NUREG-0487, Summary of 851220 Meeting W/Util & S&W Re Adequacy of Design of Downcomers at Facility.List of Attendees & Handouts Encl
| ML17055B055 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 01/06/1986 |
| From: | Adensam E Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0487, RTR-NUREG-0808, RTR-NUREG-487, RTR-NUREG-808 NUDOCS 8601150611 | |
| Download: ML17055B055 (28) | |
Text
Docket No. 50-410 January 6,
1986 APPLICANT:
Niagara Mohawk Power Corporation FACILITY:
Nine Mile Point Nuclear Station, Unit 2
SUBJECT:
SUMMARY
OF MEETING HELD DECEMBER 20,
- 1985, TO DISCUSS THE DESIGN OF THE DOWNCOMERS FOR NINE MILE POINT NUCLEAR STATION, UNIT 2 On December 20, 1985, the NRC staff met with representatives of Niagara Mohawk Power Corporation (NMPC) and their consultants, Stone and Webster Engineering Corporation (SWEC), to discuss the adequacy of the design of the downcomers at Nine Mile Point Nuclear Station, Unit 2 (NMP-2).
Mr. Robert Bernero opened the meeting stating that it was unfortunate timing to be discussing an issue of this potential effect so close to the scheduled fuel load for NMP-2.
The downcomer issue was then divided into two parts.
The first part related to the Submerged Structure Loads on the downcomers and the assumptions made in developing the SRV loads.
Enclosure 1 contains a handout provided by the applicant on the "SRV Submerged Structure Load."
Agreement was reached on the load methodology used to determine the submerged structure loads if they were applied to rigid downcomers.
There remained however a concern that loads, which had been considered as secondary loads in NUREG-0487 and NUREG-0808 (e.g.
pool swell sloshing) and, therefore, were considered negligible for the stiff, laterally-supported downcomers, might be more significant when applied, to the downcomers without lateral supports, which, consequently, have a lower natural frequency.
The second part of the discussion on downcomers was related to the structural adequacy of the downcomers.
Enclosure 2 contains the applicant's handout on "Buckling and the Functional Capability of Downcomers."
In the analysis performed by SWEC for the adequacy of the downcomers, it was noted that using ASME Code Equations with modified stress intensity factors and additional limits for deformation control for the functional capability analysis of the downcomers would yield unacceptable results.
This is the accepted method of analysis from NED0-21985, September 1978.
SWEC then elected to perform a dynamic stability analysis.
This is another option identified by the NRC staff in their safety evaluation of NEDO-21985 (ref.
February 27, 1981, letter Tedesco to Sherwood).
After reviewing the dynamic stability analysis performed by SWEC for the downcomers, the NRC staff stated that the analysis performed was actually a static analysis.
The NRC staff further stated that, in its response to question 210.53 requesting details of
- design considerations of piping in the suppression pool, the applicant did not indicate that the alternate method of performing a dynamic stability analysis had been used.
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The NRC staff expressed concern about the possibility of a buckling failure in the downcomers near the supports.
Such a failure would allow steam to bypass the suppression pool in a LOCA event.
SWEC stated that the buckling load is small.
The NRC staff, however, was concerned that the frequency content was not considered and the low natural frequency of the downcomers
( I to 2 Hz) is in the range of the frequency content of the loads.
A number of ASME Code equations were used in the downcomer analysis.
The NRC staff expressed concern that some of these equations may have been used inappro-priately since Limit Load Theory is used as a basis for some of these equations.
Limit Load Theory does not apply for piping with a D/t ratio of greater than 50.
The D/t ratio for the downcomers is 64.
The square-root-sum-of-the-squares (SRSS) method of combining loads has been accepted by the NRC staff when used appropriately for loads which can be shown to act independently (ref.
NUREG-0484, Rev. I).
The NRC staff, however, ques-tioned the way the SRSS method was applied in the downcomers analysis.
For example the following combination was used,
[(SSEI~
+ SSES~
+ SRV(ONE)~
+ SRV( I)~ + CO(LAT)~ + CO(I)~]
instead of
[(SSEI + SSES)
+ (SRV(ONE) + SRV( I))~ + (CO(LAT) + CO(r))~3~
I Where SSEI
=
=
sloshing effect from SSE SRV ONE)
=
response from activation of one SRV SRV I)
=
inertia effect from activation of one SRY CO(LAT)
=
response from LOCA condensation oscillation resulting from lateral load from adjacent downcomers CO( I)
=
inertia effect of LOCA condensation oscillation Mr. Robert Bernero, NRC Director of the Division of BWR Licensing, stated that the applicant had two options: reanalysis or a mechanical fix.
