ML20207N934

Rev 1 to Mark I Containment Long-Term Program,Addendum to MPR-734 Plant-Unique Analysis Rept,Torus Attached Piping

ML20207N934
Person / Time
Site:	Oyster Creek
Issue date:	12/31/1987
From:	MPR ASSOCIATES, INC.
To:
Shared Package
ML20207N930	List: ML20207N928 ML20207N934
References
MPR-999, MPR-999-R01, MPR-999-R1, NUDOCS 8810190486
Download: ML20207N934 (25)

Text

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li MPR ACSOCIATES, INC.

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OYSTER CREEK NUCLEAR GEf4ERATIf4G STATION MARK I CONTAlf4 MENT LONG-TERM PROGRA!!

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ADDENDUM TO MPR-734 PLANT-UNIQUE ANALYSIS REPORT TORUS ATTACHED PIPING MPR-999 Revision 1 I

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Prepared for:

General Public Utilities fluclear Parsippany, NJ December 1987 I

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• 8810190486 881014 PDR ADOCK 05000219 Q PDC 1050 CONNECTICUT Avt Nu t, N.W. WAsMiNotoN. D.C. 20036 202 659 2320

I M P R ASSOCI ATES, INC.

TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 REANALYSIS RESULTS 2.1 Vacuum Relief Piping 2.2 Containment Spray Test Return 2.3 Core Spray Test Return 2.4 SRV Discharge Piping 2.5 Small Bore Piping

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I M P R ASSOCIATES. INC.

1.0 INTRODUCTION

The Oyster Creek Nuclear Generating Station uses a containment structure for the boiling water reactor (BWR) nuclear steam supply system desig-nated as the Mark I containment system. The containment structure con-I sists of a drywell, torus suppression chamber, and connecting vent system. In August of 1982, MPR prepared a report, MPR-734, documenting I the results of analyses performed on piping systems attached to the torus suppression chamber. These analyses were performed in accordance with the Mark I Containment Long-Term Program, as documented in fiPR-734 MPR-734 dccumented that the piping systems attached to the torus suppression chamber would satisfy the Mark 1 Containment Long-Term Pro-gram provided that certain modifications were made. Subsequent changes to the piping and support arrangements made it necessary to reanalyze some of these piping systems to reconfirm that they satisfy Mark I Program acceptance criteria and to redefine the needed modifications.

I The purpose of this report is to document the reanalyses of torus attached piping systems which were performed for the reasons discussed above. Because this report is an addendum to the original Mark I long-Term Program analysis report, only the inf:rmation that differs f rom the original report, i.e., the reanalysis results, is included in this report.

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M P R ASSOCIATES, INC.

1 2.0 REANALYSIS RESULTS l

2.1 VACUUM RELIEF PIPING 2.1.1 Torus-to-Reactor Building Vacuum Breaker Line The original MPR-734 Mark I Program analysis of the Torus-to-Reactor Building Vacuum Breaker Line (TRB) included supports which had pre-viously been engineered, but not yet installed, as part of a Containment Vent / Purge System Upgrade, a program unrelated to the liark I Program.

This upgrade also included the proposed installation of supports on a branch line, the Nitrogen Purge Line, in the vicinity of its connection to the TRB. Subsequently, it was determined by GPUN that there was no need for the Containmeat Vent / Purge system upgrade. The question then I arose as to which of the supports were essential to ensure that the TRB satisfied the Mark I Long-Term Program acceptar.ce criteria. A preliminary field check of the proposed supports revealed that certain of these npports could not be installed as originally designed due to interferences. For these reasons, GPUN requested that HPR reanalyze the TRB in order to:

Determine which of the original seven TRB supports are required to satisfy the Mark I Long-Term Containment Program piping criteria.

Recommend needed changes to the support designs and any other TRB I modifications required to satisf'/ Mark I Program Criteria.

Determine updated design loads 'or any new supports required and for the existing floor support (ehe floor support had been shown to require modification in the original MPR-734 analysis).

