ML20076D320
| ML20076D320 | |
| Person / Time | |
|---|---|
| Site: | Clinch River |
| Issue date: | 05/31/1983 |
| From: | Chandra U, Mallett R, Mello R ENERGY, DEPT. OF, CLINCH RIVER BREEDER REACTOR PLANT |
| To: | |
| Shared Package | |
| ML20076D316 | List: |
| References | |
| ES-LPD-83-001, ES-LPD-83-001-R01, ES-LPD-83-1, ES-LPD-83-1-R1, NUDOCS 8305230292 | |
| Download: ML20076D320 (75) | |
Text
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3 ENCLOSURE 1 ES-LPD-83-001, Rev.1 May 1983 i
CRBRP ^' -
HEAT. TRANSPORT SYSTEM INCONTAINMENT PIPING s
RESERVE SEISMIC MARGINS l
4 l
4 PREPARED BYi
/f Mfw R. N. Meilo j
Ud h U. Chandra APPROVED BY:
M R. H. Mallett, N&na~ger Piping Design &
Mechanical Equipment 8305230292 830519 PDR ADOCK 05000537 A PDR "jt k 1
- _ - . . . = - ._ . . - . _ _
ES-LPD-83-001 Rev. 1 May 1983 SUMARY 4
- This report provides an evaluation of the inherent reserve seismic capacity of the CRBRP heat transport system incontainment piping. The evaluations have been conducted to assess the capacity of the piping system to acconino-date seismic excitation beyond the 0.25g SSE. The evaluations were made using ratios and extrapolations from linear elastic analysis.
Sources of reserve seismic capacity can be divided into the following three broad categories; (a) Conservative predictions of building and equipment response,
- (b) Conservative definitions of structural and functional per-i formance limits, and (c) Reserve seismic capacity incorporated by means of designer conservatism.
Reserve seismic capacities from Items (a) and (b) were considered in arriving
, et seismic margins for the piping system. Reserve seismic capacities from l
Item (c) are listed and discussed, but not quantified.
The approach used to calculate the reserve seismic margin for the HTS piping system is that presented in NUREG/CR-2137, " Realistic Seismic Design Margins of Pumps, Valves and Piping". The reserve seismic margin is determined by combining the design margin and nominal margin and accounting for the per-centage of seismic stress to the total stress. The design margin is defined as follows:
S Allowable Stress A Design Margin a Calculated Stress " T (DM) c The allowable stress is based on an applicable industry standard or code that always has a built-in margin of safety on ultimate strength. The margin l between the Code allowable and the ultimate strength or failure is called the nominal margin on ultimate strength and ig defined as follows:
Nom Margin =howfbe tress "
r The actual or combined margin is given by the product of the above two margins, or S
Actual Margin (AM) = DM X flM = [c If k is defined as the ratio of seismic-only stress to total calculated stress
( c), the seismic-only margin (SOM) can be defined as follows (see Section 3.1):
SOM = (NM x DM - 1) ,).0 .
k 1
ES-LPD-83-001, Rev. 1 May 1983 This seismic-only margin was used directly to determine the reserve seismic capacity of the HTS piping system.
The minimum reserve strength capacities obtained for the HTS large and small diameter piping system were calculated for the various piping and support systems components and are as follows:
(a) Piping components (elbows, tees, etc.) = 1.67 (small-diameter piping)
- 2.71 (large-diameter piping)
(b) Clamps = 3.37 (c) Snubbers = 1.86 (small-diameter piping) 1.89 (large-diameter piping)
(d) Embedments = 4.0 these results with the conservatisms in the predicted seismic piping Combining response (which is 1.45) gives the following overall reserve seismic capacity:
(a) Small Diameter Piping: 1.45 x 1.67 = 2.42 (b) Large Diameter Piping: 1.45 x 1.89 = 2.74 (c) Minimum Reserve Margin-Earthquake = 2.42 x 0.25 g = 0.605 g's i
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. ES-LPD-83-001. Rev. 1 May 1983 TABLE OF CONTENTS Page 1
. Sumary Table of Contents 3 1.0 Objer.tive 4 2.0 Introduction and Background 4 2.1 Introduction and Scope 4 2.2 System and Piping Description 5 7
2.3 Structural Design Criteria 8
2.4 Design Conditions and Loadings 9
2.5 Analysis Procedure 15 3.0 Seismic Margin Evaluation 15 3.1 Approach l 16 3.2 Margin Analysis 16
! 3.2.1 Piping System Seismic Response Coliservatisms 17 3.2.2 Piping Structural Strength Reserve Capacity 24 3.3 Designed in Seismic Reserve Capacity 24 3.4 Nargin Analysis Results Sumary 45 4.0 Summary and Conclusions 47 5.0 References 1 48 Appendix A - Derivation of Seismic-Only Margin 49 Appendix B - Small Diameter Piping Integrity Considerations l
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ES-LPD-83-001, Rev. 1 May 1983 1.0 OBJECTIVE The purpose of this report is to identify the inherent reserve :;eismic capa-city of the CRBRP heat transport system incontainment piping. Piping designed to withstand the SSE will, by virtue of the design methods, material data and criteria employed, have reserve seismic capacity to accommodate seismic exci-tations in excess of the SSE. It is the intent to assess the capacity of the CRBRP HTS piping system to accommodate seismic excitation beyond the 0.25g SSE used in the design of the plant.
It is desirable that the combination of seismic design basis and reserve mar-gins in the design be such that seismic events will not cause loss of func-tion of the shutdown heat removal system even for earthquakes larger than the SSE. It will be shown that appreciable seismic margins exist for the large and small diameter PHTS piping that are critical for operation of the shutdown heat removable system. It will also be shown that comparable margins exist for the incontainment IHTS piping which are less critical to the shutdown of .
the reactor. .
2.0 INTRODUCTION AND BACKGROUND
2.1 Introduction and Scope CRBRP components and piping systems designed to withstand the SSE will have reserve seismic capacity to accommodate seismic excitations in excess of the SSE. Factors which contribute to this reserve seismic capacity include (a) the conservative predictions of building and equipment seismic response, (b) the conservative definition of structural and functional performance limits, and (c) reserve seismic capacity incorporated by means of designer conservatisms. The evaluation procedure used to determine the seismic reserve for the HTS incontainment piping is illustrated in Figure 2-1 which is the approach derived and discussed in References 1 and 2. The lefthand side of the figure addresses the piping system or equipment seismic response conservatism. This consists of five items listed below:
(1) System damping assumptions.
(2) Development of ground accelerogram.
(3) Reduction of floor response spectra due to inelastic action of building.
(4) Development of design response spectra.
(5) Development of design time-histories.
These items have been discussed in detail for the CRBRP plant buildings and l
systems in Reference 2 and they will not be repeated here.
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l 1
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ES-LPD-83-001, Rev. 1 May 1983
{
The righthand branch of Figure 2-1 addresses the reserve seismic capacity of the piping system which is limited by structural reserve capacity of the piping components or the piping support system. The reserve capacity of piping support system must account for the strength of clamps, seismic restraints (orsnubbers)andsupportstructures(orembedments).
The total piping system reserve seismic capacity is obtained from the product i
of the structural strength reserve capacity and the piping system seismic response conservatism.
The structural strength reserve capacity for each structural component of the piping system is determined in accord with the procedure illustrated in Figure 2-2. A structural component reserve capacity is given by the product of the material minimum strength assumptions and the conservatisms provided in the ASME Code allowables. The ASME Code usually dictates that minimum strength values be used to derive allowable stresses. However to determine reserve seismic capacity, it is appropriate in general to use average strengths because stress analyses are used to predict local failure which does not necessarily mean that a gross failure of these highly ductile systems will result. To be conservative, this evaluation of reserve seismic margin will use minimum material properties of the piping components which l
are loaded by internal pressure.
! 2.2 System and Piping Description r
The CRBRP Heat Transport System consists of three almost identical cooling circuits, each of which includes a Primary Heat Transport System (PHTS) l sodium loop and an Intermediate Heat Transport System (IHTS) sodium loop, thermally coupled by an Intermediate Heat Exchanger (IHX). Each PHTS loop cor.tains the following large-diameter piping; a 36" hot leg, a 24" hot leg (crossover) and a 24" cold leg. Each large-diameter IHTS piping loop contains a 24" hot leg and a 24" cold leg within containment.
Various small-diameter piping (lines are attached to the PHTS and IHT systems and major components IHX,checkvalve, pump,etc.). The primary small-diameter piping includes a 6" bubbler line between the pump and argon gas supply, a 2" pump drain line between the pumpInand sodiumtofillthese addition system and lines, a 2" vent line between the primary pump and IHX.
there are other sodium supply / drain lines and argon gas lines attached to the primary system. The incontainment IHTS piping system includes small-diameter piping lines between the IHX and IHTS piping that serve as a startup vent l
system.
All small and large diameter piping is either elevated or surrounded by l guard vessels to ensure a minimum safe level of coolant in the reactor vessel.
The primary sodium loops transport the hot radioactive sodium coolant from the reactor vessel to the intermediate heat exchangers, which thermally link the primary and intermediate loops, and transport cooled primary sodium back to the reactor vessel. The three primary loops have common flow paths through the reactor vessel but are otherwise independent in operation.
The intermediate sodium loops circulate hot non-radioactive sodium from the tube side of the intermediate heat exchangers (located in the reactor contain-ment building) to the steam generators (located in the steam generator build-l
)
ES-LPD-83-001, Rev. 1 l
, May 1983 ing), the transport cooled intermediate sodium back to the IHX units. The intermediate sodium piping within the containment building runs under the operating floor from the intermediate heat exchangers to the containment building boundary. A rigid seal is provided at each piping penetration through the containment building wall to assure containment integrity relative to leak tightness.
The CRBRP HTS large and small diameter piping systems within containment are made up of the ASME Code Class 1 liquid metal piping configurations, as listed below (see Table 2-1): ,
- 1. PRP(A) - PHTS 36-inch hot-leg pipe from the reactor vessel to the pump suction (3 loops).
- 2. PRP(B) - PHTS 24-inch hot-leg pipe (crossover) from the pump discharge to the IHX primary inlet (3 loops).
- 3. PRP(C) - PHTS 24-inch cold-leg pipe from the IHX primary outlet to the reactor vessel inlet (3 loops).
- 4. PRP(D) and PRP(E) - PHTS 2-inch hot-leg pipe, IHX vent return line from IHX to flow restrictor to pump tank (3 loops).
- 5. PHTS 6-inch hot leg, pump bubbler piping from primary pump tank to argon gas supply system (3 loops). /
- 6. PHTS 2-inch hot leg pipe, pump drain line from primary pump tank to sodium supply system (3 loops).
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- 7. INP(A) - IHTS 24-inch hot-leg pipe from the IHX intermediate P
I outlet to the reactor containment building boundary (3 loops).
- 8. INP(E) - IHTS 24-inch cold leg pipe from the re' actor containment building boundary to the IHX intermediate inlet (3 loops).
- 9. IHTS 2-inch hot leg, continuous flow running vent connected between the IHX intermediate side outlet high point vent and the IHTS main loop hot leg piping (3 loops). ,
- 10. IHTS 2-inch pipe interconnecting line, with a manual valve, between the running vent line and IHTS cold leg main loop I
piping (3 loops).
- 11. IHTS 2-inch argon gas / rupture disc piping assembly connected to both the continuous hot leg running vent line and IHTS cold l leg main loop piping (3 loops).
- 12. PHTS 2-inch drain line off of the IHX (3 loops).
- 13. PHTS 1-inch argon line off of the 36" PHTS high point vent (3 loops).
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ES-LPD-83-001, Rev. 1 May 1983
- 14. PHTS 1-inch argon line off of the 24" cold leg check valve (3 loops). s
- 15. PHTS 1-inch argan line off of the IHX vent line (3 loops).
The piping structural system includes the piping components such as straights, elbows and tees that make up the loops and its support system (clamps, spring
. hangers, snubbers, rigid rods, support steel and embedments).
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t
- ES-LPD-83-001, Rev.1 May 1983 2.3 Structural Design Criteria The CRBRP Heat Transport System large and small-diameter piping within ron-tainment is designed and analyzed as an ASME Class 1. Seismic Category I nuclear component in accordance with the following rules:
- a. ASME Boiler and Pressure Vessel Code, 1974,Section III, Nuclear
~.
