ML20151Z230

Discusses Analyses of Selected Piping Sys & Vessels Performed to Assess Cyclic Loading Impact,Per SEP Topic Iii.I.Safety Margin Inherent in Design of Sys W/Respect to Piping Fatigue Found Adequate

ML20151Z230
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	02/10/1986
From:	Frisch R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Office of Nuclear Reactor Regulation
References
TASK-03-01, TASK-3-1, TASK-RR NUDOCS 8602140102
Download: ML20151Z230 (13)

Text

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Consumers Power Company General offices: 1945 West Parnalf Road. Jackson, MI 49201 o (517) 788-0550

. February 10, 1986 Director,

' Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT -

INTEGRATED PLAN ISSUE 90 - CLASSIFICATION OF STRUCTURES SYSTEMS AND COMPONENTS - SEP TOPIC III-1 As part of the Big Rock Point In'tegrated Assessment, Section 4.4.1, the NBC Staff requested that sample analyses of selected piping systems and vessels be performed to access the impact of cyclic loading. The analysis has been completed for a sampling of components in selected plant piping systems and has been performed in accordance with Section 4.2, Appendix A, of Technical Evaluation Report C5257-434, (NRC to Consumers Power Company dated April 16, 1982.)

The components selected for this evaluation are located in two piping systems.

These systems are the main feedwater piping to the steam drum and the emergency condenser return piping to the steam drum. These systems were selected because of the relatively frequent occurrence of cyclic temperatures experienced as a course of normal operation plus the relatively large thermal

' transients which they undergo during these cycles.

The an'alysis indicates that there is adequate safety margin inherent in the design of these systems with respect to piping fatigue.

Attachment'I to this letter characterizes the magnitude and frequency of thermal transients for the feedwater and emergency condenser piping systems based on Big Rock Point operating evaluation. Attachment 2 includes a summary of assumptions made as'a part of the evaluation. The calculations are in Attachment 3.

In addition to the calculations referenced above, conventional ANSI B31.1 analysis for axial membrane and binding stresses has also been performed.

These stresses are well within the requirements of ANSI B31.1, Section 104.8 0602140102 860210 PDR ADOCK 05000155 P PDR I\

OC0186-0015-NLO2 J

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a-Director, Nuclear Reactor Regulation 2 Big. Rock Point Plant Integrated Plant Issue 90 February- 10, 1986 for pressure, weight and the restraint of free end expansion loadings. The piping loads associated with this analysis will be used to evaluate the margin-of safety with respect to cyclic loading of the pressure vessel nozzles

. associated with these piping systems. As stated in our June 14, 1985 letter, the pressure vessel evaluation will be completed in April 1986.

Ralph R Frisch Senior Licensing Analyst CC. Director, Office of Nuclear Reactor Regulation Director, Office of Inspection and Enforcement NRC Resident Inspector - Big Rock Point OC0186-0015-NL'02 s

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n ATTACHMENT.1 CONSUMERS POWER COMPANY BIG ROCK POINT PLANT Dockat Ne-50-155 TRANSIENT DATA' FOR SEP TOPIC III-1 February 10, 1986 i (1 Page) i OC0186-0015A-NLO2 i

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ATTACEMENT 1 TRANSIENT DATA FOR SEP TOPIC III-1 The following information characterizes the thermal and pressure transients that take place in the emergency condenser and feedwater systems.

FEEDWATER The piping of interest includes the piping from the outlet of the high pressure feedwater heater to the inlet of the steam drum. The transients of consideration are a SCRAM and a load reduction. Load increases are not considered because of insignificant temperature and pressure transients.

Historical operating records indicate that following a SCRAM the feedwater temperature decreases at a rate of approximately 10*F/ min. The initial temperature of 372*F decreases to approximately 120*F, a delta T of 252*F.

Assuming complete shutdown, the pressure decreases from 1335 psig to O psig in approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The delta P is 1335. It is estimated that the Big Rock Point reactor will experience approximately 300 such cycles.

