ML18247A227
| ML18247A227 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/18/2018 |
| From: | Dominion Energy Nuclear Connecticut |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML18199A125 | List:
|
| References | |
| 18-225 | |
| Download: ML18247A227 (152) | |
Text
Millstone Power Station Unit 2 Safety Analysis Report Chapter 6: Engineered Safety Features Systems
Table of Contents tion Title Page GENERAL........................................................................................................... 6.1-1 1 Design Bases............................................................................................... 6.1-1 1.1 Functional Requirements ............................................................................ 6.1-1 1.2 Design Criteria ............................................................................................ 6.1-1 2 System Description ..................................................................................... 6.1-2 2.1 System......................................................................................................... 6.1-2 2.2 Components ................................................................................................ 6.1-3 3 System Operation........................................................................................ 6.1-3 3.1 Emergency Conditions................................................................................ 6.1-3 4 Availability And Reliability........................................................................ 6.1-4 4.1 Special Features .......................................................................................... 6.1-4 4.1.1 Assumptions................................................................................................ 6.1-4 4.1.2 Design Method for Damage Prevention ................................................... 6.1-12 4.2 Tests and Inspection.................................................................................. 6.1-15 5 References................................................................................................. 6.1-15 REFUELING WATER STORAGE TANK AND CONTAINMENT SUMP..... 6.2-1 1 Design Bases............................................................................................... 6.2-1 1.1 Functional Requirements ............................................................................ 6.2-1 1.2 Design Criteria ............................................................................................ 6.2-1 2 System Description ..................................................................................... 6.2-1 2.1 System......................................................................................................... 6.2-1 2.2 Components ................................................................................................ 6.2-3 3 System Operation........................................................................................ 6.2-3 3.1 Emergency Conditions................................................................................ 6.2-3 3.2 Cold Shutdown and Refueling .................................................................... 6.2-4 4 Availability and Reliability......................................................................... 6.2-5 4.1 Special Features .......................................................................................... 6.2-5 4.2 Tests and Inspection.................................................................................... 6.2-6 28/18 6-i Rev. 36
tion Title Page SAFETY INJECTION SYSTEM ........................................................................ 6.3-1 1 Design Basis ............................................................................................... 6.3-1 1.1 Functional Requirements ............................................................................ 6.3-1 1.2 Design Criteria ............................................................................................ 6.3-1 2 System Description ..................................................................................... 6.3-1 2.1 System......................................................................................................... 6.3-1 2.2 Components ................................................................................................ 6.3-4 3 System Operation........................................................................................ 6.3-7 3.1 Emergency Conditions................................................................................ 6.3-7 3.2 Cold Shutdown and Refueling .................................................................. 6.3-10 4 Availability and Reliability....................................................................... 6.3-10 4.1 Special Features ........................................................................................ 6.3-10 4.2 Tests and Inspections ................................................................................ 6.3-15 CONTAINMENT SPRAY SYSTEM ................................................................. 6.4-1 1 Design Bases............................................................................................... 6.4-1 1.1 Functional Requirements ............................................................................ 6.4-1 1.2 Design Criteria ............................................................................................ 6.4-1 2 System Description ..................................................................................... 6.4-2 2.1 System......................................................................................................... 6.4-2 2.2 Components ................................................................................................ 6.4-3 3 System Operation........................................................................................ 6.4-3 3.1 Emergency Conditions................................................................................ 6.4-3 3.2 Cold Shutdown and Refueling .................................................................... 6.4-4 4 Availability and Reliability......................................................................... 6.4-4 4.1 Special Features .......................................................................................... 6.4-4 4.2 Test and Inspections.................................................................................... 6.4-5 CONTAINMENT AIR RECIRCULATION AND COOLING SYSTEM.......... 6.5-1 1 Design Bases............................................................................................... 6.5-1 1.1 Functional Requirements ............................................................................ 6.5-1 1.2 Design Criteria ............................................................................................ 6.5-1 28/18 6-ii Rev. 36
tion Title Page 2 System Description ..................................................................................... 6.5-2 2.1 System......................................................................................................... 6.5-2 2.2 Components ................................................................................................ 6.5-4 3 System Operation........................................................................................ 6.5-5 3.1 Normal Operations...................................................................................... 6.5-5 3.2 Leak Rate Testing ....................................................................................... 6.5-6 3.3 Emergency Conditions................................................................................ 6.5-6 3.4 Refueling..................................................................................................... 6.5-6 4 Availability And Reliability........................................................................ 6.5-6 4.1 Special Features .......................................................................................... 6.5-6 4.2 Tests and Inspections .................................................................................. 6.5-9 CONTAINMENT POST-ACCIDENT HYDROGEN CONTROL SYSTEM.... 6.6-1 1 Design Bases............................................................................................... 6.6-1 1.1 Functional Requirements ............................................................................ 6.6-1 1.2 Design Criteria ............................................................................................ 6.6-1 2 System Description ..................................................................................... 6.6-2 2.1 System......................................................................................................... 6.6-2 2.2 Components ................................................................................................ 6.6-4 3 System Operation........................................................................................ 6.6-5 3.1 Emergency Conditions................................................................................ 6.6-5 4 Availability and Reliability......................................................................... 6.6-6 4.1 Special Features .......................................................................................... 6.6-6 4.2 Tests and Inspection.................................................................................... 6.6-8 ENCLOSURE BUILDING FILTRATION SYSTEM ........................................ 6.7-1 1 Design Bases............................................................................................... 6.7-1 1.1 Functional Requirements ............................................................................ 6.7-1 1.2 Design Criteria ............................................................................................ 6.7-1 2 System Description ..................................................................................... 6.7-2 2.1 System......................................................................................................... 6.7-2 2.2 Components ................................................................................................ 6.7-4 28/18 6-iii Rev. 36
tion Title Page 3 System Operation........................................................................................ 6.7-4 3.1 Emergency Conditions................................................................................ 6.7-4 4 Availability and Reliability......................................................................... 6.7-4 4.1 Special Features .......................................................................................... 6.7-4 4.1.1 Minimum Air Flow Required to Prevent Desorption of Radionuclides ..... 6.7-5 4.1.2 Single Failure Evaluation............................................................................ 6.7-6 4.2 Tests and Inspections .................................................................................. 6.7-7 5 References................................................................................................... 6.7-8 28/18 6-iv Rev. 36
List of Tables mber Title 1 Pipe Rupture Protection Requirements 2 Omitted 3 Design Non-Seismic Category I Components Located Inside Containment and Enclosure Building 4 Pipe Rupture Criteria Applicability (Outside Containment) Based on Normal Operating Plant Conditions 1 Refueling Water Storage Tank and Containment Sump 1 Omitted 2 Principal Design Parameters of the Safety Injection System 3 Shutdown Cooling Heat Exchanger Data 4 Omitted 5 Internal Dimensions of Containment Sump Recirculation Piping and Valves 6 Safety Injection System Failure Mode Analysis High Pressure Safety Injection 7 Administrative Error Analysis-Safety Injection System Valves 8 Failure Modes and Effects Analysis for Boron Precipitation Control 1 Containment Spray System Component Design Parameters 2 Containment Spray System Failure Mode Analysis 1 Containment Air Recirculation and Cooling Units Materials of Construction 2 Containment Air Recirculation and Cooling Units Performance Data 3 Containment Air Recirculation and Cooling System 1 Containment Post Accident Hydrogen Control Systems Component Description 2 Deleted by FSARCR 04-MP2-018 3 Omitted 4 Post-Incident Recirculation System Failure Mode Analysis 1 Enclosure Building Filtration System Component Description 2 Enclosure Building Filtration System Failure Mode Analysis 28/18 6-v Rev. 36
List of Figures mber Title 1 Safety Injection P&ID (Sheet 1) 2 Main Steam Pipe Whip Restraint 3 Pipe Restraint Design 4 Fluid Jet Expansion Model 1 Safety Injection and Containment Spray Pumps Suction Piping 2 High Pressure Safety Injection Pump Performance 3 Low Pressure Safety Injection Pump Performance 1 Area 5 Piping Containment Spray and Hydrogen Purge 2 Containment Spray Nozzles Spray Patterns (1713A Nozzle Spraying Horizontally) 3 Containment Spray Nozzles Spray Patterns (1713A Nozzle Spraying Downward on 45°)
4 Containment Spray Nozzles Spray Patterns (1713A Nozzle Spraying Vertically Downward)
-5 Not Used
-6 Not Used 7 Containment Spray Nozzle Performance Characteristics 8 Containment Spray Pump Performance Characteristics.
9 Containment Heat Removal Systems Sink Schematic 1 Containment Air Recirculation and Cooling Unit Fan Performance Curve
-2 Containment Air Recirculation and Cooling Unit Coil Performance Characteristics 1 Post-Incident Recirculation Fan Performance Characteristics 1 Enclosure Building Filtration System Fan Performance Curve 28/18 6-vi Rev. 36
GENERAL 1 DESIGN BASES 1.1 Functional Requirements ineered safety features is the designation given to those systems which are provided for the ection of the public and station personnel against the postulated release to the environment of oactive products from the reactor coolant system, particularly as the result of loss-of-coolant dents (LOCA). These safety features function to localize, control, mitigate, and terminate h incidents and to hold exposure levels below limits of 10 CFR Part 50.67.
owing a LOCA, these systems function to cool the core to limit fuel damage, to limit the nitude and duration of pressure transients within the containment, to provide post-incident ling for extended periods and limit fission products release. The adequacy of the design is onstrated and the protection of the public assured by the use of the conservative assumptions ined in Section 14.6.5 and 14.8.4 in the analysis of the effects of the LOCAs.
1.2 Design Criteria following criteria have been used in the design of the engineered safety features systems:
- a. Safety related structures, systems, and components shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed. Where generally recognized codes and standards are used, they shall be identified and evaluated to determine their applicability, adequacy, and sufficiency and shall be supplemented or modified as necessary to assure a quality product in keeping with the required safety function. A quality assurance program shall be established and implemented in order to provide adequate assurance that these structures, systems, and components will satisfactorily perform their safety functions. Appropriate records of the design, fabrication, erection, and testing of safety related structures, systems, and components shall be maintained by or under the control of the nuclear power unit licensee throughout the life of the unit.
- b. Safety related structures, systems, and components shall be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, floods, tsunami, and seiches without loss of capability to perform their safety functions. The design bases for these structures, systems, and components shall reflect:
- 1. Appropriate consideration of the most severe of the natural phenomena that have been historically reported for the site and surrounding area, with 28/18 6.1-1 Rev. 36
- 2. Appropriate combinations of the effects of normal and accident conditions with the effects of natural phenomena.
- 3. The importance of the safety functions to be performed.
- c. Safety related structures, systems, and components shall be designed and located to minimize, consistent with other safety requirements, the probability and effect of fires and explosions. Noncombustible and heat resistant materials shall be used wherever practical throughout the unit, particularly in locations such as the containment and control room. Fire detection and fighting systems of appropriate capacity and capability shall be provided and designed to minimize the adverse effects of fires on safety related structures, systems, and components. Fire fighting systems shall be designed to assure that their rupture or inadvertent operation does not significantly impair the safety capability of these structures, systems, and components.
- d. Safety related structures, systems, and components shall be designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents, including LOCAs. These structures, systems, and components shall be appropriately protected against dynamic effects, including the effects of missiles, pipe whipping, and discharging fluids, that may result from equipment failures and from events and conditions outside the nuclear power unit.
- e. Safety related structures, systems, and components shall not be shared between nuclear power units unless it is shown that their ability to perform their safety functions is not significantly impaired by the sharing.
2 SYSTEM DESCRIPTION 2.1 System engineered safety features systems are shown schematically on Figures 6.1-1, 9.9-1, and 2, and are described in detail in the subsequent sections.
systems defined as engineered safety features are as follows:
- a. The safety injection system, including as subsystems the safety injection tanks, high pressure safety injection pumps and low pressure safety injection pumps, injects borated water into the reactor coolant system. This provides cooling to limit core damage and fission product release, and assures adequate shutdown margin.
The injection system also provides continuous long term post incident cooling of the core by recirculation of borated water from the containment sump.
28/18 6.1-2 Rev. 36
the containment sump and cooled by the reactor building closed cooling water system through the shutdown heat exchangers and recirculated into the containment atmosphere.
- c. The containment air recirculation and cooling system removes heat by passing containment air over coils cooled by the reactor building closed cooling water system.
- d. The enclosure building filtration system collects and processes potential containment leakage to minimize environmental activity levels resulting from containment leakage.
- e. The containment hydrogen control systems including independent systems provided to mix and monitor the hydrogen in the containment atmosphere.
supporting systems include the engineered safety features actuation system, the normal and rgency electrical power systems, the reactor building closed cooling water system, service er and chemical and volume control system (CVCS). These systems are described in detail in pters 7, 8 and 9. All pneumatically operated values and dampers are designed to assume the position following loss of instrument air.
2.2 Components engineered safety features systems components are procured to detailed engineering cifications and tested to applicable codes listed in following sections.
3 SYSTEM OPERATION engineered safety features systems generally operate only under certain emergency ditions. Some systems operate during normal operation as the containment air recirculation cooling system and hydrogen monitoring system. Other components such as the low pressure ty injection system and shutdown heat exchangers operate during shutdown operations.
3.1 Emergency Conditions he unlikely event of a LOCA or Main Steam Line Break (MSLB) accident, the engineered ty features systems with the exception of the hydrogen control system are automatically ated to perform their respective safety function. The hydrogen control system may be ually initiated within several hours after the incident.
28/18 6.1-3 Rev. 36
4.1 Special Features components of the engineered safety features systems and associated critical instrumentation ch must operate are designed to operate in the most severe environment to which they could exposed in the event of the worst postulated LOCA or MSLB accident. These design uirements are of primary significance for those portions of the engineered safety features ems which are located inside the containment. All components of the engineered safety ures located inside containment, the auxiliary building, or the enclosure building, are ironmentally qualified per 10 CFR 50.49 to operate in the most severe post-accident ironment to which they are exposed.
forces generated by the maximum hypothetical earthquake, combined with the rupture of a tor coolant pipe, are considered in the design of the engineered safety features. The design res that the functional capability of the system will be retained. Vessels which are connected he engineered safety features systems are supported and restrained to allow controlled vement during this load condition, and piping is designed to accept these imposed movements.
lysis of the flexibility of the systems have been performed to verify that the piping can accept e additional vessel movements and still remain within code allowable stress limits. Flexibility ulations have been performed in accordance with the applicable codes, ASME Section III lear Power Plant Components - 1971 and Power Piping ANSI B31.1.0-67. The double-ended ure of the largest reactor coolant pipe is used as the design basis since the forces are the most ere.
maximum post-incident temperature, pressure and humidity in the containment are found to developed by the MSLB accident. A discussion of the analyses performed for a spectrum of k sizes, to determine these limiting service conditions, is presented in Section 14.8.2.
pipe rupture protection requirements are listed in Table 6.1-1. The following pipe whip eria are used in the layout of piping and location of restraints protecting the redundant ineered safety features systems.
4.1.1 Assumptions vent of a pipe rupture in the reactor coolant system, it is assumed the only loss of engineered ty features piping is limited to those connected to that specific segment of the coolant loop.
4.1.1.1 Damage Protection Criteria criteria for protection from results of pipe whip or rupture inside and outside of the tainment are summarized below:
- a. Whipping does not preclude safe shutdown.
- b. A secondary system failure does not cause a failure in the primary system.
28/18 6.1-4 Rev. 36
- d. The containment liner plate is protected against a rupture on the primary system or piping that is in operation during or after a LOCA.
- e. The containment liner plate is protected against main steam line whip.
