beam spanned between supports in the vertical direction. On this basis, you are requested to re-evaluate the bending stresses in the wall against ,

the corresponding allowable, or provide a justification for the apparent discrepancy in the block wall seismic evaluation.

OPPD3esponse As shown in Figure 2 of the Summary Calculation, the block wall. #9 west of column line 0 spans in the horizontal direction between block wall #10 and the steel column provided to support the wall #9. For a wall spanning in the horizontal. direction. and loaded in the horizontal direction perpendicular to the plane of the wall, the bending stresses are parallel to the horizontal plane in a direction along the bed joint, as shown in Fia 10.la of "Carnentary on Building Code Requirements for Concrete Masonry Structures (ACI 531-79)" (see attached copy). According to Table 10.1_ of ACI 531-79 and the attached Figure 10.la, the allowable stress for a wall spanning in the horizontal direction is equal to F, -1.0(m , )"2 not to exceed 50 ps1. Therefore. the 50 psi allowable stress, as calculated on Page 5 of the " Summary Calculations" is consistent with the allowables given in ACI 531-79.

e . A

• , o

-LIC-97-0122 Enclosure 1 Page 6 We agree with the ieviewer that the.way the moment of inertia was computed on Page 2-of the Summary Calc 11ation caused some confusion regarding the behavior of the wall, 1.e. the direction in which the wall is spanning 31d the corresponding direction of the bending. stresses. For a wall spanning in the horizontal direction, the moment of inertia should be c61culated about the vertical axis of the wall. The revised moment of inertia calculated about the vertical axis of the wall is 130.3 in' compared to 136.2 in' originally used in the calculation. The effect of this small_ change in the moment of inertia of the wall is negligible. However, the calculation has been revised-to recalculate the stress in the block wall using this revised moment of inertia. (See l- attached revised Pages 1-5 of the Summary Calculation.) TheLseismic adequacy of the wall is still maintained by a comfortable margin.

L

LIC 97-0122 Enclosure 2

1. Calculation FC06313'(affected pages only):

2.- Calculation FC06314 (affected pages only)

3. Tank Evaluation Based on ASME NE-3131(b). NE-3133, and NE 3222, 1995 Edition

4. Code Case Evaluation for SSE Loading Using FS of 2,0 -

5, Commentary on Building Code Requirements for Concrete Masonry Structures (ACI 531-79), Figure 10.la L 6. Summary of Calculation for Block Wall No. 9 (Revised - Pages 1-5 only)

L

.