ML20005A226
| ML20005A226 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 06/22/1981 |
| From: | Groce R Maine Yankee |
| To: | Carter J Office of Nuclear Reactor Regulation |
| References | |
| FMY-81-95, NUDOCS 8106300069 | |
| Download: ML20005A226 (9) | |
Text
Dn, mAlllEM HAllHEE 'ATOMWPUWEF:COMPAlW *
,e,,wonCes,ennoAo ggpj ENGINEERING OFFICE FRAMINGH AM, M ASSACHUSETTS 017o1
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June 22, 1981
%' ~, 2 O 2.C.2.1 FMY 81-95 United States Nuclear Regulatory Commission b(v3 Wash ington, D. C.
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Attention:
Of fice of Nuclear Reactor Regulation Division of Systems Integration E
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Reactor Systems Branch L
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Mr. James Carter MAIL STOP Pll30 A -
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Subject:
Revised Maine Yankee RETRAN Input Deck N
gg\\'b' Re ferences :
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License No. DPR-36 (Docket No. 50-309) 2)
MYAPC letter to USNRC (FMY81-21), " Maine Yankee RETRAN Input Deck",
dated February 24, 1981.
3)
MYAPC letter to USNRC (FMY 81-71), " Maine Yankee RETRAN Benchmark Analysis, dated May 1, 1981.
Dear Sir:
A revised Maine Yankee RETRAN input deck accompanies th is letter.
'Ih is deck includes corrections and modifications made during the benchmarking process, and is representative of the modelling described in the preliminary model description which accompanied the benchmark analysis (Reference 3).
As such, it is intended to update and rerlace the deck submitted along with Reference 2.
The attached deck is not a " final" deck.
Several modifications to the s team genera tor beat transfer modeling are in progress. These are described in the revised sections of the model description in Attachment A.
Revised nodalization and additional control logic diagrams are also included. The centrol block representation of the steam driven feedwater pump and turbine is not included since it is still under development.
An updated deck or the additional cards necessary to update this deck will be transmitted with the final analysis, ih 8106800 Ogd
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U. S. Nuclear Regulatory Commission Page Two June 22, 1981' A copy of the deck and transmittal letter is also being' provided under separate cover directly to Mr. Mike Kennedy at Argonne National Laboratory, per_ his reques t.
.Should you desire. additional information regarding the model, please contact Mr. Phil Guimond at Extension 2123.
Respectfully MAINE YANKEE ATOMIC POWER COMPANY Robert H. Groce Senior Engineer Licensing t
RHG/smh-cc:
M. Kennedy, ANL w/ enclosures l
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'12.0 STEAM GENERATORS The primary (RCS) side of the SGs has already been discussed in Section 4.0.
Modelling of the secondary (steam-side) of the SGs is discussed below. Figure 10.0 shows the SC nodalization. As with the feedwater lines, the two intact SGs are lumped together in the model.
The liquid in the downcomer region of the SG during power operation is a mixture of " cold" FW and saturated recirculating fluid falling down from the steam separator deck. This mixture is subcooled and denser than the saturated water covering the tube bundle. The SG inventory modelled is equal to the total tube bundle and downcomer fluid mass accounting for the differences in density. An additional amount of mass is added to compensate for the dif ference in initial enthalpy of the actual downcomer region fluid and the conditions assumed in the model.
As in the FLASH (4) modelling of the SLB transient, a semi-infinite bubble rise velocity is used in the steam gnnerators, Volumes 219 and 220.
This results in pure steam blowdown from the faulted SG.
The overall SG heat transfer coefficient, UAgg, was matched to a value calculated from plant measured data at 97% power.
An integral assumption of past SLR analyses has been the use of a constant overall SG UA.
Flash (4) was modified to maintain the UA in i
the SGs constant.
Special modelling is required to accomplish this with RETRAN. Three nonconducting heat exchangers are used to model each SG as shown in Figure 6.0.
Control blocks are used to calculate the rate of heat transfer between each of the primary side SG volumes and the SF secondary !
side volume as follows.
4 = (UA)sc (t=0) * (TPRi (t) - Tsee (t))
where 6
=: Instantaneous heat transfer rate - MWt (UA)3g (t=0) = Overall primary to secondary heat transfer coefficient at 100% power initial condition (MWt/0F)
TPRi (t)
= Average' temperature in SG primary side volume at time t,0F Tsec (t)
= Average temperature in SG secondary side volume at time t,0F Heat is removed from each broken SG primary side volume by the i
nonconducting heat exchanger at a rate, 4, determined by the calculation outlined above. The total 4 removed from the SG primary side volumes is added to the SG secondacy side volume using another nonconducting heat exchanger. This calet. : ion maintains the SG UA constant until the liquid level in the SG secondary falls below 9 feet (approximately one third of tube bundle height). The SG UA is linearly ramped to zero at a mixture level of 0.0.
A comparison is made between the linearly ramped UA and a value of UA determined by assuming the forced convection heat transfer to saturated steam (using the Dittus-Boelter correlation) over the entire SG tube heat transfer area. The maximum of these UA values is selected to calculate Q for the non-conducting heat exchangers.
When the RCPs have been tripped, the overall UA is calculated using the Dittus-Boelter (6) heat transfer correlation to determine the primary side heat transfer coefficient. The secondary side heat transfer coefficient.
is assumed to rcuain at'its 100% value if the SG 1evel is greater than 9 feet, and vary with level below that as discussed for forced primary flow.
Modelling of constast SG UA in the intact loop SCs is similar with one exception. The intact loop SCs are isolated by the closure of the EFCVs early in the t ansient. Following EFCV closure, the secondary side heat transfer coefficient falls to a low value as reverse heat flow from intact SC secondary to RCS fluid begins. This is more conservative than the assumption of constant SC UA in this reverse heat transfer mode since it retards the addition'of stored energy from the SGs to the RCS. As a result, t* e RCS will cool down slightly faster, which is conservative for return-to power calculations.
The primary to secondary AT is monitored to determine when reverse heat transfer begins. The SC UA is then calculated usfng a free convection heat transfer coefficient [6] on the SG secondary side of the SG tubes.
When the reactor coolant pumps are running, the primary side heat transfer coef ficient is assumed to be equal to its value at 100% power in the overall UA calculation. If the RCPn have been tripped, then the primary side heat transfer coefficient is determined using the Dittus-Boelter heat transfer correlation [6].
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18.0 REFERENCES
1.
Maine Yankee " Final Safety Analysis Report", nev. 6, 1971.
1 2.
YAEC-1101, ' "Ma ine Nnkee Plant Analysis Model Using CEMINI-II",
i P. A. Bergeron, Ju<ia 1976.
3.
NUREG-75-087. Branch Technical Position ASB 9-2, Rev.1, November 24, 1975.
4.
YAEG-liO4, " Maine Yankee Plant Accident Analysis Model Using FLASH-4",
W. J. Szymczak, November 1976.
5.
BNL-NUREG-25781, Informal Report, Maine Yankee Steam Line Break Analysis 3
Using RELAP-3B, W. G. Shier, March 1979, Thermal Reactor Safety Division, Brookhaven National Laboratory.
6.
' HEAT TRANSFER, J. P. Holman, McGraw-liill Publishinh Company, 3rd Ed.,
1972, pp. 213-218.
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7.
HEAT TRANSFER, J. P. Holman, pp. 175-176.
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