- f. In order to satisfy the criteria, protection against pipe whip is provided for high energy fluid systems (or portions of systems) except where:
- 1. either of the following piping system conditions are met (a) the service temperature is less than 200°F, or (b) the design pressure is 275 psig or less, or
- 2. the piping is physically separated (or isolated) from other piping or components by protective barriers, or restrained from whipping by plant design features, such as concrete encasement, or
- 3. following a single break, the unrestrained pipe movement of either end of the ruptured pipe in any possible direction about a plastic hinge formed at the nearest pipe whip restraint cannot impact any safety related structure, system or component, or
- 4. the internal energy level associated with the whipping pipe can be demonstrated to be insufficient to impair the safety function of any structure, system, or component to an unacceptable level.
- 5. Pursuant to 10 CFR Appendix A, GDC 4, Leak-Before-Break (LBB) analyses when reviewed and approved by the commission grant exemption from the protection requirements against dynamic effects associated with postulated pipe ruptures. Such an exemption has been granted for the main reactor coolant loop, for the pressurizer surge line, and for the unisolable RCS portions of the safety injection and shutdown cooling piping systems.
Subsequent to the commission review and approval, weld overlays were applied to dissimilar metal welds (DMWs) at the shutdown cooling, the safety injection and the pressurizer surge nozzles. A revised LBB analysis was performed for these nozzles and based on a 50.59 evaluation, commission review and approval of the DMW LLB analysis is not required to invoke the exemption from protection against pipe rupture dynamic effects for these nozzles.
- g. Structural failures of piping or components, whether in safety or nonsafety grade systems, in addition to the initial postulated pipe break and its direct consequences, need not be considered.
28/18 6.1-5 Rev. 36
4.1.1.2 Postulated Pipe Ruptures ASME Section III, Class I piping exceeding the pressure and temperatures conditions cated in Section 6.1.4.1.1.1 and listed in Table 6.1-1, a pipe rupture is postulated at the owing locations:
- a. the terminal ends, and
- b. any intermediate locations between terminal ends where the primary plus secondary stress intensities Sn (circumferential or longitudinal) derived on an elastically calculated basis under the loadings associated with one-half safe shutdown earthquake and operational plant conditions exceeds 2.0 Sm for ferritic steel, and 2.4 Sm for austenitic steel, and
- c. any intermediate locations between terminal ends where the cumulative usage factor (U) derived from the piping fatigue analysis and based on all normal, upset and testing plant conditions exceeds 0.1.
TE: The original plant design required a minimum of two intermediate break locations by selecting arbitrary break points when the criteria in Items (b) and (c) failed to provide this minimum number. In adopting Generic Letter 87-11 and eliminating these previously postulated arbitrary intermediate breaks from the population of high energy line breaks postulated for MP2, all existing protective hardware, originally designed to mitigate the effects of these breaks, were retained. Any subsequent removal of this hardware is required to be addressed on a case-by-case basis following the requirements of GL 87-11.
all other piping systems inside containment exceeding the pressure and temperature ditions indicated in Section 6.1.4.1.1.1 and listed in Table 6.1-1, a pipe rupture is postulated at following locations:
- a. the terminal ends, and
- b. any intermediate locations between terminal ends where either the circumferential or longitudinal stress derived on an elastically calculated basis under the loadings associated with seismic events and operational plant conditions exceed 0.8 (Sh +
SA) or the expansion stresses exceed 0.8 SA. SA and Sh are defined in Sections NC-3600 and ND-3600 of the ASME Section III Code, Winter 1972 Addenda.
TE: The original plant designs required a minimum of two intermediate break locations by selecting arbitrary break points when the criteria in Item (b) failed to provide this minimum number. In adopting Generic Letter 87-11 and eliminating these 28/18 6.1-6 Rev. 36
designed to mitigate the effects of these breaks, were retained. Any subsequent removal of this hardware is required to be addressed on a case-by-case basis following the requirements of GL 87-11.
piping systems outside containment exceeding the pressure and temperature conditions cated in Table 6.1-4, pipe rupture is discussed in Section 6.1.4.1.1.3.
type of pipe rupture at any postulated location, whether inside or outside containment, may ither of the following, regardless of the state of stress in the vicinity:
- a. Elongated slot type failure in pipes having a nominal diameter of 4 inches and larger. (The equivalent area of which is assumed to be equal to the equivalent internal cross-sectional area of the upstream section of pipe and oriented such that the resultant force is perpendicular to the axis of the pipe.) However, elongated slot type (i.e., longitudinal) breaks are not postulated at terminal ends. Terminal ends are defined as extremities of piping runs that connect to structures, large components (e.g., vessels, pumps, etc.) or pipe anchors that act as essentially rigid constraints to thermal expansion.
- b. Circumferential (Guillotine) break in pipes exceeding 1 inch nominal size (in which complete severance of the pipe is assumed perpendicular to the axis of the pipe).
ither case, the total dynamic steady thrust force in the event of a pipe rupture is computed m the following equation:
FT 2
= ( P 2 - P ) + G AB gc where:
FT = Total thrust force AB = Break flow area P2 = Exit plane pressure P = Pressure outside pipe prior to rupture G = Mass flow rate per unit area
= Fluid specific volume gc = Newtons constant ypical example of the existing pipe whip restraints designed according to the criteria in tion 5.2.5.7 of the FSAR and above is shown in Figure 6.1-2. This restraint prevents the main 28/18 6.1-7 Rev. 36
tion. Of these two conditions, the most critical one is the outward movement away from the raint supports.
total equivalent static reaction force of the pipe on the restraint, including the thrust fficients and dynamic load factors, amounted to 2PA, where:
P = maximum normal operating pressure A = internal cross-sectional area of the pipe s procedure resulted in an effective static design force of 1,600 kips on the main steam line whip restraint.
pipe whip restraints inside the containment were reevaluated by conducting a dynamic lysis, considering the restraint as a single degree-of-freedom system. Since a gap must be ntained between the restraint and the pipe, due to construction tolerances and thermal siderations, the effects of a plastic collision were also considered.
procedures to determine the effective thrust force for the dynamic analysis were revised from original assumption and are reported above. This procedure was used in all cases except for main feedwater line inside the containment, where the thrust force was determined by using computer code Relaps III and the conservation of momentum equations. In all cases, the thrust e was considered as a step function, having an instantaneous rise time and maintaining a stant (maximum) level of thrust until the pipe-restraint system has come to rest.
ce the thrust force was taken as independent of time, it is also independent of displacement.
ng independent of displacement, it can be shown mathematically that the dynamic analysis ussed above can be simplified to an energy balance calculation (i.e., the energy input into the raint by the pipe equals the strain energy of the restraint responding to the pipe impact).
ploying the Conservation of Momentum for a plastic collision and conservatively neglecting energy absorbed by bending (or hinging) of the pipe, the total deflection of the restraint is puted to be:
1 2R m y e + Tey g y m = --------------------------------------------
Rm - T 28/18 6.1-8 Rev. 36
ym = maximum deflection of the restraint ye = elastic deflection of the restraint yg = initial gap between pipe and restraint Rm = (maximum elastic structural resistance + plastic structural resistance) ÷ (2)
T = thrust force e = mp divided by (mp + mr) mp = effective mass of the pipe mr = effective mass of the restraint ure 6.1-3 shows the idealized dynamic pipe thrust force and the pipe whip restraint force as a ction of pipe deflection. Elastic deflection at this load is conservatively computed to be 0.093 es, resulting primarily from flexure. The ultimate allowable deflection that provides stance to the 1,600 kip force is taken to be 0.93 inches (i.e., elasto-plastic behavior, and a tility ratio of 10 inches flexure is considered).
pipe restraints outside the containment are designed to satisfy the requirements of tion 6.1.4.1.1.3. These pipe restraints are designed for elasto-perfectly plastic behavior, sidering the impact effects resulting from gaps between the pipe and restraint. An energy nce approach similar to the one discussed above is used.
ll cases these restraints are designed as flexible structures having a ductile failure mode. As a lt the dynamic load factors (measured as ratio of total restraint strength to steady thrust force) ged from 1.2 to 2.0. Strain limits associated with these values are within 50% ultimate strain of pipe whip restraint material. The criteria for protection against critical pipe failures for lstone Unit 2, including the criteria, as outlined in Section 5.2.5.7 of the FSAR, are in plete accordance with Bechtel Topical Report BN-TOP-2 (Rev. 1), Design for Pipe Break cts, except as noted in the following items.
Reference:
Fluid Jet Geometry as shown in Figure 2-3 of BN-TOP-2 (Rev. 1). The jet ansion model used for Millstone Unit 2 and the referenced Figure are both shown in ure 6.1-4 for comparison. The model presented in BN-TOP-2 consists of three regions. For cooled water blowdown, this model assumes half-angle approach of 10 degrees uniformly in hree regions. For steam and steam/water blowdown, the jet expands to the asymptotic area at lf-angle which exceeds 10 degrees. The area remains constant in region 2 and expands again ten degree half-angle in region 3.
steam and steam/water mixtures, the model used for Millstone Unit 2 assumes the jet expands he asymptotic area (taken to be located at five inside pipe diameters from the break exit plane) 28/18 6.1-9 Rev. 36
expansion of the fluid jet from a postulated pipe rupture attenuates the system pressure within nominal pipe diameters from the source of the jet to ambient conditions as demonstrated by REG/CR-2913, Reference 6.1-2. Unprotected components at a distance beyond ten nominal diameters from the broken pipe are considered undamaged by the jet without further lysis.
jet shape used for cold water and non-flashing/subcooled fluid is treated as a non-expanding with its area equal to that of the break exit area. In this case, conservation of load effects will ssumed and the zone of influence of the jet will be considered to end only by interaction with omponent or structure with the capacity to block and resist the full jet load. Therefore, the lstone Unit 2 model provides jet pressure intensities which are more conservative than
-TOP-2.
Reference:
Moment capacity for steel beam, Page 3-9 of BN-TOP-2.
Mu = 0.9 fy Sp (1)
Mu = 1.0 fy S (2) re Mu = yield moment fy = yield stress Sp = plastic section modulus S = elastic section modulus ation (1) is presented in the referenced BN-TOP-2 and Equation (2) is used in designing pipe p restraints for Millstone Unit 2. Since the ratios of the plastic to elastic section moduli range m 1.1 to 1.18 with an average of 1.134 (Reference 6.1-1) for structural shapes, equation (2) omes:
Mu = 0.88 fySp (3) ce Mu is the capacity moment for the restraint and is associated with the energy absorbing acity of the restraint, the lesser values of Mu used in Millstone Unit 2 will result in a more servative design than that if equation (1) is used.
Reference:
Pipe break configurations are shown on Figure 2-4 of BN-TOP-2. The referenced
-TOP-2 figure and the associated discussion on jet impingement configurations and forces bute jet impingement effects not only to full-size circumferential or longitudinal breaks, but to cracks. Millstone Unit 2 does not consider any jet impingement effects or other dynamic 28/18 6.1-10 Rev. 36
noted within the BN-TOP-2 report, jet impingement effects are important only in the first few k diameters away from the source pipe. Since the effective diameter of a crack is based on a le with an area equal to one-half the pipes inside diameter times one-half the pipes wall kness instead of the full pipe flow area considered for other breaks, its effective diameter is ificantly smaller than that of other breaks. As both the effective zone-of-influence and lting jet force due to any break are a function of the break diameter, the dynamic effects lting from a crack would also be significantly less than full-size break effects. Therefore, for lstone Unit 2, jet impingement effects resulting from cracks are considered fully enveloped by postulated full size pipe breaks.
4.1.1.3 Pipe Ruptures Outside Containment ture Criteria all piping systems with normal operating pressure and temperature conditions exceeding e defined by operating conditions A, B and C in Table 6.1-4, a pipe rupture is postulated at the owing locations:
- 1. the terminal ends, and
- 2. for stress analyzed piping, at any intermediate location between terminal ends where the calculated Primary + Secondary Stress, S, exceeds 0.8(Sh + SA), or the Secondary Stress alone exceeds 0.8SA where:
S = stresses under the combination of loadings associated with the normal and upset plant condition loadings and an OBE event.
Sh = basic material allowable stress at maximum (hot) temperature from the allowable stress table in the associated piping analysis design code.
SA = allowable stress range for expansion stresses as defined in the associated piping analysis design code.
- 3. for unanalyzed piping, at all intermediate weld connections to elbows and other pipe fittings within the line.
- 4. for type and configuration of the resulting postulated pipe ruptures at each of the above locations, refer to Section 6.1.4.1.1.2,
- 5. In addition to the above pipe ruptures, through wall leakage cracks are postulated at those locations that results in the most adverse conditions of flooding and local environmental conditions on the adjacent safe shutdown equipment. The flow area 28/18 6.1-11 Rev. 36
nt Modifications Resulting From the Elimination of Arbitrary Intermediate Breaks (GL 87-11) dopting Generic Letter 87-11 and eliminating the previously postulated arbitrary intermediate ks from the population of high energy line breaks postulated for MP2, all existing protective dware, originally designed to mitigate the effects of these breaks, were retained. Any sequent removal of this hardware is required to be addressed on a case-by-case basis following requirements of GL 87-11.
4.1.1.4 Safe Shutdown for Pipe Rupture comprehensive review of MP2 design basis documentation has been performed and a hodology was developed to select safe shutdown paths. Those components necessary to bring plant to Mode 3, Hot Standby, condition are defined by this methodology. The various rnative methods identify paths used in accomplishing the following safe shutdown functions sequent to a High Energy Line Break (HELB):
RCS Heat Removal RCS Pressure Control RCS Inventory Control Maintaining Vital Auxiliaries eral assumptions used in identifying the safe shutdown paths are described below:
Safe shutdown for a HELB is defined as Hot Standby (Mode 3) and maintaining this condition for eight (8) hours.
Only those high energy systems that are in service during normal plant operations are assumed to rupture.
Offsite power is assumed to be not available if the pipe rupture results in a unit trip.
Coincident with the postulated pipe break, a single active failure in an active component of a required safety related system is assumed.
No other extraordinary events are postulated (i.e., fire, earthquake, etc.)
4.1.2 Design Method for Damage Prevention sical separation, where possible, between critical lines is utilized by routing the piping so that ptured line is beyond reach of another line or critical component.
28/18 6.1-12 Rev. 36
ty injection pump and one containment spray pump.
h group is served by separate suction and discharge header, powered by separate sources and hysically located in separate watertight pump rooms. The third high pressure safety injection p is interconnected to the two headers. A selection switch is provided to enable the pump to w power from either emergency bus. The third HPSI pump is aligned to operate only upon oval from service of either of the other HPSI pumps.
er hammer effects are minimized in the engineered safety features system by keeping process s flooded where possible. Air pockets will be eliminated by periodic opening of isolation es during testing and by high point vents provided on the process lines.
safety injection system is flooded up to the connection to the reactor coolant system while the tainment spray system is flooded up to the risers in containment. The remaining piping is ical or sloped upward to eliminate air pockets.
motor-operated valves in the safety injection and containment spray systems are opened in onse to their associated actuation signals.
8 HPSI injection throttle valves are manually positioned to the desired open position and do open further on an actuation signal.
ther discussion of the various methods of pipe whip protection are contained in tion 5.2.5.7.1.
following criteria must be satisfied by components located in the containment and the losure building that are not seismic category I:
- a. Failure of these components cannot affect safe shutdown of the reactor.
- b. Failure of these components cannot affect the operation of Seismic Category I components.
