ML20095G096

Stresses from Applied Loadings for Level A,B,C & D Conditions Considered in Core Spray Line Fracture Mechanics Evaluation

ML20095G096
Person / Time
Site:	Cooper
Issue date:	12/18/1995
From:	Daniel R, Mehta H, Wuestefeld M NEBRASKA PUBLIC POWER DISTRICT
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ML20095G094	List: ML20095G091 ML20095G096
References
NUDOCS 9512200016
Download: ML20095G096 (8)

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,', . Attaciunent

.. o' to NLS950244 Page 1 of 8 Stresses from Applied Loadings for Level A. B. C and D Conditions Qusidered in the Core Spray Line Fracture Mechanics Evaluation Prepared by:

H.S. Mehta, Principal Engineer Structural Mechanics Projects Verified by: e luf .

. Rachelle Danlei Mechanical Engineer Structural Mechanics Projects Approved by: M _

, W.R. Wuestefeld, Manager Engineering & Licensing Consulting Services i

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I 9512200016 951218 1 l PDR ADOCK

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l Attachment I to NLS950244 l

~ Page 2 0f 8 INTRODUCTION A fracture mechanics evaluation of the indications identified by the IVVI and UT l inspection of the core spray internal piping during the current refueling outage at Cooper I Nuclear Station, was documented in Reference 1. This report provides the details on the calculated stresses for various loads, load combinations for various operating conditions and allowable flaw calculations for the indication identified at weld # 1 on A-Loop (worst case). '

STRESSES AND LOAD COMBINATIONS The significant loads on the intemal core spray line during various operating conditions

} are the following: weight, flow load during core spray operation, intemal pressure during i

core spray operation, seismic inertia, seismic and thermal anchor motions and fluid drag during LOCA.

1 1.

The weight, flow, pressure, fluid drag and OBE/SSE (Inertia) loadings are primary

loadings (i.e., membrane stress is classified as P, and the bending stress is classified as i P3). The OBE/SSE and thermal displacement loadings are classified as secondary.

Therefore, the bending stresses from these loadings were added together to obtain the P, -

stress magnitude. The P, stress was then conservatively added to 3P for the purpose of l_ allowable flaw calculations.

The calculated values of stresses for various operating conditions are sununarized next.

, Level A (Normal Operation) t

During the normal operation, the core spray line does not have any flow or intemal pressure. The only loading other than the weight is the thennal anchor displacement

[ loading. The stresses from applicable loadings are tabulated below.

Load Stress (psi)

! Membrane Bending

! Weight 0 52 f Flow 0 0 Pressure 0 0 OBE (inertia) Horz. 0 0

Sg Fa. Static i OBE (Inertia) Vert. 0 0 i lg Eq. Static OBE (Disp) 0 0 Thermal (Disp) 5 39

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The P , Pe and P, stresses for the normal condition are then obtained as follows:

2 E

F

, -n r . . - , - ,

1Attaciunent A ' ' J to NLS950244.J  !

Page 3 of 8.'

-P. = 0 psi -

-Pn '= 52 psi-

" P, = 39 psi 2

Level B (Upset) Condition It is conservatively assumed that the core spray operation and the seismic (OBE) event -

occur at the same time. The stresses are as summarized below:

Load Stress (psi)

Membrane Bending Weight 0 52 Flow 250 0 Pressure 733 0 OBE (Inertia) Horz. I17 1116 Sg Eq. Static OBE (inertia) Vert. 0 52 1g Eq. Static OBE (Disp) '

51 250 Thermal (Disp) 5 39 The P , P 3and P, stresses for the upset condition are then obtained as follows:

P. = 0 + 250 + 733 + 117

, = 1100 psi 2 2 P3 = 52 + 0 + 0 +V(1116 + 52 )

= 52 + 1117

= 1169 psi P, = 250 + 39

= 289 psi Level C Emergency) Condition

- The emergency condition loads are essentially the same as those specified for upset condition except that the seismic stress calculations are based on SSE. The USAR of Cooper station states that the horizontal ground acceleration for OBE is 0.lg and that for L SSE is 0.2g. Therefore, the stresses for the SSE event (both inertia and displacement) l_ were obtained by doubling the corresponding OBE values. This is conservative because 3

Attachment to NLS950244 Page 4 of 8 the damping during the SSE event is expected to be higher than that during the OBE event.