2.1 I

I The reanalysis of the TRB is based on the support arrangement huwn in Figure 2.1-1, which supersedes Figure 6.1-4 in MPR-734 This support arrangement requires installation of three of the additional supports which were originally proposed. The method used for this reanalysis is the same as that used originally, except for the summation method used to combine dynamic loads, which is based on square root sum of the squares (SRSS) combination of independent dynamic loads. This approach was approved by the NRC for use in Mark I analyses as documented in NUREG-0484, Rev. ., "Methodology for Combining Dynamic Responses," and NEDE-24632, "Mark 1 Containment Program Cumulative Distribution I Functions for Typical Dynamic Responses of a Mark I Torus and Attached Piping Systems," which was forwarded to the USNRC on behalf of the BWR Mark I Owners Group by GE letter HFN-147-82.

With this support arrangement the piping stresses satisfy all Mark I Containment Program Acceptance Criteria. Maximum and allowable stresses for the TRB piping are shown in Table 2.1-1, which supersedes the results shown in Table 6.1-2 in MPR-734 for the TRB (Azimuth 180*). The most limiting occasional loading stress is 8,000 psi, ?2% of the I allowaole stress. For the thermal and sustained load piping stresses, the most limiting calculated stress is 19,000 psi, 84% of the allowable stress.

Support and hanger stresses are bounded by the stresses and loads reported in MPR-734, except for the floor support (NQZ-2-H30), which is being modified to meet Mark I Acceptance Criteria. The most limiting stresses for the modified floor support are as follows: (1) Level A/B Loading - 16,920 psi, 78% of the allowble stress, (ii) Level C Loading -

27,960 psi, 97% of the allowable stress.

The following actions which result in the TRB satisfying the Mark I Pro-gram criteria are being taken:

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I additior.61 :r,p at.,.

ke. . existir; 'loor support at elevation 26'-6".

1.3. ) ,. Excaust L,0 The or'. g ; ..a i .04 x 1 Aqment Exhaust Line Mark I Program analyses were performed incl ain, , 'ffects of a proposed modification:

replacing 200 lb butterfly Lives with 1325 lb valves and adding a dead-weight support. GPUN has determined that this modification is not nec-essary; therefore, the original analysis results do not correspond to the as-built condition of the line.

To verify the adequacy of the piping without this modification, the ori-ginal MPR-734 calculations were reviewed. These 001culations contained scoping analyses which included analyses using the existing 200 lb valves.

It was, therefore, possible to compare results for the as-built piping with results obtained for the piping with the proposed, heavy valves.

From these comparisons, it was concluded that the analysis results for the original analysis (with the proposed, heavy valves) bound the I results for the as-built configuration of the Containment Exhaust Line (with the light valves). Furthermore, there is no change in the conclusion that the Containment Exhaust Line as-built configuration meets the requirements of the Mark I long-Term Program. Accordingly, no structural modifications are required.

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TABLE 2.1-1

SUMMARY

OF MAXIMUM AND ALLOWABLE STRESSES TORUS-TO-REACTOR BUILDING VACUUM RELIEF PIPING AT AZIMUTH 180' I Occasional Loading Stresses - ASME Equation (9)

Load Case .

(Note 1) Maximum Stress (ksi) Location (Note 3) Allowable Stress (ksi) la 4.0 (Note 4) Elbow G 18.0 lb 4.0 (Note 4) Elbow G 27.0 II 5.3 Elbow G 36.0 III 8.0 Elbow G 36.0 IVa 4.0 (Note 4) Elbow G 27.0 IVb 4.0 (Note 4) Elbow G 36.0 I Va 4.0 (Note 4) Elbow G j 27.0 Vb 4.0 Elbow G 36.0 Thermal and Sustained Loading Stresses - ASME Equation (10)

Load Case (Note 1) Maximum Stress (ksi) Location (Note 2) Allowable Stress (ksi)

I 17.1 Tee E 22.5 II & III 19.0 Tee E 22.5 IV & V 27.2 (Note 3) Tee E 35.3 Notes:

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3.

Load cases defined in MPR-734 Maximum stress locations defined in Figure 2.1-1.

Case IV and V evaluated in accordance with ASME Equation (11).

l 3 4 Pipe stresses for these occasional load cases are conservatively taken as the g stress for Load Case Vb.