- Power Plant Components, with Addenda through Sumner 1975 and with modifications to Sections NB-2000 and NB-3000 as presented in ASME Code Case Interpretation 1592-7 for design of Elevated Temperature Class 1 components in Section III.
- b. RDT Standard E15-2NB-T, Class 1 Nuclear Components (Supplement to ASME Boiler and Pressure Vessel Code,Section III, Subsections NA and NB), November 1974.
- c. RDT Standard F9-4T, Requirements for Construction of Nuclear System Components at Elevated Temperature (Supplement to ASME Code Cases 1592,1593,1594,1595 and 1596), September 1974.
- d. PSAR, Section 3.7A, Seismic Design Criteria for the Clinch River Breeder Reactor Plant, January 1977.
The consideration of thernal creep effects sets the elevated temperature rules (Code Case 1592) apart from the Section III, Subsection NB. rules. Unlike
. Subsection NB design rules, which basically guard against time-independent failure modes, the elevated temperature rules are applicable for service conditions where creep and relaxation effects are significant. Therefore, the elevated temperature rules require that the design / analysis of a nuclear component consider time-dependent, as well as time-independent, material properties. In addition, Code Case 1592 extends specific rules of Sub-section NB to elevated temperature service provided it can be demonstrated that the combined effects of temperature, stress level, and duration of loading do not introduce significant creep effects. This option proves to be applicable to the cold leg piping.
The HTS piping is designed to assure that stresses, strains and deformations are within the applicable ASME Code criteria and system functional limits.
As required, the analyses performed to satisfy these limits reflect both time-independent and time-dependent materials properties and structural behavior (elastic and inelastic) by considering the following relevant modes of failure:
- a. Ductile rupture from short-term loadings,
- b. Creep rupture from long-term loadings.
l l c. Creep-fatigue failure.
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- d. Gross distortion due to incremental collapse and ratchetting.
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- e. Loss of function due to excessive deformation.
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. - - - - , - - , - - - - - - - - -=
ES-LPD-83-001 Rev.1 May 1983 eratures over 800*F, the For the HTS piping that normally Code Casethe operates plement 1592 at temp ASME and Code, RDT Section Stardard III F j in-containrent HTS elevated temperature criteria limits: given inare invoke following criteria.
hot-leg piping is evaluated against the ss intensities).
1 a.
Load-controlled limits (limits on primary streities or ratchetting b.
Limit on primary-plus-secondary stress intens (or strain limits),
s
- c. Limit on creep-fatigue damage. s in a temperature ranget iping opera esceed l
The primary and *750'F HTS cold-leg while However, theas piping intermediate some normally thermal HTS operate transient cold- egconditions p ex between 400 between 400' and 673'F. l steels, the elevated temperatureRD the criteria, 800*F given limit for austenitic in ASME Code Case stain Codeess tion 1592 NB, (as Case 1592 does, however, and previously discussed) for the evaluation of the HTS ncold-leg piping. that creep extend specific rules of Section be III,demonstrated Subsec eratures effects to elevated temperature For theservice HTS cold-leg if itffects ca are piping negligible which and operates a Section at tem limits will be satisfied are insignificant.over 800'F for less than 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />, creep e i III type analysis is sufficient;quired. i.e., ratchett ngWs-secondary by limiting elastically calculated primary-pand only 2.4 D_esign Conditions and Loadings _in the Piping Design Specifica-normal, The upset, emergency, and faulted The various types of design loading am.
conditionsstress analysis is per-tion have been categorized into design, conditions; and organized into a ies. load histogr formed on the basis of these loading categornd their frequency the steady state and transient events aEach For the HTS piping, identified in the Piping Design BasedSpecificatio of occurrences are i
transient event is characterized by iping coo design specification.te cond d at the same steady state condition.
variation plots which are ral given transient in the full setevents of load are used pupon the i constructed such that they begin and enIn ge in sequence.
cycles uses the specified number of occurre the combination of loads acting From the definition of the loading lifetime cycles, was established l de the and use on the piping system The during loading the combinations plant in the analyses gh inc u the stress analysis. ter reaction (IHTS piping), and throu s load effects resulting from internal pressu j
thermal expansion, seismic, sodium atism. waThe fact that t l
wall temperature gradients. ignored in the analyses is a 8
, _ . . , _, - - - _ - - - - , .,._n, - _ - _ _ ,,_ ,._,. -
_y-.-_,---.,,y- y__, ,,.,-y---p- . _ - _ , , . _ . _ , _ . _ - - . _ , _ - . - _ - - . - , , _ , _-----,
l .
ES-LPD-83-001, Rev.1 May 1983 For the flexibility analyses, a given piping leg between equipment nozzles was modeled using a series of straight and elbow components connected at a finite number of points. A computer analysis was then used to determine elastic displacements, forces and movements in the piping leg. The five
, basic loading conditions that are considered in the HTS piping ficxibility
, analyses are:
A. Thermal expansion from 70*F to maximum normal operating temperature.
B. Dead weight with the system full of sodium.
C. Seismic motion from the Operating Basis Earthquake.
D. Seismic motion from the Safe Shutdown Earthquake.
E. Motion caused by the Sodium-Water Reaction pressure pulses (IHTS piping).
For elastic thermal flexibility analysis, the thermal motions of the nozzles i acting as anchors were imposed on the interfacing piping points. The seismic analysis of the piping was completed using the Response Spectrum Method with response spectra that enveloped the piping attachment points to the building structure, or in some cases, time-history seismic analysis was used. Damping values were selected as per NRC Regulatory Guide 1.61 where two percent and three percent of critical damping are used for OBE and SSE, respectively, for piping of nominal diameter greater than 12 inches, and one percent and two percent of critical damping are used for OBE and SSE, respectively, for piping of nominal diameter smaller than 12 inches. ,
The dynamic effects of the sodium-water reaction are comprised of time varying l
loads (force or pressure) applied at either a change in direction or a change in cross-sectional area of the piping. A computer code was used to develop l
force time histories at the elbows, tees, etc. for input into the dynamic structural analysis code flexibility analysis of the piping loops. This analysis determined peak load responses at features of concern (i.e., pipe fittings, welds, equipment nozzles, penetration anchors, supports / restraints and branch connections).
l 2.5 Analysis Procedures To perform the structura'i evaluation of the HTS piping, the loadings on the piping loop that result from the usual load effects including internal pres-sure, deadweight, support movements, thermal expansion, seismic, sodium water l
reaction, and thermal temperature gradients were obtained at particular loca-tions in the piping system (usually at piping components such as elbows, tees, reducers, transition joints, girth welds, etc.).
Computer-aided flexibility analyses (as discussed in the previous section) were used to determine the forces and moments in the piping components. All computer programs used have been verified or are in the process of being verified.
9
ES-LPD-83-001, Rey, 1 May 1983 The results of the flexibility analyses were used to formulate the combined stresses for assessment against the ASME Code limits. Moment components for ,
various loadings were combined to determine appropriate moment resultants at Stress the piping components and weld locations between the components.
values for moment loadings were computed using the simplified stress indices approach provided in NB-3600. Stress indices at the piping components were computed based on the component nominal geometry using equations or values provided in Table NB-3682.2-1 for ANSI B16.9 butt-welding components. Stress indices for the girth welds were based on the piping dimensions, using the Table NB-3682.2-1 values for a flush girth butt weld.
The following additional assumptions were used to establish and modify the appropriate stress indices:
A. When out of roundness at the piping component did not exceed 0.08t, F), was assumed unity, otherwise F), as given by Code was used 4
B. Weld shrinkage at the girth welds was 0.02R (the maximum permitted by RDT E15-2NB-T) and the C1 , C2 indices modifica-tions in RDT E15-2NB-T were employed The simplified analysis formulas given in the ASME Code,Section III are used to determine stresses resulting from internal and external pressure.
For simplified analysis, the heat transfer analysis for the individual tran-sients was performed using finite element methods. For the thermal hydraulic data, the thermal response of the piping components was evaluated by calculating the radial temperature distribution at'various time intervals during a transient and then calculating the quantities T, AT 1, and AT 2 as per NB-3653 of the ASME Code,Section III. These quantities are used to obtain the stresses in the piping component due to the temperature gradient through the component wall thickness using the appropriate simplified stress index approach in NB-3600.
/
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l TABLE 2-1 PHTS & IHTS PIPING WITHIN CONTAINENT PIPING 0.0. WALL THICKNFSS ASME DESIGNATION DESCRIPTION (in) (NOMINAL) IN. MATERIAL CLASS PRP-A PHTS - WT LEG 36.0 0.5 PIPE SA-358 1 From Reactor Vessel Outlet GRADE 316 Nozzle to Prleary Pump ELBOW SA-403 Inlet Nozzle. GRADE WP316 l
! PRP-B PHTS - WT LEG (Crossover) 24.0 0.5 PIPE SA-358 1 From Primary Pump Outlet GRADE 316 Nozzle to IHX Primary - ELBOW SA-403 Inlet Nozzle. GRADE WP316 ,
! PRP-C PHTS - COLD LEG 24.0 0.5 PIPE SA-358 1 From INX Primary Outlet GRADE 304 Nozzle to Reactor Vessel ELBOW SA-403 i
Inlet Nozzle. GRADE WP304 IMP-A IHTS - WT LEG (Within 24.0 0.5 PIPE SA-358 I III j Containment) From IHX GRADE 316
- Intermediate Outlet Nozzle ELBOW SA-403 j to the Containment Seal. GRADE WP316 INP-E IHTS - COLD LEG (Within 24.0 0.'5 PIPE SA-358 I III Containment)From GRADE 304 Containment Seal to IHX EL9OW SA-403 ,, l Intemediate Inlet. GRADE WP304 [ ,T U
Notes Oh l 1. IHTS piping is classified as ASME Class 2 Lut has been designed and analyzed to meet h Class 1 criteria. k 3
emm.
1 we
TABLE 2-1 (Contitiued) ,
PHTS & IHTS PIPING WITHIH CONTAINMENT PIPING 0.D. WALL THICKNESS ASME DESIGNATION DESCRIPTION (in.) (NOMINAL) IN. MATERIAL CLASS PRP(D) & PRP (E) PHTS IHX Vent Return Line 2.375 0.154 PIPE SA-376 1 GRADE TP-316 ELBOW SA-403 GRADE WP316
- PHTS Pump Bubbler Line 6.675 0.280 1
- PHTS Pump Drain Line 2.375 0.154 1
- IHTS Continuous Flow 2.375 0.154 I III Running Vent .
i "I - IHTS Interconnecting Line 2.375 0.154 1(I)
Between Running Vent and IHTS Cold Leg
- IHTS Argon Gas / Rupture 2.375 0.154 I III Disc Piping Line for "
IHTS Vent System i
NOTES 2F C'
- l-
- 1. IHTS piping is classified as ASME Class 2 but has been designed and analyzed to meet Class 1 ;;3 criteria. E's.
Y 8
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TABLE 2-1 (Continued)
PHTS & IHTS PIPING WITHIN CONTAINMENT PIPING 0.D. WALL THICKNESS ASME DESIGNATION DESCRIPTION (in.) (NOMINAL) IN. MATERIAL CLASS
-- IHX Drain Line 2.375 0.154 Pipe SA-376 1 Grade TP-304H
-- Argon Line Off of 36" PHTS 2.375* 0.154 1
- High Point Vent .
-- Argon Line Off of 24" Cold 2.375* 0.154 1 Leg Check Valve i -- Argon Line Off of IHX Vent 2.375* 0.154 1 Line V M
1
- The 2" line is reduced to a 1" line at the sweepolet.
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- l-G3 8
.~
M
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E'Y- I ES-LPD-83-001. Rev. 1 May 1983 RESERVE SEISMIC -CAPACITY OF HTS PIPING n
l '
PIPING SYSTEM STRUCTURAL PIPINGSYSTiM STRENGTH RESERVE CAPACITY SEISMIC RESPONSE CONSERVATISMS n n
RESERVE STRENGTH RESERVE STRENGTH SYS. DAMPING
""" PIPING COMPONENTS, OF SUPPORTS ASSUMPTIONS ELBOWS, ETC. g CLAMPS INELASTIC ACTIONS OF GLDGS.
