ML20042C071
| ML20042C071 | |
| Person / Time | |
|---|---|
| Site: | Clinch River |
| Issue date: | 03/22/1982 |
| From: | ENERGY, DEPT. OF |
| To: | |
| Shared Package | |
| ML20042C069 | List: |
| References | |
| NUDOCS 8203300139 | |
| Download: ML20042C071 (9) | |
Text
,
CRBRP-3 O
i HYPOTHETICAL CORE DISRUPTIVE ACCIDENT CONSIDERATIONS IN CRBRP VOLUME 2:
- O ASSESSMENT OF THERMAL MARGIN BEYOND THE DESIGN BASE l
CLINCH RIVER BREEDER REACTOR PLANT
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TITLE Hypothetical Core DOCUMENT NO.'
Disruptive Accident i
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Considerations in CxBRP CRBRP-3 CHANGE CONTROL RECORD volume 2 volume 2 Assessment of Thermal Margin Beyond the Design Base CHANGE REV N0/D ATE RELEASE PAGES AFFECTED REMARKS DOCUMENT 0/ March 80 All First formal is 1 of document Rev 1/5-81 i, 2-4, 2-6, 2-7, 2-10 Pages added 2-16A thru 2-16, 2-24, 2-25, thru 2-16G, 2-34A 2-26, 2-32, 2-34, 2-43, 2-44, 2-76 Rev 2/10-P1 2-16B, 2-16C, 2-16F, 2-16G Rev 3/2-82 1, 2-4, 2-18 Pa,ge added 2-18A bo U
0116 2
CRBRP-3 Vol. 2, Rev. 3 p3 TABLE OF CONTENTS Page
1.0 INTRODUCTION
1-1
1.1 REFERENCES
l-5 2.0 UESIGN FEATURES PROVIDING TERMAL MARGIN BEYOND TE DESIGN BASE 2-1 2.1 TMBDB FEATURES REQUIREENTS 2-2 2.1.1 General 2-2 2.1.2 Feature Requirements 2-3 2.1.3 Maintenance and Testing Requirements for 2-16A TMBDB Features 1
2.2 DESCRIPTION
OF DESIGN FEATURES 2-17 2.2.1 Reactor Cavity to Containment Barrier 2-17 2.2.2 Reactor Cavity Penetrations and Recirculating 2-18 Gas Cooling System 3
2.2.3 Guard Vessel Support 2-18 2.2.4 Reactor Cavity and Pipeway Cell Liners 2-18A l 3 2.2.5 Reactor Cavity and Pipeway Cell Liner Vent 2-19 System O
2.2.6 Reactor Cavity Vent System 2-22 U
2.2.7 Containment Purge Capability 2-24 2.2.8 Containment Vent Capability 2-25 2.2.9 Containment Cleanup System 2-26 2.2.10 Annulus Air Cooling System 2-27 2.2.11 Containment System Leakage Barrier 2-29 2.2.12 TMBDB Instrumentation System 2-30 2.2.13 Electrical Power System 2-34 2.2.14 Containment Structures 2-34 2.2.15 Control Room Habitability 2-35 2.3 OPERATOR ACTION SEQUENCE 2-38
2.4 REFERENCES
2-41 3.0 ASSESSENT OF TIERMAL MARGIN 3-1 3.1 TIERMAL MARGIN WITHIN THE REACTOR VESSEL 3-2 3.1.1 Core Debris Distribution 3-2 3.1.2 In-Vessel Debris Retention Capability 3-10 3.1.3 Secondary Criticality Considerations 3-15 3.1.4 Penetration of the Reactor and Guard Vessels 3-15 3.2 TKRMAL MARGIN EXTERNAL TO TIE REACTOR VESSEL 3-18 O
3.2.1 Scenario 3-18 l
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3.2.2 Containment Transients Prior to Sodium Boildry 3-26
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3.2.3 Containment Transients After Sodium Boildry 3-60 l
3.2.4 Secondary Criticality Considerations (Ex-Vessel) 3-70 1
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CRt!RP-J Vol.2 Rav.0 TABLE OF CONTENTS (Continued)
P_agg 3.3 LONCLUSIONS ON THERMAL MARGIN BEYOND THE DESIGN BASE 3-72
3.4 REFERENCES
3-73
4.0 ASSESSMENT
OF RADIOLOGICAL CONSEQUENCES 4-1 4.1 HCDA RADIOLOGICAL SOURCE TERM 4-1 4.1.1 Non-Energetic Core Meltdown 4-2 4.1.2 Energetic HCDA 4-5 4.2 RADIOLOGICAL DOSES FROM ATMOSPHERIC RELEASES 4-8 4.2.1 Methods and Data Base 4-8 4.2.2 Radiological Doses 4-10 4.3 GROUNDWATER CONSIDERATIONS 4-11 4.4 HETEROGENEOUS CORE CONSIDERATIONS 4-13
4.5 CONCLUSION
S ON RADIOLOGICAL CONSEQUENCES 4-14
4.6 REFERENCES
4-15 5.0
SUMMARY
AND CONCLUSIONS 5-1 APPENDICES:
A.'0-1 INDEX T0.S'ENSITIVITY STUDIES IN APPENDICES A.0-2 A.