Mr. Bernero indicated that the NRC would be open to a review of new material if the applicant desired to submit more information, but that the staff did not foresee that new analytical data were likely to make the current downcomer design acceptable.
Mr. Bernero also indicated that resubmittal of material already discussed would not be viewed as new information.
The applicant indicated that they wanted to continue reviewing the existing design.
The NRC staff, therefore, requested that the applicant respond to the following concerns.
1.
The downcomer analysis should be formally submitted.
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For those loads which were not identified as primary loads in NUREG-0487 and NUREG-0808, evaluate the effect of these loads on the NMP-2 downcomer system to determine if they are still negligible (e.g.
Sloshing resulting from a LOCA).
ASME Code equations were used.
ASME Code equations are based on Limit Load Theory.
Limit Load Theory is not applicable to piping with a D/t ratio of greater than 50.
The downcomer D/t ratio is 64.
The equations used in this analysis may not be appropriate, therefore, the applicant should:
4 ~
5.
a)
Review the assumptions used as a basis f'r the equations used in the downcomer analysis and justify their use on the downcomers.
b)
Determine if the structure maintains its configuration before reaching the limit load.
c)
Identify the basis (should be a test) used to justify the moment capacity of the downcomer.
Identify the maximum deflection of the downcomers.
In order to demonstrate the Functional Capability of the downcomers the option of performing a dynamic stability analysis was chosen.
The analysis presented as a dynamic stability analysis does not appear to be a dynamic analysis.
Either perform a dynamic stability analysis for the downcomers (including time factor and frequency effects), per-form a dynamic stability test or follow thk analysis method defined in NEDO 21985.
6.
7.
Clarify and justify the damping factors used in the analysis.
Justify the basis of separating loads into separate components in using the SRSS load combination method.
(i.e. splitting SSE, SRV and CO loads into separate components before squaring).
The applicant indicated that they would respond to the above concerns by January 15, 1986.
A list of meeting attendees is included as Enclosure 3.
Original Signed by Elinor G. Adensam for Mary F. Haughey, Project Vlanager BWR Project Directorate No.
3 Division of BWR Licensing MHaughey/hmc 1/ Q/86 D
W-EA ensam 1/t /86
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Mr. B.
G. Hooten Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station Unit 2 CC:
Mr. Troy 8. Conner, Jr.,
Esq.
Conner 8 Wetterhahn Suite 1050 1747 Pennsylvania
- Avenue, N.W.
Washington, D.C.
20006 Richard Goldsmith Syracuse University College of Law E. I. White Hall Campus
- Syracuse, New York 12223 Ezra I. Bialik Assistant Attorney General Environmental Protection Bureau New York State Department of Law 2 World Trade Center New York, New York 10047 Resident Inspector Nine Mile Point Nuclear Power Station P. 0.
Box 99
- Lycoming, New York 13093 Mr. John W. Keib, Esq.
Niagara Mohawk Power Corporation 300 Erie Boulevard West
- Syracuse, New York 13202 Mr. James Linville U. S. Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Norman Rademacher, Licensing Niagara Mohawk Power Corporation 300 Erie Boulevard West
- Syracuse, New York 13202 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406 Mr. Paul D.
Eddy New York State Public Service Commission Nine Mile Point Nuclear Station-Unit II Post Office Box 63
- Lycoming, New York 13093 Don Hill Niagara Mohawk Power Corporation Suite 550 4520 East West HighWay
- Bethesda, Maryland 20814
I V
Based on Wall Pressure Profile (NUREG 0802)
Differential Pressure Across the Downcomer is Calculated from Empirically Determined Multiplier
++ ~ 0.75 Pw 0.75
- PKKB
- H (4) 0.75 is the product of 2 factors, an empirically determined 0.5 differential pressure factor and a 1.5 transferring factor from KKB to MK II.
SRV LOAD ON DOWNCOMER
~ F ~ AP
- A
/I P*D
- dl Specified differential pressure conservatively bounds the differential pressure predicted from potential flow theory (1/r Law)
The differential pressure factor 0.5 has been verified against inplant test data KKB, KTG, and Caorso.