RS A NTS GROUND ACCELERG-GRAM DEVELOPMENT HORS DESIGN SPECTRA DEVELOPMENT
~~"
TIME. HISTORY
, DEVELOPMENT FIGURE 2-1 CRBRP HTS PIPING SYSTEM RESERVE SEISMIC CAPACITY EVALUATION PROCEDURE 13
ES-LPD-83-001. Rev. 1 May 1983 3.0 SEISMIC MARGIN EVALUATION 3.1 Approach The approach used to calculate the reserve seismic margin for the HTS piping system is that presented in NUREG/CR-2137, " Realistic Seismic Design Margins of Pumps, Valves and Piping" (Reference 11
'.In safety evaluation reports prepared in support of applications for nuclear power plant licenses, the adequacy of structural components, such as a piping
, system, to withstand a combination of loads (including seismic) from the SSE event is expressed in the fonn, (j )
Design Margin (OM) = Allowable Stress /LoadCaTculated Stress / Load c
The allowable stress or load is based on an applicable industry standard or code, such as the ASME Boiler and Pressure Vessel Code, that always has a built in margin of. safety on ultimate strength or failure. The calculated stress en the structural component is determined using the operating loads, deadweight loads and SSE loadings on the structure.
For a structural component to be acceptable, the seismic event design margin must be greater or equal to 1.0. If the loads on the component are underestimated such that ec is actually higher than calculated, the component may still not fail because of the reserve strength available because the Code allowable is defined to be less than the ultimate or failure stress. This built-in margin l of safety is called the nominal margin on ultimate strength or failure and is
- j. defined as follows:
b Ult. Stress / Load u ~
I2)
Nominal Margin (NM) = Allowable Stress / Load " {
Nominal margins indicate the reserve strength that is available when the seismic event design margin is unity. Nominal margins depend upon the source of the allowable stress or load, SA, which in turn depends upon material pro-perties, temperature, failure mode, functional limits, etc. For example, a nominal margin based on' ultimate strength or breaking must consider the basis used for establishing the ASME Code allowable tensile stresses. The allowable stress is a fraction of the tensile properties of the material used in the con-
- struction of the component. This nominal margin would he defined as follows:
I S" (3)
Nominal Margin = 3- for ultimate strength A
If yielding is a primary consideration in order to prevent excessive deformations, the nominal margin may be defined as follows:
NominalMargin=[S for yielding (4)
A l In a similar manner, nominal margins may be defined for buckling loads, shear i loads, bending loads, and combined loads.
15
ES-LPD-83-001, Rev. 1 May 1983 In sunnary, the nominal margin corresponding to a design margin of 1.0 depends upon the following:
(1) Material (2) Operating Temperature (3) Type of Loading -
(4) Failure Criter,ia (5) Source of allowable stress, SA, for example, ASPI Code Section III, Subsection NB allowable stress for pressure boundary integrity or Subsection NF allowable for piping supports.
The seismic event design margin has been defined by Equation (1) as SA/c ,
where oc is the calculated stress due to all loads. Becauseseismicloabings are subject to larger uncertainties, it is pertinent' to evaluate the margin that exists for seismic-only loads. If the total calculated stress, oc, for the seismic event is separated into the seismic, og , and no7-seismic stress, o "'
cn og"oes +o cn (5) the seismic-only margin may be defined as follows:
S -o u en SOM = , (6)
,Cs If k is defined as the ratio of seismic-only stress to total calculated stress (k = ors/oc), the seismic-only margin given by equation (6) can be written as follows (see Appendix A for the derivation):
50M = (NM x - 1 ) + 1.0 (7)
This argin can be used directly to determine the reserve seismic capacity.of a stractural component or piping system.
3.2 mrgin Analysis 3.2.1 Piping System Seismic Response Conservatisms The usulting system seismic response conservatism margin was determined in Refenace 2 and is listed below:
(a) System damping assumptions = 1.2 (b) Development of ground accelerogram = 1.05 fc) Inelastic action of buildings = 1.05 Gi) Development of floor spectra or time-histories = 1.1 (e) Combined margin = 1.2
- 1.05
- 1.05
- 1.1 = 1.45 16
a
. ES-LPD-83-001, R:v. 1 May 1983 3.2.2 Piping System Structural Strength Reserve Capacity The structural strength reserve capacity was calculated for the HTS five large-diameter piping legs within containment that make up Loop 1. It is expected that Loops 2 and 3 will give similar results. The analysis of three small-diameter piping legs which are representative of the HTS small piping within containment is presented; the 2-inch IHX vent return line, the 6'-inch primary pump bubbler line, and the 2-inch primary pump drain line. These lines were selected because they (1) cover the range of the HTS small-diameter pipe sizes, (2) operate at the highest temperature (10150 F), and (3) their material and construction is representative of all the small diameter piping. In addition, the vent return line is exposed to high pressures and severe thermal transients. The margins obtained from these lines bound the results for all the small-diameter piping connected to the PHTS.
l l
16a
ES-LPD-83-001, Rev.1 May 1983 Piping Components (Elbows, Tees, etc.)
For faulted (or Level D) conditions the ASME Code (Reference 3) limits on the calculated primary stress for piping can be expressed as follows (see Section III,
- Appendix F and Code Case 1592-7):
I Pt+Pb"3Sm (8) where Pg = membrane stress from pressure, deadweight and SSE loadings P = primary bending stress from pressure, deadweight and SSE loadings b
S, = time independent material allowable The safe-shutdown earthquake (SSE) event is identified as a faulted loading in the HTS piping design specification.
In terms of Equation (1), the seismic event design margin for the CRBRP HTS piping components can be expressed as follows:
S DM = A=3S m p p (9)
For austenitic stainless steels (Types 304 and 316) the Sm allowable is equal l to 0.90 Sy . The ASME Code faulted stress limits allow yielding, but provide margin against breaking or ultimate ma.terial strength failure. Therefore, the normal margin for the piping can be expressed as follows:
S (10)
NM=[S A
=hm where Su is the ultimate strength for the material. The ultimate strengths l were obtained from the NSM Handbook (Reference 4) and are based on minimum l strength values. From a study of ultimate strengths for austenitic stainless i
steels, the ratio of average-to-minimum ultimate strengths is approximately 1.10.
i However, in the present study, this safety factor is conservatively ignored l and the nominal margin is based on the minimum ultimate strength. The nominal j margins for the incontainment HTS large-diameter piping components in each I pipin, loop are listed in Table 3-1. The table also provides the nominal margins for the three small-diameter piping loops which are representative of the incontainment small piping. The margins are based on the reserve strength between the 3 S allowable and the minemen ultimate strength of l the material.
17
+ -- e +, y-- p .m --
- a ES-LPD-83-001, Rev.1 May 1983 The piping system flexibility analysis gives a set of forces and moments acting at various locations in the piping system for deadweight, thermal expansion and SSE loadings. These forces and moments along with operating loads such as pressure are converted into stresses using procedures given in Section III of the Code, Subsection NB-3600, for Class 1 piping systems.
The Ccde uses stress intensification factors (B 1 ,C,B,C 2 , etc.) to
- indicate the relative strength of a component (such)as 2at an elbow) to the strength of the straight pipe. For Class 1 piping, the combined stresses due to an SSE and associated loads (pressure and deadweight) are limited to 3 S, or the faulted limit.
The other mode of failure considered in the margin evaluation of the large-diameter piping was plastic collapse of the piping elbows. The piping restraints (or snubbers) as well as the blocks on the hangers constrain the piping system from excessive deformations or rotations under seismic loadings.
i In the actual piping configurations, the elbows will not be able to rotate sufficiently to cause collapse of the elbows or piping system. Thus,buckl-ing or collapse of a piping elbow is not a practical mode of failure in the CRBRP H15 piping systems.
The stresses at the elbow locations for the five large-diameter piping loops that comprf se the CRBRP HTS incontainment piping system are given in Tables 3-2 through 3-6. Each table provides the following information:
(1) Elbow number; the location identified in Figure 3-1 through 3-5.
~
l (2) o cn; non-seismic mertrane-plus-hending stress at the location due to pressure and oeadweight.
(3) cs; the SSE seismic stress at the location.
(4) o c ; the total stress at the location.
(5) k ; the fraction of stresses due to the SSE loadings to the total of all stresses, i .e.,
cs/ c' (6) NM ; the nominal margin presented in Table 3-1.
(7) DM ; the SSE event design margin at each location.
(8) AM ; the actual margin (DM x NM) at each location.
(9) SOM; the seismic-only' margin as calculated using equation (7) at each point.
Tables 3-7 through 3-9 provide similar information for the three small-diameter piping loops within the primary heat transport system (PHTS). The stresses at the critical stress locations for the SSE event are given along with the calcu-lated margins. Isometrics of the three piping loops are given in Figures 3-6 through 3-8 which identify the high stress locations. Comparable stresses and margins are expected for the IHTS small-diameter piping within containment.
18 ,
l' i --- - -- .- -_ _ _ - -_ _ __ _ _ _ _ __
- ES-LPD-83-001, Rev. 1 May 1983 Stresses due to restraint of thermal expansion are not included in the tables because thermal expansion loads are not considered primary loads. If stresses due to such loads are above the elastic capacity, the higher stressed portions of this very ductile piping yield to accommodate the thennal expansion.
The tables illustrate a typical aspect of piping systems in that only a few points are highly stressed. Typically for thin-walled, high temperature, low
~
~
pressure piping as used for the HTS piping system, theTherefore, elbows are theusually mar the highest stressed components in the piping loop.haveEND) been calcula for each elbow in the piping system.
A review of the tables show the following ranges of seismic-only margin for the five large-diameter HTS piping loops and the three lines selected as represen-tative of tne small-diameter HTS piping loops:
(a) PHTS 36" HL; SOM = 4.25 - 11.37 (b) PHTS 24" HL; SOM = 4.75 - 58.9 .
(c) PHTS 24" CL; SOM = 2.71 - 14.58 (d) IHTS 24" HL; SOM = 7.72 - 25.2 (e) IHTS 24" CL; SOM r S.31 - 13.58 (f) PHTS Bubbler; SOM = 1.76 - 19.64 I (g) PHTS Vent; SOM = 1.67 - 25.73 (h) PHTS Pump Drain; SOM = 1.98 - 19.43 Piping System - Clamps A typical piping restraint asse21y used on the CRBRP HTS large-diameter pip-ing is shown in Figure 3-9. The assembly included an insulated clamp, snub-bers, rigid rods or hangers attached to the clamp, and the ededment or building support structure. The CRBRP pipe clamps and snubbers have been designed and tested to meet the requirements of Subsection NF of the ASME Code for Class 1 supports. Thus they have been designed to satisfy the faulted limits (Level D) for the SSE event.
The CRBRP HTS small-diameter piping support system uses a somewhat more conventional pipe clamp (see Figure 3-10) with mechanical snubbers, rigid rods and hangers. The small pipe clamp assembly provides an insulated clamping surface for standard 3-hole pipe clamps on heated piping. Component
- parts include load-bearing insulating material wrapped with a stainless steel sheet metal shell retained by metallic straps and pipe clamps.
19
j ..
- ES-LPD-83-001, Rev. 1
. May 1983
- Detailed stress evaluations have been completed for the pre-loaded, insulated, large-diameter pipe clamp to be used on the HTS piping. The faulted stress limit used to assess the structural integrity of the clamp is as ft.,llows:
PL+PB 1
- m (II) where PL , Pb and Sm have been defined previously. Using this equation, the
- various reserve strength margins can be defined as follows:
5 2 DM = 3 = p.25 S ,-
c L pb (Su ) (bu) .
aver = aver NM =
3 2.25 5m A
The large-diameter pipe clamp is constructed using SA-387, Gra% 2, Class i material . At 300*F, the 2.25 S mallowable is equal to 52.9 ksi and the minimum ultimate strength is equal to 55.0 ksi. For carbon steels it has been shown in Reference 2 that average ultir4te strength properties are at least 120% of the minimum ultimate strengths. Therefore, for this material i the NM against ultimate failure is the following:
(S ) +
i NM =
22 =1.20(h)=1.248 The most critically stressed clamp for SSE loadings is the 24" 0D by 12" width clamp used on the 24" OD HTS piping. For the SEE event, only seismic loadings introduce primary stresses in the clamp band and the maximum com-bined membrane plus bending stress was 19.5 ksi. Thus the DM for this clamp was 52.9/19.6 = 2.699. The actual margin (and in this case the seismic-only margin also since only seismic loads are present) is:
SOM = (1.248) (2.699) = 3.37 The small-diameter pipe clamps are designed for a load rating in accordance with the NF requirements of the ASME code. The clamps are being tested to
! show that they are capable of withstanding at least 4.5 times the rated load.