DEVELOPMENT PROGRAMS SUPPORTING THERMAL MARGIN ASSESSMENTS A-1 A.1 S0DIUM-CONCRETE INTERACTIONC.,EVELOPMENT PROGRAM A-1 A.1.1 Purpose A-1 A.l.2 Program A-1 A.I.3 Schedule A-2 A.1.4 Criteria of Success A-3 A.1.5 Fallback Position A-3 A.2 HYDROGEN AUT0-CATALYTIC RECOMBINATION A-4 A.2.1 Purpose A-4 A.2.2 Program A-4 A.2.3 Schedule A-5 A.2.4 Criteria of Success A-6 A.2.5 Fallback Position A-6 e
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CRBRP-3 Vol.2, Rev.0 f.
There is not a requirement to meet the allowable site boundary or Q'
low population zone doses of 10CFR100 or the control room dose of 10CFREO under TMBDB conditions.
2.
Acceptance Criteria The public risk from accidents beyond the design base shall be a.
comparable to that from light watee teactors for events beyond the design base with similar probabilit'y of occurrence.
b.
Containment integrity shall be maintained without venting following initiation of an accident leading to core meltdown for a period of time sufficient to allow evacuation procedures to be implemented.
Per NRC guidance, the period is taken as 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
1 2.1.2 Feature Requirements The following requirements are imposed on the specific TM8DB features as fi well as other systems or components to provide thermal margin beyond the design base in CRBRP.
2.1.2.,1. Reactor Cavity-To-Containment Barrier To insure that the heat capacity of the pipeway cells is employed from 1000 seconds to 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> af ter a HCDA, the total leakage of sodium vapor through the reactor cavity to head access area seals (not through the reactor head or the' planned vent path defined in Section 2.2.6) shall not exceed 10000 pounds (for requirements before 1000 seconds see Section 2.2).
These leakagas shall be based on the pressure differential for the reactor cavity to head access area seals given on Figure 2-1, on the reactc cavity pressures on Figure 2-2, and on the reactor cavity atmosphere temperatures on Figure 2-3.
d 2-3
CRBRP-3 Vol. 2, Rev. 3 0
2.1.2.2 Reactor Cavity Penetrations and Recirculating Gas Cooling System 3
To insure that the Cell 105 hydrogen concentration does not exceed 6%, the total leakage from the reactor cavity through RC penetrations and through 3
the recirculating gas cooling system to non-inerted cells shall be less than 4000 pounds of sodium from 1000 seconds to 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> after HCDA. These
'1 leakages shall be based on the reactor cavity pressures and temperatures on Figures 2-2 and 2-3 and on the differential pressure between the reactor cavity and Cell 105 given on Figure 2-4.
In addition to the 4000 pounds of leakage allocated to the Recirculating Gas Cooling System and other reactor cavity penetrations, 1000 pounds of sodium leakage into cell 105 is allocated to the liner vent system (see Section 2.1.2.5).
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2.1.2.3 Guard Vessel Support To insure that sodium and fuel particulate redistribute in the reactor 2
cavity, a flow area of at least 10 f t shall be provided under the guard vessel skirt bottom flange.
2.1.2.4 Reactor Cavity and Pipeway Cell Liners To insure that the Reactor Containment Building hydrogen concentration does not exceed 6% (by volume) and to keep from exceeding the containment vent, purge and cleanup system capacities, the reactor cavity wall and pipeway cell liners shall prevent short term (less than 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />) sodium-concrete reactions based on the pressure on Figure 2-2 and the temperatures on Figure 2-9 and Figures 2-11 through 2-16.
