ML20010E361

Informs That Util Response to IE Bulletin 79-15, Deep Draft Pump Deficiencies, Did Not Include Enough Info to Assure long-term Pump Operability.Addl Info Showing Compliance W/ Encl Guidelines,Or Acceptable Alternative,Due in 60 Days

ML20010E361
Person / Time
Site:	Fermi
Issue date:	08/24/1981
From:	Tedesco R Office of Nuclear Reactor Regulation
To:	Tauber H DETROIT EDISON CO.
References
IEB-79-15, NUDOCS 8109030394
Download: ML20010E361 (4)

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LB#1 Rdg TERA gM 211981 DEisenhut NRC/PDR BJYoungblood L/PDR MRushbrook NSIC LKintner TIC Docket No.: SD-341' RLTedesco ACRS (16) RVollmer TMurley Mr. liarry Tauber RMattson 's Vice President RHartfield, MPA p Engineering & Construction WJohnston g {b "} I ,,1 Detroit Edison Company OELD 2000 Second Avenue OIE (3) Detroit, iiichigan 48226 2 AUG 2 G 19815 t bear Mr. Tauber- \\ 3: $ g f. N.'

Subject:

Long Tem Operability of Deep Draft Pumps fI IE Bulletin 79-15, dated July 11, 1979, was issued to all licensees and holders of construction pemits as a result of deep draft pwnp deficiencies that were identified at facilities both operating and under construction. In your response to tha bulletin you identified deep draft pumps as being utilized at your facility. However, your response to the bulletin did not include enough infomation to demonstrate and assure the long term operability of these pinps. Enclosed is a document entitled, " Guidelines for Demonstration of Operability of Deep Draft Ptnps." Within 60 days from the issuance date of this letter, you should provide infsmation on all the deep draft pumps identified in your i bulletin response and describe the extent to which your deep draft pump long term operability assurance program conforms to the various portions of these Guidelines. Emphasis should be placed on (1) the establishaent of installation procedures that are followed each time these pumps are disassembled and reinstalled, and (2) the testing requirements and bearing wear criteria. The instrumentation called for in the Guidelines should not be considered a requirenent. i These Cuidelines establish an acceptable method of assuring long tem l operability of deep draft pinps. They do not necessarily constitute the l only method for demonstrating long tem operability. The staff will review j the infomation you submit to detemine whether your long tem operability assurance program fcr deep draft pumps is. in sufficient confomance ~with t l thase Guidelines to assure long term operability. If not, the staff will deteraine whether you have established and utilized other nethods and procedures, preferably with the assistance of the pump manufacturer, that also demonstrate and assure that these pumps will perform their intended function for the length of tine required. i l lr

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,f - ~qf J AUG 2 41981 If you have any questions regarding this matter, please contact the Licensing Project Manager. Si ncerely, od e.1s W '7' Re&ert I. Tr W 4 Robert L. Tedesco, Assistant Director for Liccasing i Division of Licensing Office of Nuclear Reactor Regulation

Enclosure:

i Guidelines for Demonstration of Operability of Deep 1 Draft Pumps cc w/ enclosure: See next page N i (H > n /l ~~ iDL: B#1 D1 D D/L . orrica p ..s S'""> LKin ner.y.s...NX.qngb.l.o.od. 8.( .@.s.c o..... Ocup 8/lj./81 8 /81 8/ /81 ......p........... ..........i NRC FORM 318 t!O 80l NRCM O240 OFFICIAL RECORD COPY .uss o i w _329424

4 AUG 2 41981 If you have any questions regarding this matter, please contact the Licensing Project Manager. Si ncerely, 1 %' { e m 7 t ,x Robert L. Tedescc, Assistant Director for Licensing Division of Licensing Office of Nuclear Reactor Regulation

Enclosure:

Guidelines for Demonstration of Operability of Deep Draft Pumps cc w/eoclosure: See next page 2 t .e t 4 --,e -n.. a