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V

... .ssoc.m s

';* ,Y.*,'.~'l f

/ norE g g X - INDICATE EXISTING SUPPORT 5 x ,

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%u /

D , " <.

k @s:t3 c

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~3. f O,0 NL@ x 9' l',. X ~

% 4::g

'$ # p'" 4%4 4' g39 3 ~?:2 4 +., .

FIGURE 2.1-1 l

l TORUS TO REACTOR BUILDING VACUUM BREAKER l

PROPOSED SUPPORT LOCATIONS AND l MAXIMUM STRESS LOCATIONS

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2.2 CONTAINMENT SPRAY TEST RETURN PIPING The original Mark I Program analysis of the Containment Spray and Test Return Piping was performed using a model which contained a proposed modi fication: rerouting the two Test Return Lines such that they would penetrate the torus through their own nozzles, instead of penetrating through the torus-to-drywell vacuum relief piping, which is external to the torus. Reanalysis was required by a change in the routing planned by GPUN for these lines, and the addition on one of the lines of a special branch connection and support for returring temporary torus water clean-up flow to the torus.

As described above, each of the two containment spray and test return piping lines will continue to be connected to the torus through a torus-to-drywell vacuum relief assembly. The coupled nature of these systems rada it necessary to include the vacuum relief piping in the containment I

spray piping analysis models. Although the purpose of the reanalysis' was to account for the change in the planned routing of the containment spray piping, the stresses in the adjacent vacuum relief piping were i evaluated as well. The method used for this reanalysis is the same as that used originally, except for the summation method used to combine dynamic loads, which is based on square root sum of the squares (SRSS) combination of independent dynamic loads. This approach was approved by the NRC for use in Mark I analyses as documented in NUREG-0484, Rev. 1 "Methodology for Combining Dynamic Responses," and NEDE-24632, "Mark I Containment Program Cumulative Distribution Functions for Typical Dynamic Responses of a Mark i Torus and Attached Piping Systens," which was forwarded to the USNRC on behalf of the BWR Mark I Owners Group by GE letter MFN-147-82. It was found that the stresses in the vacuum relief piping calculated in the coupled model were bounded by the original analysis results. Figure 2.2-1 shows the model of vacuum assembly G used for this analysis, and supersedes Figure 6.3-1 in MPR-734 The model for vacuum assembly B is shown in Figure 2.2-2.

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The analysis results for the containment spray and test return piping, including the torus water cleanup discharge connection, indicate thtt the liark 1 Containment Long-Term Program structural acceptance criteria l for all required Mark I loading combinations are satisfied. These results are shown in Table 2.2-1. The stresses shown in Table 2.2-1 for the North Loop at Assembly G supersede the Out-of-Torus stress results contained in Table 6.5-1 of MPR-734 I The maximum calculated occasional load piping stress required to meet the 18,000 psi Level B allowable stress is 12,600 psi, 70% of the allow-able stre3s. The maximum calculated occasional load piping stress for the 27,000 psi Level B(3) allowable stress is 27,900 psi, and for the 36,000 psi Level D(5) allowable is 36,600 psi. Both of these stresses exceed the allowable stress by less than 4%, which is judged acceptable due to conservatisms inherent in the stress evaluation method used.

These conservatisms include peak-broadening (t10%) of response spectrum dynamic loads, and using the frequency response spectrum analysis method which provides significantly higher piping stress results (30% or more for scoping analyses performed on a typical piping system) than more accurate time history analyses. The maxiii.sm calculated thermal and sustained load piping stress of 36,200 psi is 97% of the allowable stress. The SBA post-chug thermal and sustained load case (Load Case V) is required to meet a educed allowable due to the number of effective l cycles (up to 14,000 cycles). For this thermal and sustained load case, the maximum calculated piping stress is 28,600 psi, 81% of the allowable stress.

All support and hanger stresses are within the liark I requirements I except as noted below. For the remaining supports, the maximum calcu-lated support stress is 14,300 psi, 79% of the allowable stress. The maximum calculated hanger load is 290 pounds, 94% of the allowable laad specified by the hanger manufacturer.

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To meet the Mark I criteria, the following support modificattons were and are being made:

1. The torus spray header supports were modified to withstand Itark I loads. The design loads and requirements for these supports did not change as a result of the reanalysis.

