ML18046A647
| ML18046A647 | |
| Person / Time | |
|---|---|
| Site: | Rensselaer Polytechnic Institute, Palisades |
| Issue date: | 05/15/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| TASK-03-10.B, TASK-3-10.B, TASK-RR LSO5-81-05-029, LSO5-81-5-29, NUDOCS 8105200186 | |
| Download: ML18046A647 (7) | |
Text
- Docket No-. 50*255 L805-8l-05-029 Mr. David P. Hoffman Nuclear Licensing Administrator Consumers Power Company 1945 W Parnall Road Jackson, Michigan 49201
Dear Mr. Hoffman:
//
May 15, 1981
SUBJECT:
TOPIC III-10.B, PUMP FLYWHEEL INTEGRITY (PALISADES)
Enclosed is a copy of our draft evaluation of Systematic EY.aluatfon Program Topic III-10.B. You are requested to exam1ne __ the-*facts.-upon whfth* the staff has based its eval uat1on and respond ~1.ther oy confirming tha:t. the facts are currect or by identifying err9_rs-and supplying the corrected 1nfonnation.
We encourage you to ~upply-any other material that might affect the staff's evaluat1on_q_f.the-se topics or be significant in the integrated assessment of y~UJ". fae-f11ty.
~--_....... -~-.-**.~
Your response is requested within 30 days of.receipt of th.is letter*.* *1f' no-respon;~ is received within that time, we w111 a_s,sume-'ttlat you have no corrl'ilents or corrections.
. --.~~--** ------*
In future corre~_po.ndence *regarding Systematic Eval uation.~1Program Topics, please r:-efer to the topic numbers in your cover letter.
Enclosure:
As stated cc w/enclosure:
See next page 810520 0 \\itp
~
NRC FORM 318 fl0/801 NRCM 0240
- Sincerely, Dennis M.
C~utchfield, Ch.fef Operating Reactors Branch No. 5 Division of Lfeensing OFFICIAL RECORD-COPY.*
. i> USGPO: 1980-329*824
UNITED STATES NUCLEAR REGULATORY COMMISSION Mr. David P. Hoffman WASHINGTON, D. C. 20555 May 15, 1981 Nuclear Licensing Administrator Consumers Power Company 1945 W Parnall Road Jackson, Michigan 49201
Dear Mr. Hoffman:
SUBJECT:
TOPIC III-10.B, PUMP FLYWHEEL INTEGRITY (PALISADES)
Enclosed is a copy of our draft evaluation of Systematic Evaluation Program Topic Ill-10.B.
You are reques.ted to examine the facts upon which the staff has based its evaluation and respond either by confirming that the facts are correct or by identifying errors and supplying the corrected information.
We encourage you to supply any other material that might affect the staff*s evaluation of these topics or be significant in the integrated assessment of your*facility.
Your response is requested within 30 days of receipt of this letter, If no responseis received within that time, we will assume that you have no comments or corrections.
In future correspondence regarding Systematic Evaluation Program Topics,.
please refer to the topic numbers in your cover letter.
Enclosure:
As stated cc w/enclosure:
See next page Sincerely,.
LJt.
Dennis M. Crutchfield,
- ief Operating Reactors Branch No. 5 -
Division of L io~.ns ing
.. ~
.. r:-~
.. ~
- .*~.,.*
e Mr. David P. Hoffman cc M. I. Miller, Esquire Isham, Lincoln & Beale Suite 4200 One First National Plaza Chicago, Illinois 60670 Mr. Paul A. Perry, Secretary Consumers Power Corrpany 212 West Michigan Avenue Jackson, Michigan 49201 Judd L. Bacon, Esquire Consumers Power Corrpany 212 West Michigan Avenue Jackson, Michigan 49201 Myron M. Cherry, Esquire Suite 4501 One IBM Plaza Chicago, Illinois 60611 Ms. Mary P. Sinclair Great Lakes Energy Alliance 5711 Summerset Drive Midland, Michigan 48640 Kalamazoo Public Library 315 South Rose Street Kalamazoo, Michigan 49006 Township Supervisor Covert Township Route 1, Box 10 Van Buren County, Michigan 49043 Office of the Governor (2)
Room l - Capitol Building Lansing, Michigan 48913 Director, Criteria and Standards Division Office of Radiation Programs (ANR-460)
U. s. Environmental Protection Agency Washington, D. c. 20460
- u. S. Environmental Protection A~ncy
.\\
Federal Activities Branch Region V Office ATTN:
EIS COORDINATOR 230 South Dearborn Street Chicago, Illinois 60604 Charles Bechhoefer, Esq., Chairman Atomic Safety and Licensing Board Panel
- u. s. Nuclear Regulatory Corrmission Washington, D. C.
