ML20035H030
| ML20035H030 | |
| Person / Time | |
|---|---|
| Site: | 05200001 |
| Issue date: | 04/19/1993 |
| From: | Fox J GENERAL ELECTRIC CO. |
| To: | Poslusny C Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9305030001 | |
| Download: ML20035H030 (12) | |
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GE Nuclear Energy
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' % e s,.en v 5e jzg_ CA id 17 o
e April 19,1993 Docket No. STN 52-001 i
d Chet Poslusny, Senior Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal Office of the Nuclear Reactor Regulation
Subject:
Submittal Supporting Accelerated ABWR Review Schedule - Chapter 3, -
DFSER Open Items 3.93.1-2 and 14.133.5.10-1, Thermal Striping
Dear Chet:
E Attachment A addresses the subject two DFSERitems for close-out.
Please provide copies of this transmittal to Shou Hou, Dave Terao and Jim Brammer.
Sincerely,
.AW ek Fox Advanced Reactor Programs cc: Giuliano DeGrassi(BNL)
Norman Fletcher (DOE) i Maryann Herzog (GE)
Henry Hwang (GE)
Son Ninh (NRC) l Nil Patel(GE)
Ed Swain (GE)
Go JPJ3-95 i
9305030001 930419 3
PDR ADDCK 05200001 l
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i ATTACHMENT A April 19,1993 DFSER OPEN ITEMS 3.9.3.1-2 & 14.1.3.3.5.10-1 FATIGUE DUE TO TIIERMAL STRIPING EFFECTS i
Subject:
ABWR Piping DFSER Open Items 14.1.3.3.5.10-1, ITAAC-Methodology to Address Thermal Striping, and 3.9.3.1-2, Thermal Stratification Load Definition
Purpose:
This attachment summarizes the evaluation of the thermal striping effects performed for the ABWR feedwater piping. It is shown that the thermal-striping fatigue effects are negligible in the ABWR feedwater piping.
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References:
(1) GE I)rawing 103E1414,"Feedwater Press / Temp Cycle Chart and Load Set" e
(2) " Fatigue of 131FBR Piping Due to Flow Stratification," by W.S. Woodward, j
Westinghouse Electric Corp.
(3) " Development of a Thermal Striping Spectrum fbr use in Evaluating Pressurizer Surge Line Fatigue", by A.F.
Deardorff,
Structural Integnty e
Associates, Inc.; W. Hafner and L Wolf, Battelle;J.H. Kim, EPRI.
i (4) NEDO-21821-A,1980. " Boiling Water Reactor Feedwater Nozzle /Sparger Final l
Report," by H.Watenabe.
1.0 BACKGROUND
Thermal stratification can occur in the ABWR feedwater piping as described in ABWR SSAR Subsection 3.9.3.1. Thermal stratification is specified as a feedwater piping system design load. The thermal stratification temperatures and number of occurrences are specified in Reference 1.
Under stratified flow conditions, it has been reported in References 2 and 3 that a i
relatively thin dynamic interface region exists, which oscillates in a wave pattern.
This results in undulation in the hot-to-cold interface region which produces thermal striping on the inside of the pipe wall. This thermal striping phenomenon has been observed in LMFBR water model flow tests performed by Westinghouse (Reference 2) i as well as in experimental studies performed at the German HDR test facility (Reference 3).
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These flow tests have indicated that the frequency of oscillation can range between 0.1 and 3 hz. Reference 2 states that " Fifteen percent of this total measured less than 10 percent of the fluid stratification AT. Seventy percent of the cycles were less than thirty-five percent of the fluid AT, while only two percent measured less than sixty
+
percent of the fluid AT. Thus only a small percent of the total cycles approached the maximum amplitude."
t Thermal striping stresses are the result of differences between the pipe inside surface temperatures which vary with time due to the interface oscillation and the average through-wall temperatures. Provided in this attachment is a sununary of the results of the fecchvater piping thermal striping stress analysis. These results confirm that the J
feedwater thermal striping fatigue usage is minimal and therefore, thermal striping fatigue effects are negligible per the ASME Section 111 Code fatigue evaluation requirements.
2.0 THERMAL STRIPING EVALUATION FOR FEEDWATER HEADER PIPE 2.1 Description i
The operating conditions that result in stratification in the AllWR feedwater header are different from the conditions reported in References 2 and 3. Stratification in the header is worst when the feedwater line is filled with hot water and colder water is introduced at a low (2.1%) flow rate. Striping during this period,ifit exists at all, will not be sustained for the following reason: As the hot water is flushed from the piping, the hot-to-cold interface will move upward, so the points at the pipe surfaces that could be subjected to temperature fluctuations caused by striping are constantly changing.