I 2. The existing support at the torus water cleanup line connection on the south containment spray test return line at vacuum relief assembly B (Azimuth 72') was modified to withstand Mark I loads.

I The support is located at Elevation 25 feet and is designated D in Figure 2.2-2 (H0327).

3. One existing spring hanger support on the north containment spray l test return line located at vacuum relief assembly G (Azimuth 288*)

will be replaced with a rigid vertical strut. This support is located at Elevation 14 feet and is designate'd G in Figure 2.2-1 (NQ-2-H43). The modification was required because the existing spring hanger was unable to adequately restrain oscillation of the I conbined test return line and vacuum relief assembly G. The exist-ing arrangement resulted in unacceptable stresses in both the con-tainment spray test return line and in vacuum relief piping at assembly G.

I The existing vertical support on the north containment spray and test g return line at vacuum relief assembly G ( Azimuth 288'), is currently gapped in all directions. This support is located at Elevation 30 feet, I and is designated S in Figure 2.2-1 (NQ-2-H39). During analysis, displacements were calculated at th15 support to determine if the limits of the gap would be reached. It was determined that the gap would not close during any liark I loading combinations and therefore the support may be removed without affecting the Mark I analysis results documented in this report. It is not mandatory that the support be removed to ,

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satisfy the liark I Program requirements. It should also be noted that the seismic restraint on the north containment spray and test return line designated R in Figure 2.2-1 (flQ-2-RI), at Elevation 28 feet, 3 inches, is also gapped. Using a similar approach, it was determined that the gap limits would not be reached. Thus, this support may also be removed without affecting the Mark I analysis results documented in this report.

I The vacuum relief piping assemblies to which the containment spray and test return lines are connected each have two nozzles: one connected to the torus and one connected to the vent line external to the torus. The stresses for each load combination evaluated for the torus nozzles of both vacuum relief assemblies (B and G) were less than those computed for the original load combinatinns. Also, all stresses calculated for the B and G vacuum relief piping assembly vent line nozzles were within the allowable stress values. The revised analyses show that the limiting load combination results f rom the bounding postchug combination rather than the bounding condensation oscillation load combination.

which was limiting in the original analyses; howcver, the calculated I stress to allowable stress ratio remains the same. Accordingly, the results contained in itPR-734 are representative of the structural design margins of the piping and it is not necessary to revise those results.

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TABLE 2.2-1 SLmARY OF MAXIMLN PIPING STRESSES FCR CONTAltNENT SPRAY PIPING I

Occasional Loading Stressas - ASME Equation (9)

I North Loop at Assembly G South Loop at Assembly B Load Case . Msw imum Stress Location Maximum Stress Location Allowable Stress (Note 1) (ksi) (Note 2) (ksi) (Note 4) ( ks i) l I la lb 10.0 23.0 0

0 12.6 27.9 (Note 3)

A A

18.0 27.0 I il iII 27.7 30.4 0 0 36.6 (Note 3) 34.4 A

A 36.0 36.0 I lYa IVb Ya 12.7 24.0 17.5 D

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19.9 30.6 A

A 27.0 36.0 24.7 A 27.0 I vb 26.2 0 33.4 A 36.0 Thermal and Sustelned Loading Stresses - ASME Equation (11) i North loop at Assembly G South looO at Assembly B l I Load Caso (Nota 1)

Maximum Stress (ksi)

Location (Note 2)

Maxime Stress (ksi)

Location (Note 4)

Allowable Stress (kst)

I i 1 27.1 0 21.9 A 37. 50 11 & 111 36. 2 0 32.3 A 37.50 IV & V 28.6 0 23.5 A 35.25 I

Pe tes :

1 Load cases are bounding comblr.ations of those presented in Mm-734, 2 Locations det ined in Flqure 2.2-1 3 Stress exceeds allowable by less than 45, therefore, olping stress is acceptable

( see Svt ion 2.2) .

