ML20034C740
| ML20034C740 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 06/23/1989 |
| From: | Ramsden K COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML20034C475 | List: |
| References | |
| RSA-Z-89-03, RSA-Z-89-3, NUDOCS 9005070175 | |
| Download: ML20034C740 (21) | |
Text
_
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s ZION STATION CONTAINMENT RESPONSE WITH LOSS OF RHR SPRAY DURING LOCA l
1 Document Number RSA.2 89 03 i
June 23,- l989 K. B. Ramsden l
Reactor Safety Analysis Nuclear Fuel Senices Department Commonweahh Edison Company Chicago, Ilhnois i
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Statement of Disclaimer This report was prepared by the Nuclear Fuel Services Department for use internal to Com-monwealth Edison Company. It is being made available to others upon the express under-standing that neither Commonwealth Edison Company nor any ofits officers, directors, agents, or employees makes any warranty, representation, or assumes any obligation, responsibility with respect to the contents of this report,its accuracy, or completeness.
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Abstract This report summarizes the analytical work performed in support of Zion Units I and 2 re.
garding the response of the containment to a postulated failure of RilR spray during a design basis LOCA event. The containment pressure and temperature response during the post LOCA recirculation phase is calculated.
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. Table of Contents j
Chapter 1. I nt roduction............................................. I Chapter 2. Description of Analytical Models.............................
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Chapter 3. Discussion of Results.....................................
6 Chapter 4. Conclusions...........................................
14 References
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l Table of Contents iv
List of Tables i
Table
- 1. Input Conditions and Key Assumptions.............................
4 Table
- 2. Sequence of Events............................................. g l
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List of Tables v
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. List of Illustrations E
Figure
- 1. Diagram of CONTE M PT M odel..................................
3 Figure
- 2. Containment Pressure (No RHR Spray) 9 Figure
- 3. Containment Vapor Temperature (No RHR Spray)...................
10 11 Figure
- 4. Containment Pressure (RllR Spray)
Figure 5. Containment Temperature (RH R Spray)..........................
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Figure
- 6. Benchmark Comparison Case (Contempt 4M5 = dotted line)............
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l 1.ist of Illustrations gi s
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Chapter 1. Introduction l
This report documents the analytical work performed to address the postulated loss of RilR spray capability in a post LOCA event at Zion station. This work was initiated in response to questions raised following a failure of the RilR spray valves during testing. Review of appli.
cable technical specifications and bases as well as the FSAR did not clearly determine the rela.
tive safety importance of the RilR spray function. A series of calculations was performed utilizing the CONTEMPT 4/ MODS containment analysis code to provide insight into the post LOCA recirculation phase containment behavior. This work extends analysis provided in the FSAR to support containment peak pressure response.
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Chapter 1. Introduction i
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Chapter 2. Description of Analytical Models t
Description of Model 4
I Analysis of these events was performed with CONTEMPT 4 Mods as installed on the CECO computer system. This code calculates the time response compartment pressures, temperatures, s
mass and energy inventories, heat structuie temperature distributions, and energy exchange between compartments or to the environment. This code has the ability to describe the effects of engineered safeguard systems such as containment spray, fatt coolers, and heat exchangers.
This code has been used extensively for containment analysis throughout the nuclear industry, t
The model developed for this purpose is depicted in Figure 1. This model consists of a single compartment volume representing the free volume inside the containment building. This vol-ume is a general compartment model consisting of a vapor region and a pool region. Mass and energy additions are modelled as tabular input. The fan coolers are modelled by specifying the heat removal capability versus temperature in. tabular format. The containment sprays are modelled as a tabular addition of fluid versus time during the initial phase of the LOCA During the recire phase, the spray fluid is modelled as coming from the containment sump and being cooled by the RilR heat exchangers prior to injection via the spray headers, The heat strue.
tures are modelled as one dimensional slabs. The Tagami correlation is used for surface heat i
transfer up to the end of blowdown, at which point the Uchida correlation is employed for the' duration of the event. The surface areas of concrete structures are reduced to 40% of actual values to account for less eflicient heat transfer to concrete.
Chapter 2. Description of Analytical Models 2
o This model is' a conversion of the model previously developed for use with the CONTEM PT LT.
026 computer code. Additional description and benchmarking of this model is provided in
'l Reference 2.
Selection of Transient A review of the FSAR containment integrity calculations, particularly Figure 14.3.4 9 strongly suggests that the heat load on the containment would be well within RCFC capacity during the recirculation phase (2013 seconds into event). Since the interaction of the heat structures was -
considered to be of concern if RilR spray was disabled, an analysis was performed to provide additional assurance. The case selected was the Case 2 DBA LOCA with reflood effects docu.
mented in FSAR section 14.3 4.5. The mass and energy release data for this case are provided in FSAR Tables 14.3.4 9 and 14.3.410. These tables 'provided data to 10,000 seconds, wellinto t
the recirculation phase, 4
Analysis input Assumptions The principal input initial conditions and key assumptions are listed in Table 1. These as-sumptions are consistent with the input utilized in the FSAR analysis.
