ML20214D669
| ML20214D669 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/14/1987 |
| From: | SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| Shared Package | |
| ML20214D639 | List: |
| References | |
| TAC-65417, NUDOCS 8705210424 | |
| Download: ML20214D669 (16) | |
Text
- _ _ - - - - . . - - - _ - - - - . - - - - __ __ - - - _ - - .
l-l l
ATTACHMENT I RANCHO SECO TECHNICAL SPECIFICATIONS (Pages affacted by Proposed Amendment No. 158) r h
--_______ ~'- - - - - - - - , , _ _ _ _ _ _ __
.- . 1
! RANCHO SECO UNIT 1
- TECHNICAL SPECIFICATIONS TABLE OF CONTENTS (Continued)
Section P, age 3.14.5 Fire Hose Stations 3-57 3.14.6 Fire Barrier Penetration Fire Seals 3 58 3.15 RADI0 ACTIVE LIQUID EFFLUENT INSTRUMENTATION 3-60 i
3.16 RADI0 ACTIVE GASE0US EFFLUENT MONITORING INSTRUMENTATION 3-63 3.17 LIQUID EFFLUENTS 3-70 .
l 3.17.1 Concentration 3-70 3.17.2 Dose 3-71 3.17.3 Liquid Holdup Tanks 3-72 3.18 GASEOUS EFFLUENTS 3-73 l
3.18.1 Dose Rate 3-73 3.18.2 Noble Gases 3-74 3.18.3 _!odine-131 Tritium and Radionuclides in Particulate Form 3-75 3.19 GASEOUS RADWASTE TREATMENT 3-78 l 3.20 GAS STORAGE TANKS 3-79 l
l 3.21 SOLID RADI0 ACTIVE WASTES 3-80 3.22 RADIOLOGICAL ENVIRONMENT MONITORING 3-81 3.23 LAND USE CENSUS 3-87 3.24 EXPLOSIVE GAS MIXTURE 3-89 3.25 FUEL CYCLE DOSE 3-90 3.26 INTERLABORATORY COMPARISON PROGRAM 3-92 158u 3.29 HYDR 0 GEN RECOMBINERS 3-93 i
Proposed Amendment No. 158 iv e_______---_-_______--______.__.-_ __ --- _ _ _ -
I RANCHO SECO UNIT 1 TECHNICAL SPECIFICATIONS TABLE OF CONTENTS (Continued)
Section Page 4 SURVEILLANCE STANDARDS 4-1 4.1 OPERATIONAL SAFETY REVIEW 4-1 l 4.2 SURVEILLANCE OF ASME CODE CLASS 1, 2, AND 3 SYSTEMS 4-10 l
l 4.2.1 Reactor Vessel Surveillance Specimens 4-10 l
l 4.2.2 Inservice Inspection 4-11 4.3 TESTING FOLLOWING OPENING OF SYSTEH 4-14 4.4 REACTOR BUILDING 4-15 4.4.1 Containment Leakage Tests 4-15 4.4.2 Structural Integrity 4-21 158x 4.4.3 This Specification has been deleted 4-25 4.5 EMERGENCY CORE COOLING AND REACTOR BUILDING 4-26 COOLING SYSTEM PERIODIC TESTING i
i 4.5.1 Emergency Core Cooling System 4-26 4.5.2 Reactor Building Cooling Systems 4-29
! 4.5.3 Decay Heat Removal System and Reactor Building Spray
- System Leakage 4-32 l
l 4.6 EMERGENCY POWER SYSTEM PERIODIC TESTING 4-34 4.7 REACTOR CONTROL R00 SYSTEM TESTS 4-36 4.7.1 Control Rod Drive System Functional Tests 4-36 4.7.2 Control Rod Program Verification (Group vs. Core Positions) 4-37 4.8 AUXILIARY FEEDWATER PUMP PERIODIC TESTING 4-39 4.9 REACTIVITY ANOMALIES 4-40 j
4.10 EHERGENCY CONTROL ROOM FILTERING SYSTEM 4-41 4.11 REACTOR BUILDING PURGE EXHAUST FILTERING SYSTEM 4-42 4.12 AUXILIARY AND SPENT FUEL BUILDING FILTER SYSTEMS 4-43
- 4.13 AUGMENTED INSERVICE INSPECTION PROGRAM FOR HIGH 4-44 l ENERGY LINES OUTSIDE OF CONTAINMENT Proposed Amendment No. 150 V
RANCHO SECO UNIT 1 TECHNICAL SPECIFICATIONS TABLE OF CONTENTS (Continued)
Section Page 4.26 RADIOLOGICAL ENVIRONMENTAL MONITORING 4-83 4.27 LAND USE CENSUS 4-86 4.28 EXPLOSIVE GAS MIXTURE 4-87 4.29 FUEL CYCLE 00SE 4-89 4.30 INTERLABORATORY COMPARISON PROGRAM SURVEILLANCE REQUIREMENT 4-90 4.31 NUCLEAR SERVICE ELECTRICAL BUILDING EMERGENCY HEATING 4-91 VENTILATION AND AIR CONDITIONING 1