I 4 Locations defined in Figure 2.2-2 I

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(1T TTU d,

I Hanger Modification q I uu I /

Hanger Modification (TyplCall I Branch Connection

+ un un s

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FIGURE 2.2-1 I OYSTER CREEK TORUS ARRANGEMENT OF NORTH CONTAINMENT SPRAY AND TEST RETURN PIPING LOCATIONS g FOR LOOP AT ASSEMBLY G I

E u "$ .",.',

, ,, .*0,.'"

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's: uu g  ;'s, s

nu I m Torus Water Cleanup Line

[ / support Modification

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FIGURE 2.2-2 iI OYSTER CREEK TORUS ARRANGEMENT OF SOUTH CONTAINMENT SPRAY AND TEST RETURN PIPING LOCATIONS lg FOR LOOP AT ASSEMBLY B I

I I 2.3 CORE SPRAY TEST RETURN PIPING I The original !! ark I Program analysis results from MPR-734 indicated that an existing support on the Core Spray Test Return piping which connects to Vacuum Relief Piping Assembly F (NZ-2-R13A) was overstressed and I required modification. (MPR-734 identified this support location as being near Assembly D; however, the actual support location is near Assembly F.) An MPR field check of this support in April and July 1985 I indicated that the as-built support NZ-2-R13A differed in both configuration and orientation from the Burns and Roe (B&R) design draw-ing of the support. The original Mark I analyses documented in NPR-734 were based on the configuration of this support as shown in the B&R drawing. Since those analyses were performed, the USNRC approved the Square Root Sum of the Squares (SRSS) method of combining independent dynamic loads for use in the flark I long-Term Program. In order to confirm the effects that the as-built support configuration' and SRSS summation method' have on the support and piping stresses, a partial I computer reanalysis was performed.

Reanalysis of the existing support NZ-2-R13A using the as-built config-uration and SRSS summation confirms that stresses are acceptable for Mark I Long-Term Program loads. The modeling of the actual support con-figuration resulted in a change in the dynamic response of the piping system. As a result, calculated loads in support NZ-2-R13A were greatly reduced, thus reducing the Loss of Coolant Accident (LOCA) induced loads I on the support. The reduced support stiffness, however, caused an increase in the calculated seismic loads on the support. The net effect, including the SRSS summation of independent seismic and LOCA I loads is that the support stresses are acceptable for Mark I Long-Term Program loads. Therefore, support NZ-2-R13A does not require modifica-tion to satisfy the Mark 1 Containment program acceptance criteria.

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The resulting piping stresses in the line were also affected as a result of the change in this support. The as-built support configuration caused a shift in the maximum stress location in the piping for some l load combinations. Nevertheless, all piping stresses are within Mark I Containment Long-Term Program stress limits for all loading conditions, as shown in Table 2.3-1, which supersedes the Vacuum Breaker F stresses given in Table 6.4-1 in f1PR-734. Likewise, Figure 2.3-1, which shows limiting stress locations, supersedes Figure 6.4-1 in MPR-734.

I The maximum calculated occasional load piping stress required to meet the 18,000 psi Level B allowable stress is 8,100 psi, 45% of the allow-able stress. The maximum calculated occasional load piping stress for the 27,000 psi Level B(3) allowable stress is 18,600 psi, 69% of the allowable stress. The maximum calculated thermal and sustained load piping stress of 11,700 psi is 52% of the allowable stress. The SBA post-chug thermal and sustained load case (Load Case V) is required to I meet a reduced allowable stress, due to the number of effective cycles (up to 14,000). The maximum calculated piping stress of 11,300 psi is 56% of this allowable.

All support and hanger stresses were within the flark I requirements except for one support on the core spray test return piping at assembly 0 (NZ-2-R41A), which is being replaced so as to satisfy these require-ments. For the remaining supports, the maximum calculated support stress is 23,162 psi, 80% of the allowable stress. The maxinom calcu-lated hanger load is 1,000 pounds, 83% of the allowable load specified g

by the hanger manufacturer.