During a LOAD REDUCTION, the feedwater temperature will decrease from 372*F to 200*F, a delta T of 172. The pressure change during this type of transient is insignificant as the plant remains in operation. Consider the delta P to be

0. Approximately 2000 load reductions are expected to occur at Big Rock Point.

OHERGENCY CONDENSER Only a single transient needs to be considered. That transient is a high pressure transient where the emergency condenser outlet valves suddenly open when reactor pressure reaches 1435 psig. Since the piping between the steam drum and the emergency condenser is always filled with a steam water mixture, the initiation of flow from the steam drum does not produce a thermal transient in this portion of piping. However, the section of piping between the emergency condenser itself and the outlet valves remains at approximately 100*F when not in use.

Upon opening of the outlet valves, the temperature increases to 572*F, a delta T of 472, and then gradually decreases to ambient over the course of hours.

The pressure is reduced from 1435 psig to O psig, a delta P of 1435. This particular transient is estimated to occur 75 times in the Plant life.

IC0186-0053-BQ01

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ATTACNMENT 2 CONSUMERS POWER COMPANY BIG ROCK POINT PLANT Docket No 50-155 FATIGUE CALCULATION ASSLMPTIONS FOR SEP TOPIC III-1

' February 10, 1986 f

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ATTACEMENT 2 FATIGUE CALCULATION ASSUMPTIONS SEP TOPIC III-1 A degree of conservatism can be accommodated in piping stress analysis so that fewer detailed heat transfer calculations are required. In this regard,

several assumptions have been made in this analysis. These assumptions reflect an attempt to estimate pipe thru-wall temperature gradients from complex thermal hydraulic environments. Included is the assumption that essentially adiabatic external pipe surfaces and relatively thin pipes exist through which these gradients are established. Based on heat transfer work on thick vessel walls, maximum gradients can be reasonably estimated based upon a knowledge of bulk fluid temperatures and temperatures change rates.

The following data represents the assumptions for fatigue calculation input for the feedwater and emergency condenser piping systems.

FEEDWATER

1. Complete calculations for the branch connection and one of the elbows are performed.

2. Two transient loadings are considered, SCRAM and load reduction. Heatup rates are simply too low to generate significant thru-wall gradients.

3. It is assumed that the maximum wall gradient is 75 percent of the change in bulk fluid temperatures for a SCRAM situation when the bulk fluid temperature decreases at a rate of 10*F/ min.

4. The maximum wall gradient for a. load reduction is 50 percent of the change in bulk fluid temperature since the temperature decreases at a rate of only 2*F/ min.

5. Based on operating experience, 300 SCRAMS and 2000 load reductions are i assumed.

EMERGENCY CONDENSER

1. The evaluation focuses on an elbow between the emergency condenser and either of the two outlet valves.

2. Only a single transient is considered. That transient is a high pressure transient where the outlet valves suddenly open and 572*F steam is dumped l into a line of stagnant water at approximately 100*F.

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3. The bulk fluid temperature change upstream of the outlet valves is assumed to be 472'F. The transient is very rapid but the steam / metal

. interface will likely result in a significant film temperature drop. It is assumed that the wall gradient is 50 percent of the bulk' fluid temperature change.

4 The high pressure transient is assumed to occur'75 times.

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ATTACHMENT 3 CONSUMERS POWER COMPANY BIG ROCK POINT PLANT

' Docket No 50-155 FATIGUE

SUMMARY

FOR BIG ROCK POINT PIPING

'FOR-SEP TOPIC III-L February 10, 1986 (5 Pages)

OC0186-0015A-NLO2

FATIGUE

SUMMARY

FOR BIG ROCK POINT From Page A-67 of the Franklin Research Center, TER C5257, the simplified equation for peak stress is:

[aT2 l S = .23A3 (UTS) K C33 = .85fA21 (UTS) K2 + .291 [aT3 ] + .145K3 This equation is for ferritic material. Since this evaluation considers carbon steel of less than 7,000 cycles, UTS = 60 KSI and f = 1.0. In addition, it will be assumed that AT =