158,4 4.33 HYDROGEN RECOMBINERS 4-92 5 DESIGN FEATURES 5-1 5.1 SITE 5-1 5.2 CONTAINMENT 5-2 5.2.1 Reactor Building 5-2 5.2.2 Reactor Building Isolation System 5-3 5.3 REACTOR 5-4 5.3.1 Reactor Core 5-4 5.3.2 Reactor Coolant System 5-4 5.4 NEW AND SPENT FUEL STORAGE FACILITIES 5-6 5.4.1 New Fuel Inspection and Temporary Storage Rack 5-6 5.4.2 New and Spent Fuel Storage Recks and Failed 5-6 Fuel Storage Container Racks-5.4.3 New and Spent Fuel Temporary Storage 5-6 5.4.4 Spent Fuel Pool and Storage Rack Design 5-6 Proposed Amendment No. 158 vii 1
RANCHO SECO UNIT 1 TECilNICAL SPECIFICATIONS Limiting Conditions for Operation 158> 3.29 IlYDR0 GEN RECOMBINERS Two independent containment Hydrogen Recombiner Systems shall be operable.
Applicability Applies to the recombiner systems when the reactor is subcritical by less than 1 percent ak/k.
Action 3.29.1 With one Hydrogen Recombiner System inoperable, restore the inoperable system to OPERABLE status within 30 days or be in at least hot shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
3.29.2 With two Kydrogen Recombiner Systems inoperable, restore one of the inoperable systems to OPERABLE status within seven (7) days or be in at least hot shutdown within the next twelve (12) hours.
Bases The purpose of the Hydrogen Recombiners is to provide a means of hydrogen control during post-LOCA conditions. Either recombiner unit is capable of controlling the expected hydrogen generation associated with 1) zirconium-water reaction, 2) radiolytic decomposition of water, and 3) corrosion of metals within containment.
i Proposed Amendment No. 158 3-93
RANCHO SECO UNIT 1 TECHNICAL SPECIFICATIONS Surveillance Standards 158>< 4.4.3 This specification is deleted in its entirety Proposed Amendment No 158 4-25
RANCHO SECO UNIT 1 TECHNICAL SPECIFICATIONS Surveillance Standards 150, 4.33 HYOR0 GEN REC 0!1BINERS Applicability Applies to testing of each Hydrogen Recombiner System Objective To verify that the Hydrogen Recombiner Systems are OPERABLE.
Specification 4.33.1 Each Hydrogen Recombiner System shall be demo..:,trated OPERABLE:
4.33.2 At least once per 6 months by verifying during a recombiner system functional test that the minimum hqater sheath temperature increases to greater than or equal to 700 F within 90 minutes.
Upon reaching 700*F increase the power setting to maximum power for 2 minutes and verify that the power meter reads greater than or equal to 60KW.
4.33.3 At least once per refueling interval by:
4.33.4 forfoming a CHANNEL CALIBRATION of all recombiner instrumentation and functional tests of all control circuits, 4.33.5 Verifying through a visual examination that there is no evidence of abnomal conditions within the recombiner enclosure, and 4.33.6 Verifying the integrity of the heater electrical circuits by perfoming a resistance to ground test following the above required functional test. The resistance to ground for the heater unit shall be greater than or equal to 10,000 ohms.
Bases The OPERA 0!LITY of the equipment and systems required for control of hydrogen gas ensures that this equipment will be available to maintain the hydrogen concentration within containment below its flammable Itait during post-LOCA conditions.