Therefore, for the small-diameter pipe clamps, the NM against ultimate failure is 4.5.
The PHTS and IHTS small-diameter piping use 2-inch and 6-inch size clamp assemblies. The rated load for the 2-inch clamp is 1710 pounds and for the 6-inch clamp is 4770 pounds. The maximum clamp loads and the associated DM's for the three PHTS small-diameter piping loops are given as follows:
20
ES-LPD-83-001. Rev. 1
~ May 1983 MAX. CLAMP PIPE LINE LOAD (LBS) g
- IHX Vent 1560 1.096
. Pump Drain 978 1.748 i
Pump Bubbler 4200 1.136 The minimum actual margin for the small-diameter clamps resulting from the normal margin of 4.5 and the design margin is; AM = 4.5 x 1.096 = 4.932 Since the clamp loads result predominantly from the SSE event, the seismic-only-margin (SOM) for the small clamps is approximately 4.932. - -
l Piping Sucpor_t System - Snubbers The sr.ubbers used to restrain the HTS large and small diaieter piping are of ,
i the mechanical type due to radiation considerations and have many moving parts. The vendors that supply snubbers have established faulteo (Level D) leads for their designs and have completed static tests to insum operability at the rated faulted loads. The mechanical stublers available for use have had detailed stress analyses completed on their structural parts and their '
i capanility is certified to ASME Code, Subsecticn NF requiremants for Class 1 '
l supports. Modes of failure considered in the evaluations of the snubber structural parts included ball screw snaft buckling, Brinnelling of the ball screw, buckling of the enclosure cylinoer, and failure of the pins, l
fittings and clevises. From a review of the snubber stress analyses, it was judged that buckling is the likely critical failure mode. Since the ASME Code applies a 1.5 factor to buckling for faulted (Level D) limits, the nominal margin (NM) to failure for the snubbers is at least 1.5.
Ir addition, there is in most cases for the HTS large and small diameter piping a substantial design margin (DM) between the actual calculated SSE Mubber load and the faulted condition rated load because in most cases the size of the snubber selected is based on the SMBDB (structural margin beyond the design base or hypothetical loads) loads for the primary system and on l the SWR (sodium water reaction event) loads for the IHTS piping. A review l
cf maximum SSE loads for Loop 1. large-diameter piping of the primary and intermediate systems gives the following margins (it is expected the Loops 2 and 3 will give similar results):
l l
21 l
ES-LPD-83-001 Rev. 1 May 1983 (a) PHTS 36" HL, SSE DM = 1.933 (b) PHTS 24" HL, SSE DM = 1.369 (c) PHTS 24" CL, SSE DM = 1.258 -
(d) IHTS 24" HL, SSE DM = 1.407 (e) IHTS 24" CL,'SSE DM ='2.45 The maximum actual margin (AM), and in this case the seismic-only margin, for the snubbers in the HTS large-diameter piping system is:
SOM = 1.5 x 1.258 = 1.89 The maximem snubber loads and the associated DMs for the PHTS small-diameter -
piping are listed below:
MAX. SNUBBER
. PIPE LINE LOAD (LBS.) OM, ;
~
IHX Vent 8 30 2.771 Pump Drain 846 2.719 i' Pump Eubbler (Size 1 3800 3.079 l (Size 2 1850 1.243 she vinimum actual margin (AM) and in this case the seismic-only-margin (SOM) for the snuobers in the PHTS small-diameter piping system is:
SOM = 1.5 x 1.243 = 1.86 .
Piping Support System - Concrete Anchor Bolts The final component of the support train that must be considered is the supporting structure or_ embedment. A major aspect of seismic capability of piping systems is to assure that they are adequately held to the building structure (see Reference 1). For piping, this means adequately attaching the snubbers to the building. The weak link in attaching supports to the building are usually the concrete anchor bolts.
Embedment connections to concrete can be made either by installing the embedment before pouring the concrete or by drilling a hole in the concrete l and inserting an anchor bolt.
i Bolts or embedments installed before the concrete is poured have not produced any known field-installation problems. The embedded ends of the bolts can be hooked or installed with large washers; thereby, the tensile and shear strength of bolting like SA-307 Grade B can be developed. However, anchor bolts installed after pouring the concrete have given field-installation problems. Considerable skill and care in the installation process are required to consistently obtain anchor bolts that, as installed, develop the tensile and shear strength indicated by Manufacturers' catalogs.
22
ES-LPD-83-001, Rev.1 May 1983 From review of Reference (1) data, it appears that the tensile 'and shear strength of anchor bolts given in Manufacturers' catalogs can, with appro-priate skill and care, be achieved in field installations. Manufacturers
- commonly recommend (a) that design loads for anchor bolts should not exceed one-quarter of the manufacturer's tensile or shear strength, and (b) that a linear interpolation should be used for conbinations of tensions and shear.
If the recommendation is used for both SSE and OBE and associated loadings, 1
the average Nominal Margin would be 4.0.
For CRBRP HTS large and small-diameter piping support anchor or embedment bolts are being designed for installation before the pouring of concrete, thus the use of the recommended nominal margin of four on the seismic-only margin for the embedments given in Reference 1 for anchor bolts in concrete is conservative. The design margin ('0M) is also conservatively ignored.
3.3 Designed-in _ Saismic Fererve Capacity In the previous se:: tion, the reseeve seismic margin for HTS piping was quan-tified on the basis of pipir.g system seismic response prediction conservatisms and the piping structural strength reserve capacity. In addition to these, tnere are other seismic reserves incorporated in the design of the piping i system as a result of designer / analyst conservatisms. These are more diffi-CJ1t to quantify, but from experience it is kDCWn that they exist. These ,
seimic reserves ara present due to soru or all cf the following:
l (a) L:se of 11 rear-eld;s tic dynamic and~ stress enelysis.
(b) Envelope . spectra for a multiple-supported piping system.
(c) 'Jse of response spectrum analysis methods versus time--
history analysis (in most cases).
(d) Exclusion of non-structural elements.
! (e) Structural redundancy of the piping elements.
(f) Absolute combination of seismic loads with'other loads. .
3.4 Margin Analysis Results Summary l
Seismic design margins were calculated as a result of seismic response con-servatisms and piping system structural strength reserve capacity. The evaluation procedure used was that as discussed in Section 2.1 and shown in Figure 2-1. The minimum margins obtained for the HTS piping system are identified on Figure 3-11. The results show that the minimum seismic
' reserve for the small-diameter piping is 1.07 and is governed by the struc-tural strength of the IHX vent return line piping components. The minimum seismic reserve for the large-diameter piping is set by snubber buckling loads and is equal to 1.89.
23
~
. ES-LPD-83-001, Rev.1 May 1983 Accounting for the conservatisms in the predicted piping system seismic response, the overall seismic reserve capacity for the HTS piping system is 2.42 for the small. diameter piping and 2.74 for the large-diameter
. piping. Thus, the reserve strengths for the small and large diameter pipings are essentially the same. These margin results translate into a reserve margin earthquake of 0.605 g's for the CRBRP large and small HTS piping system within containment. The results obtained for the HTS piping are very comparable to those obtained for the CRBRP building, structures, and equipment in Reference 2.
J r
1 A
8 l
24
. u-ES-LPD-83-001. Rev. 1 May 1983 TABLE 3-1 NOMINAL MARGINS (NM) FOR INCONTAINMENT HTS PIPING Sg (3 S ,)
PIPING LOOP MATERIAL TEMP. 'F (ksi) S,(ksi) NM 36" PHTS HL 31655 1015 45.93 57.554 1.253 24" FHTS HL 31555 1015 45.93 57.554 1.253 24" PHTS CL 304SS 750 46.50 57.450 1.236 24" IRTS HL 31655 965 46.41 59.772 1.286 24" THTS CL 3045S 690 47.62 57.61E 1.209 6" PHTS Bebbler 31655 1015 45.93 '
57.554 1.253 2" PHTS Vert 31655 1015 45.93 57.554 1.253 2" PHTS P.D. 31655 1015 45.93 '
57.554 1.253 o
l l
l 25
l TABLE 3-2. PHTS _36" HOT LEG ,
i l
LOCATION j "cn 'c 'cs K DESIGN NOMINAL ACTUAL SEISMIC ONLY RGIN M MRGIN NM mRGIN AM (CYCLE 17-U) (CYCLE 18-U) (oc - 'cnI I*cs *c)I MARGIN SOM 1-8EG 1.69 13.28 11.59 . 8727 3.4586 1.2531 4.3339 4.820 i -MID 5.46 12.35 6.89 . 5579 3.7190 1 .2 S 31 4.6602 7.561
-END 0.92 7.91 6.99 . 8837 5.8066 1.2531 7.2761 8.102 2-BEG 0.94 7.45 6.51 . 8738 6.1651 1.2531 7.7254 8.697 i -MID 1.57 14.76 13.19 . 8936 3.1118 1.2531 3.8993 4.245
-END 2.00 11.75 9.75 . 8298 3.9089 1.2531 4.8982 5.698 1
3-BEG 0.78 9.51 8.73 . 9180 4.8297 1.2531 6.0519 6.503
-MID 0.85 11.54 10.69 . 9263 3.9801 1.2531 4.9873 5.305 i -END 1.47 11.60 10.13 . 8733 3.9595 1.2531 4.9616 5.536 4-BEG 1.35 10.00 8.65 . 865 4.5930 1.2531 5.7554 6.498
-MID 5.14 14.47 9.33 . 6448 3.1742 1.2531 3.9775 5.618 M -END 1.27 8.49 7.22 . 8504 5.4099 1.2531 6.7790 7.796 5-BEG 2.56 9.63 7.07 . 7342 4.7695 1.2531 5.9765 7.778
-MID 8.01 14.32 6 .31 . 4406 3.2074 1.2531 4.0191 7.852
-END 1.13 6.71 5.58 . 8316 6.8450 1.2531 8.5773 10.112 6-BEG 1.24 7.65 6.41 . 8379 6.0039 1.2531 7.5234 8.785
-MID 1.61 11.90 10.29 . 8647 3.8597 1.2531 4.8365 5.437
-E ND 1.12 6.08 4.96 . 8158 7.5543 1.2531 9.4661 11.378 7-BEG 2.40 9.06 6.66' . 7351 5.0695 1.2531 6.3525 8.281
{ -MID 7.55 14.56 7.01 . 4815 3.1545 1.2531 3.9529 7.133
-END .98 7.80 6.82 . 8744 5.8835 1.2531 7.3787 8.295 1 8-BEG .95 6.99 6.04 . 8641 6.5709 1.2531 8.2338 9.371 l -MID 1.41 10.81 9.40 . 86 % 4.2488 1.2531 5.3241 5.973
-END 1.30 9 .31 8.01 . 8604 4.9334 1.2531 6.1820 7.023 Material: S5316 1-See Figure 3-1 for elltow locations. yg Temperature: 1015'F w j._
Sg = 57.554 ksi ;;;g Sg = 3 x S,= 45.93 ksi 8h c>
g
. 5 s . - -
t l TABLE 3-3. PHTS 24" HOT LEG I "cn "c "cs K DESIGN NOMINAL ACTUAL SEISMIC ONLY LOCATION (CYCLE 17-U) (CYCLE 18-U) (og - oc ,) Min M MIN W MMM MMM (ac3{o) c l-BEG 4.89 6.06 1.17 .1931 7.5792 1.2531 ,
9.4974 45.005 9.808
-MID 7.34 12.46 5.12 .4109 3.6862 1.2531 4.6191
-END 4.47 7.28 2.81 .386 6.3091 1.2531 7.9058 18.891 i 2-BEG 4.41 8.15 3.74 .4589 5.6356 1.2531 7.0618 14.210
-MID 4.76 10.30 5.54 .5379 4.4392 1.2531 5.5878 9.529
-END 4.58 5.48 0.9 .1642 8.3814 1.'2531 10.5076 58.872 3-BEG 4.27 9.78 5.51 .5634 4.E963 1.2531 5.8849 9.670
-MID 5.54 10.52 4.98 .4734 4.3660 1.2531 5.4709 10.444 l
-END 4.39 8.16 3.77 .4620 5.62G7 1.2531 7.0532 14.102 4-BEG 4.45 8.95 4.50 .5028 5.1318 1.2531 6.4306 11.801
-MID 5.58 16.49 10.91 .6616 2.7353 1.2531 3.4902 4.764 to -END 4.25 13.13 8.88 .6763 3.4981 1.2531 4.3834 6.003 5-BEG 4.80 12.52 7.72 .6166 3.6685 1.2531 4.5970 6.8 34
-MID 6.93 16.94 10.01 .5909 2.7113 1.2531 3.3975 5.057
-END 4.23 9.19 4.96 .5397 4.9978 1.2531 6.2627 10.751 6-BEG 4.22 8.98 4.76 .5301 5.1147 1.2531 6.4091 11.204
-MID 4.29 13.84 9.55 .6900 3.3186 1.2531 4.1585 5.578
-END 4.44 11.79 7.35 .6234 3.6957 1.2531 4.8816 7.226 Material: 55316 1-See Figure 3-2 for elbow it, cations.
