ML20113H496
| ML20113H496 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 04/30/1992 |
| From: | Axline J, Froehlich C NUTECH ENGINEERS, INC. |
| To: | |
| Shared Package | |
| ML20113H494 | List: |
| References | |
| TVA-17-100, TVA-17-100-R, TVA-17-100-R00, NUDOCS 9208040109 | |
| Download: ML20113H496 (14) | |
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LICENDING TOPICAL REPORT NUTECH FEEDWATER NO12LE DYPADB LEAKAGE NONITORING DYSTF.H APPENUTX: RESULTs FOR UROWNQ FERRY UNIT 2 JUNE-DECEMDER 1981 Prepared for:
Tennesseo Valley Authority Prepared by:
Pacific Huclear Systems, Inc.
HUTEC11 Engineers Group u a D-Arprovsc by:
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Prepared by:
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[J,fikf/f',P.E.
o lm Axline Carl li. Prochlich, P.E.
Enginee Ing Manager Q Project bigineer
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Carl 11. Prochilch, P.E. , g gg ,
Proicct Manager g,47,g, ggggy S
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d.b REVISION CONTROL SHEET imm: Ucensing Top 6calRoport - fJUTECH Foodwator pocour ur not eso. TVA017.0100 j s '
IJoulo Dypass Leakago Monitoring System -
Appendix: Results for Browns Ferry Unit 2 -
Ju .9 - December 1991 - TVA-17-100 ,
emurrnt. John K. Miwa / Consultant I ni'w s: _ //;//2
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embrme: James W. Axlino / Steff Enginoor urw.s: dN@[or- 7W/l-
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.i TABLE OF CollTEllTS EMIS 1.O IllTRODUCTION ,
D.4 2.0 dISCUSSIOli B.5 3.0 METl!OD OF ANALYSIS B.6 i
.i 4.0 LEAKAGE MollITORIllG DATA 5.O LEAKAGE MollITOR1!!G RESULTS B.S 6.0 FATIGUE USAGE FACTOR B.12 7.0 CONCLUSIollS B.13 8.0 REFEREllCES B.14 1
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1.O Jl{1'RQpUCTION The feedwater nozzles o.' Tennessee Valley Authority's Browns Ferry Unit 2 nuclear powgr plant were modified by 1 i
installing triple thermal sloove spargers. This modification was made to minimize thermal sloove bypass
' leakage, which 1 cads to rapid thermal cycling due to turbulent mizing of cold feedwater and hot reawetor water. Rapid thermal cycling has been identified as the major cause of observed cracking of feedwater nozzles, as
! discussed in NUREG-0619 (Reference 1).
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llUT2Cil provided Tennessee Valley Authteity with a leakage monitoring system (LMS) to monitor the eflectivness of the new thermal sleeves in preventing leakage (Reference 2). Data taken from the LMS during plant operation during the period of July 1991 through December 1991 were I sont to MUTECil (Reference 3) for analysis. The results of this analysis are presented in this report.
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2.0 piscUBDION The leakago monitoring system consists of four thermocouples attached to the optside of each of tho foudwater nozzles, throo on the bottom and ono.,on the top. Those thermocouplos monitor nozzio outsido
'bomparatura downstream of the t.hormel sloovo seal. The temperaturo at this location correlatos well with the amount of bypass lankage. If Icakago should occur, the cold foodwater should movo downwards as the hot reactor water mo3*cs upwards, causing the bottom of the nozzio to be cooled. The greater the leakage, the greator will be the decrease in temperature of the nozzle.
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3.0 ti E l llD D O P .. A H A L Y S I D The amount of feedwater leakage, L, in gallons per minute, is calculated from the f,ollowing equation:
' T o -T,,
L = 1. 5
- To-T 3 ,3, s'
Where:
f T, = llormalized nozzle temperature, derived from
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thermocouple readings 1 To a llormalized ncztle temperature corresponding to zero leakage T, ,3 = Normalized nozzle temperature corresponding to leakage of 1.5 gallons per minute i
Baued upon a finite element analysis of the feedwater nozzle configuration, To and T ,3 have been assigned values 3
of 0.57 and 0.12, respectively (Reference 4). A negative value of L has no meaning, and la assuned to indicate l
that no leakage has occurred.
l The normalized nozzle temperature, T,, is calculated from:
TT'C~T'"
T" = Tgx-T,y Where:
T,fe = Average of bot m three thermocouples Tg = Feedwater temperature Tg a Reactor Vater temperature The value of T,y is obtained from comparing the naturated i steam pressure with known tabulated values relating 8 absolute steam pressure to temperature (Reference 5).