The results of structural analysis will be used to determine the liner failure times assumed in the TMBDB scenario.
To limit the consequences of liner failures, the liner system shall have physical barriers behind the liners between the reactor cavity floor and reactor cavity wall and at 8 feet and 26 feet above the reactor cavity floor. Likewise, the pipeway cells shall have physical barriers behind the liners to separate the vent spaces of the walls, floor, and roof of each cell. Only the spaces of adjacent walls with different liner f ailure times will be separated.
2-4
CRBRP-3 Vs1.2, Rev.0
2.2 DESCRIPTION
OF DESIGN FEATURES The design features that are provided to meet the requirements in Section 2.1 are described below. These features are considered in the analysis of thermal and radiological margins discussed in Sections 3 and 4.
Although some of these features may serve a function as Safety Class equipment or as Engineered Safety Features to mitigate a CRBRP design basis event, the features are not considered Engineered Safety Features for the, purpose of performing their function of mitigating a core melt event beyond the design basis. However, as noted in Section 2.1.1 these features are designed to the specifications and requirements associated with Safety Class 3 components and systems.
2.2.1 Reactor Cavity to Containment Barrier The response of the reactor closure head and head-mounted components, and their associated seals to the TMBDB dynamic loadings requires that the head assembly remains intact and integral and the sealing structures remain d
functional and meet their leakage requirements for 1000 seconds af ter the dynamic loads. For head mounted components, no special TMBDB seals are required since the sealing systems used for normal operations and to meet SMBDB requirements can meet the TMBDB requirements. These sealing systems are described in Section 5.2.1.3 of the PSAR. For annuli between the head plugs, a special margin seal is provided to the riser annuli sealing system (see Section 5.2.4.4 of the PSAR) to meet the TMBDB leakage requirements.
The margin seal design has elastomer-to-metal contact in the area of the bearing races to limit leakage through the bearing.
The reactor cavity to head access area sealing system consists of the reactor cavity seal, which is a low alloy steel circular membrane with an L-shaped cross-section. This reactor cavity seal is bolted to the reactor vessel closure head and to the edge of the reactor cavity support ledge.
Sealing is provided between the reactor vessel closure head and the reactor cavity seal by a Grafoil gasket. High temperature packing provides the seal between the reactor cavity support ledge and the reactor cavity seal.
Gasket caps provide sealing over the reactor vessel holddown bolts and nuts.
,v 2-17 i
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CRBRP-3 Vol. 2, Rev. 3 0
2.2.2 Reactor Cavity Penetrations and Recirculating Gas Cooling System 3
The Reactor Cavit) Sas Cooling System provides cooling of the atmosphere of l3 the reactor cavity during normal operation.
The special features of this system which are not specifically for TMBDB but whici provide additional thermal margin for the plant are the automatic gas isolation valves on the cavity cooling system inlet and outlet lines which are capable of withstanding the thermal and pressure condi. ions encountered at the valves. The valves are located in Cell 105 just outside the reactor cavity wall and are actuated by the sodium leak detection system or by a high gas temperature signal. The process temperature that the valves are exposed to is expected to be substantially less severe than the conditions in the reactor cavity because the piping configuration acts like a large loop seal. Before sodium or sodium vapors could reach the valves the long run of piping allows cooling of the atmosphere in the piping.
In addition, the closure of the valves would occur within seconds after the penetration of the reactor vessel and guard vessel so the flow conditions in the piping would be essentially stagnant. Finally, outside of the isolation valves the system is a closed circuit system so the small amount of sodium leakage through the valves would not enter Cell 105. Other penetrations of the Reactor Cavity whose failure could permit sodium vapor flow to Cell 105 are designed to limit total leakage over the sodium boildry period to the total 3
specifieo in Section 2.1.2.2.
2.2.3 Guard Vessel Support The design requirements for the guard vessel support are accomplished by raising the guard vessel support skirt approximately 5 inches off the floor on steel blocks. This provides 48 openings which are each approximately 5 inches by 6 inches and allows disnersion of the liquid sodium and fuel particulate underneath the guard,
al support and into the reactor cavity. Figure 2-32 depicts the aails of this arrangement.
2-18
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Vol. 2, Rev. 3 l@
2.2.4 Reactor Cavity and Pipeway Cell Liners i
i The reactor cavity (RC) and pipeway cell liner are described in Section i
j 3A.8.2 of the PSAR and in Section 3.2.2.5 of this report. Two additional l
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