- c. Non seismic Category I components are located in such areas that missiles projected from their failures remain isolated from seismic I components.
le 6.1-3 lists the Non seismic Category I components located inside the containment and losure building.
components of the clean liquid waste processing systems are located at the lower elevations ontainment, away from safety related equipment. The pressurizer quench tank operates at 35 maximum. The primary drain tank operates at 2 psig. At these relatively low operating sures, these components do not sustain sufficient energy to become potential missiles. The 28/18 6.1-13 Rev. 36
vents, drains and sample connections to the reactor coolant pressure boundary are analyzed the design basis earthquake beyond the second isolation to the first anchor.
containment floor drain system is embedded in concrete and vented to containment. These atmospheric pressure and therefore, do not sustain sufficient energy to become a potential sile or to whip into Category I equipment. The sump pumps are located at the lowest elevation ontainment, away from safety related equipment. The discharge pressure of the sump pumps pproximately 25 psig. This pressure is not sufficient to create a potential missile or to whip.
components of the RV Head decontamination system are located at lower elevations in lded compartments away from safety related systems. The system is no longer used and efore will not generate any missiles due to rupture.
containment elevator is completely contained within the elevator shaft structure which is a egory I structure. The stud storage racks are anchored during normal operation. The CEDM lers are connected to the RBCCW and are analyzed for the design basis earthquake. The DM coolers are located on the missile shield, away from any safety related equipment. The olving maintenance truss is analyzed for the design basis earthquake. The containment iliary circulation fans and duct work are located above the operating floor, away from safety ted equipment.
instrument air receiver tank, which operates at a pressure of 80 psig, is located at elevation 14 feet 6 inches outside of the secondary shield wall.
refueling pool skimmer filters are located in shielded compartments at elevation (+) 14 feet 6 es outside the secondary shield wall. The skimmer system is in operation only during eling.
reactor coolant system is shielded from potential missiles by the primary and secondary ld walls and the missile shield. The steam generators are shielded by the secondary shield ls and by a doghouse extended above the operating floor.
blowdown quench tank, heat exchanger and pump are located within a concrete enclosure ugh which the main steam piping is routed. The blowdown tank is located within the losure building proper and is normally operating at approximately 1 psig. At this low pressure system does not sustain sufficient energy to become potential missiles or to cause the pipe to
- p. The closed quench tank system operates at approximately 50 psig. This energy is not icient to cause damage to the Category I systems following a postulated pipe whip.
cellaneous duct work and unit heaters which operate at relatively low pressure shall not attain icient energy to cause damage to Category I systems.
28/18 6.1-14 Rev. 36
engineered safety features system components are procured to detailed engineering cifications and tested to applicable codes as described in the subsequent section. In addition, cial testing of actual or prototype components under proposed service conditions of pressure, perature and humidity are conducted on various components. Engineered safety features em components are incorporated with provisions for on-line testing.
ineered safety feature systems are incorporated with provisions for full system actuation and ormance tests.
mponents located outside the containment are accessible for periodic maintenance and ection. Components located inside the containment are accessible during normal shutdown.
5 REFERENCES 1 Plastic Design in Steel, 2nd Edition, ASCE Manual Number 41, 1971.
2 NUREG/CR-2913, Two-Phase Jet Loads, January 1983.
28/18 6.1-15 Rev. 36
CATEGORIES LINE SERVICE A B C D E F fety Injection Lines X X X X X arging Line X X X actor Coolant Letdown Lines X X X X am Generator Blowdown Lines X X X X edwater Lines X X X X X X in Steam Lines X X X X X X actor Coolant System Piping X X X X following categories have been listed in Table 6.1-1 to describe the criteria mentioned:
egory A Lines that must be restrained from damaging the reactor coolant system.
egory B Lines that must be restrained from damaging the containment liner plate.
egory C Lines that must be protected from damage by ruptured reactor coolant system piping egory D Lines that must be restrained from damaging the secondary system.
egory E Lines that must be protected from damage by the secondary system.
egory F Lines that must be protected from damage by or restrained from damaging their parallel redundant lines.
28/18 6.1-16 Rev. 36
28/18 6.1-17 Rev. 36 INSIDE CONTAINMENT AND ENCLOSURE BUILDING ontainment Building A. Clean Liquid Waste Processing System Components (FSAR Figure 11.1-1)
- 1. Primary Drain Tank and Pumps
- 2. Primary Drain Tank and Quench Tank Heat Exchangers
- 3. Associated piping and valves B. Reactor Coolant System Components (FSAR Figure 4.1-1)
- 1. Quench Tank and associated piping and valves
- 2. Vent, sampling and drain piping and valves beyond second isolation valve C. Drain Systems (FSAR Figure 11.1-3)
- 1. Sump pumps
- 2. All drain piping and valves for non Category I equipment beyond second isolation valve of primary pressure boundary.
D. Reactor Vessel Head Decontamination System
- 1. Mixing tank
- 2. Pump
- 3. Filters (2)
- 4. Piping and valving E. Miscellaneous
- 1. Containment elevator
- 2. Stud storage racks
- 3. CEDM Coolers
- 4. Revolving maintenance truss
- 5. Containment auxiliary circulation fans and ductwork
- 6. Instrument air receiver tank & associated equipment
- 7. Refueling pool skimmer filter & associated equipment
- 8. Containment Surveillance camera & associated equipment 28/18 6.1-18 Rev. 36
nclosure Building A. Main Steam System Components (FSAR Figure 10.3-1)
- 1. Blowdown Tank
- 2. S. G. Blowdown Quench Tank, Heat Exchanger, Recirculation Pump, valves and associated piping B. Containment Penetration Cooling System
- 1. Fans
- 2. Ductwork C. Miscellaneous
- 1. Miscellaneous ductwork
- 2. Unit heaters 28/18 6.1-19 Rev. 36
CONTAINMENT) BASED ON NORMAL OPERATING PLANT CONDITIONS Operating Condition Temperature (Degrees F) Pressure (PSIG)
A Equal to or Greater than 200 Equal to or Greater than 275 B Equal to or Greater than 200 1 Less than 275 C Less than 200 Equal to or Greater than 275 D Less than 200 Less than 275 e Rupture postulation at MP2 is separated into four distinct groupings, which are dependent on normal service temperature and pressure of the line; e.g., the state of temperature and pressure he system during Normal Plant Operation (NPO) from plant heatup through power operation plant shutdown to the hot standby condition. Where a piping system operates within the meters of Operating Conditions A, B, or C for only a short period of its operating time (i.e.,
than 2%) it is considered to be a Moderate Energy System and is treated as an Operating dition D System.
- 1. Lines whose normal operating condition is defined by condition A are defined as High Energy Lines with postulated pipe rupture effects of pipe whip and jet impingement and the related effects of pressurization, flooding and environment. Includes Charging System which operates substantially above 275 psig, but less than 200°F.
- 2. Lines whose normal operating condition is defined either by condition B or C are defined as High Energy Lines with postulated pipe rupture effects of jet impingement and the related effects of pressurization, flooding and environment.
- 3. Lines whose normal operating condition is defined by A, B, or C are defined as High Energy Lines with postulated effects of piping cracks (includes flooding and environmental conditions) at the most adverse equipment locations.
- 4. Lines whose normal operating condition is defined by operating condition D are considered Moderate Energy Lines (MELs) and require no postulation of rupture effects.
Lines with temperature 200°F, and pressures approximately atmospheric are not considered as High Energy Lines since the calculated jet impingement force will be negligible for such low pressure.
28/18 6.1-20 Rev. 36
figure indicated above represents an engineering controlled drawing that is Incorporated by erence in the MPS-2 FSAR. Refer to the List of Effective Figures for the related drawing ber and the controlled plant drawing for the latest revision.
28/18 6.1-21 Rev. 36
figure indicated above represents an engineering controlled drawing that is Incorporated by erence in the MPS-2 FSAR. Refer to the List of Effective Figures for the related drawing ber and the controlled plant drawing for the latest revision.
28/18 6.1-22 Rev. 36
figure indicated above represents an engineering controlled drawing that is Incorporated by erence in the MPS-2 FSAR. Refer to the List of Effective Figures for the related drawing ber and the controlled plant drawing for the latest revision.
28/18 6.1-23 Rev. 36
06/28/18 6.1-24 Rev. 36 28/18 6.1-25 Rev. 36 28/18 6.1-26 Rev. 36 1 DESIGN BASES 1.1 Functional Requirements refueling water storage tank (RWST) functions to provide the initial source of borated water the safety injection and containment spray pumps.
containment sump functions to collect the water from the safety injection, containment spray reactor coolant blowdown for recirculation after the water has been nearly exhausted from the ST.
1.2 Design Criteria following criteria have been used in the design of the RWST and containment sump:
- a. The system shall provide a reliable source of borated water for the safety injection system and the containment spray system.
- b. The system shall be designed to permit inspection of important components, such as sump, tank, valves and piping to assure the integrity and capability of the system.
- c. The components shall be designed to the general criteria as described in Section 6.1.
2 SYSTEM DESCRIPTION 2.1 System location and interconnection of the RWST and containment sump in the system are shown ematically in Figure 6.1-1.
RWST is an atmospheric tank which stores borated water during normal operation. The ST is the initial source of suction for the high pressure and low pressure safety injection ps (Section 6.3) and the containment spray pumps (Section 6.4). The RWST is provided with separate, independent outlet headers, each of which supplies borated water to each grouping minimum engineered safety feature pumps as described in Section 6.1.4.1. The A RWST et header also supplies a suction connection that facilitates portable diesel driven RCS ction Pump deployment. This connection supports the discharge connection described in tion 6.3.2.1 and is a defense-in depth design feature that is available for coping with an nded loss of AC power (ELAP) event. The location of this BDB RCS FLEX suction nection is shown on Figure 6.1-1, Sheet 2.
28/18 6.2-1 Rev. 36
0 ppm boron.
containment sump is formed by the floor and the lowest elevation of containment. The ated water from the safety injection (Section 6.3), containment spray system (Section 6.4) and tor coolant system is collected and subsequently recirculated to the pumps suction. Two 24 containment sump recirculation pipes are provided from the sump to the suction of the safety ction and containment spray pumps. The recirculating piping inside the containment extends roximately 11 inches above the floor Elevation (-) 22-6. A vortex breaker is provided on each tainment sump recirculation pipe inlet to avoid any air ingestion.
containment sumps are located at the bottom of the containment building at elevation 2-6. The containment sump strainer has an enclosure that surrounds the pump suction pipes ted in this sump. Two headers extend out from this enclosure in an eastern and northern ction. Perforated hollow fins are attached to these headers and flow is draw through these fins into the headers and directed to the sump enclosure. The sump enclosure is solid plate and has anway in the side to allow access to the sump for inspections.
strainer is constructed of 304/304L SS or equivalent materials. The fins are made of thin ugated stainless steel perforated with 1/16 inch holes. This perforation size prevents larger icles from passing and thus avoids any clogging of any downstream equipment including p flow clearances, containment spray nozzles or HPSI throttle valves. The total filtration ace area of the strainer is approximately 6,000 square feet.
strainer is designed to support the full flow rate from both trains of ECCS simultaneously.
strainer is a single unit that is shared by both trains. It is a passive component with no moving
- s. Evaluations in accordance with Section 6.1.4 have determined that there are no credible ure modes that will cause loss of the strainer and redundant trains are not required.
strainer is designed to accommodate the debris load from either a SBLOCA or a LBLOCA.
s debris load consists of fibrous and particulate materials generated by the force of the pipe k in the steam generator cubicle. In addition, it considers latent particulate and fibrous debris m the containment walls, floors and equipment that is washed to the sumps by containment
- y. The design also considers the formation of particulate due to chemical reactions between substances suspended or dissolved in the containment sump water post accident. The head loss ss the strainer, including this debris, is limited to a value that will not adversely affect the ilable net positive suction head for the safety injection and containment spray pumps.
RWST capacity is adequate to provide a minimum water level in the containment sump for ration of the safety injection and containment spray pumps during post-accident operation for h LBLOCA and SBLOCA.
ineered safety features piping connected to the containment sump is an extension of reactor tainment during the recirculation mode of core and containment cooling. The following items ain to suction piping from the sump to the first isolation valve:
28/18 6.2-2 Rev. 36
Pumps and Valves for Nuclear Power, Class II.
- b. The recirculation lines from the containment out to and including the first isolation valve are enclosed in leakage controlling encapsulation barriers. The barrier will control leakage resulting from postulated pressure failure of the pipe or valve. This leakage control function is provided by gaskets, seals, and the concrete to steel interfaces at the encapsulation embedment plates. These features will physically limit potential fluid releases from the encapsulations to an extent that does not significantly deplete the water level in the containment sump during sump recirculation; that does not impact ECCS pump NPSH requirements or measurably alter ECCS flow capabilities; and that does not pose a threat of flooding, spraying, or otherwise shorting-out the ECCS pumps in the A safeguards room of the Auxiliary Building. The leakage control function of the encapsulations will also assure that post accident radioactive fluids released from these structures will be collected in the A safeguards room or in the liquid radwaste system in the Auxiliary Building, and processed or retained in a manner that protects public health and safety. The barrier is tightly attached to the exterior concrete of the containment. The encapsulation barrier is designed for 60 psig and is in accordance with the criteria for Seismic Class I structures.
- c. Pipe material is Type 304 stainless steel.
first isolation valve in each recirculation line is a motor-operated double-disk gate valve.
ture disks are installed to prevent the possibility of thermal expansion of trapped fluid in the e bodies causing the valves to become pressure locked prior to initiation of sump rculation. The rupture disks are installed in piping connected to the body drain of each ation valve. The discharge of the rupture disks is contained within the closed piping system.
djust the pH of the containment sump water following a postulated LOCA, wire-mesh baskets taining trisodium phosphate dodecahydrate (TSP) are provided on the lowest level of the tainment as shown on Figure 1.2-11. The baskets contain a Technical Specification required ume of solid granular TSP, a quantity sufficient to raise the sump water pH to a value equal to reater than 7.0.
2.2 Components major system components and associated fabrication data are listed in Table 6.2-1.
3 SYSTEM OPERATION 3.1 Emergency Conditions valves on the RWST suction headers are normally in the open position. The safety injection containment spray systems are flooded from the RWST to their respective containment 28/18 6.2-3 Rev. 36
he unlikely event of a LOCA, borated water from the RWST is immediately available to the ps suction without additional active operations.
en the RWST level reaches 46 inches, the safety injection and containment spray pump ion is automatically transferred to the recirculation mode with suction from the containment
- p. This is initiated by the sump recirculation actuation signal (SRAS) and is described in tion 7.3.
recirculation mode can also be initiated manually by the operator.
SRAS opens the isolation valving (2-CS-16.1A and 16.1B on Figure 6.1-1) on the tainment sump recirculation piping and therefore, permits the pumps to take suction from the tainment sump.
external heater is provided to maintain the contents of the RWST 50°F in Modes 1 and 2, 35°F in Modes 3 through 6 (Section 6.2.4.1). RWST temperature is monitored by perature indication in the control room. Low water temperature is alarmed to alert operators remedial action is required. RWST water level is indicated in the control room. Low water l alarms are provided to alert operating personnel. Sample points located within the safety ures system indicate water chemistry. Provisions are incorporated for filling draining and ring the water chemistry of the tank contents. Purification of the RWST contents is provided he spent fuel pool purification system.
owing a postulated LOCA, the TSP stored in dissolving baskets at the lowest elevation of the tainment will dissolve in the sump water as the safety injection water fills the containment.
tainment sump water recirculation will provide the required mixing to achieve a final pH ter than or equal to 7.0 for the sump water.
3.2 Cold Shutdown and Refueling owing cold shutdown and after the reactor vessel head is removed, the refueling cavity is d by the LPSI pumps with borated water from the RWST. The RWST is sized to provide a icient quantity of borated water to maintain a water level of 24 feet above the reactor vessel ge. Shutdown cooling operation and refueling operations are described in Section 9.3.
owing the refueling operation, the water from the refueling cavity is pumped back to the ST.