3 .75aT,and 6T2 = .25aTy . Therefore, the above equation becomes:

Sp= 13.8A K C3 3 3 + 51.0A 2i K

2 + .218 [aTy] + .036 K3 IO w} 9 (I where: K,K,K and C are stress indices per ASME Code 3 2 3 3 Section III, Table NB-3682.2-1

~

A y = range of service pressure in cycle divided by design pressure A = range f metal temperature in cycle divided 21 by maximum operating temperature minus 70 F AT = maximum pipe wall gradient during service cycle CASES FOR EVALUATION ARE AS BELOW:

A. Feedwater Line - Branch Connection K1 = 2.2, K2 = 2.0, K3

• I" *"d 1

= 1. ( a le -3682.2-1)

Thus, Eq (1) becomes:

Sp = 45.5A3 + 102A2i + .218 [6T,] + .061 [aT,] Eq (2)

OC0186-0015A-NLO2

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FATIGUE

SUMMARY

FOR BIC ROCK' POINT 2

== (Contd)

1. . Scram

.A

. 3 = 1335/1700 = .785 A21.(372-100)/(372-70) = .901 AT,= 189*F' q = 300 anticipated cycles 7

Eq (2) becomes:

Sp = 35.73 + 91.90 + 41'.20 +-11.53 + 180.4 KSI S

a-

=S = 90.2 KSI 1

2 Entering the fatigue curve, N = 1000 cycles 3

U 3

=q l

= 300 = .3 EI'y 1000

2. Load Reduction A3 = % KSI A

22 = (372-200)/(372-70) = .57

.AT,= 86*F q = 2000 anticipated cycles 2

OC0186-0015A-NLO2

c, 3 FATIGUE

SUMMARY

FOR BIG ROCK POINT 3 a' (Contd)

'Eq~(2) becomes:

Sp = 0 + 58.09 + 18.75 + 5.25 = 82.09 KSI S' =S

a. :y = 41.05 KSI 2

From the fatigue curve:

N2 = 10,000 cycles Thus:

U 2,000 = .2 2 = 10,000 U Total = Ug+U2 = .3 + .2 = .5 < 1.0 Acceptable B. Feedwater Line - Elbow g

2R - r K =K2*E3 = 1.0 and C3 = 2(R - r)

For a 10.75 0.D. Elbow of 15-inch radius, C3 = 2(15) - 5.375 = 1.28 2(15 - 5.375)

For a 8.625 0.D. Elbow of 12-inch radius, C3 = 2(12) - 4.313 = 1.28 2(12 - 4.313)

OC0186-0015A-NLO2

a FATIGUE

SUMMARY

FOR BIG ROCK POINT 4

. (Contd)

These stress invoices are clearly less limiting than those for a branch connection.

Thus, feedwater piping is acceptable with regard to fatigue.

C. Emergency To Drum - Elbow There is only one loading to evaluate. That is the scram due to system overpressure. The limiting component is an LR elbow. .

K *K =K3 = 1.0, and C) = 2R-r 1 2 2(R-r)

C3 = 2(6) - 2.25 = 1.30 2(6 - 2.25)

Substitution into Eq (1) yields:

Sp = 17.94 A7 + 51.0A2 + .218 [6T,] + .036 [6Ty ] Eq (3)

For this loading:

Ag = 1435/1700 = .884 A2 = (572 - 100)/(572.70) = .94 ATw = 236*F Substituting into Eq (3) yields:

S = 15.14 + 47.94 + 51.45 + 8.50 = 123.03 KSI P

S a

=? = 61.5 KSI

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FATIGUE

SUMMARY

FOR BIG ROCK POINT- 5

-,. (Contd)

From the fatigue curve, N = 2800 cycles.

The anticipated number of cycles is 75.

U= 75 = .03 < 1.0 2800 Acceptable e

Therefore, the condensate return is acceptable in fatigue.

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