This prevents a large number of temperature cycles occurring at any one point on the l
pipe surface. Further, the interface between the hot and cold water will not remain sharp along the header; the diffusion zone at the interface will continually widen because of heat transfer and turbulence between the hot and cold fluids.
i However, calculations summarized in Section 2.2 through 2.3 show that stresses at the pipe wall due to striping are well below the metal endurance limit, and are therefore negligible, even when these very conservative assumptions are made:
I a) The elevation of the stratification interface remains at the same elevation in the feedwater header for kmg periods of time.
b) The step change in temperature at the interface is assumed to be equal to the maximum difference in temperature between the hot and cold fluids.
c) The interface between the hot and cold fluids is assumed to be sharp.
d) The frequency of striping at the interface is assumed to be the frequency that results in the maximum thermal stress at the pipe wall.
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j 2.2 Feedwater Line Header Striping Stress Evaluations The maximum thermal stratification ATin the horizontal feedwater header pipe inside the containment is 120 F, per Reference 1. This is the maximum temperature l
difference between the top and the bottom of the pipe. Reference 3 indicates that the j
striping temperature range is less than 60% of the top and bottom pipe stratification AT.
l In this analysis,it is conservatively assumed to be 120 F.
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The striping frequency can be between 0.1 to 3 Hz. Based on Reference 3 test data, l
striping occurs at a combination of all frequencies between 0.1 to 3 Hz (period 10 see to j
0.33 sec). Because the pipe inside surface is assumed to be subject to a step change in l
temperature, the longer the period is assumed, the higher the stress will be. The i
t reason is that during very short period of a cycle the metal temperature does not have -
enough time to react before the temperature is reversed. Therefore, the worst period of i'
10 second (0.1 Hz) is assumed in the calculation. Another case with 0.5 Hz (2 sec period) is also considered to show the difference in the results.
The surface heat transfer coefficient (hc) during striping is calculated as follows:
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Flow rate
= 2.1% rated flow i
= 420 gpm (use 600 gpm for conservatism)
Pipe inside diameter = 19.25" i
Water temperature
= 420 F, assumed maximum for hc calculation Viscosity
= 0.164E-5 ft-sq/sec k
= 0.375 btu /hr ft F 4
V
= 0.66 ft/sec Re
= 0.647E6 l
Pr
= 0.907 I
hc
= 0.023 (k/D)(Re)**0.8 (Pr)**0.333 (Eq.1)
= 232 btu /hr ft-sq F The maximum top layer temperature is 270* F. Assuming this temperature, the heat j
transfer coeflicient is calculated to be as follows:
c Viscosity
= 0.249E-5 ft-sq/sec k
= 0.396 btu /hr ft F Re
= 0.425E6 Pr
=1.342 V
= Of>6 ft/sec hc
= 0.023 (k/D)(Re)**0.8 (Pr)**0.333
= 199 btu /hr ft-sq F
)
It will be conservative to use hc=232 btu /hr ft4q F for temperature gradient analysis.
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2.3 Results of Calculations for Header Pipe The heat transfer coefIicient was input to a heat transfer program to compute the temperature gradient time histories. The heat transfer program is a finite difference 1
program. The pipe wall thickness was divided into 10 elements to obtain accurate temperature gradients. The time step is 0.00549 minutes. The print out times are set.
d by the program.
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The temperature gradient time histories at the pipe inside surface, as it responds to striping, for each case of striping period, are tabulated in Tables 1 and 2. The combined stress due to DT1 and DT2 (linear and nonlinear components of temperature gradient, respectively) is as follows.
i Stress K3 E(alpha)DTl/(2(1-0.3)) + E(alpha)DT2/(1-0.3)
=
1.0 x 27.9 x (6.41) x DT1/1.4 + 27.9 x (6.41) x DT2/0.7 l
=
127.7 DTl + 255.5 DT2 (Eq.2) i
=
For 10 sec (0.1 Hz) case, the stress reaches its maximum at 2205 psi as indicated by Table 1. This maximum alternating stress is below the endurance limit of 10000 psi for carbon steel. Table 2 shows that,if the period is 2 sec (0.5 Hz), the maximum alternating stress is only 1106 psi.
l This confirms that even if striping exists under the assumed conservative conditions,it will not cause any significant high-cycle fatigue efTect in the header pipe, j
3.0 THERMAL STRIPING EVALUATION AT FEEDWATER NO7ZLE 3.1 Description l
i Thermal stratification in the AllWR feedwater pipe at the RPV nozzle is defined in l
Reference 1. The worst stratification occurs when thermal sleeve and sparger are filled with 270 F water and cooler make up water is introduced to the RPV at a low l
(2.1%) feedwater flow rate. Stratification is caused by transfer of heat from the RPV into the cooler water in the thermal sleeve and sparger. This heat transfer causes a
thermally driven convective pattern in the horizontal pipe section" which does not create striping as easily as the hot and cold stream flow.