28/18 6.2-4 Rev. 36
4.1 Special Features assure availability of borated water for post-accident operation, the RWST is normally aligned operation with the outlet valves opened. The tank contents are maintained 50°F in Modes 1 2, and 35°F in Modes 3 through 6 by recirculation through an external heat exchanger ch is heated by unit steam. The supply and return connections for the RWST heating system etrate the upper portions of the tank, above the minimum water level of 32.5 feet, to prevent essive tank drainage following a postulated pipe rupture. The supply connection to the heat hanger is provided with a siphon breaker to prevent siphoning of the tank following a tulated pipe rupture. The siphon breaker is located immediately above the minimum tank er level to assure suction for the RWST heating system and to minimize drainage following a tulated pipe rupture.
maintain the RWST contents at 50°F with zero (0)°F outside air temperature, heating is uired at a rate of 1.21 x 106 Btu/hr. The RWST borated water temperature is measured and med should it decrease below 55°F. Remedial action can be taken by the operator by routing tank contents through one shutdown cooling heat exchanger using one containment spray p and aligning a recirculation path to the RWST by opening valves 2-SI-456 (or 2-SI-457),
2-SI-460 (Figure 6.1-1). The RBCCW is used as the heating medium. Assuming a servative 60°F RBCCW temperature, the tube side (RWST) water leaving temperature is F.
spent fuel pool cooling system may be used as back-up for the above to maintain the RWST tents at the required temperature.
motor-operated isolation valves on the RWST headers remain open following the switch over he sump recirculation mode of operation. These valves may be closed manually. However, this ration is not required for system operation. The elevated pressure within containment under t-accident conditions maintains the check valves (2-CS-14A and 14B) on the RWST headers closed position. Under no normal circumstance can the header from the RWST be emptied e the elevation head from the containment sump at Elevation (-) 22-6 maintains the water l in the RWST headers at this minimum elevation. The interconnection between the tainment sump recirculation line the RWST header is located at Elevation (-) 30-1 5/8 and 33-7.
containment sump recirculation piping is embedded in the concrete containment floor to vent leakage of the post-accident containment atmosphere. Although completely redundant p recirculation piping is provided, one pipe is encased in a guard pipe for protection where h pipes are located in the same safety features pump room. Therefore, any failure of one line s not render the redundant line inoperable.
RWST is located at grade Elevation 14-6. The containment sump inlet is located at the lowest ation in the auxiliary building, (-) 45-6. Therefore, all suction lines are flooded to assure ing.
28/18 6.2-5 Rev. 36
r greater than 7.0 when considering the total quantity of borated water that could be available the containment sump following a LOCA, the amount of hydrochloric acid from the radation of electric cable insulation, and the amount of nitric acid from the irradiation of the tainment air and sump water. Maintaining sump pH equal to or greater than 7.0 ensures iodine ntion capability following a LOCA. Tests have demonstrated that the TSP will readily olve in the containment sump water. In addition TSP experiences no significant deterioration ecomposition upon storage.
4.2 Tests and Inspection RWST was acceptance tested in accordance with the ASME Code,Section III, Class 3. Since RWST performs no active function, online testing is not provided. The RWST header valves erwent acceptance testing prior to initial start up. The test procedure is described in tion 13.
RWST is accessible for periodic maintenance and inspection during normal operation.
containment sump recirculation isolation valves (2CS-16.1A and 16.1B) may be tested for ning capabilities during normal operation. A check valve is located downstream of each of e valves to prevent flow from the RWST entering the containment.
containment sump recirculation isolation valves undergo a preoperational test prior to start Test procedures are described in Section 13.
containment sump and TSP baskets are accessible for inspection and maintenance during mal shutdown.
28/18 6.2-6 Rev. 36
ST Manufacturer Company Richmond Engineering Company Model Number 3736-4x6-13DV Quantity 1 Design Pressure Atmospheric Design temperature (°F) 120 Shell Material SA-240, Type 304 Net Capacity (gal.) 475,000 Code ASME Code,Section III, Class 3 (1971 edition)
Seismic Class 1 ng erial ASTM A-312, Type 304 2.5 inch and larger Sch 10S 2 inch and smaller) Sch 40S ings 2.5 inch and larger Butt-welded except at flanged equipment 2 inch and smaller) Socket-welded ves 2.5 inch and larger Butt-welded, ANSI 600 lb rating stainless steel 2 inch and smaller) Socket-welded, ANSI 600 lb rating stainless steel ndard - Piping ANSI B 31.1.0 e - Valves Draft ASME Code for Pumps, and Valves for Nuclear Power, Class 2, 1968 mic Class 1 28/18 6.2-7 Rev. 36
tainment Sump tainment Sump Recirculating Piping erial ASTM A-312, Type 304 24 inches Sch 10S ings Butt-welded ves Butt-welded, ANSI 150 lb rating, stainless steel ndard ANSI B 31.7 Class II mic Class 1 tainment Sump Screen ntity 1 roximate Overall dimensions (feet): Two branches of headers 4 feet high, one header is 42 feet long, and one is 39 feet long. They are both connected to a 6 foot wide by 12 foot long by 4 foot high enclosure over the sump inlet piping.
erial: 304 / 304L or approved equal size: 37.75 inches high by 2 inches thick by various lengths perforation opening 1/16 inch e area (%) approximately: 40 mic: Class 1 Baskets ntity 3 rall dimensions (feet) 5 L x 5 x 1 H (approx.)
erial TP 304 stainless steel e Mesh 80 ntity 2 rall dimensions (feet) 5 L x 5 x 5 H (approximate) erial TP 304 stainless steel e Mesh 80 28/18 6.2-8 Rev. 36
1 DESIGN BASIS 1.1 Functional Requirements safety injection system must function to supply core cooling in the unlikely event of a loss-oolant accident (LOCA) for all breaks in the reactor coolant system piping up to and uding the equivalent of a double-ended break in the largest coolant pipe; i.e., up to a flow area 9.2 square feet (Section 14.6.5). This cooling must be sufficient to ensure that consequences within the acceptance criteria of 10 CFR 50.46. The cooling function must be maintained for nded periods of time following a LOCA - until decay heat is sufficiently low that rculation of borated water is no longer required.
safety injection system also must inject borated water into the reactor coolant system in order imit fuel damage and increase shutdown margin following a main steam line rupture ction 14.1.5).
1.2 Design Criteria safety injection system is designed in accordance with AEC General Design Criteria 35, 36, 37 in Appendix A to 10 CFR Part 50 and General Criteria as described in Section 6.1.
2 SYSTEM DESCRIPTION 2.1 System safety injection system is treated as an integrated system consisting of three complementary systems; i.e., high pressure and low pressure injection subsystems which utilize centrifugal ps, and a passive injection subsystem which maintains a reservoir of borated water under sure in the safety injection tanks. Figure 6.1-1 shows the piping and instrumentation rams of the safety injection system.
high pressure system is capable of delivering emergency coolant when the discharge pressure reases below approximately 1200 psia. Two high pressure safety injection pumps take suction m two independent suction headers. These headers are initially supplied with borated water m the refueling water storage tank and after that tank is nearly exhausted, borated water is rculated from the sump of the containment. The third high pressure pump is available as an alled spare.
low pressure safety injection system utilizes two, low pressure safety injection pumps. Each he two pumps is connected to one of the two independent suction headers to assure an quate supply of borated water.
water from the safety injection tanks recovers the core following a reactor coolant system wdown to minimize core damage until the safety injection pumps can provide adequate water 28/18 6.3-1 Rev. 36
, thereby limiting clad temperature and metal-water reaction (see Section 14.6.5. One tank is nected to each of the four reactor vessel inlet pipes. The driving head for water injection is vided by nitrogen gas pressure within the tanks at a minimum pressure of 200 psig. As the tor coolant system pressure falls below tank pressure, check valves open in the line necting each tank to the system. The tanks operate as a passive stored-energy safety feature; outside power or signal is required for their operation. A remotely operated valve is provided olate the tanks during a normal depressurization of the reactor coolant system. Position of this e is displayed in the control room. A vent isolation valve is provided on each tank to vent ogen into containment, when the tanks cannot be isolated during RCS depressurization owing small break LOCA. A small drain valve controlled manually from the control room is d to drain any in-leakage from the reactor coolant system. The safety injection tanks are ected from overpressure by relief valves. Piping to each tank is arranged such that the rability of each tank can be demonstrated.
ety injection actuation signal is initiated either when the pressurizer pressure drops below 4 psia, or when the containment pressure rises above 4.42 psig. Diversity of the safety ction actuation signal is thus provided.
n initiation of safety injection, two high pressure and two low pressure safety injection pumps t and 12 safety injection line isolation valves receive signals to open, allowing water to be ped from the refueling water storage tank into the reactor coolant system. After most of the er has been transferred from the tank, a continuous source of borated water is provided by rculating containment sump water directly to the pump suctions. Recirculation is matically initiated by low water level in the refueling water storage tank. Transfer to the rculation mode may also be manually initiated.
minimum time at which switch over to the recirculation mode (SRAS) occurs is based upon ration of two high pressure pumps, both low pressure pumps, and the two containment spray ps. The system is designed to keep the core covered following initial safety injection.
owing SRAS high pressure pump has sufficient capacity assuming spillage from a pipe break aintain core water level.
he recirculation mode, the high pressure safety injection pumps take suction directly from the tainment sump. At the discretion of the operator, a portion of the cooled water from the tainment spray system may be diverted to the suction of the high pressure injection pumps.
s method of operation provides additional cooling margin, but is not necessary to meet core ling requirements. However, there is no design basis whereby this flow path is utilized. The ve description is maintained here to provide a basis for the physical plant design (i.e.,
ing).
28/18 6.3-2 Rev. 36
mptions:
- a. Pipe and fitting losses based on actual plant configuration;
- b. Maximum and minimum combinations of HPSI, LPSI, and CS pumps operating during LOCA injection, recirculation, and boron precipitation control modes;
- c. Assumed pressure drop for sump strainer and debris bed;
- d. Containment pressure is equal to the saturation pressure of the containment sump water. For the recirculation modes, the containment sump temperature is 212°F and the containment pressure is 14.7 psia;
calculated available NPSH for the HPSI, LPSI, and CS pumps based on the above mptions is greater than required NPSH for all operating modes evaluated.
assumption that the containment pressure will be equal to the saturation pressure of the tainment sump water was used in these NPSH calculation. In this method of calculating ilable NPSH, no credit is taken for increased containment pressure above the saturation sure of the containment sump water.
operator is not required to perform any immediate actions in the event of a LOCA except to firm that automatic action of equipment and the notification and protection of plant personnel nder way. Operator actions following a LOCA are provided in plant Emergency Operating cedures.
safety injection water contains at least 1720 ppm of boron; consequently, the safety injection em also provides additional shutdown capability whenever the system is required to operate.
s shutdown capability assists in maintaining the reactor subcritical following the rapid ldown of the reactor coolant system caused by a rupture of a main steam line (see tion 14.1.5). The negative reactivity provided by the safety injection system exceeds the imum required for cold shutdown.
low pressure safety injection pumps are also used to supply coolant flow to remove heat from reactor following reactor shutdown and to maintain a suitable temperature for refueling and ntenance operations (Refer to Section 9.3).
system does not differ in any significant respect from those described in other C-E lications such as Calvert Cliffs (Docket Number 50-317 and 50-318) and Palisides (Docket mber 50-255).
28/18 6.3-3 Rev. 36
gn feature that is available for coping with an external loss of AC power (ELAP) event. The tion of the discharge BDB RCS FLEX connection is shown on Figure 6.1-1, Sheet 2.
2.2 Components h pressure Safety Injection Pump high pressure safety injection pumps are sized to ensure that one high pressure pump will p the core covered at the start of recirculation, assuming spillage outbreak in one leg at ospheric pressure.
requirements for boron injection for the steam line break and the injection requirements for ll break sizes are also analyzed to ensure that the pumps are adequately sized. The high sure pumps are designed for the thermal transient conditions of 40°F to 300°F in ten seconds 300°F to 40°F in ten seconds.
high pressure pumps are seven-stage horizontal centrifugal units. Mechanical seals are used are provided with leakoffs to the radwaste system which collects any leakage past the seals.
seals are designed for operation with a pumped fluid temperature of 350°F. To permit nded operation under these conditions, a portion of the pump fluid is externally cooled by the CCW system and recirculated to the seals. The pump motor is capable of starting and elerating the pump to full speed with only 70 percent of rated voltage in eight seconds. The ps are provided with drain and flushing connections to permit reduction of the radiation ore maintenance. The pressure containing parts of the pump are stainless steel with internals cted for compatibility with boric acid solutions. The materials selected were analyzed to ure that differential expansion during the design transient can be accommodated. The owing inspections and tests were performed on the high pressure safety injection pumps:
- a. materials used for pressure containing parts were inspected in accordance with techniques and acceptance standards of the Draft ASME Code for Pumps and Valves for Nuclear Power, Class II, dated November, 1968;
- b. pressure-containing parts were hydrostatically tested in accordance with API Standard 610.
pumps are provided with minimum flow protection to prevent damage resulting from ration against a closed discharge. One Millstone Unit 2 pump was subjected to the following sient tests:
The pump was operated under conditions where suction temperature both increased 260°F in ten seconds and dropped 260°F in ten seconds. The pump was operated at rated speed for over ten minutes following the test in order to demonstrate satisfactory survival of the transient.
28/18 6.3-4 Rev. 36
raulic Institute and the ASME Power Test Code, PTC-8.2. This included verification of sfactory operation at the stated NPSH. Figure 6.3-2 shows the pump performance obtained ng the hydraulic testing.
high pressure pump data are shown in Table 6.3-2.
design temperature for the high pressure safety injection pumps is based upon the saturation perature of the reactor coolant at the containment design pressure, about 300°F, plus a design rance of 50°F, resulting in design temperature of 350°F. The design pressure for the high sure pumps is based upon the sum of the containment spray pump shutoff head and the toff head of the high pressure pump.
pressure Safety Injection Pumps low pressure safety injection pumps are vertical, single-stage centrifugal units equipped with hanical face seals backed up by a bushing, with a leakoff to collect the leakage past the seal.
permit extended operation at the design temperature of 350°F, a portion of the pump discharge ooled by reactor building closed cooling water and is used to cool the seals. The pump motor is able of starting and accelerating the pump to full speed with only 70 percent of rate voltage h eight seconds. The pumps are provided with drain and flushing connections to permit uction of radiation levels before maintenance. The pressure-containing parts are fabricated m stainless steel; the internals are selected for compatibility with boric acid solutions. The ps are provided with minimum flow protection to prevent damage when starting against a ed system. The low pressure pump data are summarized in Table 6.3-2.
following inspections and tests were performed on the low pressure safety injection pumps:
- a. materials used for pressure-containing parts were inspected in accordance with techniques and acceptance standards of Draft ASME Code for Pumps and Valves for Nuclear Power, Class II, dated November, 1968;
- b. pressure-containing parts were hydrostatically tested in accordance with API Standard 610.
full-scale hydraulic test of the pumps was performed. Figure 6.3-3 shows the pump ormance obtained during the testing.
e Millstone Unit 2 pump was subject to a transient test consisting of operating while its ion temperature was increased 260°F in less than ten seconds. The pump was operated at rated ed for over ten minutes following the transient to demonstrate satisfactory survival of the test.
design temperature for the low pressure safety injection pumps is based upon the temperature he reactor coolant at the initiation of shutdown cooling, about 300°F nominal, plus a design rance of 50°F, resulting in 350°F. The design pressure for the low pressure pumps is based 28/18 6.3-5 Rev. 36
ety Injection Tanks four safety injection tanks are used to flood the core with borated water following a ressurization as a result of a LOCA.
volume of water in the safety injection tanks is selected so that the contents of three of the tanks injecting into the reactor coolant system following the worst LOCA will cover the top he core.
tank gas/water fractions, gas pressure, and outlet pipe size are selected to ensure sufficient ty injection is available such that 10 CFR 50.46 criteria are met for all postulated LOCAs.
tanks contain borated water at a minimum boron concentration of at least 1720 ppm. The s are pressurized with nitrogen at a minimum pressure of 200 psig.