Temperature = 1015'F Sg = 57.554 ksi SA = 3 x S, = 45.93 ksi .,.
D,,,
4 gE wg e,
S
-a
~
- TABLE 3-4. PHTS 24" COID LEG ,
"cn "c "cs K DESNN NOMINAL ' ACTUAL SEISMIC ONLY I MWNM MRGIN NM MEN M mRGIN SM LOCATION (CYCLE ll-U) (CYCLE 15 U) (oc ~ "cn) I'cs/"c i
1-BEG 3.42 14.44 11.02 .7632 3.2202 1.2361 3.9806 4.905
-MID 4.07 18.20 14.13 .7764 2.5549 1.2361 3.1582 3.780 l
-END 3.55 7.25 3.7 .5103 6.4133 1.2361 7.9283 14.577 2-BEG 3.72 9.77 6.05 .6192 4.7595 1.2361 5.8833 8.886 I -MID 3.56 13.97 10.41 .7452 3.3236 1.2361 4.1145 5.179 l -END 3.39 11 .71 8.32 .7105 3.9710 1.2361 4.9086 6.501 1 3-BEG 3.44 15.49 12.05 .778 3.3014 1.2361 3.7108 4.484
- -MID 3.53 18.54 15.01 .6096 2.5081 1.2361 3.1003 3.594
-END 3.58 11.26 7.68 .6821 4.1297 1.2361 5.1048 7.018 4-BEG 3.79 12.44 8.65 .6933 3.7379 1.2361 4.6206 6.207
-MID 5.89 17.78 11.89 .6687 2.6153 1.2361 3.2328 4.339 '
i . -END 3.82 8.59 4.77 .5553 5.4133 1.2361 6.6915 11.249 E 5-BEG 3.25 10.3 7.05 .6845 4.5146 1.2361 5.5806 7.692 ;
-MID 3.24 12.74 9.5 .7457 3.6499 1.2361 4.5118 5.709 *
-END 3.71 10.03 6.32 .6301 4.6361 1.2361 5.7308 8.508 6-BEG 4.04 10.60 6.56 .6189 4.3868 l'.2361 5.4226 8.146
-MID 4.75 16.03 11.28 .7037 2.9008 1.2361 3.5858 4.675
-END 3.70 11.45 '7.75 .6769 4.0611 1.2361 5.0201 6.939 '
l 7-BEG 4.37 12.90 8.53 .6612 3.6047 1.2361 4.4558 6.227 i -MID 4.94 19.97 15.03 .7526 2.3285 1.2361 2.8783 3.496 i
-END 4.63 14.02 9.39 .6698 3.3167 1.2361 4.0999 5.628 i 8-DEG 3.22 14.47 11.25 .7775 3.2135 1.2361 3.9724 4.823
-MID 3.24 23.28 20.04 .8608 1.9974 1.2361 2.4691 2.707
-END 4.26 17.89 13.63 .7619 2.5992 1.2361 3.21 30 3.905 9-BEG 4.50 13.52 9.02 .6672 3.4393 1.2361 4.2515 5.873 'g g
-MID 6.78 15.73 8.95 .5690 2.9561 1.2361 3.6542 5.665 *< l_
-END 5.77 18.85 13.08 .6939 2.4668 1.2361 3.0493 3.953 g i -
I Be Material: SS304 1-See Figure 3-3 for elbow locations. [
Temperature = 750 F o Sg = 57.48 ksi -
l SA = 3 x S,= 46.50 ksi , [
i l
TABLE 3-5. IHTS 24" H0f LEG ~ '
~
I "cn "c "cs K DESIGN HOMINAL ACTUAL SEISMIC ONLY LOCATION (CYCLE 17-U) (CYCLE 19-U) (oc ~"cn) I"cs/"c) MRGIN W MRGIN NM MRGIN M MARGIN SOM 1-BEG 6.88 1 3.35 6.47 .4846 3.4764 1.2568 4.4736 8.168
-MID 10.47 16.85 6.38 .378G 2.7543 1.2868 3.5443 7.720
-END 6.13 11.47 5.34 .4656 4.0462 1.2860 5.2068 10.035 2-BEG 6.21 10.70 4.49 . .4196 4.3374 1.2868 5.5815 11.919
-MID 7.89 12.53 4.64 .3703 3.7039 1.2868 4.7663 11.171
-END 6.09 8.99 2.90 .3226 5.1624 1.2868 6.6432 18.493 3-BEG 6.15 8.28 2.13 .2572 5.6051 1.2868 7.2128 25.156
-MID 8.35 11.50 3.15 .2739 4.0357 1.2868 5.1932 16.309
-END 6.01 9.23 3.22 .3489 5.0282 l 1.2868 6.4704 16.679 4-BEG 5.98 8.82 2.84 .322 5.2619 '
1.2868 6.7712 18.923
-MID 6.66 9.87 3.21 .3?S2 4.7021 1.2868 6.0509 16.532 g -END 6.66 10.28 3.62 .3521 4.5146 1 1.2868 5.8095 14.660 5-BEG 5.73 8.94 3.21 .3991 5.1913 l 1.2868 6.6803 16.818
-MID 5.87 9.72 3.85 .3961 4.7747 1.2868 6.1442 13.987 l
-END 6.18 10.05 3.87 .3851 4.6179 1.2%8 5.3425 13.834 l
I i Material: 316SS '1-See Figure 3-4 for elbow locations.
Temperature = 965*F SU = 59.22 ksi SA = 3 x S, = 46.41 ksi Fe
?
TABLE 3-6. IHTS 24" COLD LEG '
I "cn "c "cs K DESIGN NOMINAL ACTUAL SEISMIC ONLY LOCATION (CYCLE l -U) (CYCLE 18-U) (oc - oc ,) (oc3,'oc ) MARGIN DM MARGIN NM MARGLN AM MARGIN SOM
! l-BEG 6.24 11.42 5.18 .4536 4.1874 1.2091 5.0629 9.957
-MID 6.44 14.39 7.95 .5525 3.3231 1.2091 4.0179 6.462
-EhD 6.60 11.51 4.91 .4266 4.1546 1.2091 5.0233 10.431 2-BEG 7.14 13.33 6.19 .4644 3.5874 1.2091 4.3374 8.187
-MID 9.64 15.69 6.05 .3856 3.0478 1.2091 3.6850 7.963
-END 6.70 10.58 3.88 .3667 4.5198 1.2091 5.4648 13.176 3-BEG 6.76 10.52 3.76 .3574 4.5456 1.2091 5.4960 13.580
-MID 7. 39 13.84 6.45 .4660 3.4552 1.2091 4.1776 7.819
-END 6.99 12.81 5.82 .4543 3.7330 1.2091 4.5135 8.734 4-BEG 6.45 11 .31 4.86 .4297 4.2281 1.2091 5.1121 10.570
-MID 6.72 14.94 8.22 .5502 3.2000 1.2091 3.8700 6.216 u,
c'
-END 6.85 11.82 4.97 .4205 4.0457 1.2091 4.0915 10.254 5-BEG 6.31 12.27 5.96 .4857 3.8973 1.2091 4.7121 8.643
-MID 6.41 16.09 9.68 .6016 2.9720 1.2091 3.5934 5.311
-END 6.54 11.85 5.31 .4481 4.0354 1.2091 4.8792 9.657 6-BEG 6.39 11.33 4.94 .4360 4.2207 1.2091 5.1031 10.411
-MID 6.86 15.42 8.56 .5551 3.1012 1.2091 3.7495 5.953
-END 6.50 12.14 5.64 .4646 3.9390 1.2091 4.7626 9.099 c
Material: SS304 1-See Figure 3-5 for elbow locations.
Temperature = 690*F Sg = 57.818 ksi SA = 3 x S, = 47.82 ksi g mp G3 B6 Y
O e
l l '
l TABLE 3-7. IHX VENT REl"RN LINE ,
l "cn "c "cs K DCSIGN ft0MINAL ACTUAL SEISMIC ONLY LOCATION (j)(CYCLE 17-U) (CYCLE 18-U) RI RGI M R IN AM M RGIN SOM l (oc - 'cn) I"cs "c I
l '
i 1-MID 3.03 26.33 23.30 0.8849 1.744 1.2531 2.186 2. 340 2-MID 2.96 24.65 21.69 0.8799 1.86 3 1.2531 2 . 3 35 2.517 3-MID 3.32 24.55 21.23 0.8648 1.871 1.2531 2. 344 2.555 4-MID 3.30 17.43 14.13 0.8107 2.635 1.2531 3.302 3.840 >!
5-MID 3.11 13.45 10. 34 0./688 3.415 1.2531 4.279 5.265 l[
6-MID 2.38 8.14 5.76 0.70/6 5.643 1.2531 7.0 71 9.579 -
7-MID 2.99 6.58 3.59 0.5456 6.980 1.2531 8.747 15.199
-END 1.98 4.14 2.16 0.5217 11.094 1.2531 13.902 25.729 8-MID 4.10 13.07 8.97 0.6863 3.514 1.2531 4.404 5.959 ,,
9-MID 5.89 14.82 8.93 0.6026 3.099 1.2531 3.884 5.785
- 10-MID 2.04 25.65 23.61 0.9205 1.791 1.2531 2. 244 2.351 11-MID 6.13 15.73 9.60 0.6103 2.920 1.2531 3.659 5.357
- ,', 4.12 13.59 9.47 0.6958 3.330 12-MID 1.2531 4.235 5.642 13-MID 4.59 17.17 12.58 0 7327 2.675 1.2531 3.352 4.210 14-MID 2.03 16.17 14.14 0.8745 2. 840 1.2531 3.559 3.927 15-MID 2.09 15.98 1 3.89 0.8692 2.874 1.2531 3.602 3.993
- 16-MID 3.16 15.79 12.63 0.7999 2.909 1.2531 3.645 4.307 17-MID 2.56 20.04 17.48 S.8723 2.292 1.2531 2.872 3.146
18-MID 4.48 -
20.32 15.84 0.7795 2.260 1.2531 2.832 3.351 c.
19-MID 3.06 20.49 17.43 0.8S07 2.242 1,2531 2.809 3.126 20-MID 3.74 12.02 8.28 0.6889 3.821 1.2531 4.788 6.499 21-MID 3.16 26.27 23.11 0.8797 1.748 1.c531 2.191 2.354 '
22-MID 6.40 33.72 27.32 0.8102 1. 362 1.2531 1.707 1.872
! 23-MID 1.47 35.15 33.68 0.9582 1 .307 1.2531 1.637 1.665 ..