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' The values found in the steam table have been approximated by the following equation:
T,y = Ao + As P)('
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Where P,y is the absolute steam pressure in the reactor 1 vessel. The values of Ao thru A were determined 7 numerically from the data in the utcam tabic and are shown in Table 3.0-1 below.
l Tabic 3.0-1 I STEAM TADJjE POLYNOMIAL COEFJICIENTH C. 1.031 x 10' C, ' 1.150x10' C, ,1.4 4 0 x 10' C, 1.7 56 x 10' C. -3.3 6 2 x 10' d
C. 2.070x 10' C. 5.273x10' C, 5.837x 10' C. 2.325x 10' NUTECH TVA-17-100 B.7 EN0tt 4EERS
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4.0 LEAKAGE HONITollTNG DATA Data for this analysis connisted of hourly readings of the thermocouple temperaturwa, reactor vencel pressures, and feedwater temperatures for each day during.,the period June 1, 1991 to Documber 31, 1991. Often, however, data here missing for one or more variables. In particular, no reactor vessel pressure or feedwater temperature data were received for the month of June. In addition, data were usually missing during periods of start-up and shut- I down. Thus it was not possible to evaluote leakage as a function of power level. The evaluation of leakage was performed only for essentially full power operations.
The analysis was performed for five to seven days for each month starting in July 1991 and ending December 1991. For each day selected, data were used corresponding to the 3:00, 9:00, 15:00, and 21:00 hours, although, in isolated instances, readings for other times were used. The four data values for those time points were averaged to obtain one value per day. Certain thermocouples were inoperative during portions of the j
evaluation period. When inoperative, these thermocouples were not used in computing the daily averages.
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l 5.0 LEAKAGE HONLTDAll{G REDULTD The results of this ovaluation are summarized in "'able 5.0-1 und are shown graphically,in Figure 5.0-1. Some leakage is indicated in nozzlo 4. llownver, the computed leakage is minor and sporadic. !!egativo valuen
', amount of in the table correspond to zero leakage. 11oto that this nozzle has only two functioning bottom thermocouplos.
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1 'iable 5. 0-1 cALcog Ten LEArAaB MTIE i
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Dev 2 3 4 5 6 i Date _ _ .
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July 5 186 0.95 0.84 0.68 0.71 0.76 -0.86 July 11 192 0.75 -0.63 -0.47 0.33 0.44 0.57 July 14 195 0.73 -0.63 0.45 0.37 0.39 0.60 July 22 203 -0.53 0.42 0.27 0.19 0.27 -0.42 l 207 _-043 0.28 0.18 0.12 0 20 0 30 Jutv 26 August 10 222 0.49 0.42 0.23 0.16 0.26 -0.36 August 15 227 0.41 -0.34 0.14 0.10 0.23 0.31 August 20 232 0.39 0.32 0.11 0.10 0.22 -0.29
'l August 25 237 0.33 -0.27 0.06 0.05 -0.17 0.23 Agust 30 242 0.3R 0. 3 ) 0.12 -009 0,20 -0.30 September 5 248 0.,13 0.22 0.06 0.01 0.09 0.25 Sepieneet 9 252 0.27 0.11 0.02 0.04. 0.08 -0.19 i
Septeneer 13 250 -0.27 0.18 0.01 0.04 0.09 0.19 Spetember 17 260 -0.66 -0.58 0.39 0.27 0.38 0.53 !