el and pressure instrumentation is provided to monitor the availability of the tanks during t operation. The position of the motor operated isolation valves (SI 614, 624, 634 and 644) ween the safety injection tanks and headers is displayed by the use of lights on the main trol boards. An alarm is annunciated if any of these valves are closed. Signals are also vided to open any of these valves on SIAS, or when RCS pressure during plant heatup eases to approximately 280 psig.
tanks are provided with vent isolation valves SI-613, 623, 633 and 643 which are assisted by ogen from the tanks for remote operation.
visions have been made for sampling, filling, draining, venting and correcting boron centration. The tanks are carbon steel internally clad with Type 304 stainless steel. Design struction and overpressure protection are in accordance with the ASME Code Section III, ss C, 1968 Edition through Summer 1969 Addendum. The data summary for the safety ction tanks is given in Table 6.3-2.
tdown Cooling Heat Exchanger shutdown cooling heat exchangers are used to remove decay and sensible heat during plant ldowns and cold shutdowns. The units are sized to hold refueling water temperature (130°F) h the design RBCCW temperature (95°F) 27.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after shutdown following an infinite od of operation.
units are further specified to accept a 40°F to 289°F transient in ten seconds when the tainment spray pump suction is switched to the containment sump. During this period of ration, the tube-side flow is specified as the output of two containment spray pumps and the tor building closed cooling water inlet temperature is specified at 115°F. The units are gned and constructed to the standards of ASME,Section III, Class C; and TEMA Class R 28/18 6.3-6 Rev. 36
design parameters for the shutdown heat exchangers are found in Table 6.3-3, Section 6.3.
a on containment spray pump operation is available in Table 6.4-1, Section 6.4. Data on tor building closed cooling water system operation is available in Table 9.4-1, Section 9.4. A cription of integrated system performance during a Main Steam Line Break or LOCA is tained in Section 14.8.2.
le 9.3-1 shows the design cases for the shutdown heat exchangers for accident transients.
design temperature and pressure for the shutdown cooling heat exchangers are compatible h the design temperature and pressure for the low pressure safety injection pumps (see tion 6.3.2.2).
ety Injection Piping safety injection system piping is fabricated of austenitic stainless steel and conforms to the dards set forth in ANSI B31.7. Flexibility and seismic loading analyses have confirmed the ctural adequacy of the system piping.
ng is shop fabricated in accordance with the ANSI B31.7, Nuclear Power Piping. The piping eld erected and tested in accordance with ASME Section III, 1971. Material and shop welds e inspected, tested and documented in accordance with the applicable class of B31.7. Valves manufactured in accordance with the Draft ASME Code for Pumps and Valves for Nuclear er, dated November 1968. The material and welds were inspected, tested and documented to same code.
3 SYSTEM OPERATION 3.1 Emergency Conditions ondition which causes a sufficiently low pressurizer pressure or high containment pressure result in a safety injection actuation signal (SIAS). This signal will start the two high pressure ty injection pumps, both low pressure safety injection pumps, open 12 safety injection system ation valves and close the four check valve leakoff lines at the safety injection tanks. (The S also performs some functions in the Chemical and Volume Control System; see ures 7.3-2A through 7.3-2D.) The 8 HPSI injection throttle valves are manually positioned to desired open position.
en reactor coolant system pressure falls below approximately 1200 psia, the high pressure ty injection pumps start delivering flow through both high pressure headers.
eactor coolant pressure falls below approximately 200 psig, the passive pressurized safety ction tanks will start delivering borated water into each cold leg along with the low pressure ty injection pumps. In the event of a Small Break LOCA, the Safety Injection Tanks (SITs) 28/18 6.3-7 Rev. 36
trol over the plant cooldown and depressurization, it is undesirable to have the SITS pletely discharge to the point where nitrogen is introduced into the RCS. Therefore, the rators are directed to close the SIT outlet valves once RCS pressure is reduced.
single failure loss of power to the SIT outlet MOV(s) was to occur, the SIT(s) would be olable from the control room. Therefore, the operator would be directed to operate the SIT ting system and depressurize the SIT(s) by bleeding off nitrogen cover pressure.
safety injection pumps initially draw borated water from the refueling water storage tank ST). This tank has sufficient water volume to supply safety injection flow assuming two high sure and two low pressure safety injection pumps and two containment spray pumps are ning. When the refueling water storage tank is nearly empty, a sump recirculation actuation al (SRAS) from refueling water storage tank water level closes the minimum flow rculation lines, opens the isolation valves in the two lines from the containment sump and ts down the low pressure safety injection pumps. The refueling water storage tank outlet es remain open initially during the transfer to the recirculation mode to preclude the loss of ply to a high pressure safety injection pump in the unlikely event the isolation valve in the tainment sump line should experience delay in opening. Back flow through either refueling er storage tank suction line is prevented by check valves. In addition, the operator may ually close the refueling water storage tank outlet valves after verifying the opening of the tainment sump line valves. The earliest automatic recirculation (SRAS) would occur is when 2 I, 2 HPSI, and 2 CS pumps are in operation following a SIAS and the RWST contains the imum Technical Specification volume. The recirculation mode can also be initiated manually he operator.
ESF pump minimum-flow recirculation line contains two series air-operated stop valves se SRAS function is to close and prevent sump water from being returned to the RWST.
se valves are provided with key-lock switches in the Control Room to disable the valves open ng normal operations to ensure a recirculation flow path for the low pressure safety injection ps. The valves are enabled to be closed by placing the key-lock switches to operate prior to rculation following a LOCA.
the recirculation mode the high pressure safety injection pumps take suction from the tainment sump. The safety injection flow spilling from the break in the reactor coolant system ooled by mixing in the containment sump with the cooled containment spray water.
ing normal operation, the containment sump recirculation lines between motor operated es (2-CS-16.1A and 2-CS-16.1B) and the high pressure safety injection pumps (See ure 6.1-1) will be filled with stagnant water. The portion of piping between the containment p inlets and the motor-operated valves is designed to be full of water.
se portions of line will flood gradually as the sump level rises. In portions of the lines where pockets would form, vent and fill connections are provided.
28/18 6.3-8 Rev. 36
able 6.3-5.
analysis of the design basis accident for the safety injection system (Section 14.6.5) is ormed assuming that only a minimum amount of the system components function during the CA. Minimum safety injection is defined as follows:
- a. For a cold leg large break LOCA, the entire contents of one of the four passive safety injection tanks spill through the break and is not available for emergency core cooling. For a Small Break LOCA downstream of the ECCS Injection location, ECCS is injected into the broken loop and the portion of this injection which spills out the break is calculated as a part of the transient simulation. For a hot leg break, all four safety injection tanks discharge into the intact cold legs;
- b. One of the two online, high pressure safety injection pumps functions. For a cold leg large break, the flow from one of the four injection lines is assumed to be spilled via the break. For a cold leg small break, flow is injected into the broken loop and the portion of this injection which spills out the break is calculated as part of the transient simulation. For a hot leg break, the entire pump discharge reaches the core;
- c. One of the two low pressure safety injection pumps functions. For a cold leg break, one-half of this pumps discharge reaches the core. For a hot leg break, the entire discharge from this pump reaches the core.
assumed maximum delay time for operation of the safety injection pumps is 45 seconds after SIAS, a 45 second delay for the LPSI system and a 25 second delay for the HPSI system. This ased on the assumption that outside power has been lost and includes an allowance for the start and loadings of the emergency diesel generators. These and other conservative assumptions given in the Loss of Coolant Analysis, Section 14.6.5.
safety injection system can provide both long term cooling and boron precipitation control in event of a LOCA. This is accomplished by simultaneous injection to both the hot and cold legs he RCS. Hot leg injection is necessary for cold leg breaks to provide a flushing flowpath ugh the core region such that boric acid solubility limits are not reached during post-LOCA off periods. The preferred method of boron precipitation control is to employ one LPSI pump nject via the shutdown cooling system warmup and return line piping, past 2-SI-400, 2-SI-709, I-651 and 2-SI-652, into the RCS hot leg. Cold leg injection would be provided by a HPSI p and also by LPSI flow diverted through at least one of the four LPSI injection lines. No e than two of the LPSI injection valves 2-SI-615, 625 and 645 are to be open in this figuration and valve 2-SI-635 cannot be open in combination with any other open LPSI ction valve.
alternate method of providing boron precipitation flushing flow is to use HPSI pump P-41A to ct via the charging system header to the pressurizer auxiliary spray line and thus to the hot leg 28/18 6.3-9 Rev. 36
auxiliary spray line. Normal HPSI injection lines to the cold leg from pump P-41A are cked by closing 2-SI-617, 627, 637 and 647. In this arrangement, cold leg injection is omplished by the LPSI system.
quate flushing flow to preclude boron precipitation as well as adequate long term cooling are vided by either the preferred LPSI or alternate HPSI hot leg injection methods.
3.2 Cold Shutdown and Refueling obtain cold shutdown, operation of the system is discussed in Section 9.3. During the eling, the shutdown cooling heat exchangers are aligned with the low pressure safety injection ps and used to cool the refueling water.
4 AVAILABILITY AND RELIABILITY 4.1 Special Features design basis and system requirements during a DBI are met with the operation of the safety ction tanks and one high pressure and one low pressure safety injection pump, delivering rated and assuming spillage through the break as defined in Section 6.3.3.1. During recirculation, high pressure safety injection pump has sufficient capacity to maintain the water level in the tor vessel above the core.
lity to meet the core protection criteria is assured by the following design features:
- a. A high capacity passive system (safety injection tanks) which requires no power source and will supply large quantities of borated water to rapidly recover the core after a major LOCA up to a break of the largest reactor coolant system pipe.
- b. low pressure and high pressure pumping and water storage systems with internal redundancy which will inject borated water to provide core protection for reactor coolant system break sizes equal to and smaller than the largest line connected to the reactor coolant system (the 12 inch pressurizer surge lines or the shutdown cooling and safety injection lines). The pumping systems also provide borated water to keep the core covered and to continue cooling the core after the passive water supply has been exhausted. In addition, the high pressure system will remove reactor core decay and sensible heat during long term operation after the reactor coolant system rupture. Instrumentation and sampling provisions allow monitoring of the recirculated coolant.
- c. Separated pump rooms and redundant pumping systems which will permit minimum safety features equipment to operate should one pump room flood in the event of a passive failure during long term operation.
28/18 6.3-10 Rev. 36
- e. All active components which must function individually for the system to meet the performance criteria stated for core protection can be tested during reactor operation. Instrument sensors are tested for function at operating conditions. In addition, extensive shop and preoperational tests are performed to verify adequate component and system operation.
- f. Most of the active components are located outside the containment where they are protected from incident-generated missiles and from post-incident environmental conditions. Those active components located inside the containment need only operate for a short time period after the accident.
- g. The four injection lines are arranged such that movement of a ruptured reactor coolant pipe will not cause a subsequent failure of injection lines in non ruptured loops. The maximum movement of the reactor coolant pipe at the injection nozzle in the non ruptured loop will not damage the injection line.
- h. The safety injection system have been designed to meet the single failure criterion.
This includes the fluid systems and the electrical control and instrument systems.
All pumps and critical power-operated valves can be actuated from their respective switch gear or control centers.
- i. All components, piping, cabling structures, power supplies, etc., in the safety injection support systems are designed to Class 1 seismic criteria.
ctiveness of the safety injection system to satisfy the criteria stated for core protection can be wn by the blowdown and refill transient curves following a LOCA. This analysis is presented Section 14.6.5, Loss-of-Coolant Accident. The analysis shows that 10 CFR 50.46(b),
ceptance Criteria for Emergency Core Cooling Systems for Light Water Nuclear Power nts, is satisfied by this design.
high pressure safety injection system is designed to minimize the amount of equipment which t operate when a safety injection signal is received. All valves not required to operate on ation of safety injection are either isolated from the safety injection flow path or locked in the ty injection position during operation. Administrative controls ensure that the locked valves in the correct position.
ee parallel pumps are provided in the high pressure system. One pump is available as a spare.
se pumps are located outside the containment. The pump rooms are in a controlled access pump room location outside of the containment is most favorable for extended operation and ipment life following a major LOCA. This location is accessible for service and inspection of 28/18 6.3-11 Rev. 36
pumps are appropriately segregated in separate watertight rooms. This arrangement permits ess to and operability of those pumps required for minimum safety features operation.
undant flow paths are provided from the discharge of the high pressure injection headers.
se headers, in turn, both supply the four individual safety injection lines, one leading to each leg of the reactor coolant system. Normally closed, power-operated valves isolate the two h pressure safety injection headers from each other and also provide the capability to switch discharge from the pumps to either header.
mal plant operating procedures include routine testing to ensure the operability of the pumps.
attention given to the selection of these pumps, the redundancy of power supplied, the design gins, and the fact that multiple pumps are installed assures a high degree of pump availability.
high pressure safety injection valves are designed for 2735 psig. These valves are located ide of the containment and are thus not subjected to the environmental conditions existing in containment following any LOCA. The attention given to the selection of these valves, design gins, and the fact that eight high pressure safety injection valves are in parallel assure a high ree of valve availability. Both header supply valves are normally open.
r high pressure safety injection valves on one header are powered from one emergency power
. The remaining four high pressure safety injection valves are powered from the second rgency power bus. The valves are equipped with remote position indicators in the control
- m. The 8 HPSI injection throttle valves are manually positioned to the desired open position do not open further on an actuation signal.
ing recirculation the high pressure safety injection pumps continue to operate, taking suction m the containment sump. The pump recirculation lines, the heat exchangers, the containment y pumps, and the recirculation suction headers are arranged to provide two independent flow
- s. The low pressure safety injection pumps can also be used for recirculation, if necessary.
low pressure safety injection system is also designed to minimize the amount of equipment ch must operate when a safety injection signal is received. All valves not required to operate nitiation of safety injection are either isolated from the safety injection flow path or locked in safety injection position during operation. Administrative controls insure that the locked es are in the correct position.
mal plant operations, augmented by routine testing, insure the operability of the pumps. The ntion given to the selection of these pumps, the redundancy of power supplied, the design gins, and the fact that two pumps are supplied assures a high degree of pump availability.
power-operated, low pressure injection valves are located outside of the containment and are not subjected to the environmental conditions existing in the containment following any CA. The attention given to the selection of these valves, design margins, and the fact that four 28/18 6.3-12 Rev. 36
uld the inadvertent closure of valve 2-SI-306 in the Low Pressure Injection System line occur, ould result in the inability of that system to perform its function following a LOCA. It is ipped with both a power (pneumatic) actuator and a manual overriding actuator connected to osite sides of the valve plug shaft. Each half of the valve plug shaft is splined into the valve
- g. The power actuator is a spring-to-open diaphragm type. To prevent inadvertent closure by device, solenoid valve HV-306, which is located in the pneumatic signal line to the diaphragm he actuator, will be electrically disabled during plant operation to prevent air pressure from hing the diaphragm. As a result, the actuator spring will hold the valve plug in an open ition. Spring force is sufficient to hold the valve in the open position. To provide additional rance that the valve will not close, the manual operator on the opposite side of the shaft is ned and locked to the handwheel to prevent movement of the valve plug due to the mechanical antage of the handwheel drive nut. Also the handwheel is locked in position to prevent vertent operation. Thus, multiple means are provided to assure that valve 2-SI-306 will ain in an open position during all operations except shutdown cooling and that it will allow system to perform its function following a LOCA.
four safety injection tanks comprise a completely independent and redundant source of low sure injection water which requires no outside signal or source of power operation. The lysis in Section 14.6.5 shows that core recovery will occur for all postulated LOCAs such that CFR 50.46 acceptance criteria are met.
ailure modes and effects analysis has been performed of the safety injection system. The lysis for both the injection and recirculation modes of operation can be found in Table 6.3-6.
m the analysis, it has been concluded that the SIS can withstand any single failure as defined ein and still perform its intended function.
re is no undue risk to the health and safety of the public from the failure of a single active ponent during the injection mode of operation or from a single failure of any passive or active ponent during the recirculation mode of operation.
failure mode analysis presented in Table 6.3-6 was performed using the following mptions.