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5 TABLE 2.3-1

SUMMARY

OF MAXIMUM AND ALLOWABLE STRESSES CORE SPRAY TEST RETURN P' PING AT VACUUM BREAKER F Occasional Loading Stresses - ASME Equation (9)

Maximum Allowable Load Case Stress location Stress (Note 1) (ksi) (Note 2) (ksi) la 7.7 Elbow B 18.0 lb 15.5 Elbow B 27.0

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. 14.9 Branch C 36.0

!!! 16.7 Branch C 36.0 IVa 7.0 Elbow B 27.0 l IVb Va 10.1 8.4 Elbow 3 Elbow B 36.0 27.0 Vb 16.1 oranch 36.0 I Thermal and Sustained Loading Stresses - ASME Equation (10)

Maximum Allowable Load Case Stress Location Stress

! (Note 1) (ksi) (Note 2) (ksi)

I 7.8 Elbow A 22.50 11 4 !!! 9.1 Elbow B 22.50 IV A V 8./ Elbow A 20.25 Notes: .

1. Load cases defined in MPR-734, l

2. Maximum stress locations defined in Figure 2.3-1, 1

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CPR ASSOCIATES F-8 3 10 4/13/87 MODEL TERMINATED ELEVATION 67 FT-0 IN 6-INCH I --s I g N I '

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CHECK VALVE f y I M' ' 6-INCH 24-INCH I TORUS N0ZZLE

1. v MITER pet 4ETRATION AZIMUTH 144' I ELEVATION 15 FT-0 IN I

I FIGURE 2.3-1 l LIMITING STRESS LOCATIONS CORE SPRAY RETURN PIPING l AT VACUUM BREAKER F

I I 2.4 SRV DISCHARGE PIPING I The original Mark I Conte nment Program analysis of the drywell SRV pip-ing restraints resulted in loads that woulo require major structural modifications to most of the pipe restri.ints and the supporting drywell structu r : . A partial reanalysis which had been performed for the in-torus SRV discharge piping (MPR-772) using a more detailed analysis technique resulted in more realistic (and significantly lower) dynamic I pipe responses. In order to obtain a more realistic assessment of the restraints for the out-of-torus SRV South Header and North Header drywell piping, this same detailed analysis technique was used to reanalyze this piping.

I The original analysis of the SRV piping was performed with a response spectrum analysis technique in which the response of the structure for each mode is determined independently. These responses were then added assuming random phasing between the input for each mode. The response I for each anchor point was considered separately and the results combined using an absolute sumation method. The revised analysis used a time history approach based on the harmonic analysis technique. This tech-nique accurately accounts for the phase relationship between the responses of each mode to the various components of anchor point excita-tion, in addition, the original analysis combined the independent load contributions by suming the absolute value of the components. The revised analysis load combinations are based on the Square Root Sum of the Squares (SRSS) of the independent dynamic loads.

The following approach war used in the evaluation of the SRV dryweli I piping restraints: the standard components of the pipe restraints (e.g., snobbers) were evaluated by comparing the support rating to the revised support design load. The stresses in the support / pipe and the support / anchor attachment assemblies were calculated for the revised l Support loads using the as-built support dimensions obtained in the 2.17 l

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'I November 8, 1985 field check of the .,apports. These stresses were com-pared to the allowable stress level specified in the ASME Code Sec-tion III, Subsection NF. For the north SRV header, the maximum calcu-lated support stress was 17,560 psi, which is 84% of the allowable stress. For the south SRV header, the support stress closest to the allowable was 12.120 psi, which is 87% of the allowable stress. These analyses demonstrated that no modifications are required for any of the SRV discharge drywell piping or piping suppor'.s to satisfy the require-I ments of the Mark 1 Containment Long-Term Program.

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2.5 SMALL BORE PIPittG Af40 CORE SPRAY SUCT!0ft STRAINERS The original Mark I Containment Program analysis concluded that addi-tional structural supports were required for certain branch lines to ensure that each piping natural frequency is above 50 Hz so that exces-sive amplification of the LOCA acceleration loads does not result. The affected branch lines are:

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• Torus level reference line at vacuum relief assembly E, Containment spray pump minimum flow return lines at torus-to-drywell vacuum relief piping assemblies B and G (north and south sides of the Reactor Building), and Air test line on north containment spray test return piping (at vacuum relief assembly B).

The purpose of the new calculations was to quantify the number of struc-tural supports required for each of 1.he branch lines identi;'ad above.

