ML20028A820
| ML20028A820 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 10/29/1982 |
| From: | Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20028A821 | List: |
| References | |
| RTR-NUREG-0793, RTR-NUREG-793 19405, NUDOCS 8211290084 | |
| Download: ML20028A820 (12) | |
Text
T Consumers Power James W Cook C0mpBRY Vice President - Projects, Engineering and Construction oeneral off6ces: 1945 West Pernell Road, Jackson, MI 49201 + (517) 78&O453 October 29, 1982 Harold R Denton, Director Office of Nuclear Reactor Regulation Division of Licensing US Nuclear Regulatory Commission Washington, DC 20555 MIDLAND NUCLEAR C0 GENERATION PLANT MIDLAND DOCKET NOS 50-329, 50-330 SINGLE LOOP NATURAL CIRCULATION COOLDOWN ANALYSIS FILE: 0505.16, 0928.6 SERIAL:
19405
Reference:
J W Cook to H R Denton, CP Co Serial 18434 Dated 08/26/82
Enclosure:
(1) Babcock & Wilcox Report, Single Loop Natural Circulation Cooldown (2) F J Levandoski (B&W) to T J Sullivan, CPCO: 4029 Dated 10/20/82 Natural circulation cooldown analyses were identified as Outstanding Open Item 7 in Section 1.7 of the Midland Plant SER (NUREG-0793). Enclosure (1) provides the requested information and should be sufficient to close the item.
Natural circulation cooldown with both reactor coolant loops will be demonstrated during natural circulation testing.
Consumers Power Company has addressed the recommendations in the report as l
follows:
e Venting of the reactor vessel head - As outlined in the referenced letter, the vessel head will be vented continuously to the top of a hot leg.
Enclosure (2) provides an analysis of the effect that the head vent will have on natural circulation cooldown.
e Measurement of the reactor vessel head fluid temperature - Data gathered during natural circulation testing will establish cooldown and depressurization rates. The need to measure the reactor vessel head fluid temperature is obviated.
00/
oc1082-1380a131 8211290084 821029 PDR ADOCK 05000329 E
2 e Measurement of reactor coolant system loop boron concentration - The existing sampling systems were reviewed and are considered adequate, w 60. M JWC/JRW/fms CC RJCook, Midland Resident Inspe or RHernan, US NRC WLJensen, US NRC DBMiller, Midland Construction RWHuston, Washington r
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r CONSUMERS POWER COMPANY Midland Units 1 and-2 Docket.No 50-329, 50-330 Letter Serial 19405 Dated October 29, 1982
'At the request of the Commission and pursuant to the Atomic Energy Act of 1954, and the Energy Reorganization Act of 1974, as amended and the
-Commission's Rules and Regulations thereunder, Consumers Power Company submits the B&W Report " Single Loop Natural Circulation Cooldown" and the letter F J Levandoski (B&W) to T J Sullivan CPCO: 4029 dated October 20, 1982.
CONSUMERS POWER COMPANY M,
L By J
Cook,'Vice PrVsident Pro cts, Engineering and Construction Swornandsubscribedbeforemethis/4 day of M./78d.
n$M tt.)
i&l Notary PublicF Bay County, Michigan My Commission Expires 3'Y-[b i x
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Babcock & Wilcox w
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,.u oi.e.m a McD.rmott company 3315 Old For.st Road P.O. Box 1260 Lynchburg, Virginia 245051260 (804) 385-2000 October 20, 1982 CPCO: 4029 File: 12B/T1.2 Consumers Power Company 1945 Parnall Road Jackson, MI 49201 Attention:
Dr. T.J. Sullivan Manager, Safety & Licensing
Subject:
Consumers Power Company Midland Plant, Units 1 and 2 NATURAL CIRCULATION C00LDOWN RATES WITH HEAD VENT - PRELIMINARY
Dear Dr. Sullivan:
Attached please find the subject analysis.
This is being sent to you in its present form on a preliminary basis at the request of J.R. Webb.
Prior to issuing the analysis results in their final form, B&W intends to make the following revisions and additions:
- The. text will be reviewed for clarity and completeness,
- Figures 1 and 2 will be expanded to show the Driving Head and Flow-Rate, respecti,vely, for a RV Head Temperature of
- 3500F,
- Figure 3 will be expanded to show at least two (2) additional vent flow rates in the 0.9 to 6.0 range, and to include flow rates for an initial head temperature of 3500F.
The calculated pressure drops and flow rates in the attachment are based on an assumed 100 feet of pipe length from the service structure to the hot leg containing eight 900 elbows. We have just recei.ved an unofficial piping layout drawing from Bechtel which shows our assumptions to be conservative.