~ ~
Rayleigh Bubble Formulation Bubble Located at the center of the Quencher device.
Bubble Radius
~ Radius of the Quencher Bubble Pressure
~ 1/4 Ramshead Bubble Pressure Shoreham A lication Same as above except using 1.5 PKKB as bubble pressure.
Hybrid DFFR/KWU Methodology Coupled Fluid - Structure System Approach Source Terms:
Bubble Pressure equivalent to Shoreham Bubble Radius same as Shoreham Flow field calculated from Rayleigh Bubble with a negative image to satisfy the pool surface boundary condition (conservative compared to Shoreham)
Interference effect of adjacent structures on the acceleration dram coefficent comply with NUREG 0487 Supplement l l.l Asymmetric Factor applied comply with NUREG,0487
KWU Multi lier Method Apply KWU differential pressure load on downcomer 0 l5p<<e ~ H ~g,)
NMP2 Procedure Without Cou led Fluid Structure Interaction Touching bubble at downcomer tip Bubble Pressure Wall Pressure The downcomer responses are within 1X of each other.
Downcomer is flexible, this motion must be considered.
Fluid structure coupling flow field is needed to calculate the relative motion of the downcomer with the fluid.
Fluid structure coupling method is stan-dard textbook practice, Ref. R.D. Blevins "Flow Induced Vibrations," Van Nostraud,
- Reinhold, 1977.
'r
Determine the ultimate buckling moment of the downcomer and estab-lish that collapse by buckling will not occur from the postulated dynamic loadings.
Determine the effects of ovalization caused by the dynamic loads and demonstrate that the reduction in area is within acceptable limits.
Ultimate buckling moment is obtained from an expression which consi-ders critical strain (i.e. strain at the point of instability), and geometric and material properties of the pipe.
The basis of calcul-ating the ultimate moment involves expressing the critical strain in terms of the thickness and radius of the pipe, obtaining a relation-ship between rotation and strain at instability, describing a non-linear stress-strain relationship for the material and integrating stress over a cross-section to determine the bending moment.
This basis is documented in literature and substantiated by testing.
Moment from the worst dynamic loading combination is calculated at the downcomer fixed end.
The ultimate buckling moment is 40X higher than the maximum moment calculated from the postulated dynamic loading combinations, thus buckling is not expected to occur.
V
Assume that moment causes the initially round pipe to become elliptical in shape.
Determine principal axes of the ellipse using the strain energy method (or the principle of least work).
The reduction in the area of cross-section is determined to be about 1%,
which is within the acceptance criteria.
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ENCLOSURE 3
LIST OF ATTENDEES NAME Mary F. Haughey Y. C.
(Renee)
Li E.
G.
Adensam Divakar Bhargava Chen P.
Tan Nick Rapagnani R.
M. Bernero 8.
D. Liaw Donald L. Hill Alan W.
Chan Mark A. Durka David Terao Farouk Eltawi la Jack Kudrick Jerry Hulman Gus Lainas R.
Wayne Houston Peter Antony-Spies L. P. Prunotto C.
V. Mangan A. F. Zallnick E.
R. Klein R. A. Cushman D.
E. Vandeputte T. L.
Wang ORGANIZATION NRC-Licensing Project Manager
~ NRC-BWR-EB NRC-BWR-PD¹3 Stone 8 Webster Eng.
Corp.
NRC-BWR-EB SWEC-Lead Engineer NRC-DBL NRC-DBL-EB NMPC Licensing Stone 5 Webster-Division Manager SWEC-Assistant Project Engineer NRC-DPL-8 NRC-RIB-DSRO NRC-DBL-PSB NRC-DBL-PSB NRC-DBL NRC-DBL KWU NMPC-Struct. Engineering NMPC-VP NMPC-Mgr. Licensing NMPC-NMP2-Project Manager Design NMPC-Licensing SWEC-Licensing SWEC
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MEETING
SUMMARY
DISTRIBUTION et No(s): ~d - gl ~
NRC PDR Local PDR BWD ¹3 r/f J. Partlow (Emergency Preparedness only)
E.
Adensam
- Attorney, OELD E. Jordan B. Grimes ACRS (10)
Project Manager E. Hylton NRC PARTICIPANTS bcc:
Applicant 8 Service List
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