20555 Dr. George C. Anderson Department of Oceanography University of Washington Seattle, Washington 98195 Dr. M. Stanley Livingston 1005 Calle largo Santa Fe, New Mexico 87501 Resident Inspector c/o U. S. NRC P. O. Box 87 South Haven, Michigan 49090 Palisades Plant ATTN:
Mr. J. G. Lewis Plant Manager Covert, Michigan 49043 William J. Scanlon, Esquire 2034 Pauline Boulevard Ann Arbor, Michigan.48103 -
CONSUMERS POWER COMPANY PALISADES, DOCKET NO. 50-255 SYSTEMATIC EVALUATION PROGRAM BRANCH 1.
COMPONENT lNTEGRITY SECTION SAFETY EVALUATION REPORT SEP TOPIC III-10.B - PUMP FLYWHEEL INTEGRITY I.
Introduction*
The safety objective of this review is to assure that the integrity of the primary reactor coolant pump flywheel is maintained thus preventing failures at normal operating speeds and speeds that might be reached under accident conditions thereby precluding the generation of missiles.
II.
Review Criteria The basis for the review is outlined in Standard Review Plan (SRP) Section 5.4.1.1 and the Regulatory Guide 1.14, which describes and recommends a method acceptable to the NRC staff of implementing General Design Criterion 4, "Environmental and Missile Design Bases" of Appendix A of 10 CFR 50, with regard to minimizing the potential for failures of the flywheels of the reactor coolant pumps.
III.
Related Safety Topics and Interfaces Internally generated missiles protection is evaluated under SEP Topic 111-4.C.
IV.
Review Guidelines There are two parts to the recommendations of Regulatory Guide 1,14. The first part is related to the evaluation of materials of construction, design, fabrication, proof testing and pre-service inspection of the pump flywheels.
The second part is concerned with the evaluation of the procedures used for the inservice inspection of pump flywheels.
V.
Evaluation A.
Material and Fabricatio~
The flywheels for each pump are divided into three sections, two above the rotor spider, and one below.
The two upper flywheels are bolted together and the upper flywheel (72" diameter) is keyed to the lower (52" diameter) one by means of an offset. At operating speed (900 rpm at Palisades) the bore stress due to rotation is 8300 psi and 4100 psi is due to shrink fit. The operating temperature of the Palisades flywheels, which are enclosed by motor stator coils, will be above l00°F.
The disc material is SAE 1017, type 1020, which is equivalent to ASTM A 108 (1017), low carbon steel with a minium yield Strength of 2~000 psi and tensile strength of 50,000 psi.
The pump flywheels are
- \\.
machined from cross rolled blanks.
Regulatory Guide requires that the nil-ductility transition temperature (NDT) for the flywheel material be no higher than l0°F, that the Charpy V-notch (CVN) upper shelf energy should be at least 50 ft-lb., and that at normal operating temperature the material should have a dynamic stress intensity factor of at least 100 ksijln.
This later require..
ment can be satisfied by demonstrating that the material has a CVN energy level of 50 ft-lb. at normal operating temperature.
Based on our review we have determined that the NDT of the flywheel material at Palisades is no more than 40°F and an average CVN energy of 100 ft-lb. at 70°F.
Based on these data we conclude that the NOT requirement of Regulatory Guide 1,14 has not been met while the CVN and fracture toughness requirement have been met.
Based on this infor-mation we conclude that the flywheels have adequate fracture toughness.
Our conclusion is based on the following:
Although the NOT is 40°F rather than l0°F, the operating temperature of lQQOF is still 6QOF above NOT, This margin above NOT coupled with a CVN energy at 70°F that far exceeds the 50 ft-lbs. required by the Regulatory Guide ensures that brittle fracture is unli~ely and that a large tolerance *to flaw-induced fracture exists. This flaw tolerance and operation ~n a tempera-.
ture region where the potential for brittle fracture is reduced meets the intent of Regulatory Guide 1.14 although one specific requirement of the guide has not been met.