Mr. Harry Taubgr Vice President Engineering & Construction Detroit Edison Company 2000 Second Avenue Detroit, Michigan 4S226 cc: Eugene B. Thomas, Jr., Esq. LeBoeuf, Lamb, Leiby & MacFre 1333 New Hampshire Avenue, N. W. Washington, D. C. 20036 Petet A. Marquardt, Esq. Co-Counsel The Detroit Edison Company 2000 Second Avenue Detroit, Michigan 48226 Mr. William J. Farner Project Manager - Fermi 2 The Detroit Edison Company 2000 Second Avenue Detroit, Michigan 48226 Mr. Larry E. Schuerman Detroit Edison Company 3331 West Big Beaver Road Troy, Michigan 48084 David E. Howell, Esq. 3229 Woodward Avenue Berkley, Michigan 48072 Mr. Bruce Little U. S. Nuclear Regulatory Commias sor. Resident inspector's Office 6450 W. Dixie Highway Newport, Michigan 48166 Dr. Wayne Jens Detroit Edison Company 2000 Second Avenue Detroit, Michigan 48226 A

'i ENCLOSURE GUIDELINES FOR DEMONSTRATION OF OPERABILITY OF DEEP DRAFT PUMP 5 DISCUSSION I.E. Bulletin 79-15 dated July 1979, identified problems associated with deep-draft pumps found at operating facilities and near term operatir.g licensee facilities. Deep draf t pumps,which are also called

• vertical turbine pumps" are usually 30 to 60 feet in length with impe11ers located in casing bowls at the lowest elevation of the pump.

The motor (driver) is located at the highest pump elevation with the discharge nozzle just below the motor. Bulletin 79-15 was initiated because several nuclear power plant facilities could not demonstrate operability of their pumps. The ~ pumps were experiencing excessive vibration and bearing wear. The-~ ~ rapid bearing wear suggested that these pumps could not perform their required functions during or following an accident. As a result of the staff's initial review cf the responses to IEB 79-15,- several plants were identif'ied as having potential probicms with their deep draft pumps. These guidelines are provided for thesc plants so that the licensee or applicant involved may have a method l l acceptable to the staff for demonstrating the operability of deep-l draft pumps. I C, 9@q 24MO B.L

GUIDELINES FOR DEMONSTRATION OF OPERABILITY OF DEEP DRAFT PUMPS DISCUSSION 1.E. Bulletin 79-15 dated July 1979, identified problems associated with deep-draft pumps found at operating facilities and near term operating lic~ensee facilities. Deep draft pumps,which are also called " vertical turbine pumps are usually 30 to 60 feet in length with impe11ers located in casing bowls at the lowest elevation of the pump. The motor (driver) is located at the highest pump elevation with the discharge nozzle just below the motor. Bulletin 79-15 was initiated be:ause several nuclear power plant facilities could not demonstrate operability of their pumps. The pumps were experiencing excessive vibration and bearing wear. The'~ ~ rapid bearing wear suggested that these pumps could not perform their required functions during or following an accident. As a result of the staff's initial review of the responses to IEB 79-15,. ~ several plants were identified as having potential problems with their deep draft pumps. These guidelines are provided for these plants so that the licensee or applicant involved may have a method acceptable to the staff for demonstrating the operability of deep-draft pumps. e

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a s, e DEEP D.7 AFT PUMP OPERATING CHARACTERISTICS In order to better understand the operating characteristics of 1 these pumps, a rotor (ynamics analyses was performed to ascertain the response of the pump rotor under steady state operation. Tne analyses. considered journal bearing to shaft dynamic response ~ at various eccentricities and fluid viscosities. The model for the analysis depicted a typical deep draft pump utilized by the nuclear industry. The analysis resulted in recommendation,s for improving the stability of the pump rotor from externally applied inputs and by self-generated inputs. The conclusions which were derived from the analysis and staff evaluations of North Anna, Beaver Valley and Surry facilities with similar pumps include: 1.) Pumps with this type of configuration are prone to bearing whirl vibration problems due to the flexibility cf the rotor and casing structure. This phenomenon is accentuated as journal bearing clearance becomes large. This phenomenon leads to bearing wear (Jourmal bearings). 1 " Low Head Safety Injection Pucp Rotor Dynamic Analyses", by Franklin Research Center, Report FC4982, dated May 1980. D .m u l