Proposed Amendment No. 158 i 4
4-92 ,
l i
u_.___._... _ _ __ _ _ _ . _ . _ _ _ _ __. _ _ _ _ _ _ _ _ _ _ . . _ _ _ _ _ _ . _ _ _ . _ . _ _ _ _ _ _ _ . _ _ _ _ _ _ _ . . _ _ . _ _ . _ _ _ _ _ _ _ _ _ _ _ . _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ . _ _
t ATTACIDGNT II l
l P30POSgD AMBIDMgNT SAFETY ANALYSIS PAGE 1 0F 7 I PgDFOSgD AMBIDMBIT No. 158 l
DgSCRIPTION:
The Sacramento Municipal Utility District plans to improve the operability of Rancho Seco's Combustible Gas Control System by installing internal hydrogen recombiners. The present combustible gas control equipment consists of redundant hydrogen purge trains and dedicated penetrations for the installation of an external hydrogen recombiner. The District intends to replace the present equipment with redundant internal hydrogen recombiners.
The proposed recombiners are of a standard design (Model A) made by Westinghouse. Similar Westinghouse Model A hydrogen recombiners have been installed in several other nuclear plants.
The Proposed Amendment No. 158 would 1) license operation with two proposed thermal hydrogen recombiners to be installed in the containment to replace the existing hydrogen purge system and 2) license revised Technical Specifications to reflect this facility change by deleting Technical Specification 4.4.3 and adding Technical Specifications 3.29 and 4.33.
RNASON FOR CHANGEt Purpoma The installation of internal hydrogen recombiners improves the operational reliability and maintainability of the Combustible Gas Control System. Both the present and proposed systems are in compliance with NRC reguistions. '
Further, the replacement of the hydrogen purse system with internal r recombiners improves plant safety by providing a high capacity, hydrogen ,
control system which operates without the need for venting the containment c gases to the atmosphere. ,
i EVALUATION AND BASIS FOR SAFsTY FINDINOS:
Hynteen. Huhnystemn. Components / Safety Functionn Affected Rancho Baco la a Pressurised Water Reactor (PWR) with a large dry containment. The Reactor building internal not free volume is 1.98 X 106 cubic feet (USAR Section 5.2.1, " Reactor Building, Containment Structure").
The NSSS was designed by Babcock & Wilcox. The plant was built by Bechtel Power Corp. The construction permit was issued on October 11,1%8. Large dry containment designs, like that of Rancho Seco, have a greater inherent capability than other designs to accommodate large quantities of hydrogen l because of their high design pressure and large volume. :
The purpose of the Combustible Cam Control System in to provide the functional i capability to assure containment integrity is maintained. The Combustible cas control System, required by 10CFR50.44(b), is to have the capability toi L_____________________
I
! . ATTACHMENT II (CONT.)
l PROPOSED AME DM W T SAFETY ANALYSIS PAGE 2 0F 7 PROPOSED AMMDMENT NO. 158 Systems, Subsystems. Components / Safety Functions Affected (Cont.)
50.44(b)(1) measure hydrogen concentration in the containment, 50.44(b)(2) mix the containment atmosphere, and 50.44(b)(3) control tha combustible gas concentration in the ,
j containment. '
The design change proposed for Rancho Seco is limited to item (3), above. The ,
District plans to change only the type of equipment used.
The present combustible gas control equipment meets the criteria of 10CFR50.44(c)(3)(ii)(A). A purge system is the primary means for post-LOCA ,
combustible gas control with dedicated containment penetrations for connection ;
of an external recombiner. The District propo.ns to satisfy 10CFR50.44(b)(3) !
with the installation of a combustible gas control system (internal recombiners) of the type that does not result in a significant release fron l the containment (defined in 10CFR50.44(h)(2)(ii)). As evidenced by :
10CFR50.44(e), the NRC has shown a degree of regulatory preference in favor of !
internal recombiner systems over purge systems as the primary means of L combustible gas control. The capability for controlled purging is available i via the non-safety-related Reactor Building (RB) Purge System.