24-MID 1.39 19.69 18.30 0.9294 2.333 1.2531 2.923 3.069 I 25-MID 1.58 16.83 15.25 0.9061 2.729 1.2531 3.420 3.670
, 26-MID 1.56 22.47 20.91 0.9306 2.044 1.2531 2.561 2.678 27-MID 1.66 20.30 18.64 0.9182 2.263 1.2531 2 .8 35 2.999 28-MID 1.82 24.05 22.23 0.9243 1.910 1.2531 2. 39 3 2.507 Material: SA-403 Type WP316 1-See Figure 3-6 for elbow locations. ,
Temperature: 1015'F 3xS = 45.33 ksi S , = "57.554 ksi
. . . - _ ~ . -
TABLE 3-8. 6" B9BSLER LINE ,
"cn "c "cs K DESIGN NOMIhAL ACTUAL SEISMIC ONLY LOCATION (j)(CYCLE 17-U) (CYCLE 18-U) MARGIN :DH MARGIN NM PRRGIN AM MARGIN SOM (oc - "cn) I"cs/"c) 1-BEG 1.14 21.51 20.37 0.9470 2.135 1.2531 2,676 2.769
-MID 2.69 31.62 28.93 0.9149 1.453 1 .2S 31 1.820 1.896
-END 0.41 21.97 21.56 -0.9813 2.091 1.2531 2.620 2.650 2-BEG 0.43 21.69 21.26 0.9802 2.118 1.2531 2.654 2.687
-MID 0.86 33.04 32.1 8 0.9740 1.390 1.2531 1.742 1.762
{ -END 0.47 21.74 21.27 0.9784 2.113 1.2531 2.647 2.6 84 3-BEG 0.97 10.02 9.05 0.9032 4.584 1.2531 5.744 6.252
-MID 1.68 13.05 11.37 0.8713 3.520 1.2531 4.410 4.914
-END 0.66 8.52 7.86 0.9225 5.391 1.2531 6.755 7.238 4-BEG 0.58 20.14 19.56 0.9712 2.281 1.2531 2.858 2.913 '
-MID 0.75 27.27 26.52 0.9725 1.684 1.2531 2.111 2.142
-END 0.86 19.01 18.15 0.9548 2.416 1.2531 3.028 3.124
- k! 5-BEG 0.76 15.29 14.53 0.9503 3.004 1.2531 3.764 3.909
-MID 2.37 19.63 17.26 0.8793 2 .340 1.2531 2.932 3.197
-END 0.61 12.14 11.53 0.9498 3.783 1.2531 4.741 4.939
. 6-BEG 0.47 10.28 9.81 0.9543 4.468 1.2531 5.599 5.819 I -MID 0.98 15.30 14.32 0.9359 3.002 1.2531 3.762 3.951
. -END 0.61 9.93 9.32 0.9386 4.625 1.2531 5.796 6.110
- 7-BEG 0.23 6.19 5.96 0.9628 7.420 1.2531 9.298 9.61 8 1 -MID 0.30 11.72 11.42 0.9744 3.919 1.2531 4.911 5.013
-END 0.45 7.01 6.56 0.9358 6.552 1.2531 8.210 8.705 8-BEG 0.42 7.17 6.75 0.9414 6.406 1.2531 8.027 8.464
! -MID 1.21 6.67 5.46 0.81 86 6.886 1.253' 8.629 10.319
-END 0.43 4.79 4.36 d.9102 9.589 1.253' 12.016 13.102 4 9-BEG 0.41 6.31 5.90 0.9350 7.279 1.2531 9.121 9.685
-MID 1.17 11.54 10.37 0.8986 3.9 80 1.2531 4.987 5.437
-END 0.21 3.13 2.92 0.9329 i 14.674 1.2531 18.388 19.638 Material: SA-403, Type WP316 1-See Figure 3-7 for c1 bow locations.
Temperature = 1015'F 3 x S, = 45.93 ksi S , = 57.554 ksi .
W m+ r m g
TA8LE 3-9. 2" PUPF DRAlti LIX l
Ill "c "cn "cs K DESIGN NOMINAL ACTUAL ksi ksi SEISMIC ONLY ELBOW f . NODE ksi (o 3/n ) MARGIN DM MARGIN NM MARGIN AM MARGIN SOM 1 2 9.441 1 .319 8.122 0.8603 4.855 1.2531 6.096 6.924 3 21.111 1.034 20.077 0.9510 2.1 76 1.2531 2.726 2.815 2 6 3.376 0.437 2.9 39 0.8706 13.605 1.2531 17.048 19.434 7 11.298 0.683 10.615 0.9395 4.065 1.2531 5.094 5.358 I
- 3 13 8.880 1 .766 7.114 0.8011 5 .1 72 1.2531 6.481 7.842 j 14 15.081 0.487 14.594 0.9677 3.046 1.2531 3.816 3.910 l 4 16 8.649 1.798 6.851 0.7921 5,310 1.2531 6.655 8.138 17 29.647 1.128 28.519 0.9620 1.549 1.2531 1.941 1.979
- E!
i Material of Elbows: SA-403. Type WP316 1-See Figure 3-8 for elbow locations.
Temperature - 1015'F 3 x S, = 45.93 ksi c S , = 57.554 ksi l
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j ES-LPD-83-001 Rev. 1 May 1983
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FIGURE 3-8. Primary Sodium Pump Drain Line Loop 1 Seismic Model 41
ES-LPD-83-001, Rev. 1
.. May 19B3 e
SUPPORT STRUCTURE
/////////b//
CONSTANT SUPPORT
[ I 5 HANGER l /i;+i ; ,
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INSULATION MECHANICAL SNUBBER l
Figure 3-9. Typical 24" Pipe Restr Int Assembly for CRBRP 42
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FIGURE 3-10. Typical Small-Diameter Pipe Clang
ES-LPD-83-001, Rev. 1 May 1983 RESERVE SEISMIC CAPACITY OF HTS PIPING
" 2.42 (Small Pipe) l1.45 2.74 (Large Pipe) l PIPING SYSTEM PIPING SYSTEM STRUCTURAL SEISMIC RESPONSE STRENGTH RESroVE CAPACITY
-r CONSERVATISMS
" 1.67 or 1.89 o
I SYS. DAMPING RESERVE STRENGTH RESERVE STRENGTH
~~
ASSUMPTIONS PIPING COMPONENTS, OF SUPPORTS ELBOWS, ETC. n 3.37 1.67(SmallPipe)
INELASTIC 2.71 (Large Pipe) --
CLAMPS
~~
ACTIONS OF BLDGS. 1.89 Lara-Pipe) 1.86 ((Smail Pipe)
~~
SEISMIC GROUND ACCELERO- RESTRAINTS GRAM DEVELOPMENT 4.0
~~
EMBEDMENTS, DESIGN SPECTRA & CONCRETE ANCHORS HISTORIES DEVEL-l OPMENT l
FIGURE 3-11 CRBRP HTS PIPING SYSTEM MINIMUM RESERVE SEISMIC CAPACITY RESULTS l 44 i _
/
- ES-LPD-83-001. Rev.1 May 1983 4.0
SUMMARY
AND CONCLUSIONS The inherent reserve capacity of the CRBRP heat transport system incont&in-ment piping has been determined using the approach developed by Rodabaugh and Desai in NUREG/CR-2137. The sources of reserve seismic capacity were divided into the following three broad categories:
(a) Conservative predictions of the piping seismic ~ response, (b) Conservative definitions of structural and functional performance limits, and (c) Reserve seismic capacit analyst conservatisms. y incorporated by means of designer /
Reserve seismic capacities from Items (a) and (b) were considered in arriving at seismic margins for the piping system. Reserve seismic capacities from i
1 Item (c) are listed and discussed, but not quantified.
The reserve seismic margin was determined by combining the design margin for the SSE event and the nominal margin (margin between ASME Code allowable and ultimate failure). The various margins were defined as follows:
Design Margin (DM) = Allowable Stress A CalculatedStress"(
Ult Stress u Nominal Margin (NM) = Allowable Stress *k .
The actual or combined margin was determined from the product of the above
- two margins, or
ActualMargin(AM)=DMxNM=[S c
If k is defined as the ratio of seismic-only stress or load to the total calculated stress (o c), the seismic only margin (50M) was determined as follows:
SOM = (NM kx DM - 1) + 1.0 This margin was used directly to determine the reserve seismic capacity of the HTS piping system.
The reserve strength capacity for the HTS piping system was dependent on seismic-only margins (SOMs) for the piping components (elbows, tees, etc.) and the pip-ing restraints system. The reserve margin calculations for the piping restraints system accounted for the behavior of the pipe clamps, restraints (or snubbers),
and the embedments (concrete anchor bolts). The minimum reserve strength capacities obtained for these components are listed below:
45
' ,V ES-LPD-83-001 Rev. 1 May 1983 (a) Piping Components = 1.67 (b) Clamp = 3.37 (c) Snubbers = 1.86 (d) Embedments = 4.0 In addition to the strength reserves, conservatism was introduced into the piping seismic response predictions. These result from such items as (a) system damping assumptions, (b) development of ground acceleration, (c) reduc-tion of floor response spectra (or time histories) due to inelastic action of the buildings and (d) development of design response spectra (or time histories).
The net effects of these items are responsible for a 1.45 factor on predicted seismic responses.
Combining the results for the reserve strengths and the response predictions conservatisms, gives an overall reserve seismic capacity of 2.42 which trans-lates into a reserve margin earthquake of 0.605 g's.
I 46
/
ES-LPD-83-001 Rev. 1 May 1983
5.0 REFERENCES
- 1. NUREG/CR-2137, " Realistic Seismic Design Margins of Pumps, Valves and Piping". E. C. Rodabaugh and K. D. Desai, June 1981.
- 2. "CRBRP Reserve Seismic Margins"., ACRS Presentation on February 11. 1983 A. Morrone.
- 3. ASME Boiler and Pressure Vessel Code,1974.Section III Nuclear Power Plant Components, with Addenda through Summer 1975.
- 4. TID-26666, Nuclear Systems Material Handbook, i .
i i
47
ES-LPD-83-001, Rev. 1
- May 1383 APPENDIX A DERIVATION OF SEISMIC-ONLY MARGIN (SOM)
J, 3'
u 1 r. tb trg ,
o .
u g, J ,
Icn i' qr a
- 5 -a en Thus, SOM = cs , u
- sC #cs Su ~ I'c - 'es)
Cs (1 ,cs )
a cs/'c cs/a c
, AM - (1-k) k
, ( AM-1 ) , j k
or, SOM = (NM.DM - 1) , )
k 48
3 . . . . . . . . . . . . . . . . . . .- - .
ES-LPD-83-001, Rev. 1 May 1983 APPENDIX 8 SMALL-DIAMETER PIPING INTEGRITY CONSIDERATIONS B.1 INTRODUCTION AND
SUMMARY
It was shown in the body of this report that the predicted reserve seismic margins for the CRBRP large di.ameter piping and small diameter piping are comparable. On the face of it, this may seem to contradict experience with LWRs which indicates a higher rate of failure for small-diameter piping (Reference 1).
This apparent contradiction is addressed in the following paragraphs. It is concluded that comparable reserve seismic margins for the CRBRP large and small-diameter piping are realistic.
Firstly, it is important to understand that reserve seismic margin and observed failure rates are very different measures of integrity. Observed failure rates for small pipe tend to derive from high cycle vibration, environmental effects and detailed design features. Failures associated with a seismic event are overload type failures rather than fatigue type failures. Therefore, it is reasonable for large and small-diameter piping to have comparable reserve seismic margins in spite of the higher failure rat.e observed for small piping in LWR experience.
There is also a reason why overload failures in piping tend to arise as failures in connected small diameter piping. Evaluations of extreme loads beyond the design base on piping systems are usually very conservatively performed in that failure is predicted without fully accounting for load redistribution away from peak load locations. Extensive load shedding occurs in very ductile redundant piping typical of both LWR and LMFBR j systems. Very large displacements of main piping can occur under extreme l
loads without failure of the main piping. The failures from such extreme r
loads tend to occur in the attached small diameter piping because it is restrained against the large ductile motions of the large pipe and .is the weaker of the two items. Therefore, a more refined analysis of reserve seismic margin would tend to increase the reserve seismic margin predicted for 'large piping rather than reduce the reserve seismic margin predicted for small piping.
There are important additional reasons why the reserve seismic margin for l the CRBRP small-diameter piping is judged to be comparable to the large l diameter piping. The diameter of the small diameter HTS piping is larger l than the diameters of the lines with the highest failure rates. The HTS l small diameter piping is as fully engineered as the main piping; no field run lines, no socket fittings, etc. Design codes are equivalent. The leak-before-break characteristic is established and inspection and leak detection are equivalent to ensure that the piping is not weakened signifi-cantely prior to a seismic event. These considerations are discussed in the following subsections.
' Overall, it is concluded that the reserve seismic margin predicted for the HTS small-diameter piping is realistic.