,l 0.23 0.34 0.42 September 22 265 -0.52 0.47 , 0.20 ;
September 27 270 0 33 0.28 0.12 ' O 01 .4 19 0,22 October 1 274 0.35 0.29 -0.11 0.01 0.19 0.23 7
October 6 279 0.35 0.29 0.12 0.01 0.19 0.24 284 -0.33 -0.28 0.03 0.02 0.19 0.21 Octobot 11 October 16 289 0.33 0.29 -0.10 0.01 0.21 -0.23 295 0.93 0.82 -0.65 -0.69 0.72 0.89 Octobet 22 October 26 299 0.37 -0.37 0.20 0.06 0.22 0.32 304 0.34 -026 0.11 0.03 0,19 -0.25 Octotier 31 305 0.34 0.26 -0.10 . 0.02 0.19 0.24 Novencer 1 312 0.31 0.78 0.11 ' O.02 -0.11 0.22 Noventer 8 317 0.33 0.29 0.09 0.01 0.18 0.22 No.endset 13 322 0.35 0.28 0.07 -0.04 0.18 0.23 Noveneet 18 Noveneer 23 327 -0.35 -0.29 0.07 -0.03 0.19 0,23 November 27 331 0 32 -0,27 -0 E_Qf1 - -017 0 19 345 0.65 -0,60 0.44 -0.29 -0.38 0.51 December 11 349 -0.33 0.29 0.14 0.00 0.19 0.20 December 15 353 0.33 0.29 0.14 0.01 -0.18 0.19 Decenter 19 361 0.33 0.30 -0.13 0.00 -0.19 -0 11 Decentet 27 366 0.34 0.29 0.1 J 0.00 0.19 0. .'O Deconht 31 ,
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014ozz]e 1 + tiozzle 2 oriozzle 3 A liozzle 4 X liozzle 5 v liozzle 6 Figure 5.0-1 C_h.L011 LATED LEAKAGE RATES v
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i . I'1 6.0 }'hTIGUE UDAGE FACTOR Figure 6.0-1 shows a plot of the amount of fatigue usage as a function of constant leakage over a 40-year period fdr the Browns Ferry stations (Reference 4). As the figure shows, the amount of fatigue usage is small for
'fatos below 1.0 gallons per minute, but increases substantially above this value. The fatigue usage factor after 40 years of constant leakage of 1.5 gpm is 0.b43 Table 5.0-1 shows that the maximum calculated leakage -
during the period June 1991 to December 1991 was less than 0.1 gallons per minute. Therefore, fatigue is not considered to be a problem during this evaluation period.
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' ' ' i 0-0 0.25 0.5 0.75 1 1.2 5 1. 5 LEAKAGE (GPM) d i
Figure 6.0-1 40 YEAR FATIGUR USAGE PACTOR8 AT CONSTANT LEAEAGE (Reference 4)
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9 The data from the leakage monitoring z.ystem showed that one of the triple sleeve spargers may have had a sinall amount of Icakage during the period between June 1991 and '
December 1991. Itowever, the leakage was miniscule (<0.1 6pm) and sporadic, and thus poses no concern in terns of fatigue crack growth. Continued teroperature inonitoring of the outside surface of the feedwater nozzles is i irnportant to further confirm this hypothesis and to ensure that any future leakage will be detected.
Data should be taken on an hourly basis when the plant is in start-up or shut-down, and bi-weekly when the plant is at or near full power. This data should be plotteo versus time, to determine trends of thermal sleeve seal ~
performance. Step changes in the calculated Icakage rate may be an indication of a malfunction in the LMS.
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8.0 REFERENCEB
- 1. NUREG-0619, "BWR Feedwater Hozzle and Control Rod Drive Return Line Nozzle Cracking", April 1980.
- 2. " Licensing Topical Report - HUTECl! Feedwater Nozzle Ecakage Monitoring System, Rev. O, dated October 1982, File No. 165.1501.001P.
- 3. Unit 1 Leakage Monitoring System and Main Steam / Reactor Feedwater Pressure and Temperature, data June 1991 through December 1991, File No. 165.1501.0015.
- 4. " Structural Integrity Assessment of Browns Ferry Foodwater Nozzles", Rev. O, Document No. XTV-02-008, File No. 165.1501.0017.
- 5. D.M. Himmelblau. Basic Principles and Calculations in Chemical Enaineerinu, Third Edition, p 473-475.
Prentice-Hill. Inc.
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