Load Stress (psi)

Membrane Bending Weight 0 52 Flow 250 0 Pressure 733 0 SSE (Inertia) Horz. 234 2232 10g Eq. Static SSE (Inertia) Vert. 0 104 2g Eq. Static SSE (Disp) 102 500 Thermal (Disp) 5 39 The Pm, P 3 and P, stresses for this condition are then obtained as follows:

Pm = 0 + 250 + 733 + 234

= 1217 psi 2 2 123 = 52 + 0 + 0 +V(2232 + 104 )

= 52 + 2234

= 2286 psi P. = 500 + 39

= 539 psi Level D (Faulted) Condition A simultaneous occurrence of LOCA and SSE events is considered in developing the load combinations for the Level D condition. A postulated occurrence of a recirculation or main steam line double-ended break is expected to generate drag forces from the escaping fluid. It was determined that fluid drag forces from the main steam line break will be more severe than those produced by the recirculation line break. The fluid drag forces are expected to peak in the first few seconds after the break. Because the core spray initiation would occur at a later time and the full flow is established in 10 seconds, it is reasonable to assume that the core spray initiation loads and the fluid drag loads are not additive and that the two loads should be considered individually. Thus, there are two  ;

cases to consider for the faulted condition. In the first case, the fluid drag loads are considered along with the SSE loads. The second case is essentially the same as the emergency condition in which core spray initiation loads are considered along with the SSE loads.

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Page 5 of 8 Case 1: LOCA Fluid Drag Loads j l

Load Stress (psi) l Membrane Bending )

Weight 0 52 l Flow 0 0 )

Pressure 0 0

{

Fluid Drag 0 1128 SSE (Inertia) Horz. 234 2232 10g Eq. Static SSE (Inertia) Vert. 0 104

. 2g Eq. Static SSE (Disp) 102 500 Thermal (Disp) 5 39 The P , P 3and P, stresses for this condition are then obtained as follows:

Pm = 0 + 0 + 0 + 234

= 234 psi 2 2 P3 = 52 + 0 + 0 +V(2232 + 104 ) + 1128

= 52 + 2234 + 1128 '

= 3414 psi j

P. = 500 + 39 )

= 539 psi l

I Case 2: Core Spray Initiation l l

Load Stress (psi)

Membrane Bending Weight 0 52 Flow 250 0 Pressure 733 0 SSE (Inertia) Horz. 234 2232 10g Eq. Static I SSE (Inertia) Vert. 0 104 l 2g Eq. Static I SSE (Disp) 102 500 Thermal (Disp) 5 39  !

The P , P and P, stresses for this case 2 of the faulted condition are then essentially the same as those for the emergency condition.

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Attachment to NLS950244 Page 6 of 8 Determination of Limitine Condition

. A review of calculated P., P and P. values for various operating conditions shows that between the normal and upset conditions, the upse condition is governing (i.e., has higher stresses). The stresses for the emergency and faulted condition case 2 are the same. Therefore, the allowable flaw values for the upset condition and the two faulted condition cases were determined to ascertain as to which one gives the smallest allowable flaw value. The allowable flaw calculations were conducted using the equations given in Appendix C of ASME Section XI. This weld was made by GTAW process which is a nonflux welding procedure. Therefore, the equations corresponding to base metal or nonflux welds were used which do not involve the use of a 'z' factor'. For conservatism, the P. stress was added to the P5 stress for the purpose of allowable flaw calculation. The core spray line material is Type 304 stainless steel. The S. value was taken as 16.9 ksi, corresponding to the design temperature of 550 F. It should be noted that the use of 550 F temperature is conservative (a more appropriate temperature is 406*F, the temperature at widch the core spray injection initiates).