49
ES-LPD-83-001, Rev. 1 May 1983 B.2 DESCRIPTION OF SMALL-DIAMETER PIPING AND INSTRUMENTATION A description of the small-diameter piping and reactor heat transport system
. instrumentetion that attach to the Primary and Intemediate Heat Transport System piping and components within containment is provided. Emphasis is placed on those design features which enhance the integrity of the piping and components or limit the consequences in the unlikely event of a failure of the pressure boundary.
The arrangemen' of heat tecnsport system and the locations of the major components relative to the reactor vessel are shown in Figure B-1. The primary system small-diameter piping includes three identical loops made up of a 2" nominal vent return line between the IHX and primary pump and from the vent line itself to the argon receiving system, a 6" nominal bubbler line between the pump and argon gas receiving system, and a 2" nominal drain line attached to the bottom of the pump and extending to the auxiliary liquid metal fill system.
The 2-inch IHX vent line is routed from the IHX to the primary pump tank to prevent gas accumulation in the IHX. The line connects to the IHX at an elevation near the highpoint of the shell side and runs to a point on the pump tank which is below the specified minimum safe level of the pump.
The elevational location for the vent line at the pump prevents. flow of gas from the pump cover gas space into the IHX and consequent loss of syphon in the event of a leak.
The portions of the small-diameter PHTS piping below the reactor minimum safe level are located in guard vessels to provide protection against loss l of coolant in the event of a leak.
In addition to the small-diameter piping attached to the primary system, there are special branch connection nozzles provided in the PHTS system for attaching (1) the high point vent to 36-inch hot leg, (2) the high point vent to the cold leg check valve, and (3) the fill / drain connection at the primary cold leg piping near the primary outlet from the IHX. Instru-mentation (including temperature and pressure sensors) is attached to the primary system large-diameter piping using these special branch connections also.
The special branch connection nozzle fittings are contoured and integrally reinforced to minimize pressure and thermal discontinuity stresses (see Figure B-2). The basic method of lap type reinforcements and joints for attaching branch piping to vessels or large piping create geometries that produce areas of high stress concentrations. The contoured branch fittings used for CRBRP fully integrate the branch and run pipes and are attached with full penetration welds. They are contoured both in shape and thickness for low stresses with the insert and branch welds far away from critically stressed areas.
50
e , J ES-LPD-83-001, Rev. 1 May 1983 Temperature sensors in the PHTS piping are installed in dry thermowells
.(see Figure B-3 for configuration). A special branch connection is used as a transition from the pipe to the thermowell assembly to avoid abrupt discontinuities (see Figure B-1 for locations). This installation is
~ designed to withstand the normal environment including pressure and tem-perature transients defined in the piping design specification. The use of this thermowell maintains the integrity of the primary pressure boundary while permitting replacement of the sensor. A secondary seal is provided by.the connection head enclosure and the cable entrance fitting.
Branch connection nozzle fittings are also provided for attaching pres-sure sensors (see Figure B-1 for locations). The actual pressure sensor -
is not in the primary sodium but primary sodium pressure is transmitted to the sensor through a l,ellows which has primary sodium on one side and NaK on the other side (see Figure B-4). The primary side installa-tion is designed to meet the requirements of the piping design specifi-cation. The use of a bellows to separate the primary sodium from the pressure sensor permits replacing the pressure . censor while maintaining the primary pressure boundary.
The intemediate heat transport system within containment has small-diameter piping between the IHX intermediate side and the main IHTS piping loops (see Figure B-5) which serves to vent the IHX. The IHTS vent system includes (1) a 2" nominal hot leg between the IHX intermediate side outlet high point vent and the IHTS main loop hot leg piping, (2) a 2" nominal interconnecting line, with a manual valve between the running vent line and IHTS cold leg main loop piping, and (3) a 2" argon gas / rupture disc piping assembly connected to both the continuous hot leg vent line and IHTS cold leg main loop piping.
The IHTS small diameter piping is attached to the main IHTS piping and IHX with integrally contoured nozzles or branch connections.
The primary small diameter piping and the intermediate piping within con-tainment are contained in separate, shielded and inerted cells. Concrete shielding between cells minimizes neutron activation of piping, supports and components and prevents propagation of postulated structural failures. The cells are steel-lined to restrict leakage of the nitrogen gas used for inert-ing and to avoid a sodium-concrete reaction in the event of a sodium spill.
The inert environment (with a maximum oxygen concentration of 2% by volume and moisture content of about 1000 vppm) minimizes corrosion and retards flaw growth. Also, the inert environment limits cell pressure transients for any postulated leaks. A lower bound of 0.5% on the oxygen concentration is
! imposed to prevent nitridation of coolant boundary materials. The average
! temperature in the cells is maintained at or below 120'F by cooling the nitrogen atmosphere. This feature assures that the pipe sntbbers and hangers will not experience the elevated temperatures seen by the piping.
51
ES-LPD-83-001, Rev. 1 May 1983 Special consideration has been given to the design of pipe supports to assure their integrity and to minimize the impact of postulated support failures on piping integrity. Pipe clamps for attachment of pipe supports are.of the
.non-integral type. These clamps are located away from elbows and girth welds
.to permit access for inservice inspection of the welds without having to dis-mantle the clamps. The design of the piping insulation is such that there is no mechanical interference with the. pipe clamps. Mechanical snubbers are used exclusively for the piping within containment. No axial snubbers are used so as to eliminate the possibility of a pair of seized axial snubbers interfering with free axial thermal expansion of the piping. Redundant constant load and rigid type pipe hangers are used to support the weight of the insulated piping filled with sodium. Pipe supports are welded to steel plates embedded in the concrete walls.
Removable, replaceable insulation is used where equipment or piping within containment requires removal of insulation for access, inservice inspection and maintenance. The requirements for insulation provide for a minimum of chlorides and other corrosive materials. The insulation' material is jacketed to protect it from mechanical damage and deterioration in service. Addi-tionally, the inst 1ation is designed with a gap surrounding the piping or component with small openings arranged to assure adequate purging of this area with inert cell gas and to provide for leak detection.
B.3 DESIGN / ANALYSIS CONSIDERATIONS The piping design specification provides a complete basis for the construc-tion of the HTS small-diameter piping within containment. Both the primary and intermediate piping (Class 1 and supplemental requirements. including the large and constructed to ASME Code The pressure containing components and instrumentation attachments will be designed and built to meet the requirements of the ASME Code and those RDT Standards which have been designated applicable to the CRBRP piping. ASME requirements will also be met for structural members such as piping supports and seismic restraints.
l l The ASME Code includes basic requirements governing materials, design, fabri-l cation, examination, testing and installation. Requirements unique to the RPT Standards and/or based on FFTF experience are added as deemed necessary.
The installed HTS small-diameter piping must satisfy the CRBRP piping design l
specification and be designed and constructed in accordance with ASME Code, l supplemented by several RDT Standards mandated for the CRBRP Project; most notably RDT E15-2NB-T. The design specification defines features needed in l
the piping to assure system performance. The ASME Code and RDT Standards l insure quality and safety through all phases of the Project from inception l
through operation.
l r
l l
52 1
_. ___ -__ _ _ . .~ - ___ _ _ _ . _
u l -
~ ES-LPD-83-001, Rev. 1 May 1983 B.4* QUALITY ASSURANCE CONSIDERATIONS CRBRP Specifications provide explicit requirements derived from the source
- Codes, standards and experience described abote.
- Prior'to issue and use of CRBRP Specifications, the quality requirements come under intensive scrutiny by qualified experts in all allied activities: .
design; analysis; material application; manufacturing; quality assurance; construction; safety; and licensing. All revisions or deviations receive comparable review.
Since the finished piping must meet ASME Code requirements for Class 1 piping, the Authorized Inspector will conduct an independent review of quality and safety aspects, as defined in the Code, and certify that these have been satisfied. This certification with the inspections by manufac-turer, fabricator and purchaser provide confidence that all specified requirements will be net.
In accordance with approved project procedures, all of the activities at
- j. supplier's facilities are periodica.11y monitored by knowledgeable indivi-duals both from the Project and the ASME Code Authorized Inspection Agency (where applicable}. Permanent records of these examinations and tests are kept so that quality verification is naintained in a fashion that permits re-verification if required.
B.5 FAILURE EXPERIENCE There are two sources of piping failure experience on which to predicate reliability estimates for CRBRP large and small diameter HTS piping; (1) piping failures in existing sodium cooled nuclear reactors and various liquid sodium test facilities and (2) those in commercial water-cooled nuclear reactor (LWR) plants. The fa.ilure history for liquid sodium piping is of limited extent and it should be recognized that the CRBRP piping dif-fers from previously constructed sodium piping in some significant respects (Reference 2).
- 4 e
53
^ ' ~ '
ES-LPD-83-001 Rev.1 May 1983 Sodium test facility piping is often not a fully engineered design. Such s
' ing is typically installed using "off-the-shelf" components and with non pip- '
nuclear construction techniques. The CRBRP HTS piping is a Class 1 component ,
' designed, analyzed, and constructed in accordance with the stringent, !
conservative requirements of the ASME B&PV Code. Comparisons to existing liquid metal-cooled nuclear reactors are complicated by the various differ-ences in reactor design and by the fact that the old designs do not embody the many advances in design, analysis and metallurgy which have been made in the intervening peri,od (Reference 3).
The history of piping failures in comercial water-cooled nuclear reactor (LWR) plants is in some respects superior to the history of failures in I sodium piping as a base on which to evaluate reliability of CRBRP HTS large and small diameter piping. The LWR history is significantly larger than the liquid metal piping sample, and the LWR history reflects the behavior of nuclear-quality piping, which should more closely resemble the quality level of the CRBRP piping than does existing liquid metal piping. The data base for the LWR piping failure categorization is a collection of sumaries of more than 800 Licensee Event Reports (LERs) filed with the NRC by holders of operating licenses for those nuclear facilities under NRC jurisdiction.
An evaluation of piping failures based on the review of abnormal operation reports or LERs was conducted in Reference 1, and the incidents were grouped by reactor type, pipe size, location of failure and cause of failure. The j
significant aspect of data is the large number of cases of failure in
. lines 1-inch or less in diameter (more than 60% of the failures). These failures occurred predominantly at welds (usually socket) and in most instances were at the attachment point of small lines to a much larger line. In most cases failures of the small pipe were in welds due either to fatigue or to construction because of weld porosity or fit-up usually in socket welds.
The higher rate of failure for the LWR i-inch or smaller piping can be attributed to many reasons. Firstly, the ASME Code waives many design, analysis, fabrication and inspection requirements for pipe of this size.
Secondly, piping of this size is in many cases field run. Field run pip-ing is -usually arranged based on engineering judgement with limited ana-lysis backup. Lastly, this piping is usually attached to vessels or large pipe with socket joints. Socket joints use fillet welds that are diffi-cult to inspect, they introduce stress concentrations, and their fabri-cation correctness is difficult te confirm.
0 54 w.,-, ..m..m-,.---._,.--,_.--.-..-~n,_.__,,-,------v...,.---,___y,
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J ES-LPD-83-001 Rev. 1 May 1983 For CRBRP HTS small-diameter piping within containment, the same rigid ASME Code requirements being used for the large-diameter piping will be applied.
Detailed analysis will be used to establish the design and the same quality assurance program during fabrication and installation will be used. In addition, the use of socket joints to attach small-diameter liquid metal *
. piping and instrumentation will be prohfbited. Special contoured branch
~
connections will be used. Full penetrations welds will be used to attach the branch connection or nozzle fitting to the large pipe or vessel, and to attach the branch piping'to the branch connections. The smallest branch connection size for CRBRP incontainment small piping is 1.5-inch nominal diameter. These extra design and fabrication precautions should insure that the CRBRP small diameter piping will be as reliable as the large sodium piping.