A single internal recombiner system train is capable of maintaining the l hydrogen concentration below the flammability limits specified in the l applicable regulatory guidance, i.e., Safety Guide 7 (1971). Subsequent to l the licensing of this plant, Regulatory Guide 1.7, Rev. 2 (November, 1978) was
! issued. It changed the method of computing metal water reactions based on ,
l research findings that calculated metal-water reaction amounts to be only a l fraction of one percent of the fuel cladding mass. Under Safety Guide 7 -
t hydrogen control systems were designed to cope with an initial metal-water l reaction with 5% of the cladding mass. Safety Guide 7, under which Rancho '
Seco was licensed, is cicarly more conservative.
A single internal recombiner unit has almost five times the hydrogen removal capability of a single train of the hydrogen purge system. Each hydrogen purge system train processes 20 cfm of hydrogen / air mixture at 100% efficiency (USAR Appendix 14C.6, " Reactor Building Ilydrogen Purga System Description").
Each internal recombiner system train procer.ses 100 cfm of hydrogen / air mixture at 95% efficiency. 6 An appropriate margin of 0.5 v/o is maintained between the lower flammability I l
concentration limit (4.0 v/o) and the control concentration limit (3.5 v/o) at which the hydrogen recombiners will be actuated. Safety Guide 7 did not address this. Issue. USAR Appendix 14C.4.3, " Justification of Control Limit",
has taken credit for hydrogen control actuation at 3.5 v/o and this will not -
l change, despite the larger capacity of the hydrogen recombiners and the elimination of purge delay and purge duty cycles. ;
! i
= . .
. ATTACHMENT II (CONT.)
PROPOSED AMENDMENT SAFETY ANALYSIS PAGE 3 0F 7 PROPOSED AMENDMENT NO. 158 Systems, Subsystems. Components / Safety Functions Affected (Cont.)
The Westinghouse Model A internal recombiners are designed to be capable of withstanding all related environmental conditions imposed on them, without loss of function. The generic seismic and qualification report issued by Westinghouse for Model A hydrogen recombiner components (WCAP-7709-L, including Supplements 1-7) has been reviewed and approved by the Commission Staff. The Westinghouse environmental qualification program consisted of a series of tests including aging in steam for one year, high temperature tests, overpressure tests, irradiation tests, and long term operation simulating post-LOCA duty. The inherently passive and rugged design has shown itself suitable for long term applications. The postulated post-LOCA environmental conditions at Rancho Seco are enveloped within the conditions demonstrated in the Westinghouse qualification program.
In the Model A unit, hydrogen is recombined with oxygen in the recombiner by passing the containment gases over heated surfaces which supply the energy needed for recombination to occur. Since this type of recombination does not rely on catalytic effects of the recombiner surfaces, it cannot be poisoned by impurities which may exist in the containment atmosphere af ter an accident.
The gases flow through the recombiner by natural convection. The recombiner is of a completely passive design with no moving parts. The air flow rate is regulated by a fixed orifice and with the supply of electric power determined by a control station outside the reactor building. The gases pass through an opening in the vertical walls of the unit, which are protected by louvers against impingement from spraying water. The air stream is heated above a threshold temperature of 12250F, above which spontaneous recombination of hydrogen and oxygen occurs at 95 percent efficiency for gases containing less than 3.5 v/o hydrogen. The containment cooling system has sufficient capacity to remove the additional heat generated by the recombiners.
The major recombiner structural components are manufactured from stainless steel and Inconel-600, except the base which is carbon steel. Incoloy-800 is used for the heater sheaths and for other parts such as the heater ducts, which operate at high temperature. Each of the five heater banks contains 60 individual U-type electric resistance heating elements. Operation of the unit is virtually unaffected by the failure of a few individual heating elements.
The following USAR sections will be revised to reflect the installation of the internal recombiners:
1.5.37, " criterion 41-containment Atmosphere Cleanup",
1.5.38, " Criterion 42-Inspection of Containment Atmosphere Cleanup",
1.5.39, " Criterion 43-Testing of Containment Atmosphere Cicanup Systems",
9.7.2.1.6 " Reactor Building Atmosphere Hydrogen Honitoring and Recombination," and Appendix 140, "An Evaluation of Purging As A Heans of Controlling Post-Accident Reactor Dutiding Hydergen Concentration."
l
. ATTACIDGNT II (CONT.)
