ML20092E308
| ML20092E308 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 09/08/1995 |
| From: | Saccomando D COMMONWEALTH EDISON CO. |
| To: | NRC (Affiliation Not Assigned), NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9509150150 | |
| Download: ML20092E308 (6) | |
Text
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Commonwealth Etlimn Comguny I HM) Opm Place Dow nets Grme, 11. 4)515 9
September 8,1995 i
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn: Document Control Desk
Subject:
Additional Information Regarding Commonwealth Edison Company's Request to Increase the Interim Plugging Criteria for Byron Unit 1 and Braidwood Unit 1 NRC Docket Numbers 50-454 and 50-456
Reference:
September 7,1995, Commonwealth Edison Company Meeting with the Nuclear Regulatory Commission Regarding the Hydrodynamic Load Model At the reference meeting Commonwealth Edison Company (Comed) discussed with the Nuclear Regulatory Commission (NRC) the hydrodynamic load models that were submitted to the Staffin support of Byron and Braidwood's request to increase the interim plugging criteria (IPC) to 3 volts. During this meeting the Staff requested more information regarding the calculation of crossflow resistance in the Comed RELAP model. Enclosed is the requested information.
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O NRC Document Control Desk September 8,1995 If you have any questions concerning this, please contact this office.
Sincerely, 1
< Denise h. acc ando Nuclear Licensmg Administrator cc:
D. Lynch, Senior Project Manager-NRR R. Assa, Braidwood Project Manager-NRR G. Dick, Byron Project Manager-NRR S. Ray, Senior Resident Inspector-Braidwood H. Peterson, Senior Resident Inspector-Byron H. Miller, Regional Administrator-RIII Office of Nuclear Safety-IDNS i
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i Estimation of Crossflow Resistance Terms for RELAP5 Model A review of the Westinghouse TRANFLO input / output indicated that the TRANFLO model employed a special connector type at several locations in the D4 model. This connector type is a crossflow junction, and employs a correlation to determine the flow l
resistance due to crossflow through the tubes. This application leads to a variable flow j
resistance being applied that has a functional dependence on mass flow rate through the connection. This crossflow model is applied at the TRANFLO connectors 35,36, 39,47,48,52,54,56, and 58. Physically these areas correspond to the entrance from the downcomer to the tube bundle, the preheater areas, and the curved section of the U-tubes near the top of the bundle. To approximate this resistance in RELAP, the Zukauskas correlation as presented in " Nuclear Systems I" Kazimi/Todreas_on page 390 was used. This provided an independent check of the pressure drops developed by TRANFLO.
t The method of implementing the crossflow resistance was to take the pressure drop
. predicted by the correlation and convert it into an equivalent K value to be added to a junction local loss coefficient (for a junction near the crossflow location). To facilitate i
comparison with TRANFLO generated values, the flow rates from a TRANFLO output j
at.57 seconds were used, along with the tube pitch, crossflow length and area, and j
tube size, also taken from the input " echo" of the TRANFLO results. This approach
~
provided a crossflow resistance based on reasonably high flow rates. Since this results in the lowest K-value, due to the dependence of K value on Reynolds number (for the l
Zukauskas correlation, the f factor increases with decreasing Re), it represents a conservative estimate of the crossflow resistance effects.
The actual values used were calculated via a MATHCAD file. This file is attached on the following pages. As can be seen, the Zukauskas correlation compares favorably with the TRANFLO calculated pressure drops. As stated above, the most appropriate way to handle this effect would be to employ a K-value that varied with the flow rate.
i The use of a single point value derived at high Reynolds number flows will provide a l
reasonable prediction of the crossflow effects, but remain on the conservative side by i
predicting less pressure drop at lower flowrates.
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CIlculation of Crossflow R:sist nca Term Th2 crossflow rcsistines of the tube bundla nMds to be accounted for, particularly at the U-bend portion of the tubes. This will be handled by calculating a K value to be added to the separator inlet loss coefficient, using a correlation by Zukauskas obtained from p390 of " Nuclear Systems I" j
Kazimi/Todreas. The values for crossflow length and area are taken from the TRANFLO output previously provided.
g := 32.2 p : = 45.5 Density of fluid 4
p := 19.710 g viscosity of sat liq at 1000 psi D ::.1234 hydraulic dia from TRANFLO INPUT O := 11000 Mass flux from TRANFLO Output at.57 sec 36.39 S :=.0885 S =1.416 Tube lattice aspect pitch over dia
.751 l
12 3 1
J Re::G-s Reynolds number needed to obtain f Re = 5.88 10 1
~1 f :: 0.24 f-factor from figure Z: 1 square lattice, no Z correction a
N ': 4.25 number of rows of tubes, estimate by crossflowjunction length / pitch
.0885 4
4 I"
DP::
Z DP at estimated flow 2 p l44 g DP = 2.496 At a flow of 11000 lb/sec the expected dp is about 2.5 psi. This compares with the TRANFLO generated dp of 2.84 at.57 seconds. Now need to convert this dp into a K value to be added to the separator inlet.
- I A gp := 22.01 -
2 DP A 144 g 2.p wp 2
W K = 4.216 i
This is added to the losses associated with the junction between 102 and 135-5.
Simil:rly f;r the entr:nca 12 tha tube bundla g := 32 3 p := 45.5
- = 19.7 10~ 7. g D
- =.1234 0 := #
l.559 Re:=GE Re = 3.244 10' p
S ;=.08 S = I.416 1 -
i12j i
f : = 0.24 Z := 1 1
N := 1.107
.0885 2
MO
. pp =
Z 2 pl44 g DP = 19.788 At a flow of 2600 lb/sec the expected dp is about 19.7 psl. This compares with the TRANFLO generated dp of 18 at.57 seconds. Now need to convert this dp into a K value to be added to the downcomer infet.
in
- 5 7350 A
2 W := 2600 DP A in 'I44'8 'P 2
2 W
K = 40.633 This is being added to the junction between the downcomer and the entrance regions to the tube region 112-5 to 100.
T e.
Similarly for connector 52
- g := 32.2 9 := 45.5 p := 19.710'7g D :=.1234 -
830 O:=
4.2478 Re := G E Re = 3.801 10 5
p S :=. 8 S = 1.416 l
l (12j f := 0.24 N '= 4.0729
.0885 Z := 1 2
O DP :=
Z 2.p l44.g DP = 0.999 i
' At a flow of 830 lb/sec the expected dp is about 1 psi. This compares with the TRANFLO generated dp of 1.038 at.57 seconds. Now need to convert this dp into a K value to be added to the preheater junctions.
4 Ain := 4.2478 i
W := 830 DP Ain 144 g 2 p g
K = 11.045 This value will be used for connector 56 as well as connector 54/58 due to similarity.in the RELAP model these junctions are in volume 133 and the entrance to 133.
.