B.6 LEAK-BEFORE-BREAK CONSIDERATIONS In Reference 4, an evaluation of the large-diameter HTS piping was per-formed to demonstrate that a leak-before-break characteristic is appli-cable to the HTS piping. This is an experimental assessment of margin in which extreme conditions are imposed such that extensive crack growth is forced to occur. First, a critical crack length is established by model elbow burst tests. This is the crack length at which a crack begins to bulge open and thereby permit gross leakage. Secondly, model elbows with intentional surface defects are tested under cyclic loading to demon-strate that substantial crack growth results in development of a through-wall (leakage) crack at relatively short crack lengths.
l Extensive experimental data which are available for stainless steel straight i pipe and elbows, show that, for the HTS large and small diameter piping, the critical crack is a very long through-wall crack. For the 2-inch nomi-nal IHX vent return line (the most highly loaded small-diameter pipe) at normal operating pressure, the critical crack length is predicted to be 8.6 inches.
l The extensive experimentation of scale models (4-inch) of the large-L diameter HTS piping elbows show that crack growth proceeds through the pipe wall before substantial crack growth extension occurs. It is reasonable to expect that these test results apply to elbows with 2-inch nominal diameter also. Therefore a growing crack would develop a leak long before the critical crack size could be reached. Studies of the IHX vent return line show that the PHTS design basis leak (DBL) will be reached by a through-wall crack before the critical crack size
- of the 2-inch nominal pipe has been obtained. Having established the leak-before-break characteristic for the HTS large and small diameter piping, it remains only to consider leakage and leak detection to preclude gross failure of the pipe.
l l
55 L -_ - . . - . _.
ES-LPD-83-001, Rev. 1 May 1983 The CRBRP leak detection system design is the same for large and snell diameter piping. It was shown in Reference 4, that the system can detect leaked sodium in times much less than the time required for a leaking crack to grow to a critical length. This ensures that the snell diameter piping will not be weakened significantly prior to occurrence of a seismic ivent.
B.7 REFERENCES
- 1. in Light-Water Reactors", Nuclear S. H. Bush, Safety, " Reliability Vol .17, No. 5, 568 -of Piping (September-October 1976) 579 .
- 2. " Failure Data Handbook for Nuclear Power Facilities: Volume I, Failure Data and Applications Technology" LMEC-Memo-69-7, Volume I, LMEC, Canoga Park, California, August 15, 1969.
- 3. R. C. Bertucio, "Effect of Repair Times on Relative SHRS Reliability".
WARD-SR-3045-6, Westinghouse Electric Corp., Advanced Energy Systems Division, Madison, PA, November 1978.
4 1. H. Mallett and B. R; Nair. " Clinch River Breeder Reactor Plant:
Integrity of Primary and Intermediate Heat Transport System Piping in Containment", CRBRP-ARD-0185, Westinghouse Electric Corp., Advanced Energy Systems Division, Madison, PA, October 1977.
55a -
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6-*-=i- -g%a .m.m-imi -mm. 4 ENCLOSURE 2 i EFFECTS OF POSTULATED SMALL-DIAMETER PHTS PIPING LEAKS ON SHRR AVAILABILITY The guard. vessel-elevated piping approach used in CRBRP assures adequate primary coolant inventory for decay heat removal after any postulated primary coolant boundary leak, including a leak from any branch line. Figure 1 shows the normal sodium level in the reactor vessel (794'9"). The argon cover gas over the sodium is maintained at a pressure of approximately one atmosphere.
The level of sodium in the reactor vessel depends on the operat-ing state of the heat transport system (HTS). Under full power, full flow operation the normal sodium level (NSL) in the reactor vessel is 794'-9" (See Figure 1). When the reactor is shut down and decay heat is being removed by forced convection with pony motors (nominally 7-1/2 - 10% flow) the reactor vessel sodium level will rise nearly two inches due to a redistribution of flow betwen the reactor vessel annulus and plenum due to a decrease in core pressure drop. (See Figure 2.) The reactor vessel sodium level in this case can be referred to as the " shutdown sodium level" (SSL). To place the Direct Heat Removal Service (DHRS) into operation the flow rate through the reactor overflow nozzle is increased from 150 gpm to 600 gpm by increasing make-up to the reactor vessel. The increase makeup flow for DHRS operation causes the reactor vessel sodium level to rise to a steady state level of 795' 7.6". This level, which corresponds to the DHRS operating with a single active f ailure (loss of an EM pump), can be referred to as the DHRS sodium level (DSL) . The Minimum Safe Level (MSL, 782' 4") is 12 feet 5 inches below the Normal Sodium Level (NSL). This is the elevation at which it is conserva-tively assured that sodium can be drawn out of the PHTS outlet nozzle as necessary for heat removal through the heat transport loops. This level is 2'-5" above the top of the reactor vessel outlet nozzles. Figure 3 is a PHTS hydraulic profile which illustrates the guard vessel-elevated piping approach.
The consequences of a leak from small-diameter PHTS piping at the numbered locations (illustrated in Figure 3 as locations 1 through 14) are summarized in Table 1. The size of the postu-lated small-diameter pipe leak is not significant with regard to the long term impact on decay heat removal capability because the long term coolant level is essentially independent of the leak I
rate. However, because of make-up capability and excess PHTS sodium inventory (see Figure 4), many of the system funtional
" failures" discussed herein would not occur until long after the leak is initiated, especially if the leak is small.
For illustrative purposes, the consequences of leaks in small diameter PHTS piping can be classified into five general cate-gories based on leak location. These categories are shown as end states in Figure 5. The end states are based on a combination of i
answers to the nodal questions (criteria) of Figure 5 regarding the location of the leak.
The first category of leaks is one where the leak occurs in piping inside a guard vessel and at elevations lower than the reactor-shutdown sodium level. Since all piping inside a guard vessel is below shutdown sodium level, the "above SSL" node was bypassed. An example would be Location 1, where a leak is postulated to occur in the 2" IHX vent line between the PHTS pump and the IHX, but within the IHX guard vessel. Following such a leak, the reactor vessel sodium level would fall until the sodium level difference between the reactor vessel and the IHX guard vessel is equal to the pump head at the leak location *, The elevation of each guard vessel lip is more than five feet above the MSL. Therefore, the reactor vessel sodium level would remain above the MSL. This concept is illustrated in Figure 6 for a .
PHTS cold leg leak inside the IHX guard vessel. Because the l
reactor vessel sodium level would remain above MSL (and syphon would not be broken in the leaking loop), heat removal through all three heat transport loops would be possible. For this
! reason the " main flow unaffected" node in Figure 5 was not applicable to this leak category and therefore, bypassed.
However, because the reactor vessel sodium level would fall below the DSL level, DHRS operation would not be possible.
The second category of leaks is those that are above the reactor i vessel shutdown sodium level and do not disable DHRS. If a leak above the shutdown sodium level is (1) in a location that is upstream of the pump or (2) downstream of the pump but at an elevation that is high enough above shutdown sodium level to compensate for the pump head, then the reactor vessel sodium level could rise to the DSL and DHRS operation would be possible.
Sodium level would remain above MSL and syphon would not be broken in the leaking loop; heat removal through all three HTS loops would be possible. Small diameter piping in Locations 6, 13 and 14 fall into this category.
Category three corresponds to small-diameter piping leaks that are above shutdown sodium level and impact the main PHTS flow path (i.e., a sweepolet leak) by breaking syphon and thereby precluding decay heat removal through the affected loop. If the leak location falls into this third category, as it does in Location 11, the reactor vessel sodium level could rise to the DSL and DHRS operation would be possible even though the affected l
heat transport loop is disabled.
- It is conservatively assumed throughout this assessment, that the pony motors were running continuously without any operator intervention to turn them off. When operating with pony motors the pump shut off head is 4.2 ft Na at pump discharge.
Pipe leaks that are postulated to occur outside of.a guard vessel and at elevations below the reactor vessel shutdown sodium level constitute the fourth and fifth categories of leaks. All large and small-diameter PHTS piping outside of the guard vessel is sufficiently above the MSL such that the reactor vessel sodium level could never fall below the MSL in the event of a. pipe leak.
An example that falls within the fourth category is a pipe leak in the IHX vent return line as shown in Location 3 of Figure 3.
Th'e main PHTS flow path is not connected to the IHX vent return li~ne and is, therefore, not affected by a leak in that line.
Following the leak, the reactor vessel sodium level will fall until the pump and static head is insufficient to drive sodium up
! the elevated piping and out of the leak location. The reactor I vessel sodium level would remain above the MSL and, because a leak at this leak location would not break syphon in the main PHTS flow path, decay heat removal through all three heat transport loops would be possible. However, this category of leaks, like the first category, would prevent DHRS operation.
Location 7 and Location 9 on Figure 3 correspond to locations where a 2" sweepolet joins the main PHTS hot leg piping. These locations would fall into a fifth category of leaks. The
- characteristics of a leak in either of these locations would be l
similar to the characteristics of the fourth category of leaks l
discussed above, except in this case the sodium would drain until I siphon is broken in the hot leg piping, and the reactor vessel sodium level would fall until the combined reactor vessel sodium head and pump head is insufficient to drive sodium up the elevated piping and out of the leak location. Since this leak location and siphon break is in the main PHTS flow path, decay heat removal through the affected PHTS loop is precluded. As before, the reactor vessel sodium level will remain above MSL allowing decay heat to be removed through the two remaining heat transport loops. This concept is illustrated for a PHTS cold leg leak outside a guard vessel in Figure 7.
In summary, the guard vessel-elevated piping approach assures that an adequate primary coolant inventory exists for any postu-l l lated primary coolant boundary leak, including a leak from any i branch line. There is only one category of leaks in the small-
! diameter PHTS piping that could result in the loss of a heat transport loop And DHRS. This category applies only to those pipe leaks that are outside guard vessels, below shutdown sodium l
level and have the potential to affect the main PHTS flow path.
All large and small-diameter PHTS piping outside the guard vessel
! is sufficiently above the MSL such that the reactor vessel sodium
! level could never fall below the MSL in the event of a pipe leak.
At a very minimum, two heat transport loops will be available to provide decay heat removal following this, or any postulated l primary coolant boundary leak.
i .
TABt2 1 Shatdown Heat location On Deseval Pathe r.t a= . upiranlic Profile rm+1on of r-tutated rmk it-,.et m ms trM** limpct on aims *** Auml1*h1.
IIHK 2" Vent 1 In Guard Vessel ;None Fails 3
. .!HX 2* Vent 2 BetweentIHX and Guard None rails
- 3 - 4*
Vessel (at connect toIIHK) .
IHK 2" Vent 3 Beyond Guard vessel .None Fails 3 Drain 2' 4 Inside or Outside None Fails 3 (Both Ramp and.IHX) Gaard Vessel 6" Pusp Stand Pipe 5 In Guard Vessel None Fails 3 Butbler 6 Outside Guard vessel None Depends on 3 - 4**
Exact IAcation**
i 2" Sweepolet for 7 1) Elevated Section Hot Im3 Fails Falls 2 Pressure Detector 8 1) Elevated Section Cold tag Fails Fails 2 Temperature 2" 9 2) Elevated Section Hot IAg Falls Fails 2 Sweepolet 10 5) Elevated Section Cold tag Fails Falls 2 2" High Point Vent 11 Elevated Section Hot tag Falls None 3 12 Elevated Section Cold Leg Fads Fails
- 2-3*
(Check Valve) 13 Top of IHK None None 4 14 Top of IHX Na Vent None None 4
- No failure of DHRS if operatorashuts down the pony motor within I hour of leak initiation.
- No less of DHRS for leak locations above 795' 7.6" (DSL)
"* 'Ihe impct m the Iris loop or DHRS would not occur until long after the leak is initiated, especially if the leek issumall.
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T . . . . . . . ... . . . - - - - I- Sodium Level Normal Sodium During DHRS Level (NSL) l Operation (DSL) 794'-9" 795'-7.6" i
Minimum Safe : - - - - ---
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Figure 1. Reactor Vessel Na Levels 4 83 3342 1
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IlIX REACTOlt VESSEL -
l Inside GV Above SSLW fna ft. d .
Inside GV (1) Loop Available, DHRS Unavailable 1, 2*, 4, 5 Unaffected (2) Loop Available. DHP.S Available 13, 14, 6 Above SSL (3) Loop Unavailable, DHRS Available Outside GV '
Unaffected (4) Loop Available, DHRS Univallable 3, 6 Below SSL l
Affected (5) Loop Unavailable, DHRS Unavailable 7, 8, 9, 10, 12*
FIGURE 5
- No failure of DHRS if operator shuts down the pony motor within one hour of leak initiation.
- This node acknowledges the fact that a leak downstream of the pump must be about 4' higher than the NSL to prevent the reactor vessel sodium level from falling below the NSL.
NOTE: If the criterion of each node is met, the logic branches upward and if the criterion is not met, the logic branches downward.
4 Figurc 6 . . -
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4 Figurc 7
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