PROPOSED AMENDMENT SAFETY ANALYSIS PAGE 4 0F 7 PROPOSED AMENDMENT NO. 158 l
t l Systems, Subsystems, C~mponents/ Safety Functions Affected (Cont.)
l l
Although the means for hydrogen control is upgraded, the means by which Rancho Seco achieves hydrogen measurement and mixing are unaffected (in accord with l 10CFR50.44(b)(1) and (2)). Measurement is accomplished as described by USAR Section 9.7.2.1.6, "RB Atmosphere Hydrogen Monitoring and Recombination,":
The hydrogen monitoring sample system provides continuous indication of Reactor Building atmosphere hydrogen concentration following a hydrogen producing accident. Samples may be taken from several containment locations. The monitor suction shares the Reactor Building pressure equalization penetration. Exhaust from the monitor is returned to the reactor building through the steam generator acid cleaning and containment pressure testing penetration (Section 10.2). The monitors are located in the ventilation room and radiation monitoring rooms of I the Auxiliary Building and indication is provided at the system control panels located at grade level in the Auxiliary Building. Connections are provided to and from the post accident sampling system (Section 9.3) for post accident Reactor Building atmosphere sampling.
l l
Mixing is accomplished by the containment emergency cooling system and/or the ,
containment spray system (USAR Section 1.5.37, " Criterion 41-Containment Atmosphere cleanup"). Research, performed subsequent to the date of original plant licensing, has better characterized the mechanisms of convective mixing and molecular diffusion within the Reactor Building. The mechanisms of natural convection currents and molecular diffusion will disperse the hydrogen generated from the steam generator cavities into the upper containment region and throughout the Reactor Building (See also NUREG/CR-0304). Based upon this new understanding, the District has proposed the removal of the emergency upper done circulators as not being essential for the elimination of regions of high hydrogen concentration (see Proposed Amendment No.121, June 18, 1986). The performance of the hydrogen measurement and mixing systems is not l
affected by either the installation of the recombiners or the removal of the l hydrogen purge system.
Effects on Safety Functions / Analysis of Effects
, The hydrogen recombiner installation will meet the design, quality assurance, redundancy, energy source and instrumentation requirements for safety-related equipment. In addition, the internal recombiners will not themselves introduce safety problems that may affect containment integrity. The internal hydrogen recombinors were designed, maintained and will be installed in accordance with the appropriate 10CFR50, Appendix B requirements.
The recombiner systems are redundant and independent. A failure of one recombiner system is mitigated by the proper functioning of the other system.
Each recombiner is powered by a separate onsite energency (Class 1) power bus backed by diesel generators. The recombiner installation is designed to l withstand the Rancho Seco Design Base Earthquake without loss of function.
1 t
+
ATTACIDENT II (CONT.)
PROPOSED AMENDISNT SAFETY ANALYSIS PAGE 5 0F 7 PROPOSED AMENDMENT NO. 158 l Effects on Safety Functions / Analysis of Effects (Cont.)
l The installation of the recombiners permits periodic inservice inspection and operability testing which will be performed in accordance with the requirements of Proposed TS 4.33.
The hydrogen recombiner units are located inside containment on top of the "D l
Ring" walls at opposite sides of the Fuel Transfer Canal ~(see attached). This location is above the hydrogen sources (i.e., reactor vessel, reactor coolant system, etc.) and is in accordance with the manufacturer's guidance. A l location above the +60 f t elevation will provide an inflow source of hydrogen-air mixture from the largest free volume inside containment. In addition, the location and orientation of the recombiner intake outward from the "D Ring" will minimize the impact of high velocity air streams emanating from emergency fan cooler exhaust or from outside the "D Rings" themselves.
Further, the arrangement of the intake and exhaust ports serves to ensure that, for downflow air currents external to the recombiner, there would be little tendency for recirculation of the recombiner process gases (from the exhaust back into the intake). The location of the recombiner units assures
! that the units will receive uniformly mixed gases from all locations inside the containment.
Proposed Tech Specs 3.29, " Hydrogen Recombiners," and 4.33, " Hydrogen Recombiners," provide the necessary operability and surveillance requirements. The new specifications are based on the " Standard Technical Specifications for Babcock and Wilcox Pressurized Water Reactors" (NUREG-0103, l Rev. 4) as applicable to Westinghouse electric hydrogen recombiners. Proposed l Tech Spec 3.29 requires two independent recombiner systems to be operable. It l also specifies the procedure to be followed if one or both of the recombiners l becomes inoperable. Proposed Tech Spec 4.33 specifies the type and frequency l of surveillance operations to be performed on the recombiner system to assure l its operability. The specification requires, un a semi-annual basis, that the l operability of the recombiners be verified by performing prescribed tests. In l addition, the specification requires that during each refueling interval, the i entire system, including instrumentation and electrical circuits, is l thoroughly checked.