- a. The SIS is composed of the electrical, instrumentation and fluid segments. In compliance with single failure criteria, only one failure is assumed to occur in the system; e.g., a failure of a diesel generator cannot occur simultaneously with a safety injection valve failure.
- b. Only one active failure is considered for injection mode of the safety injection operation. For the recirculation mode, the single failure considered can be either active or passive.
28/18 6.3-13 Rev. 36
- d. Failure of valve internals, including check and stop valves, is a passive failure.
Passive failures are considered in the recirculation phase only, no earlier than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after an accident.
- e. The transition to the recirculation mode of operation occurs upon initiation of recirculation from the sump.
- f. The analysis considers only failures or malfunctions which occur during the time period of SIS operation. Failures or malfunctions that might occur during normal reactor operation are not considered.
reviations used in the Table 6.3-6 are:
CRI - Control Room Indication HPSI - high pressure Safety Injection LPSI - low pressure Safety Injection SIAS - Safety Injection Actuation Signal SRAS - Sump Recirculation Actuation Signal RWST - Refueling Water Storage Tank RCS - Reactor Coolant System SIS - Safety Injection System administrative error analysis has been performed which evaluates the effect of improper itioning of administratively controlled safety injection system valves. The results of this lysis can be found in Table 6.3-7.
HPSI and LPSI systems may be relied upon to provide long term cooling and boron ipitation flushing flow in the event of a LOCA. A break size of sufficient magnitude that the tor coolant system is not filled at 8 to 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after the start of the accident requires a ultaneous hot and cold leg injection alignment to provide both long term cooling and boron ipitation control because the break location is unknown.
rator action both inside and outside the control room would be required to align for ultaneous injection.
preferred method of boron precipitation control is to have LPSI pump injection to the RCS leg past opened valves 2-SI-400, 709, 651 and 652 in the shutdown cooling system warmup suction piping. Some of the LPSI flow would be diverted to the cold leg by having at most of valves 2-SI-615, 625 and 645 open. LPSI injection valve 2-SI-635 cannot be open in bination with any other open LPSI injection valve. The ability to align an alternate vital er source to 2-SI-651 in the shutdown cooling return line ensures single-failure criteria are 28/18 6.3-14 Rev. 36
alternate method of boron precipitation and long term cooling can be accomplished by ning HPSI pump P-41A to the charging header past valves 2-CH-440, 340, the regenerative t exchanger and 2-CH-517 for injection to the RCS hot leg through the pressurizer auxiliary y line and surge line. The ability to align an alternate vital power source to 2-CH-517 and 2-
-519 in the charging lines ensures single-failure criteria are met.
quate margin to HPSI and LPSI pump NPSH exists for the various boron precipitation control nments.
ailure modes and effects analysis has been completed for post-LOCA periods of combined hot cold leg injection necessary for boron precipitation control and long term cooling. The results his analysis are presented in Table 6.3-8.
Section 14.6.5.3 for a description of boron precipitation control and long term cooling under t-LOCA conditions.
4.2 Tests and Inspections h safety injection pump is shop tested for hydraulic performance at sufficient head-capacity nts to generate complete performance curves. Figures 6.3-2 and 6.3-3 show the resultant ves for one high pressure and one low pressure safety injection pump, respectively.
destructive examinations are performed on all pressure-retaining components of each safety ction pump and tank in accordance with the Draft ASME Code for Pumps and Valves for lear Power, Class II, 1968, and ASME Boiler and Pressure Vessel Code, 1968 Edition through mer 1969 Addendum,Section III, Class C, respectively. The safety injection system ergoes a preoperation test prior to plant startup. The test procedure is described in Chapter 13.
following preoperational tests and checks are planned:
- 1. Each of the high pressure safety injection (HPSI) pumps will be capacity tested while discharging into the reactor vessel through the HPSI injection lines. Tests will be run with various discharge heads to verify pump capacity over the range of break sizes where its function is of most importance. During these tests, flow distribution through the four HPSI line flow orifices will be checked.
- 2. Each of the low pressure safety injection (LPSI) pumps will be capacity tested while discharging into the reactor vessel through the (LPSI) injection lines. Tests will be run with discharge heads associated with maximum, design and minimum recirculation flow rates. During these tests, flow distribution through the four LPSI line flow orifices will be checked.
28/18 6.3-15 Rev. 36
- 4. A simulated SIAS signal will be used to verify functional operation of all valves and pump breakers.
- 5. A simulated sump recirculation actuation signal (SRAS) will be impressed on each detector and functional operation of all valves and pump breakers.
- 6. Each Safety Injection tank will be tested by allowing its contents to be discharged into the reactor. Tank volume and pressure change versus time will be checked.
odic tests and inspections of the Safety Injection System components and subsystems are ormed to insure proper operation in the event of an accident. The scheduled tests and ections are necessary to verify system operation reliability since during normal plant, safety ction system components are aligned for emergency operation and serve no other function.
tests defined permit a complete checkout on the subsystem and component level during mal plant operation. Satisfactory operability of the complete system may be verified during mal scheduled refueling shutdowns. The test data recorded during the periodic testing provides itive assurance of the system to perform its intended function. Deteriorated performance will etected by comparison of the periodic performance test data to the preoperational test data.
tine operational testing of major portions of the logic circuits, pumps and power-actuated es in the safety injection system is described in Section 7.3.
pumps are located outside the containment for access and to permit maintenance during mal plant operations. A recirculation line is provided on the discharge of each pump. Periodic ing will be performed by recirculating water back to the refueling water storage tank.
veillance requirements to verify that the safety injection system will respond promptly and orm its intended function, if required, are given in Sections 4.5.1 and 4.5.2 of the Technical cifications.
28/18 6.3-16 Rev. 36
28/18 6.3-17 Rev. 36 SYSTEM ection Water Boron Concentration (ppm) 1720 gh-Pressure Safety Injection Pumps nufacturer Ingersoll-Rand antity 3 pe Seven-stage Horizontal Centrifugal tor Voltage, volts 4160 sign Pressure, psig 1600 sign Temperature, °F 350 esign Flow (per pump), gpm (excluding minimum 315 w) esign head, ft. 2500 mped fluid Water (Borated) mperature of Pumped Fluid, °F 35-300 utoff Head, ft 2850 Maximum Flow, gpm 640 ead at Maximum Flow (one pump), ft 1620 terial ASTM-A-351 Gr CF8M rsepower (motor) 400 aft Seal Mechanical celeration Time, seconds (at rated voltage) 4 nimum Flow, gpm 20 PSH Available (minimum), ft (at 640 gpm) 21.9 PSH Required at 640 gpm, ft 20 sign Maximum Suction Pressure, psig 250 w-Pressure Safety Injection Pumps antity 2 pe Single stage Vertical Centrifugal tor Voltage, volts 4160 nufacturer Ingersoll-Rand sign Pressure, psig 500 28/18 6.3-18 Rev. 36
sign Temperature, °F 350 sign Flow (per pump), gpm (excluding min. flow) 3000 esign Head, ft 350 umped Fluid Water (Borated) mperature of Pumped Fluid, °F 35-300 utoff Head, Ft 420 Maximum Flow, gpm 4500 ead at Maximum Flow (one pump), ft 275 sic Material ASTM A351 GR CF8M rsepower 400 als Mechanical celeration Time, seconds (at rated voltage) 4 PSH Available (minimum), ft (at 3000 gpm) 25 PSH Required at 3000 gpm, ft 13 sign Maximum Suction Pressure, psig 300 nimum Flow, gpm 100 fety Injection Tanks nufacturer Air Preheater Co.
antity 4 tal Volume, each, ft3 2019 ter Volume, ft3, nominal 1137 ter Volume, ft3, minimum 1080 sign Pressure, psig 250 erating Pressure, psig, nominal 215 erating Pressure, psig, minimum 200 sign Temperature, °F 200 erating Temperature, °F 120 lief Valve Setpoint, psig 250 ight, inches 399.75 tside Diameter, inches 109 3/4 28/18 6.3-19 Rev. 36
The pump flows, heads, and NPSH values presented in this table are based on the original design specifications. The pumps will actually operate over a range of conditions during safety injection, sump recirculation, long-term cooling and boron precipitation control post LOCA. System hydraulic and NPSH analyses have been performed for these operational modes based on the pump design and degraded capacities.
e: The original design basis for available NPSH was based on a total sump recirculation flow on one suction header of 2980 gpm (consisting of 1 CS pump flow of 1700 gpm and 2 HPSI pumps flow of 640 gpm each).
28/18 6.3-20 Rev. 36
nufacturer Engineers & Fabricators, Inc.
antity 2 pe Shell and Tube des be Side, Shell Side ASME Section III, Class C 1968 Edition through Summer 1969 Addendum be Side id Reactor Coolant, 1.5 wt. % Boric Acid sign Pressure, psig 500 sign Temperature, °F 400 ximum pressure drop at rated flow, psi 10 terials Austenitic Stainless Steel ell Side id Reactor Building Closed Cooling Water sign Pressure, psig 150 sign Temperature, °F 250 ximum pressure drop at rated flow, psi 10 terial Carbon Steel at Exchanger Design Parameters (1) (Shutdown Cooling Mode) be Side w, Million lb/hr 1.5 et Temperature, °F 130 tlet Temperature, °F 111.9 ell Side w, Million lb/hr 2.41 et Temperature, °F 95 tlet, Temperature, °F 106.3 at Load, Million Btu/hr 27.2 rvice Transfer Rate, Btu/hr - ft2 - °F 256 Refer to Table 9.3-1 for shutdown cooling minimum design basis parameters.
28/18 6.3-21 Rev. 36
28/18 6.3-22 Rev. 36 RECIRCULATION PIPING AND VALVES e
Component Internal Diameter (inches)
"-HCB-1 23.5
-HCB-1 8.329
-GCB-3 8.125
-GCB-3 6.357 ves Component Internal Diameter (inches)
CS-16.1A, B 23.25 CS-15A, B 23.5 SI-401, 410 8.0 SI-402, 470 6.0 SI-411, 412 8.0 28/18 6.3-23 Rev. 36
HIGH PRESSURE SAFETY INJECTION COMPONENT IDENTIFICATION FAILURE EFFECT ON METHOD OF
& QUANTITY MODE SYSTEM DETECTION MONITOR REMARKS HPSI Loop Flow Malfunction None Comparison of Flow CRI Indicator (4) to Other Flow Indicators and Valve Position Indicators HPSI Valve (8) Fails to open None Flow Indication, CRI The valves are norm Pressure Indication, open and positioned Valve position throttled position.
Indication Pump Discharge None None, Locked Open N/A* N/A
- Isolation Valve (3) valve Pump Minimum Flow None None, Locked Open N/A
- N/A
- Recirculation Stop valve Valve (3)
HPSI Pump (3) a. Fails to Start Loss of HPSI flow from Pump Motor Lights, CRI Flow from at least o 1 pump Header Pressure available.
- b. Stops Loss of HSPI flow from Pump Motor Lights, CRI Flow from at least o 1 pump Header Pressure available.
Pump Suction None None, Locked Open N/A
- N/A
- Isolation Valve (2) valve 06/28/18 6.3-24 Rev. 36
COMPONENT IDENTIFICATION FAILURE EFFECT ON METHOD OF
& QUANTITY MODE SYSTEM DETECTION MONITOR REMARKS HPSI Discharge Fails Closed 1. Valve in ruptured Flow Indication, CRI Flow is sufficient to Check Valve (4) loop-no effect. Pressure Indication core.
- 2. Valve in nonrupture loop --at least 67%
of HPSI flow from 2 pumps reaches core.
HPSI Loop Flow Malfunction None Comparison of flow CRI Balancing of flow is Indicator (4) to other flow essential during long indicators and Valve cooling.
Position Indicators Check Valve Fails Closed 1. Valve in ruptured Flow Indication, CRI Flow is sufficient to Associated with HPSI loop--no effect. Pressure Indication core.
Valves (8)
- 2. Valve in nonruptured loop--
at least 70% of HPSI flow from 2 pumps reaches core 06/28/18 6.3-25 Rev. 36
COMPONENT IDENTIFICATION FAILURE EFFECT ON METHOD OF
& QUANTITY MODE SYSTEM DETECTION MONITOR REMARKS HPSI Valve (8) Fails Closed 1. Valve in ruptured Flow Indication, CRI loop--no effect. Pressure Indication
- 2. Valve in Valve Position nonruptured loop Indication but flow to core still greater than minimum required HPSI Pump Discharge Fails Open Partial Loss of HPSI None CRI Loss of flow will be Relief Valve (3) flow insignificant.
Pump Discharge Fails Closed Loss of HPSI flow from Flow Indication, CRI At least 1 HP pump Isolation Valve (3) 1 pump Pressure Indication available. Each pum capacity.
Pump Minimum Flow Fails Closed None, valve is not None Recirculation Stop necessary after RAS Valve (3)
Pump Discharge Fails Closed Loss of HPSI flow from Flow Indication, CRI At least 1 HP pump Check Valve (3) 1 pump Pressure Indication available.
06/28/18 6.3-26 Rev. 36
COMPONENT IDENTIFICATION FAILURE EFFECT ON METHOD OF
& QUANTITY MODE SYSTEM DETECTION MONITOR REMARKS HPSI Pump (3) a. Stops Loss of HPSI flow from Pump Motor Lights, CRI At least 1 HP pump 1 pump Header Pressure available
- b. Seal Failure Slight reduction in Sump Level Alarm CRI At least 1 HP pump output from affected available pump
- c. Loss of Seal Loss of HPSI flow from None None At least 1 HP pump Coolant 1 pump available Pump Suction Fails Closed Loss of suction to 1 HP Pressure Indication, Local CRI At least 1 HP pump Isolation Valve (2) pump Possible Flow available Indication Pump Suction Check a. Fails Closed Loss of suction to 1 Pressure Indication, CRI At least 1 HP pump Valve (2) (no cooled pump Possible Flow available suction) Indication
- b. Fails Open Loss of suction to 1 Flow Indication, CRI At least 1 HP pump (cooled pump Pressure Indication available suction)
Cooled Suction Fails Closed when Loss of cooled suction Pressure Indication, CRI Pump design is base Isolation Valve (2) cooled suction is to the suction header Flow Indication suction from the desired containment sump w use of the shutdown exchangers.
