ML19319D144
| ML19319D144 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 01/24/1977 |
| From: | Suhrke K BABCOCK & WILCOX CO. |
| To: | Varga S Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8003130712 | |
| Download: ML19319D144 (6) | |
Text
c r; uD U.s. NUCLE An EEGULAToRY Cowe SSICN l DOCKET M
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!!r Stolz J Fla Power Corp DATE oF ooCUMgg St Petersburg, Fla DATE RECEIVE o 1-29-77 J T Rodgers
_LETTrn ONoronizEn enor iseuT reau NuusEn or ComiEs nECEivED
. jo::f GIN AL 8 UNC LAS$1FIE D DCorv 33 g DESCRi? Tion ENCLOSURE Ltr te 1-21-77 meeting..... notarized 1-27-17 Info relat ive t'o B&W topical BAU-10104A
.......trans the following:
'.'B&W's ECCS Evaluation Model" as revised
.....ad. s ing that it pertains to Crystal River....(40 Cys enc 1 rec'd) 2p 10p i
PLANT NAME:
Crystal River #3
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P.O. Box 1260. Lp:2.tura. Va. 24',C5 Telep$ione:(804)3s4 5111 January 24, 1977 Mr. S. A. Varga, utief LWR Branch #4 Division of Project Management Office of Nucicar Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555 f
Reference:
D. F. Ross December 2, 1976 Ictter to K. E. Suhrke on B4W ECCS Evaluation Model.
.)
Dear Mr. Varga:
A revision to B5W's ECCS Evaluation Model is proposed herein which addresses the NRC Staff concern regarding the use of a nucleate boiling heat transfer correlation during blowdoun af ter critical heat flux (CHF) is first predicted.
This proposed revision supersedes the revision submitted in our letter of Decemaer 16, 1976 from K. E. Suhrke to S. A. Varga.
We believe this revision adequately addresses
-NRC concernd with the information provided in.the December 16, 191; submittal.
Your expeditious review and approval is requested to ensure an orderly progression of licensing and startup activities in plants utilizing the B6W NSS.
Following approval, we will incorporate the change into Topical Report BAW-10104A, Rev. 1, "B6W's ECCS Evaluation Model."
We would be willing to meet with you to discuss this change at your convenience.
If you.have additional questions, pledsc contact H. A. Bailey of my staf.
g.
3 Very truly yours, j
~
~%.
Kenneth E. Suhrke I
Manager, Licensing 9
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?.oltan it. Ron:toeny (NRC) h T. 11. Novah (.'!RC) -
J. Angelo (NRC) 1 D
J. F. Stol: (NRC)
R. B. Borsum (BGW)
.j lho Datrock & Wilcoi Cem;uny / Cot.iblished 1667
t-1.
Introduction It has been determined by.fiRC Staff that the post-CHF heat transfer calculations performed in the BDI THETA 6F computer code r6ay not be consistent with the requirements set orth in Appendix K of 10 CFR 50.
In particular, the calculation of local heat transfer by nucleate boiling subsequent to the
- occurrence of CHF as is performed in THETA 6F was considered questionable.
An investigation was undertaken at BMI tc. establish an alternate post-CHF heat transfer model for implementation in the THETA code.
The scope of resulting nodifications to be proposed includes both revisions of the post-CHF switching logic and eliminatiori of the post-CHF return to nucleate boiling.
I,(
. ~.. '
- v.
2.
THETA Code 1,4odification
.. According to BAW-10094 (p. 26-4):
r
. "If departure from nucleate boiling (DNB) has been calculated to have
. occurred for a particular axial node, both transition flow boiling and nucleate bailing will be. calculated; the lower heat flux is useEl."
Examination of the
~
THETA 6F switching logic showed that the,ccmparison of transition. boiling heat flux to nucleate boiling heat flux was not made.
Rather, referring to Figure 1, 2'
a trial value of.the heat flux was calculated for a particular axial noda according to the fluid void fraction.
l for: 01ai.80 nucleate boiling (mode 2)
.h
.80 < a <.90 interpolation between nucleate boiling (mode 2) and forcedconvectionvaporization(mode 3) 1
. 90 l a < l.0
' forced convecticn vaporization If the trial heat flux was less than CHF, the trial value was taken as the
-l
' local heat flux.
If the trial value exceeded CHF, transition boiling (~.ede 4)
-]
. heat flux was used.
To correct this, the post-CI:F switching logic was r: edified so th'at subsequent to CHF at a particular axial node, regressica on the h
, transition b' oiling curve is restricted to heat fluxes (1) less than CMF for
,1
" loc'al fluid void fractions less than 80 percent, (2) less than the heat flux
. calculated by interpolation between nuciente boiling (meda 2) and forced convection vaporization (mode 2) for local void fractions between 80 cercent l
4
T
~3-4.
Spectrum Studies The validity of the Spectrum Analysis results and trends reported in References 3 and 4 was demonstrated by re-analyzing the worst soectrum case for each of,these two plant categories.