I 1 The proposed Tech Specs are adequate to assure proper operation of the hydrogen control system based on the proposed recombiners.
The installation of internal recombiners meets the requirements of 10CFR50, Appendix A, Criterion 41 " Containment Atmosphere Cleanup," by providing satisfactory means for post accident hydrogen control in the containment. The
! requirements of GDC 42, " Inspection of Containment Atmosphere cleanup," and l GDC 43, " Testing of Containment Atmosphere cleanup Systems," are met by j compliance with the proposed revised Technical Specifications.
l l
- w .. :
ATTACIDENT II (CONT.)
-PROPOSED AMENDMENT SAFETY ANALYSIS PAGE 6 0F 7 PROPOSED AMENDMENT NO. 158 Summary The Sacramento Municipal Utility District proposes to change the Combustible Gas Control System at Rancho Seco from a system based on a redundant Hydrogen Purge System (with capability to install an external hydrogen recombiner) to a system using a redundant Internal Hydrogen Recombiner System as the means for controlling combustible gas concentrations in containment following a postulated LOCA.
To reflect this change, the District proposes to delete Specification 4.4.3,
" Hydrogen Purge System," and add Specifications 3.29 and 4.33, " Hydrogen Recombiners," to be consistent with the " Standard Technical Specifications for Babcock and Wilcox Pressurized Water Reactors," NUREG-0103 (Rev. 4, Fall, 1980) for atmospheric containments as applicable to Westinghouse Electric Hydrogen Recombiners (pages 3/4 6-32J and B 3/4 6-5J).
Both the existing system and the Internal Hydrogen Recombiner System are in compliance with the regulatory requirements of 10CFR50.44, " Standards for Combustible Gas Control System in Light-Water-Cooled Power Reactors." Both systems are consistent with associated regulatory guidance:
- Regulatory Guide 1.7 (Rev. 2, November, 1978) and Safety Guide 7 (1971), as applicable.
- General Design Criteria 41, 42 and 43.
- Standard Review Plan 6.2.5, as applicable.
The Combustible Gas Control System is not being changed for regulatory reasons, but is being changed due to considerations of' operational reliability and maintainability. The required capabilities for mixing or measuring combustible gases are maintained.
The proposed change does not involve an.unreviewed safety question as defined by 10CFR50.59(a)(2) because operation of Rancho Seco in accordance with this change would nott
- 1. Involve an increase in the probability or consequences of an accident previously evaluated.
Installation of internal hydrogen recombiners improves hydrogen removal capability while minimizing the consequences of a postulated Loss of Coolant Accident (LOCA). The proposed system change will affect the type of equipment used to meet the regulatory requirement for the control of combustible gas concentration in containment (10CFR50.44(b)(3)).
- 2. Create the possibility of a new or different kind of accident from any accident previously evaluated.
-_s
ATTAODGNT II (CONT.)
PROPOSED AMENDMENT SAFETY ANALYSIS PAGE 7 0F 7 PROPOSED AMENDMENT NO. 158 Summary (Cont.)
The hydrogen recombiners have been environmentally qualified. They are to be installed in locations which will ensure their effectiveness and have no negative impact on other safety-related equipment. They will be.
consistent with regulatory requirements relating to Combustible Gas Control Systems.
- 3. Involve a reduction in a margin of safety as defined by the bases of the Technical Specifications.
The proposed equipment change is from a type of combustible gas control system which allows for the controlled release of gases from containment-(10CFR50.44(h)(2)(1)) to a type of system that does not result in a release from containment (10CFR50.44(h)(2)(ii)). A single internal recombiner unit has almost five times the hydrogen removal capability of a single train of the hydrogen purge system. The hydrogen control actuation limit of 3.5 v/o is retained despite the larger capacity of the hydrogen recombiner and the elimination of the purge delay _and purge duty cycles. The recombiner system has been given regulatory preference because of its characteristic of not generating releases during a postulated LOCA. The proposed recombiner system has greater hydrogen removal capability than the current purge system, in the event that it-should be used. Although both systems meet the applicable regulatory requirements, the proposed system is an improvement over the system currently in place.