06/28/18 6.3-27 Rev. 36
COMPONENT IDENTIFICATION FAILURE EFFECT ON METHOD OF
& QUANTITY MODE SYSTEM DETECTION MONITOR REMARKS Safety Injection Pump Fails Open None Valve Position CRI 2 Valves are in serie Minimum Flow Indicator Recirculation Stop Valve (2)
LPSI Valve (4) Fails to Open 1. Valve in ruptured Valve Position CRI 50% of flow from on loop - no effect Indication L.P.S.I. pump is ade
- 2. Valve not in Flow Indication, ruptured loop - at Pressure Indication least 50% of LP flow reached core L.P.S.I. Segment to None None N/A
- N/A
- Shutdown Cooling Heat Exchange Isolation Valve (1)
Shutdown Cooling None None N/A
- N/A
- Failed open valve Flow Control Valve (1)
Pump Discharge None None N/A
- N/A
- Locked open valves Isolation Valve (2)
Pump Minimum None None N/A
- N/A
- Locked open valves Recirculation Stop Valve (2) 06/28/18 6.3-28 Rev. 36
COMPONENT IDENTIFICATION FAILURE EFFECT ON METHOD OF
& QUANTITY MODE SYSTEM DETECTION MONITOR REMARKS LPSI Pump (2) a. Fails to Start Loss of L.P.S.I. flow Pump Indication CRI Other pump starts.
from one pump Lights
- b. Stops Loss of L.P.S.I. flow Flow Indication CRI Other pump starts from one pump simultaneously. Eac is full capacity
- c. Fails to stop Pumps may cavitate Pump Indication CRI Operator may stop p with the unless flow is reduced Lights, Flow close LPSI valves. O SRAS Indicator action ensures press Fluctuations in ECCS suction stra remains within desig Pump Suction None None N/A
- N/A
- Locked open valves Isolation Valve (2)
S.I. Tank Isolation a. None None N/A
- N/A
- Valves are maintaine Valve (4) with closing coil rem
- b. Fails to close Intrusion of nitrogen SI tank level and CRI Vent Isolation valves following into the RCS at low pressure; pressurizer affected tanks can be Small Break RCS pressure pressure < 600 psia operated remotely to LOCA nitrogen into contain Drain and Fill None None, valve is Fail N/A
- N/A
- Isolation Valve (4) Closed valve Check Valve Leakage None None, valve is Fail N/A
- N/A
- Control Valve (4) Closed valve 06/28/18 6.3-29 Rev. 36
COMPONENT IDENTIFICATION FAILURE EFFECT ON METHOD OF
& QUANTITY MODE SYSTEM DETECTION MONITOR REMARKS S.I. Tank Purge Valve None None, valve is Fail N/A
- N/A *
(4) Closed valve N2 Supply Line Stop None Valve is Fail Closed N/A
- N/A
- Valve valve S.I. Tank Vent a. None None, valves are Fail N/A
- N/A
- Isolation Valves Closed
- b. Fails to open Nitrogen intrusion into Valve position CRI Single failure of SIT to bleed RCS indication valve already consid nitrogen Therefore, this failur following applicable SBLOCA Refueling Water Inadvertently Loss of suction to Valve Position CRI Second full capacity Storage Tank, Tank closed during use affected pumps Indication, Flow line available. Poten Isolation Valve (2) of tank Indication damage to isolated p Sump Isolation Valve Inadvertently None. Check valve Valve Position CRI Operator Error. Oper (2) opened during use restricts flow Indication. Possible should detect abnor of refueling water loss of flow valve position by ind tank lights.
RWS Tank Check a. Fails Closed None during long-term None None Valve (2) cooling
- b. Fails Open None-Isolation valve in None None series stops flow to RWS tank 06/28/18 6.3-30 Rev. 36
COMPONENT IDENTIFICATION FAILURE EFFECT ON METHOD OF
& QUANTITY MODE SYSTEM DETECTION MONITOR REMARKS RWS Tank Isolation Inadvertently None - Check valve Valve Position CRI Operator error. Ope Valve (2) Open during restricts flow to RWS Indication should detect positio recirculation tank indicator light and cl cooling valve.
Sump Isolation Valve Inadvertently Loss of suction to one Valve Position CRI Operator error. Full (2) closed during pump header Indication available through pa recirculation leg. Operator should cooling position indicator lig open valve. Potentia damage to isolated p Suction Line Between Leakage None - Piping None None Containment Wall and Encapsulated Isolation Valve (2)
Sump Check Valve (2) a. Fails Closed Loss of suction to one None None Full flow is availabl pump header. through parallel leg.
- b. Fails Open None None None Potential damage to pumps.
- Not applicable where no failure mode is indicated.
06/28/18 6.3-31 Rev. 36
VALVES Valve Administrative umber Normal Position Error Position Result
-306 Locked Open Closed Low pressure safety injection flow not available.
-402 Locked Open Closed Closure of one of these valves will result in no flow from its associated
-406 Locked Open Closed high-pressure safety injection (HPSI)
-428 Locked Open Closed pump. One pump remains.
-470 Locked Open Closed
-653 Closed Open Loss of isolation between two HPSI headers. No effect during injection.
-655 Closed Open
-411 Closed Open Separation of the two redundant HPSI paths is lost during recirculation.
-412 Closed Open
-432 Locked Open Closed No flow from associated low- pressure safety injection (LPSI) pump. One
-435 Locked Open Closed pump remains.
-444 Locked Open Closed
-447 Locked Open Closed
-421 Locked Open Closed Loss of safety injection pump minimum flow. Slight increase in injection flow.
-423 Locked Open Closed
-425 Locked Open Closed
-449 Locked Open Closed
-450 Locked Open Closed
-452 Locked Closed Open Some of flow from one containment spray (CS) pump will be injected into
-453 Locked Closed Open Reactor Coolant System through LPSI header.
-456 Closed Open No effect
-457 Closed Open
-662 Closed Open One HPSI pump will take suction from discharge of one CS pump. Partial loss
-663 Closed Open of CS flow.
28/18 6.3-32 Rev. 36
Valve Administrative umber Normal Position Error Position Result
-654 Locked Open Closed HPSI flow not available through associated header.
-656 Locked Open Closed
-657 Closed Open No effect
-659 Open Closed Loss of minimum flow for all pumps.
Slight increase in injection flows.
-660 Open Closed Valves controlled by key lock switches to disable them open during normal operation.
-460 Locked Closed Open No effect on safeguards system performance.
-461 Closed Open
-462 Closed Open
-463 Locked Closed Open
-661 Closed Open No effect
-611 Closed Open No effect on safeguards system performance.
-621 Closed Open
-631 Closed Open
-641 Closed Open
-612 Closed Open If any one of these valves is in the incorrect position, it will result in an
-622 Closed Open inability to maintain its corresponding
-632 Closed Open safety injection tank within the Technical Specifications requirements.
-642 Closed Open Redundant alarms will alert the plant
-613 Closed Open operator who will take corrective action.
-623 Closed Open
-633 Closed Open
-643 Closed Open 28/18 6.3-33 Rev. 36
Cold Leg Injection Single Failure Effects of Failure Actions Required Path Boron Precip Cont
- 1. Loss of Facility Z1 (B51) LPSI LPSI 1. B HPSI train P42B LPSI Pump vi coincident with SIAS (using P41C 2-SI-306 through 2-pump) and 2-SI-652
- 1. 2-SI-651, 2-SI-615, Open 2-SI-651 with 2. P42B LPSI pump 2-SI-625 remain closed Facility Z2 power. via 2-SI-645
- 2. P42A LPSI pump out of Close 2-SI-635 service
- 3. 125V DC (DV10) will Open 2-SI-400 and not be available (battery 2-SI-709 has 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> coping factor)
- 1. 2-CH-518 fails open due Verify B HPSI train in to loss of DC power service to cold leg (unused) injection
- 2. A HPSI train out of Close 2-SI-636 and service 2-SI-646 06/28/18 6.3-34 Rev. 36
Cold Leg Injection Single Failure Effects of Failure Actions Required Path Boron Precip Cont
- 2. Loss of Facility Z2 (B61) LPSI LPSI P42A LPSI pump via HPSI pump P41A vi coincident with SIAS 2-SI-615 and 625 2-CH-517 to pressur auxiliary spray line
- 1. 2-SI-652, 2-SI-635, Establish LPSI to cold 2-SI-645 remain closed leg injection 2-SI-615
& 625 are open
- 2. P42B LPSI pump train out of service
- 3. 125V DC (DV20) will not be available (battery has 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> coping factor)
- 1. 2-CH-517 fails closed Power 2-CH-517 and due to Facility Z2 DC 2-CH-519 with 125V battery DC (DV10)
- 2. 2-CH-519 fails open Align A HPSI pump to pressurizer auxiliary spray line via: Open 2-CH-340, 440 and 517
- 3. B HPSI train out of Close 2-CH-518 and service 2-CH-519 06/28/18 6.3-35 Rev. 36
Cold Leg Injection Single Failure Effects of Failure Actions Required Path Boron Precip Cont
- 3. Loss of Facility Z1 LPSI LPSI 1. B HPSI train P42B LPSI Pump vi (B51)Post SIAS (using P41C 2-SI-306 through 2-pump) and 2-SI-652
- 1. 2-SI-651 remains closed Open 2-SI-651 with 2. P42B LPSI pump Facility Z2 power via 2-SI-615 and 625
- 2. 2-SI-615 and 2-SI-625 Close 2-SI-635 and remain open 2-SI-645
- 3. LPSI P42A out of service Open 2-SI-400 and 2-SI-709
- 4. 125V DC (DV10) will not be available (battery has 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> coping factor)
- 1. 2-CH-518 fails open due Verify B HPSI train in to loss of DC power service to cold leg (unused) injection
- 2. HPSI P41A out of Close 2-SI-616 and service 626 06/28/18 6.3-36 Rev. 36
Cold Leg Injection Single Failure Effects of Failure Actions Required Path Boron Precip Cont
- 4. Loss of Facility Z2 (B61) LPSI LPSI P42A LPSI pump via P41A HPSI pump vi Post SIAS 2-SI-635 and 645 2-CH-517 to pressur auxiliary spray line
- 1. 2-SI-652 remains closed Establish LPSI to Cold Leg Injection
- 2. 2-SI-635 and 2-SI-645 Close 2-SI-615 and remain open 2-SI-625
- 3. 125V DC (DV20) will not be available (battery has 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> coping factor)
- 1. 2-CH-517 fails closed Power 2-CH-517 and due to Facility Z2 DC 2-CH-519 with 125V battery DC (DV10)
- 2. 2-CH-519 fails open Align P41A HPSI pump to pressurizer auxiliary spray line via: Open 2-CH-340, 440 and 517
- 3. HPSI P41C pump out of Close 2-CH-518 and service 2-CH-519 06/28/18 6.3-37 Rev. 36
Cold Leg Injection Single Failure Effects of Failure Actions Required Path Boron Precip Cont
- 5. Loss of 125V DC LPSI LPSI 1. B HPSI train P42B LPSI Pump vi (DV10) coincident with (using P41C 2-SI-306 through 2-SIAS pump) and 2-SI-652
- 1. Facility Z1 Diesel is shut Open 2-SI-651 with 2. P42B LPSI pump down Facility Z2 power via 2-SI-645
- 2. P42A LPSI pump out of Close 2-SI-635 service
- 3. 2-SI-615, 2-SI-625 Open 2-SI-400 and remain closed 2-SI-709
- 1. 2-CH-518 fails open Verify B HPSI train in (unused) service to cold leg injection
- 2. P41A HPSI train out of Close 2-SI-636 and service 646 06/28/18 6.3-38 Rev. 36
Cold Leg Injection Single Failure Effects of Failure Actions Required Path Boron Precip Cont
- 6. Loss of 125V DC LPSI LPSI P42A LPSI via P41A HPSI pump vi (DV20) coincident with 2-SI-615 and 625 2-CH-517 to pressur SIAS auxiliary spray line
- 1. Facility Z2 Diesel is shut Establish LPSI to Cold down Leg Injection
- 2. P42B LPSI pump out of 2-SI-615 & 625 are service open
- 3. 2-SI-635 and 2-SI-645 remain closed
- 1. 2-CH-517 fails close Power 2-CH-517 and 2-CH-519 with 125V DC (DV10)
- 2. 2-CH-519 fails open Align P41A HPSI pump to pressurizer auxiliary spray line via: Open 2-CH-340, 440 and 517
- 3. B HPSI train out of Close 2-CH-518 and service 2-CH-519 06/28/18 6.3-39 Rev. 36
Cold Leg Injection Single Failure Effects of Failure Actions Required Path Boron Precip Cont
- 7. Mechanical Failure of a P42A or P42B LPSI pump LPSI P42A or P42B LPSI P42A or P42B LPSI LPSI pump fails to operate via 2-SI-645 via 2-SI-306 through 2-SI-651 and 2-SI-6 Align the operating HPSI B train LPSI pump hot leg injection 2-SI-645 is open Close 2-SI-636 &
646 Close 2-SI-615, 625 and 635
- 8. Mechanical or Loss of 2-SI-306 is pinned and Air Failure of 2-SI-306 locked at preset throttled open position and remains open. Therefore, this case is not considered a credible failure case.
- 9. Mechanical Failure of Failure of any one of these Establish HPSI to Hot One LPSI pump P41A HPSI pump vi 2-SI-651, 2-SI-652, 400 valves will disable LPSI hot Leg Injection through any two of 2-CH-517 to pressur or 709 leg injection. the four LPSI spray line injection valves.
06/28/18 6.3-40 Rev. 36
Cold Leg Injection Single Failure Effects of Failure Actions Required Path Boron Precip Cont
- 10. Mechanical Failure of A HPSI train out of service None 1. B HPSI train P42A/B LPSI pump P41A HPSI pump or (using P41C 2-SI-306 through 2-2-CH-340, 440, 429, pump) and 2-SI-652 517, 518 or 519 2. P42A/B LPSI pump via2-SI-645
- 11. Mechanical Failure of 2-SI-635 remains open Establish HPSI to Hot One LPSI pump P41A HPSI pump vi 2-SI-635 Leg Injection through any two of 2-CH-517 to pressur the four LPSI auxiliary spray line injection valves 06/28/18 6.3-41 Rev. 36
06/28/18 6.3-42 Rev. 36 06/28/18 6.3-43 Rev. 36 28/18 6.3-44 Rev. 36 1 DESIGN BASES 1.1 Functional Requirements containment spray system functions as an engineered safety feature to limit the containment sure and temperature after a loss-of-coolant accident (LOCA) and Main Steam Line Break LB) accident and thus reduces the possibility of leakage of airborne radioactivity to the ide environment. The containment spray system in conjunction with the containment air rculation and cooling system (described in Section 6.5) provides sufficient heat removal ability to limit the post-accident containment pressure and structural temperature below the gn values of 54 psig and 289°F, respectively (Section 14.8.2) by directing sprays of cooled ated water downward from the upper regions of the containment.
ing shutdown or refueling, as a back-up to support maintenance activities of the shutdown ling system, a containment spray system pump can be aligned to cool the spent fuel pool (see tion 9.5).
1.2 Design Criteria following criteria have been used in the design of the containment spray system:
- a. The system has two redundant, independent subsystems, each having 50 percent of the required heat removal capability.
- b. The system has suitable subsystem and component alignments to assure operation of the complete subsystem with its associated components.
- c. Capabilities are provided to assure system operation using either on site power (assuming off site power is not available) or off site electrical power.
- d. A single failure in either subsystem does not affect the functional capability of the other subsystem.
- e. The system is designed to permit inspection of important components, such as containment sump, containment spray pumps, heat exchangers, spray nozzles, valves, and piping to assure the integrity and capability of the subsystem.
- f. The containment spray system is designed to permit appropriate periodic pressure and functional testing to assure: (1) structural and leak-tight integrity of its components; (2) operability and performance of the active components of the system; (3) operability of the active components of the system as a whole. Under conditions as close to the design as practical, the performance of the full operational sequence that brings the system into operation shall be demonstrated.
This includes operation of applicable portions of the protection system, the transfer 28/18 6.4-1 Rev. 36
- g. The system is consistent with the design criteria as described in Section 6.1.
- h. The components of the containment spray system are designed to operate in the most severe post-accident environment described in Section 6.1.
- i. The containment spray pumps are designed in accordance and with the conditions given in Safety Guide 1.
2 SYSTEM DESCRIPTION 2.1 System containment spray system is shown schematically in Figure 6.1-1. The containment spray em consists of two identical, redundant, independent subsystems, each with a heat removal ability of 120 x 106 Btu/hr under design post-accident conditions. Each containment spray em consists of a containment spray pump, shutdown cooling heat exchanger, spray nozzles, ng, valves and instrumentation. The refueling water storage tank serves as the source of water is described in Section 6.2. The shutdown cooling heat exchangers are described in tion 6.3.
tainment integrity is maintained following the limiting containment transient, the design basis LB, by utilizing one containment spray subsystem in combination with two containment air rculation and cooling units (Section 6.5). This combination has a heat removal capability of million Btu/hr under design post-accident conditions (Section 14.8.2). The heat sink for the tainment spray system is shown in Figure 6.4-9.
system is designed assuming the containment spray water is heated to the average perature of the containment atmosphere while falling through the steam-air mixture within the tainment. In order that the spray droplets approach thermal equilibrium during the fall, a imum distance of 65 feet is provided between the spray nozzles and the highest obstruction in containment.
h spray subsystem is provided with spray headers oriented to provide near equal distribution hin the containment cross section.
containment spray header locations and spray nozzle orientations are shown in Figure 6.4-1.
re are two different types of nozzles employed in the system as listed in Table 6.4-1. Of the total nozzle locations, 64 are Lechler model 372.975.17.BL which deliver 8 gpm of flow at a psid pressure differential. The remaining nozzles are Spraco model 1713A with a flow acity of 15 gpm at the same 40 psid differential pressure. The mass-mean droplet diameter for Lechler nozzles is less than that for the Spraco nozzles. Typical spray patterns for the Spraco zles are shown in Figures 6.4-2, 6.4-3 and 6.4-4 while spray patterns for the Lechler nozzles given in Figure 6.4-4A.