The results of this're-analysis are presented in Table 2.
For both cases, the hot spot peak clad temperature
. increased less than 20 F.
Since the worst spectrum cases were reanalyzed, th.e peak clad temperature increases should provide an coper bound for all other spectrum cases.
Hence, the spectrum results and trends in References 3 and 4 are still valid.
Furthermore, since the spectrum trends in Reference 2 are basically the same as those in References 3 and 4 and since the THETA analyses for the worst spectrum cases in References 2,3, dd 4 all proceed in a similar nanner, the spe:trum results :and these presented in Reference 2 should also still be valid.
5.
LOCA Limits Studies The final modification (Case 5) presented in Reference 1 showed
- no significant impact on the LOCA limits presented in References 2,3, and 4.
TXis lack of impact is due to the fact than in these base LOCA limit cases
-(those presented in References 2,3, and 4) minimal time is spent in transition
--boiling and oscillating between transition and nucleate boilina type heat fluxes.
By approximately 0.5s the ruptured and the hot spot nodes are locked
" int _o film and/or film pool boiling by virtue of the 300 F temperature difference
~
criteria.
Hence, for the THETA code modification presented herein,(Section 2),
eno impact on the LOCA limits should be evidenced.
During the course of this THETA code modification program it was determined v
that by evaluating the ruptured and unruptured node temperature differer.ces j
dbdified - Tbasecase) nce the forced convection to superheated ster.n coolir.g Mode (code 8) was established (sl3s) an accurate determination of the final
'cffect on peak clad temperatures,can be made.
Of fact, the Ats at approximately
'13s translate one to one relative to the peak clad temperatures of the base cases.
Use of the method allows an accurate deternination of the ruptured and unruptured node peak clad temperatures by executing cases on acdificd THETA versions to only 15s.
This method is restricted by assuring that significtnt 4
1
bqiR81KK~E ilDEAT. 'l'iA::S1'I'.R 1:0DF.S Y
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LL 5
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7
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1 e
Temp.
D u%
Tur, -- Trin;g a
==
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?! ode.1: -Forced Convection to Liquid tiode 2:
Nucleate Eoiling
't
' Mode 3: Forced Convection Vaporization Mode 4; Flow Transition Boiling Mode 5:
Flow Film Boiling Mode 7:
Fool Film Boiling ibde 8:
Forced Convection to Gas L
Hode.10: Reflood Cooling
.i g
S.
e h
- - - - 3 TABLE 1
.CA. S.E C0 GARIS. OlI Case 1 '.
2 Version.
Original 6F THETA 6 CY=1 Post-CHF Old llew Switch Logic (ifodi5"or3)
(Mo'de4)
~~
~
Returnable Modes
~
-from Mode 4 - -
- Mode 2-and.
Mode 5 or 7 -
~~
O Reak T F 1746'
~;'
181g
~
Ruptured flode (Base)
(+67 F)
~
0 Peak T F 1992 202g Unruptured !!ade
-' (Base) ' -
(+31 F) 4 g
C
- 4.
e e
o e
L
~
L
y
G=90.@s
[
Tengra ture:. 4 Elevation
[Tsic81 Ft.
IMde Case Hodified 1
. ~g, g 1
1316 1317
+1 2
1531 1531 0
3 1645 1645 0
MV.10103 2
Clad 4(ruptured) 1530 1530 0
Fef. 02 5(hot spot)
M70 1670*
0 6
1645 1645 0
7 1544 1547
+3 1
1402 1402 0
2 1667 1667 0
3 1024 1824 0
Fuel 4
1950 1950 0
5 1872
.1871
-1 6
1847 1847 0
7 1757 1761
+4 1
2 1659 1658 0
1687 1687 0
3(ruptured) 1693 1698 0
.__------6 Clad 4(hot spot) 1698 1699
+1 5
1691 1692.
+1 6
1675 1676
+1 7
1644 1644 0
1 1855 1855 0
2 1885 1885 0
3 1893 1893 0
Fuel 4
18E5 1883 ~
42 5-1871 1872
+1 6
1843 1844
+1 7s 1792 1792 0
1-1291 1291 0
2 1591 1591 0
3 1763 1764
+1 BN4-10105, 2
Clad 4(ruptured) 1843 1847
-1 P.cv. 01 5(hotspot) 1832 1832 0
6 1751 1752
. +1 7
1685 1689
+3 1
1373
- 1373 0
2-1688 1688 0
3 1859 1869 0
Feel 4
1953 1958 0
5 1933 1930 0
6 1854 1854 0
7 1785 1789
+3 1
1553 1550
+7 2
1651 1651 0
3 1657 1559
+2 6
Cird 4
1674 1676
+2 6
1652 1654
+2-5 1655-1563
+2
' " ~
7-1625 1025 0
1 1716 1725
+9 2
10 0 1841
+1 3'
1855 1857 42 s
Teci 4
1057 1050
+3 5
1840 1842 42 0
1013 1816
+3 7
1705 17f6
+1 s
-1
,3
..c
.