ATTACHMENT III i' _.-
-NO SIGNIFICANT HAZARDS CONSIDERATION PAGE 1 0F 2 PROPOSED AMENDMENT NO. 158 The Sacramento Municipal Utility District proposes to change the Combustible Gas Control System at Rancho Seco from a system based on a redundant Hydrogen
' Purge System (with capability to-install an external hydrogen recombiner) to a system using a-redundant Internal Hydrogen Recombiner System as the means for controlling combustible gas concentrations in containment following a postulated LOCA.
To reflect this change, the District proposes to delete Specification 4.4.3,
" Hydrogen Purge System," and add Specifications 3.29 and 4.33, " Hydrogen Recombiners," to be consistent with the " Standard Technical Specifications for Babcock and Wilcox Pressurized Water Reactors," NUREG-0103 (Rev. 4, Fall, 1980) for atmospheric containments as applicable to Westinghouse Electric Hydrogen Recombiners (pages 3/4 6-32J and B 3/4 6-5J).
The deletion of specification 4.4.3 includes the testing of the Hydrogen Detectors (specification 4.4.3.2) of the Hydrogen Purge System. Hydrogen analysis for the Internal Hydrogen Recombiner System is specified in LCO and Surveillance Tables 3.5.5.1-1, Item 3 and 4.1-1, Item 60, respectively.
l Both the existing system and the Internal Hydrogen Recombiner System are in compliance with the regulatory requirements of 10 CFR 50.44, " Standards for Combustible Gas Control System in Light-Water-Cooled Power Reactors." Both systems are consistent with associated regulatory guidance:
Regulatory Guide 1.7 (Rev. 2, November,1978) and Safety Guide 7'
- (1971), as applicable.
- General Design Criteria 41, 42 and 43.
- Standard Review Plan 6.2.5, as applicable.
The Combustible Gas Control System is not being changed for regulatory reasons, but is being changed due to considerations of operational reliability and maintainability. The required capabilities for mixing or measuring combustible gases are maintained.
The proposed change does not involve an unreviewed safety question as defined i by 10 CFR 50.92(c) because operation of. Rancho Seco in accordance with this change would not:
- 1. Involve a significant increase in the probability or consequences of an accident previously evaluated.
Installation of internal hydrogen recombiners improves hydrogen removal capability while minimizing the consequences of a postulated Loss of-Coolant Accident (LOCA). The proposed system change will affect the type of equipment used to meet the regulatory requirement for the control of
, combustible gas concentration in containment (10 CFR 50.44(b)(3)).
]
ATTACHMENT III NO SIGNIFICANT HAZARDS CONSIDERATION PAGE 2 0F 2 PROPOSED AMENDMENT NO. 158 4
- 2. Create the possibility of a new or different kind of accident from any i accident previously evaluated.
The hydrogen recombiners have been environmentally qualified. They are to i be installed in locations which will ensure their effectiveness and have no negative impact on other safety-related equipment. LThey will be consistent with regulatory requirements relating to Combustible Gas Control Systems.
- 3. Involve a significant reduction in a margin of safety.
The proposed equipment change is from a type of combustible gas control system which allows for the controlled release of gases from containment (10 CFR 50.44(h)(2)(i)) to a type of system that does not result in a release from containment (10 CFR 50.44(h)(2)(ii)). A single internal recombiner unit has almost five times the hydrogen removal capability of a ;
single train.of the hydrogen purge system. The hydrogen control' actuation '
limit of 3.5 v/o is retained despite the larger capability of the hydrogen recombiner and the elimination of the purge delay and purge duty cycles.
The recombiner system has been given regulatory preference because of its characteristic of not generating releases during a postulated LOCA. The proposed recombiner system has greater hydrogen removal capability than the. current purge system, in the event that it should be used. Although both systems meet the applicable regulatory requirements, the proposed system is an improvement over the system currently in place.
On the basis of the above considerations, the District concludes that the proposed changes, replacing the Hydrogen Purge System with an-Internal.
Hydrogen Recombiner System, do not constitute any significant hazard, and in no way endangers the health and. safety of the public.
I l
l i
l 4 -