B.
Design.
We have evaluated the pump flywheels at Palisades to compare the ductile strength levels and the fracture toughness at Palisades with the require-ments of Regulatory Guide 1.14, "Reactor Coolant Pump Flywheel Integrity."'
Regulatory Guide 1.14 requires that the ~argin against ductile rupture at normal operating speed arid design overspeed be 3 and 1.5, respectively, compared to the minimum speci'fied yield strength.
For the.flywheels at Palisades the margins against ductile rupture at normal operating speed is 3,07 and 2.0 at a design overspeed of 125%, **Therefore the margin at normal operating speed is 2% more than that required by the Regulatory Guide while the margin at design overspeed exceeds the required margin by 30%.
Hence, the margins against ductile fracture required by Regulatory Guide 1.14 have been met~
~-.,. C.
Inservi ce Inspection Program The Palisades plant has three flywheels that are made of SAE 1017, Type 1020, low carbon steel,with a minimum Yield strength of 27,000 psi. Other flywheels we have reviewed recently were made of higher quality materials, either A533B or A516, Gr65 with yield strength of 50,000 and 65,000 psi respectively.
Two of the flywheels have a dia-meter of about 52 inches and are located within the stator windings of the motor.
The third, and uppermost flywheel has a diameter of 72 inches and is located within the motor housing but above the windings of the motor.
Unlike previously reviewed designs, the Palisades fly-wheels are shrink fitted to the motor shaft.
The staff concluded in the presentation of the safety aspects of the Palisades plant to the ACRS committee on November 18, 1969 that no additional protection against the effects of missiles from the small flywheels need be required because the pump speed being only 900 rpm and the stator windings of the motor and the motor housing have the capacity to absorb the kinetic energy of the missile.
Howev~r, in view of the use of material of lower toughness than provided in other designs, the ACRS recommended the following inspection program;
- 1.
1.00% UT baseline inspection of the upper 72-inch flywheels, including the disc-shaft interface.
- 2.
100% UT inservice inspection of the upper 72-inch flywheel including the disc.. shaft interfa.ce, at each refueling shutdown.* (about every 19 months.)
- 3.
A visual inspection~ to the extent practical, using optical means to provide' interior access where required, of all three flywheels in each motor each time UT inspections of the upper flywheels are performed.
Regulatory Guide 1.14 as well as the ASME Code Section XI requires the following inservice inspection program for each flywheel:
- 1.
An in place ultrasonic.volumetric examination of the areas of higher stress concentration at the bore and keyway at approximately three-year intervals.
- 2.
A surface examination of all exposed surfaces and complete ultrasonic volumetric examination at approximately 10 year intervals,
i I
.J*.*,,
VI. ***-* - -*
In lieu of the requirements of Regulatory Guide 1.14, UT examination of the areas_ of higher stress concentration at three-year intervals and complete volumetric examination at ten-year intervals, the staff imposed the requirement of 100% volumetric inspection of the upper flywheel at \\
each refueling which occurs approximately every 18 months.
In accordance with the Palisades Plant Technical Specifications 4.3 and 4.12, inservice inspection no, 6 was conducted during the period September 8, 1979 to May 28, 1980.
No deterioration has been found in the upper pump flywheel.
The analysis performed by Combustion Engineering shows that a 3.5" through crack will be required to cause failure at 125% overspeed at lower temperature and not extrapolated to operating temperature.
The experience of motor flywheel combinations similar in design to Palisades units has been very favorable.
No flywheel failure, or other associated flywheel problem, has ever been experienced with this type design.
- We recommend that the Palisades plant continue performing 100% volumetric inspection of the upper flywheel at each refueling and in addition shoul~_
include a visual inspection of other two flywheels whenever _a pump -*-***-- ____ _
motor overhauling is required. _______.. _____________...
Conclusions We have reviewed the materials, fabrication, design and inspection aspects of the pump flywheelsat Palisades for compliance with Regulatory Guide 1.14.
Based on our review we conclude that the requirements for fabrication and the margins against flow induced fracture and yielding required by Regulatory*
Guide 1.14 have been satisfied for the flywheels.
The present inservice inspection of the upper flywheel is more stringent than Regulatory Guide 1.14.
However, the other two flywheels (52 11
) are not inspected at present, hence a visual inspection during _a pump motor overhaul will
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