ALLOWABLE FLAW LENGTII CALCULATIONS The allowable flaw lengths for the upset condition and the two faulted condition cases were calculated using equations (1) and (3) of Appendix C, ASME Section XI. These equations are applicable to throughwall flaw configurations also as discussed in References 2 and 3.

The allowable flaw length in terms of angle 0 was obtained using a circumference of 20.03 inch, corresponding to a sleeve diameter of 6.375 inches. The Appendix C equations are restated below:

(For neutral axis located such that 0 + p < n)

Pb' = (6S /n)(2 sin p - a/t sin 0)

E = [(n- Oa/t) - (P./3S. )n]/2 where, t = pipe thickness, inches 0 = crack half-angle p = angle that defines the location of the neutral axis P. = membrane axial stress P6 = failure bending stress a = crack depth (assumed = t for this evaluation)

The safety factor is then incorporated as follows:

P6 = SF (P. + P ) - P.

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Page 7 of 8 Upset Condition Pm = 1100 psi

'P 3 = 1169 +289 = 1458 psi Sm = 16900 psi Safety factor = 2.8 ' -

Assume 0 = 1.8488 radians Then,.

p, = 0.612 radians 123 = 6065 psi Pb = 1459 psi The above value of P3is close enough to the load combination value of 1458 psi, indicating that the assumed value of 0 is correct.

Allowable flaw length = (0/n)xCircumference

= (1.8488/n)x20.03

= 11.8 inches

' Faulted Condition (Case 11 P. = 234 psi P3 = 3414 + 539 = 3953 psi S. = 16900 psi Safety factor = 1.4 Assume 0 = 1.9635 radians Then, p, = 0.5818 radians P3 = 5654 psi P3 = 3972 psi The above value of P3is close enough to the load combination value of 3953 psi, indicating that the assumed value of 0 is correct.

Allowable flaw length = (0/n)xCircumference

= (1.9635/n)x20.03

= 12.5 inches Faulted Condition (Case 2)

Pm = 1217 psi 4

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H I' ' ~ to NLS950244 Page 8 of 8 P, = 2286 + 539 = 2825 psi S. = 16900 psi Safety factor = 1.4

' Assume 0 = 1.9321 radians Then, p, = 0.5671 radians -

P3 = 4482 psi P3 = 2853 psi The above value of P3 is close enough to the load combination value of 2825 psi, indicating that the assumed value of 0 is correct.

Allowable flaw length = (0/n)xcircumference

= (1.9321/n)x20.03

= 12.3 inches Among the two faulted condition cases, the allowable flaw length is the least for case 2.

Between the upset condition case and the faulted condition case 2, the upset condition allowable length of 11.8 inches is the least and thus governing.

REFERENCES

[1] "Intemal Core Spray Line Flaw Evaluation at Cooper Nuclear Station," Report No. GENE-523-A121-1195, November 1995.

[2] Ranganath, S. and Mehta, H. S., " Engineering Methods for the Assessment of Ductile Fracture Margin in Nuclear Power Plant Piping," Elastic-Plastic Fracture:

Second Symposium, Volume II - Fracture Resistance Curves and Engineering Applications, ASTM STP 803, C.F. Shih and J. P. Gudas, Eds., American Society for Testing and Materials,1983, pp. II-309 - I1-330.

[3] " Evaluation of Flaws in Austenitic Steel Piping," Journal of Pressure Vessel Technology, Transaction of ASME, Volume 108, August 1986, pp. 352-366. ,

1 File: 121S4. doc DRF # 137-0010-8 l

Item # GENE-523 Al21-1195 '

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