Thus, flow rates will increase.
This will be factored into the final analysis.
l 1
PAGE: 2 CPC0: 4029 FILE: 12B/T1..
If you or your people have any specific requests for additional information
.to be included in the final transmittal, pleas,e call me.
Very tr
- yours, F.. Levandoski Associate Project Manager For:. SENIOR PROJECT MANAG D.F. JUDD Attachment FJL/leh cc: JR WEBB LS GIBSON EM HUGHES RC BAUMAN 4
9
F Review of Past Work Previous analyses determined the reactor vessel cooldown rate during natural circulation with stagnant conditions in the RV upper hesd.
The cooldown was governed by ambient losses from the coolant through the shell and insulation and conductive losses from the head metal. downward to the RV flange region where cooler water was available to remove heat.
These mechanisms combined for a maximum head cooldown rate of approximately 1.7'F/hr.
Effect of Vent Line The RV vent line provides an additional means of heat removal from the head.
- Thus, the cooldown rate increases as a function of vent flow rate.
The vent flow rate is dependent on the driving head induced by the RV head-hot leg temperature differential and the unrecoverable pressure losses between the RV head and hot leg.
Since the unrecoverable losses are fixed, it is important to maximize the driving head.
Driving head calculations assume an adiabatic vent line.
Departure from this condition will reduce the driving head and consequently, the head cooldown rate (see Analysis Limitations).
RV Head Cooldown Code Modifications The finite difference computer code used previously to analyze the stagnant condition cooldown was modified to reflect the presence of the vent line.
The program was run for various flowrates and the results are shown in Figure 3.
The same initial conditions (see Figure 3) and program were used as in the stagnant case with the following modifications:
e addition of the RV head vent and flow distribution model in the upper head region e
addition of a mixing subroutine to prevent cold fluid above hot fluid layering change of fims distribution below the cover to more accurately e
model this flow.
-t-
Figure 4 shows the flow model used in these analyses.
Since the vent is located off the center line of the head, a stagnant region fonns at the top of the head.
This area limits the cooldown rate.
A vent in the center of the head would prevent stagnant regions from forming and the head would cool down twice as fast as in the asymmetric case.
The cooldown rates achievable with the head vent flow can be estimated using the following figures.
e Figure 1 - Vent flow driving head as a function of fluid conditions in the RV head and hot leg e
Figure 2 - Vent flow rate as a function of pressure drop, i.e.
driving head e
Figure 3 - RV head cooldown rate as a function of vent flow Therefore, given the hot leg temperature the driving head can be found from Figure 1, a flow rate can be found from this driving head and Figure 2, and a cooldown rate can be found from the flowrate and Figure 3.
For example, if T
RV head = 600*F, Thot leg = 500*F, Ps2000 psia then from Figure 1, aPdriving head = 1.94 psid and from Figure 2, Overt flow = 4.5 gpm and from Figure 3, the cooldown rate %10*F/hr.
Recall that the stagnant condition cooldown rate was %1.7*F/hr.
Smaller temperature differences between the RV head and hot leg will result in smaller driving heads, vent flow rates, and cooldown rates, while larger temperature differences will result in the opposite effects.
For example, a 43 gpm vent flow (highly unrealistic) results in a 40*F/hr. cooldown rate, while a.9 gpm vent flow rate causes a cooldown rate only marginally better than the stagnant case. The relationship betweert the driving head for vent flow and head cooldown
- 2. -
rates is therefore nonlinear.
Vent flow rates are expected to be between 0 and 5 gpm depending on the RV head-hot leg temperature difference and the ambient heat loss rate.
This will result is cooldown rates betweeh 1.7 and 10*F/hr.
Analysis Limitations The analysis for determining the driving head assumes that the vent line is adiabatic.
Because of the low vent flow rates and high transit times (for 3.3 gpm flow the transit time is about one minute), heat losses to the containment atmosphere will decrease the vent line temperature and consequ,ently the driving head. An uninsulated vent line can reduce the driving head by as much as 20% and the vent flow by 10%.
Therefore, to maximize the head cooldown rate, the heat losses must be minimized through the use of insulation.
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5.0 4.0 P = 2000 psia RV Head Temp = 600*F 3.0 3
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Vent Flow = 43 gpm u
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Initial Conditions g
Circulating Mass Flow Rate = 1140.67 #/s e
Initial Shell Temp = 604*F I
Initial Water Temp = 585*F f
Ambient Temp = 120*F 350 Circulating Coolant 100*F/hr. cooldown 300 2.5 5
7.5 10 12.5 15 Time, hrs FIGURE 3.- Cooldown Rates vs. Vent Flow Rates
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