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The condition identified in Reference 4 is different from the conditions reported in References 2 and 3. There is no back flow of hot RPV water into the system. Instead there is only gradual heating of the fluid in the feedwater pipe by the thermally driven convection patterns.
Striping during this period, ifit exists at all,is not significant for the following reasons:
A). The hot to cold interface does not remain at the same elevation in the pipe at the nozzle. As the heated water in the thermal sleeve and sparger flows by convection into the top of the feedwater pipe, the hot to cold interface will continuously move downward until a surge of cooler feedwater flow purges the hot water from the piping.
The process will then start again. As a result, the points at the pipe surfaces that could 1
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be subjected to temperature fluctuations caused by striping, are constantly changing.
This prevents the accumulation of a large number of temperature cycles at any one point on the pipe surface.
B) As the convection driven hot water Dows into the feedwater pipe the initial j
temperature difference between the hot and cold water will be small and will gradually increase. Only at the end of the process will temperatures differences reach maximum values.
i C) The interface between the hot and cold water is not a step change. The convection driven flow of hot water into the feedwater pipe will result in a relatively wide diffusion zone at the interface. This diffusion zone will continually widen because of heat transfer and turbulence between the hot and cooler fluids.
D) Calculations summarized in section 3.2 show stresses at the pipe wall due to striping are well below the metal endurance limit, and are therefore negligible, even when the very conservative assumptions listed in Section 2.1 are made.
i 3.2 Striping Stress Evaluations I
Although the possibility of striping at the nozzle is small as indicated in paragraph 3.1, a study similiar to the one performed on the header pipe has been made for the piping at the feedwater nozzle. The worst possible striping temperature of 282 F was assumed per Reference 1.
)
The analysis procedures used in the header striping calculations are also used for the l
pipe at the nozzle. The heat transfer coefficient used is 270 btu /hr-ft sq-F instead of 232 l
for the header.
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The results of the calculations are tabulated in Tables 3 and 4. Tabic 3 provides the j
results of the evaluation for a thermal striping frequency of 0.1 Hz. For 0.1 Hz case, the i
stress reaches maximum at 5391 psi. This maximum alternating stress is below the endurance limit of 10000 psi for carbon steel. Table 4 shows that if the period is 2 sec i
(0.5 Hz), the maximum alternating stress is only 2831 psi.
I Another case with a higher heat transfer coeflicient has also been studied. The heat i
transfer coefficient is assumed to be 540 bru/hr-ft sq-F, which is two times the value used in the calculations for Tables 3 and 4. The striping temperature range is assumed l
l to be 60% of the stratification AT. This assumption is based on Reference 2 and is discussed further in Paragraph 1.0. The period is conservatively assumed to be 10 j
seconds (0.1 Hz).The results of the analysis showed that the maximum alternating 4
stress is 5517 psi. The stress is still below the endurance limit of the material.
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4.0 CONCLUSION
S Evaluations for the worst postulated thermal striping conditions have been performed.
Consenative values of striping temperatures and frequencies of oscillation were used J
in the calculations. These evaluation results confinn that thermal striping fatigue is insignificant. Therefore,it is concluded that thermal striping need not be considered as a design load for ABWR feedwater pipmg.