. 2.) There may be natural frequencies associated with the pump assembly which occur near the operating speed of the pump. Pump operation will drive these frequencies and can cause bearing wear. The severity of this condition is dependent on bearing diametral clearance, rotor unbalance conditions and housing flexibility. As an example, if the wear in column journal bearings becomes sufficiently large (twice the original diametral clearance)~so that these bearings are no longer active and the undamped critical frequency near the operating speed of the pump i is allowed to expand, the additional uncontrolled bearing wear will occur. This wear can continue until the shaft rubs against the support structure of the bearing and can potentially sever the shaft. j 3.) One acceptable method for correcting instabilities in the pump shaft is to utilize a journal bearing design which exhibits stable characteristics. One such design is the

• Taper land bearing". This design is more stable than the l

plain journal bearing, is less susceptible to wear because l of the taper and will cause the bearing to form a hydro-(ynamic film quickly during startup. 1 l e

s . 4.) Stiffening of the column sections of the pump is advantageous if there is a column frequency near the operating speed of the pump. The shifting of the column frequency to a higher level will eliminate any coupling between the pump operating speed and the column frequency. 5.) Ficw inlet conditions to the pumps and sump designs can be important to pump operability. Certain installations have demonstrated flow characteristics which produced vortexing at the be11 mouth of the pump. This vortexing is due to sump design or sump supply line entrance con- ~~ ~ ditions. This condition can contribute to additional pump vibration and wear. Flow straightener devices, reduction of be11 mouth diameters, and bottom clearance reductions have proven to be effective in eliminating this problem. 6.) This type of pump has exhibited operational problems due to design and installation deficiencies. The high s flexibility of the shaft and column make this design rather forgiving when it comes to installation deficien-cies such as misalignment between the shaft and column,

low-precision coupling assemblies, and non-perpendicular mounting flanges. This fact however, can lead to excessive bearing wear without significant noticeable change in pump operating characteristics. To ensure proper pump operation, proper alignment should be established between all mating surfaces and measures should be emphasized which prevent column and shaft eccentricities. These measures can include optical alignment of the column segments, use of high precision couplings and use of accurate techniques to establish that the sump plumb line is perpendicular to the pump mounting fl ange. The above findings and conclusions have contributed significantly to the development of these guidelines. The guidelines listed below are divided into installation and test areas. The subjects to be addressed in these areas are considered to be of prime importance when establishing a pump operability assurance program. The extent to which each of the two are~as are implemented at a specific facility is dependent on spe;ific symptoms which have s been identified with these pumps while in operation and during service periods. e' s e

s, u (, ., Implementing the measures outlined below, at North Ar.na 1 & 2 in total has been shown to provide reasonable assurance that the pumps will be operable when required for their safety function. These guidelines are not intended to replace the requirements of Standard Review Plan 3.9.3, Regulatory Guide 1.68 or any other requirements presently enforced by the staff. Rather, the guidelines are to be used as supplementary material for establishing deep-draf t pump operability. GUIDELINES FOR OPERABILITY INSTALLATION 1.0 INSTALLATION PROCEDURES Experience has shown that these pumps are prone to having operability problems as a result of poor installation procedures. The guidelines emphasize those areas of the installation procedure,which if implemented, could significantly improve the likelihood of an operable pump. The ~ procedures utilized should be submitted to the staff for review. I.1 PUMP INSTALLATION Determine by measurement that all shaft segments are straight a. within tolerances specified by the manufacturer. b. Determine by measurement or provide certification that all couplings (for shaft segments & ' pump to motor coupling) are of high precision as specified by the manufacturer. Determine by measurement that all pump segment flanges are c. perpendicular to the centerline of the segment, that the l segments are straight and that any mating surfaces are concentric to an established datum. Where journal l t