I LOCA acceleration loads and allowable piping stresses used in these cal-culations were as specified in the original MPR-734 analyses. It was concluded from these calculations that a minimum of two supports are required for each branch line in order to limit piping stresses to allowable values for Mark I loading 3.

Originally, GPUti had planned to remove the torus level reference line piping and cap the connection to the core spray suction header. GPUll subsequently decided to leave the torus level reference line installed.

I Accordingly, the line required analysis for Mark I loads.

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I The torus level reference line is connected to the top of the torus through torus-to-drywell vacuum relief assembly E and to the bottom cf the torus through the core spray suction header. Both of these connections provide dynamic evcitation and thermal expansion loads to this piping as a result of torus LOCA loads. Additionally, the torus level reference line is located in close proximity to the torus room wall . As a result, supporting the line induces thermal dresses in the line due to the radial thermal growth under LOCA conditions of the I torus, core spray suction header and vacuum relief assembly E. Although other small bore and branch piping lines were analyzed using hand cal-I culations6 the complexity of this lii~ with its two excitation points and thermal growth restrictions dictated the use of a finite element computer code. The piping stress analysis was performed using the analysis and evaluation methods documented in MPR-734.

I All piping stresses for the torus level reference line are acceptable for both LOCA loads and torus thermal expansion, in accordance with the Mark I Containment Program acceptance criteri&, The new stresses for the torus level reference line are shown in Table 2.5-1, which super-I sedes the stresses for this system given in Table 6.7-2 in 11PR-734. The new analysis determined that a total of four supports must be added to the line. The supports are located so as to accommodate loads from torus thermas expansion as well as liark I loads.

I Analysis results for an additional branch line, the nitrogen purge line, are shown in Table 2.5-1. This line is connected to the torus to reactor building vacuum relief piping (TRB) at a location son distance from the TRB connection to the torus. This branch line was not analyzed as part I of the original Mark 1 Containment Program because Mark I loadings from the TRB line at the purge line connection were insignificant. This line I was analyzed, however, as part of the TRB reanalysis described in Section 2.1.1 of this report, because the change it the TRB support configuration increased the loads at the purge line branch connection.

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I The limiting stress in the nitrogen purge line branch connectjon (l.ocation H in Figure 2.1-1) of 38,700 psi exceeds by 8% the Mark I Program allowable stress of 36,000 psi. This condition is judged to be acceptable due to the conservatisms inherent 'n the stress evaluation method used. For example, a significant con.ervatism was use of the response spectrum method, rather than time history methods. The former has been shown to be very conservative for the piping systems analyzed and loadings applied as part of the Mark I Containment Program.

As stated in itPR-734, the original Mark I Containment Program analysis of the core spray suction strainers was based on design information available at the time, and on assumptions that would be confirmed during subsequent inspection. This later inspection, however, concluded that I the strainers were not as substantial as assumed, and would need to be redesigned in order to meet Mark I Program acceptance criteria.

The most limiting calculated to allowable stress ratio for the redesigned stro;ners occurs at the flange, where the calculated stress is 15.0 ksi, 97% of the 15.5 ksi allowable stress. This value supersedes the strainer stress results shown in Table 6.7-1 of MPR-734. The redesigned stainers thus satisfy the Mark I Program acceptance criteria.

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TABLE 2.5-1

SUMMARY

OF MAXIMUM AND ALLOWABLE STRESSES IN BRANCH PIPING I Stresses (psi) lI Load Combination !! to V (Note 1)

Piping Line Maximum Allowable Torus Level Reference Line <9,100 27,000 9,100 36,000 <

ll Nitrogen Purge Line (Note 2) <27,000 27,000 h

h 38,700 36,000 l

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1. Load Case I w:s evaluated and the 18,000 psi allowable was met.

Thermal expansion stresses were evaluated for Load Cases I to V

! using ASME Equation 11 for the Torus Level Reference Line, and ASME l

Equation 10 for the Nitrogen Purge Line. The allowable stresses of 37,500 psi for Equation 11 and 22,500 psi for Equation 10 were met.

l l 2. The maximum calculated stress exceeds the allowable stress by 8%.

This condition is judged acceptable due to the conservatisms inherent in the stress evaluation method used (see Section 2.5).

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