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j TABLE 1. STRIPING STRESSES IN FEEDWATER IIEADER (Period 10 sec,120 F striping, hc=232 btu /br ft-sq F) l 1
i Time DTl DT2 STRESS (min)
F F
(Fo. 2) l 0.0 0.0 0.0 0
0.011 4.634 -2.638 -751 i
0.022 -1.788 -3.382 -1086 0.027 -2.337 -3.632 -1219 i
0.038 -3.399 -4.022 -1453 0.049 -4.425 -4.324 -1660 1
0.06 -5.427 -1.576 -1852 0.071 -6.408 -4.796 -2032 0.082 -7.372 -4.994 -2205 (max) 0.087 -7.848 -2.026 -1511 0.098 -5.249 3.433 205 0.115 -2.123 4.889 972 0.131 0.486 5.428 1440 0.148 2.728 5.612 1772 i
0.169 5.273 1.81 1129 I
0.18 2.891 -2.939 -379 0.191 0.942 -4.109 -924 0.202 -0.756 -4.711 -1293 i
0.219 -2.969 -5.14 -1683 j
0.24 -5.452 -5.303 -2039
.l 0.262 -4.024 3.234 310 l
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0.279 -1.029 4.726 1070
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0.301 2.205 5.383 1647 1
0.322 4.856 5.521 2019 0.339 4.709 -2.012 87 1
0.361. 0.672 -4.543 -10G9 i
0.383 -2.454 -5.215 -1636 l
0.399 -4.417 -5.355 -1921 0.421 -6.G16 -1.95 -1339 O.443 -2.05 4.373 850 0.459 0.597 5.152 1384 0.481 3.532 5.494 1844 0.497 5.396 5.525 2089 0.552 -2.478 -5.204 -1637
[
0.601 -2f>03 3.874 653 j
0.65 4.49 5.483 1963 Ofi99 1.285 -4.604 -1006 1:
0.749 -5.161 -5.424 -2033
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O.798 2.039 5.198 1579 i
l-0.831 5.897 5.443 213]
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p TABLE 2 STRIPING STRESSES IN FEEDWATER HEADER (Period 2 sec,120 F striping, hc=232 blu/hr ft-sq F)
Time DTI DT2 STRFSS (min)
F F
Wo. 2) 0.0 0.0 0.0 0
0.011 -0.714 -3.199 903 0.022 -2.24 0.929
-19 0.027 -1.135 2.792 565 0.038 0.706 -1.226 -222 0.049 -1.208 -3.75 -1106 (max) 0.06 -0.933 2.952 631 0.071 0.88 -1.128
-175 0.082 -1.054 -3.688 -1071 0.087 -1.875 1.185 63 0.098 0.144 3.763 974 0.115 -0.939 -3.674 -1052 0.131 0.245 3.768 988
-0.148 -0.851 -3.675 -1042 0.164 0.323 3.765 997 15
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' TABLE 3 STRIPING STRESSES AT FEEDWATER NOZ71 E i
(Period 10 sec,282 F striping, hc=270 btu /hr ft-sq F)
' l Time DTI DT2. STRESS l
(mini F
F Wo.2) 1 0.0 0.0 0.0 0
0.01 -5.549 -8.352 -2826 0.021 -10.902 -9.182 -3717
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0.029 -14.393 -9.238 -4174 0.04 -18.003 -9.055 -4586 i
0.05 -20.932 -8.775 -4887 l
-0.061 -23.305 -8.479 -5113 0.069 -24.869 -8.251 -5254 0.08 -26.476 -7.988 -5391 (max) 0.09 -19.148 8.129 -367 j
0.101 -8.913 10.676 1580 0.115 2.029 11.073 3070 0.13 10.24 10.583 3989 0.151 18.588 9.665 4816 0.17 20.536 4.274 3694 0.18 10.0M
-9.1
-1033 0.191-L993 -10.168 -2330 l
0.201 -4.518 -10.225 -3171 l
0.22 -13.362 -9.62 -4140 0.241 -20.047 -8.816 -4785 0.26 -12.993 8.495 508 0.281 3.284 10.748 3147 0.299 13.073 10.232 4259 i
0.339 18.991 -5.95 901 0.32 20.472 9.391 4985 0.36 1.114 -10.332 -2483 O.379 -9A8 -10.017 -3748 0.4 -17A98 4).19 -4557 O.421 -16.847 6.238
-555 0.44 -0.554 10.57 2614 0.461 11.357 10.317 4063 O.48 18.628 9.574 4798 0.501 24.095 5.291 4404 0.551 -12.334 -9.817 -4060 O.601 -5.668 10.163 1862 0.649 19.037 9.491 4828 l
0.699 --3.084 -10A04 -3034 0.75 -22.156 -8.633 -5007 0.8 12.816 10.15 4206 0.833 23.352 8.864 5217 I
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TABLE 4 STRIPING STRESSES AT FEEDWATER NOZZLE l
. (Period 2 sec. 282 F striping, hc=270 btu /hr R-sq F) j Time DTl DT2 STRESS (min)
F F
(Eo.2) l f
0.0 0.0 0.0 0
0.01 -5.549 4.352 -2826 0.021 -4.937 5.504 771 0.029 1.3 8.475-2318 0.04 -1.168 -6.449 -1786
-l 0.05 -7.494 -2.068 -1477 l
0.061 1.031 8.122 2194 0.069 3.008 -3.678
-559 0.08 -4.362 -8.212 -2 640 0.09 -1.303 6.752 1550 l
0.101 5.507 1.862 1172 0.115 -5.158 -8.567 -2831 (max)
'l 0.13 3.328 8.438 2566 l
0.151 -6.113 -1.892 -1257 f
0.165 4.769 8.72 2821 (max) y l
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