7-bearing guides (SPIDERS) are used, establish con-centricity between this assembly and its mating surf ace. d. Align full pump casing assembly optically to assure maxis:um straightness and concentricity of the asse=bly. Any equivalent method is acceptable, as long as the procedure stresses column straightness and concentricity. Assure pump to motor flange perpendicularity and that e. proper coupling installation is perforrred. f. Assure that all mating surf ace bolting is properly attached and that manufacturer torquing sequences are adhered to. 1.2 fjMP INSTALLATION Assure (where used) that sump / pump mating flange a. is perpendicular to the sump pump line. b. Assure that sump design prevents fluid anomalies such as vorte) ag or turbulence near the intake to the pump bellmouth and that incoming piping is not so designed as to allow fluid conditions favorable to these anomalies (i.e., sharp bends in piping prior to entrance into sump). c. Assure that interference does not exist between the sump and arty pump appendage such as a seismic restraint. m

1 t. e. e 8-2.0 Testing Recuirements The installation procedures are essential in establishing pump operability. In addition to careful installation, testing rey be required which will verify proper operation of these pumps. After corpletion of the installation checks, licensees or appli-cants should evaluate the need for further testing and report the.results of this evaluation together with the details of any test plans to tSe staff. Should tests be required, an acceptable test procedure should include the items listed below. The staff recognizes that the instrumentation and procedures outlined below may be difficult to implerent at all facilities and, therefore, the staff is emphasizing good installation practices which lead to operable components. If tests demonstrating operability cannot encompass all the itens listed below, then alternative procedures should be proposed for evaluation by the staff. The tests should emphasize reasurement of pump dynamic characteristics and wear data at different stages of testing, culminating with an extrapolation of the data to the desired life goal for the pump. 2.1 Test Instrumentation The following instrumentation should be incorporated into the test procedure aside f rom normal flow measu' ement, pressure and r vibration instrumentation: O e 9

-9 a.- ) X, Y proximity probes at three axial locationt on the pump column, for measuring and recording radial p2sitions of shaf t with respect to the column. b.) X, Y, accelerometers (at proximity probe locations) for measuring and recording radial accelerations of the column. c.) Dynamic pressure transducers for ceasuring fluid pressure at the following locations: 1. Bottom of Column (suction) ~~ 2. Mi d-Column 3. Top of Column. d.) Shaft Rotational speed and dynamic variation instrument. 2.2 PRE-TEST DATA ~ ' With the pump disassembled, measure all journal bearing 0.D.'s, bearing 1.D. 's and calculate bearing diametral clearances. In addition with pumps fully assembled and using the proximity probes, obtain the " clearance circle" at each of the three axial stations by rolling the shaft section within the clearance volume of its bearings and in this way, establish proper operation of the probes.

s, a s. . 3.1 PNASE 1 Testing (6 hours plus start-stop) This phase of testing should be comprised of 6 hours of testing (Break-in) followed by start-stop testing. Test conditions should simulate as nearly as possible nomal and accident conditions. Parameters to be considered are flow, temperature, debris, and chemical composition of fluid being pumped. Static torque tests should be performed before'and after the test (i.e. measure amount of torque required to turn shaft by hand). Data should be taken during the six hour test at 1/2 hour intervals. A total of 12 start-stop tests will be perfomed con-sisting of a start up from zero speed up to full-speed, 10-minute dwell at full-speed and a sr.utdown from full speed to zero speed, with recording of all instrumentation during full cycle of start-stop. Upon completion of Phase 1 testing,the fo110 wit'9 data should be obtained and recorded: 1.) Obtain the " clearance circles" using the'three sets of proximity probes. 2Tests at North Anna 1 & 2 and Manufacturers input indicates that 6 hours is an adequate time interval for bearing " break in" period. a ~- +