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INITIAL CONDITIONS AND Ab'SUMPTIONS
- Containment Free Volume 2.715E6 cuft i
- Pressure 15.0 psia -
- Temperature 120F i
- RWST Temperature 100F
- Service Water Temperature 80F-
- Number of Spray pumps operable 2
- Flow rate per pump 2615 spa
- Actuation time 45 seconds
- Number of RCFCs available 3
- Actuation time 45 seconds I
- RCFC performance basis Marlo data
- Containment heat sinks FSAR Tables 14.3.4-3, 14.3.4-8
+ Heat transfer coefficients Tagoni/Uchida e
- Hass/ Energy Release Data FSAR Tables 14.3.4-9, 14.3.4-10
- RHR Spray Assumptions:
- Spray Flow Rate 2200 ppm j
-* RHR Heat Exchanger UA 1.66E6 BTU /hr-F l
Chapter 2. Description of Analytical Models J
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Diagram of CONTEhlPT Afodel l
l Chapter 2. Description of Analytical.Tiodels 5
. Chapter 3. Discussion of Results The first calculation performed assumed that the RiiR spray was inoperable after entry into the recirc phase at 2013 seconds. The results of this calculation indicate that the RCFCs are indeed able to control the heat load without substantial repressurization. A sequence of events for this a
transient is provided in Table 2.
i Containment pressure is shown in Figure 2. As can be seen in this figure, the initial peak pressure occurs at the end of the blowdown (29 seconds), a secondary peak occurs at 161 sec.
onds due to the reflood energy addition to the containment. The pressure is reduced signif.
l icantly by the time the recire phase is entered at 2013. The effect of the spray up to this point has been to cool the vapor space. At the recirc point, the sump is at a higher temperature and flashing occurs leading to some repressurization.
The vapor space temperature is shown in Figure 3, and clearly illustrates the impact of the RilR spray failure. After the loss of normal spray, the temperature rises to a peak value of l
231.4 degrees F as the thinner structures return heat to the cooled vapor region. Note that the temperature remains well below the equipment qualification temperature of 271 F.
An additional calculation was performed for comparison showing the effect of an active RHR l
i spray system. The containment pressure response is shown in Figure 4, and shows that very i
little difTerence in repressurization occur. Figure 5 shows the vapor space temperature re-l
.ponse, in this figure it can be clearly seen that the principal effect of the RilR spray would be to continue the temperature reduction started by the containment spray.
A benchmarking comparison was performed to confirm that the CONTEMPT 4 Mod 5 model-exhibits reasonable comparison to the original FSA R case and the previous CONTEMPT LT-026 model developed at CECO. The results of this comparison (pressure only)
Chapter 3. Discussion or Results 6
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,, 9 e are shown in Figure 6, and clearly demonstrate that the CONTEMPT 4 Mod $ model is per.
4 ferming in a consistent and conservative manner. The principal difTerences.between the models are _. due to the - manner in which the' structure heat transfer coemcients are applied, l
t CONTEMPT 4 tending to underpredict the coemeients relative to the FSAR case.
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EVENT TIME (soc)
- Rupture occurs 0
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- End of blowdown 28.7
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- Reflood steaming begins 30.6
- RCFCs, Spray initiate 45 t
- Peak pressure occurs 161 i
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- RWST Empties, Recire begins 2013 Table 2. Sequence of Events J
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ZION DSA CONTAINMENT RESPONSE i
j NO RHR RECIRCULAT10N SPRW i
. Merlo RCFC Curves ProY#ri' (,lg),, _.. _
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Co vfvament Pres.tr. e (No RHR Spray)
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9 ZION DBA CONTAINMENT RESPONSE g
NO RHR REClRCULATION SPRAY 4
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Containment Vapor Temperature (No RHR Spray)
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RNA RECIRCULATION SPRAY-r Mario RCFC Curves.
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ZION DBA CONTAINMENT RESPONSE' RHR RECIRCULATION SPRAY i
Mario RCFC Curves
- To%$roture (F)
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Containment Temperature (RHR Spray) i l
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Benchmark Comparison Case (Contempt 4M5 =-dotted line) s l
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Chapter 3. Discussion of Results 13
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. Chapter 4. Conclusions-The results 'of the calculations clearly demonstrate the effects of the RHR spray. system on containment response. The assumption that th'e RCFCs can handle the post recirculation heat
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loads is valid. The loss of the RHR spray function caures a temperature rise in the containment vapor space, but does not resul't'in the violation of the design basis equipment qualification-envelopes. Therefore, the safety significance of the RHR spray function is considered minimal i
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-4 Chapter 4. Conclusions 3,4 1
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" Zion. UFSAR Chapter 14".
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Zion Containment Analysis with CONTEMPT LT 026 Code", NFSR 0025, K. B. Rams.
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" CONTEMPT 4/ MOD 5: AN 1mprovement to CONTEMPT 4/ MOD 4 Multicompartment 3.
Containment - System - Analysis Program for ICE Containment-Analysis",
e NUREG/CR 4001, C. C. Lin, i
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