6 f 2. ) Measure and record the following dimensions for each bearing:

a. ) Journal 0.D.

b.) Bearing 1.D. c.) Bearing to Jc. -nal diametral clearance d.) - Establish Pb s; i test bearing wear. THE ACCEPTANCE CRl fERI A 15 AS FOLLOW 5: 3 1.) If wear is)* 5 mils for any bearing, wear is unacceptable '~' and test -should be terminatet. ~ 3 2.) If wear is( 5 mils for all bearings a.) Reassemble the pump

b. )

Obtain " clearance circles"

c. ) Reinstall pump in test loop. -

2.4 Phase 2 Testing (48 hours) ~ l Phase 2 testing is to be perforced at full system pressure. and teaperature and fluid conditions simulating those expected during accident and nornel operation. Before start and at corpletion of Phase 2 test,obtain reasurement of static torque. Data should be recorded continaously faring the start-up period, i 3This acceptable wear value ray be modified based on manufacturers l recommendation. l e e n a

s s. i 12 - and during the shutdown period. Data should also be recorded at 1-hour time intervals during the 48 hour test. The following reasurements should be made at the cocpletion of Phase 2 of the test: 1.) Obtain the " clearance circles" using the three sets of proximity probes. 2.) Measure and record the following dimensions for'each bearing: a.) Journal 0.D. b.) Bearing I.D.

c. ) Bearing to Journal diametral clearance.

d.) Establish accuculated bearing wear. THE ACCEPTANCE CRITERIA 15 AS FOLLOW 5: 1.) If accumulated bearing wear on any bearing 's )P7 mils, wear is unacceptable and test should be t ermi nated. 2.) If accumulated wear on all bearings is(7 mils forallbearings$. a.) Reassemble pump

b. )

Obtain " clearance circles"

c. )

Reinstall pump in test loop. O e ei g

5.) Phase 3 Testing (96 hours) Phase 3 testing is to be perfomed at full system pressure and temperature and fluid conditions simulating those expected during accident and normal operation. The same procedures should.be followed as in Phase 2 testing except that data may be taken with less frequency. The same measuren.ents should be taken at the completion of this phase as with the other phases with the following acceptance criteria: 1.) If accumulated bearing wear is)8 mils for any bearing 3 wear is unacceptable and test should be teminated. 2.) If accumulated wear is ( 8 mils for all bearings, a s decision needs to be made to establish: a.) the need for additional testing or e b.) whether or not the bearing wear will be acceptably low. i The recommended decision process is outlined below. i Plot the values of accumulated wear versus time (H) for each bearing after Phase 2 and Phase 3 tests, namely. l Vcar at H2 = 54 hour Wear at H3 = 150 hours 1 =.

a s, - Straight lines are then drawn through the plotted values of wear and extended to the v.ght (See example Figure 1). If the extension intercepts the maximum acceptable value of wear (8 mils) at a value H less than the life goal for this pump, additional testing should be perfonned. If the intercept of the line with wear of 8 mils exceeds the life goal for this pump, no additional testing is required and bearing wear is acceptable. If additional testing is deemed necessary it should be done in a similar manner to that ~ performed during Phase 3 with similar acceptance criteria and decision process. It is expected that such additional testing will either show a stable pump operation with no increase in bearing wear or increased bearing wear with unacceptable results. 2.6 Evaluation of ? ump Acceptability l If bearing wear (after all testing phases) is acceptably low (as per decision process) and if vibration levels over the frequency spectrum of 3 cps to 5000 cps are acceptably low and show no unfavorable trend of increasing magnitude during the testing, the pamp may be judged acceptable for its intended ur,s. O ~ 1.

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