28/18 6.4-2 Rev. 36
2.2 Components major system components and associated fabrication and performance data are listed in le 6.4-1.
3 SYSTEM OPERATION containment spray system operates only under certain emergency conditions. With the eption of the cold shutdown and refueling conditions, valve alignment for all other operating des is as described under emergency conditions.
ing shutdown or refueling, as a back-up to support maintenance activities of the shutdown ling system, a containment spray system pump can be aligned to cool the spent fuel pool (see tion 9.5).
3.1 Emergency Conditions he event of a LOCA or MSLB accident, the containment spray system is automatically ated by the containment spray actuation signal (CSAS) as described in Section 7.3. The tainment spray pumps initially take suction from the refueling water storage tank. When low l is reached in this tank, the pump suction, in the absence of operation action, is automatically sferred to the containment sump by a sump recirculation actuation signal (SRAS) as described ection 7.3. The recirculated spray water is cooled by the shutdown heat exchangers prior to harge into the containment through the spray headers. The RBCCW serves as the cooling ium and is discussed in Section 9.4. Emergency power is provided by the emergency buses as cribed in Section 8.3.
prevent the refuel pool from capturing water, the pool drain line isolation valves are locked n during the operating cycle and a screened enclosure is installed over the two drain openings he floor of the refuel pool.
tem operation and performance is monitored in the control room. The containment spray ps are monitored by the pump pressure gauges, motor trip alarms, and flow metering to cate abnormal operation. The tube side of the shutdown heat exchangers is monitored by em water temperature to indicate abnormal heat exchanger operation. The shell side of the tdown heat exchanger is described in Section 9.4.
motor-operated valve in each containment spray header opens automatically upon the tainment spray actuations signal (CSAS). The position of these valves is monitored in the trol room.
manual valves in the system are aligned for containment spray operation and are inistratively locked in their respective operating positions.
28/18 6.4-3 Rev. 36
3.2 Cold Shutdown and Refueling ing refueling operations the shutdown heat exchanger is isolated from the containment spray em and aligned with the low pressure safety injection system for shutdown cooling operations Section 6.3). This alignment is made by closing manual valves 2-CS-3A and 2-CS-3B on the tainment spray pump discharge and 2-CS-4A and 2-CS-4B downstream of the shutdown heat hanger, and opening the manual isolation valves upstream and downstream of the shutdown t exchanger to the low pressure safety injection header 2-SI-452, 453, 456 and 457. This nment is made only after the safety injection actuation signal is blocked (see Section 7.3).
ing shutdown or refueling, as a backup to support maintenance activities of the shutdown ling system, a containment spray system pump can be aligned to cool the spent fuel pool (see tion 9.5.
4 AVAILABILITY AND RELIABILITY 4.1 Special Features components of the containment spray system are designed to general requirements including mic response as described in Section 6.1. All components are protected from missile damage pipe whip by physically separating duplicate equipment, as described in Section 6.1.
assure the availability of water to the pumps, separate suction headers from the refueling water age tank are provided for the spray pump located in the two separate and shielded pump ms, which house the pumps of the engineered safety features systems. Each of the two pump ms contains one spray pump, one low pressure safety injection pump and one high pressure ty injection pump. Two separate headers, one to each of these pump rooms, are also provided m the containment sump.
containment spray pumps are located in the lowest elevation of the auxiliary building at vation (-) 45-6 to assure a flooded suction. This assures pump priming and protects the hanical seals in the spray pumps. In this location, the available NPSH is always greater than required NPSH (see Table 6.4-1).
assure adequate design margins, the minimum available NPSH for the containment spray ps is conservatively calculated during the recirculation mode in accordance with Safety de 1. Refer to Section 6.3.2.1 for assumptions used in calculating.
ncrease system reliability, the containment spray pump motors have the capacity to start with motor-operated valves on the discharge header fully opened.
refueling water storage tank (RWST) and containment sump assure sources of water for the tainment spray system. These components are described in Section 6.2.
28/18 6.4-4 Rev. 36
dvertent initiation of the spray system does not affect the safety of the unit, since within the tainment all the instruments are drip-proof or weatherproof, all the motors are drip-proof or lly enclosed and signal cable runs are enclosed in waterproof jackets. All piping or equipment lation which may come in contact with sprays are of the metal reflective type or jacketed to vent large quantities of water from penetrating the insulation. Small amounts of seepage do not ent any significant thermal shock to hot equipment.
dvertent operation of the system is monitored by pressure, flow and valve position indicators the operator, so the situation would be quickly observed and remedial action taken.
design basis case for containment pressure analysis is a Main Steam Line Break accident at power with the single failure of vital bus cabinet VA-10 and VA-20. The analysis assumes one train of containment spray and one train (two units) of containment air recirculation R) are also operable. The containment pressure response based on all other combinations of ipment which would be available assuming any other single failure is bounded by this med single failure.
owing a LOCA, the containment spray efficiency decreases with the containment post dent steam/air mass ratio (hence with containment temperature and pressure). The efficiency he containment air recirculation and cooling units remains relatively constant since these units designed to remove sensible heat (FSAR Section 6.5). The spray system, even operating at a er efficiency over the long term, in combination with the containment air recirculation and ling units, provides ample heat removal capabilities.
4.2 Test and Inspections h containment spray pump was shop tested for hydraulic performance at sufficient head-acity points to generate complete performance curves. These performance tests were run for gn NPSH at runout conditions and calculated back to rated conditions. This containment y pump performance test curve is shown in Figure 6.4-8.
destructive examinations were performed on all pressure-retaining components of each tainment spray pump in accordance with the Draft ASME Code for Pumps and Valves for lear Power, Class II, 1968.
h types of spray nozzles listed in Table 6.4-1 were performance tested to assure the desired at a specified pressure drop across the nozzle is achieved. The 129 Spraco nozzles are able of delivering 15 gpm of flow at a 40 psid pressure difference while the remaining 64 hler nozzles deliver 8 gpm at the same pressure drop. Type, location and orientation of the y nozzles is shown in Figure 6.4-1. The containment spray nozzle performance racteristics for both types of nozzles are provided in Figure 6.4-7.
containment spray system underwent a preoperation test prior to startup. The test is described ection 13.
28/18 6.4-5 Rev. 36
or-operated valves are tested for operability by manually initiating (Section 7.3.4.2.1) the AS for each component. Valve operation can be verified by position indication in the control m and locally by visual inspection. Pump operation is indicated by local pressure indication by status lights in the control room.
rability testing, response time testing and inservice testing of the containment spray system its components are performed as required by plant Technical Specifications in accordance h plant procedures.
design and location of the containment spray pumps and shutdown cooling heat exchangers mit access for periodic testing and maintenance during normal operation.
28/18 6.4-6 Rev. 36
TABLE 6.4-1 CONTAINMENT SPRAY SYSTEM COMPONENT DESIGN PARAMETERS tainment spray pumps Manufacturer Goulds Pump Model Number 3736-4x6-13DV Quantity 2 Type Vertically split, horizontally centrifugal with mechanical seals backed up with an auxiliary gland Material Casing ASTM A351 Gr CF8M; Bolting A-193 B7; Impeller A-296 Gr CG8M Design temperature (°F) 300 Fluid pumped Borated water (1720 ppm)
Codes Draft ASME Code for Pumps and Valves for Nuclear Power, Class II, 1968; Standards of Hydraulic Institute Seismic Class 1 tainment spray pump motor Manufacturer General Electric Horsepower rating (hp) 250 Horsepower rating (hp) B Type Induction Frame designation 8188S Codes NEMA, MG-1 Seismic Class 1 28/18 6.4-7 Rev. 36
Mode of Operation Injection Recirculation
- Capacity (each) (gpm) 1350 ** 1650 **
- Head (ft) 450 360
- NPSH available (ft) 64.0 27.0
- NPSH required (ft) 15.5 21.0 Brake horsepower (bhp) 202 215 Temperature transient (°F) 50 to 300 inch, 10 seconds Pump speed (rpm) 3560 Fluid pH 5.5 to 10.5 ng, Fittings and Valves tion Pipe Sizes Wall Thickness 2 inch and smaller Schedule 40S 2.5 inch and larger Schedule 10S Material ASTM A-312, Type 304 Design pressure (psig) 60 Design temperature (°F) 300 Standard ANSI B-31.7 Class II Seismic Class 1 28/18 6.4-8 Rev. 36
Construction Piping Valves 2 inch and smaller; Socket welded 2 inch and smaller: Socket-welded 600 lb ANSI rating, stainless steel ***
2.5 inch and larger: Butt-welded except at 2.5 inch and larger: Butt-welded, 150 lb flanged equipment ANSI rating, stainless steel charge Pipe Sizes Wall Thickness 3 inch and smaller Schedule 40S 4 inch through 6 inch Schedule 10S 8 inch through 14 inch Schedule 20 Material ASTM A-312, Type 304 Design pressure (psig) 500 Design temperature (°F) 300 Standard ANSI B-31.7, Class II; ANSI B-31.1.0 Modified (inside containment)
Code (valves) Draft ASME Code for Pumps and Valves for Nuclear Power, Class II, 1968 Seismic Class 1 Construction Piping Valves inch and smaller: Socket welded 2 inch and smaller: Socket welded, 600 lb ANSI rating, stainless steel ***
.5 inch and larger: Butt welded except 2.5 inch and larger: Butt welded, 300 lb ANSI langed equipment rating, stainless steel 28/18 6.4-9 Rev. 36
Spray nozzles Manufacturer Spraco Lechler Model number 1713A 372.975.17.BL Quantity 129 64 Type Ramp Bottom Ramp Bottom Pattern Hollow Cone Hollow Cone Material Type 304 or 316 stainless Type 316 Stainless Nozzle size (inches) 1, 3/8 inch orifice 3/4, 0.28 inch orifice Rated flow, each (gpm) 15 8 Rated pressure drop (psid) 40 40 The pump flows, heads, and NPSH values presented in this table are based on the original design specifications. The pumps will actually operate over a range of conditions during containment spray from the RWST following a SIAS and from the containment sump following SRAS. System hydraulic and NPSH analyses have been performed for these operational modes based on the pump design and degraded capacities.
Includes 50 gpm for minimum flow recirculation.
600 pound ANSI rating represents minimum requirements. 800 pound ANSI rating valves are utilized on a case-by-case basis.
28/18 6.4-10 Rev. 36
METHOD COMPONENT OF DETRIMENTAL IDENTIFICATION FAILURE DETECTION EFFECT ON CORRECTIVE RESULTANT
& QUANTITY MODE & MONITOR SYSTEM ACTION SYSTEM STATUS REMARKS Motor-operated Fail as is Position None Repair operator Normal operation, Valve can be Valves (2) HV3010, indication. valve normally open manually operate HV3011 CRI Motor-operated Fail as is Position Loss of one (1) Repair operator One header out of One header Valves (2) HV3008, indication CRI containment sump service. Alternate sufficient for HV3009 recirculation line header is operable containment cooling with combination of two containment air recirculation cooling units.
Containment Spray Pump Pressure Loss of water flow Isolate pump and One containment One containment Pump (2) stops indication & in CTMT spray repair spray header out of spray header flow indication header service, alternate sufficient for containment spray emergency header in normal cooling.
operation Motor-operated Fail to Pressure Loss of flow from Repair operator One containment One containment Valves (2) VHV3021, open on indication & one containment Spray header out of Spray header HV3022 CSAS flow spray header service, alternate sufficient for indication. All containment Spray emergency cooli CRI header in operation 06/28/18 6.4-11 Rev. 36
figure indicated above represents an engineering controlled drawing that is Incorporated by erence in the MPS-2 FSAR. Refer to the List of Effective Figures for the related drawing ber and the controlled plant drawing for the latest revision.
28/18 6.4-12 Rev. 36
(1713A NOZZLE SPRAYING HORIZONTALLY) 28/18 6.4-13 Rev. 36
(1713A NOZZLE SPRAYING DOWNWARD ON 45°)
28/18 6.4-14 Rev. 36
(1713A NOZZLE SPRAYING VERTICALLY DOWNWARD) 28/18 6.4-15 Rev. 36
FIGURE 6.4-4A TYPICAL SPRAY COVERAGE PATTERNS 06/28/18 6.4-16 Rev. 36
28/18 6.4-17 Rev. 36 28/18 6.4-18 Rev. 36 06/28/18 6.4-19 Rev. 36 CHARACTERISTICS.
28/18 6.4-20 Rev. 36
06/28/18 6.4-21 Rev. 36 1 DESIGN BASES 1.1 Functional Requirements function of the containment air recirculation and cooling system is to remove heat from the tainment atmosphere during normal operation. In the event of a Loss-of-Coolant-Accident CA) or Main Steam Line Break (MSLB) accident, the system, in conjunction with the tainment spray system described in Section 6.4, provides a means of cooling the containment osphere to reduce the containment building pressure and thus reduce the leakage of airborne gaseous radioactivity.
containment air recirculation and cooling system is independent of the safety injection and tainment spray systems. It is sized such that, assuming the most adverse containment heat-oval single failure, following a LOCA or MSLB accident, two of the four containment air rculation units in conjunction with one train of the containment spray system limits the tainment pressure and structural temperature to less than the containment design values (54
, 289°F).
1.2 Design Criteria following criteria have been used in the design of the containment air recirculation and ling system:
- a. The system has two redundant, independent and separate subsystems, each consisting of two containment air recirculation and cooling units.
- b. The system has suitable subsystem and component alignment to assure operation of the complete subsystem with its associated components.
- c. Capabilities are provided to assure that the system can operate using either on site power (assuming off site power is not available) or with off site electrical power.
- d. The containment air recirculation and cooling system is designed to permit inspection of important components, such as cooling coils, fans, motors and reactor building closed cooling water (RBCCW) piping to assure the integrity and capability of the system.
- e. The containment air recirculation and cooling system is designed to permit appropriate periodic pressure and functional testing to assure: (1) structural and leak-tight integrity of its components; (2) operability and performance of the active components of the system; and, (3) operability of the active components of the system as a whole. Under conditions as close to the design as practical, the performance of the full operational sequence that brings the system into operation, including operation of applicable portions of the protection system, the transfer 28/18 6.5-1 Rev. 36
The system is designed to the criteria described in Section 6.1.
The components of the containment air recirculation and cooling system are designed to operate in the most severe postaccident environment as described in Section 6.1.
2 SYSTEM DESCRIPTION 2.1 System containment air recirculation and cooling system is shown schematically in Figure 9.9-1.
containment air recirculation and cooling system is designed to maintain the containment mal ambient temperature at 120°F with three of the four units operating. Each unit is designed 2.2 x 106 Btu/hr, one-third of the normal containment heat load.
h containment air recirculation and cooling unit is designed for removing 80 x 106 Btu/hr er Main Steam Line Break accident or LOCA conditions prior to the containment Sump irculation Actuation Signal (SRAS). Following the SRAS, a portion of the Reactor Building sed Cooling Water (RBCCW) flow is directed through the shutdown cooling heat exchanger ool the sump water prior to being sprayed into containment. RBCCW is isolated to nonvital de containment loads by manual closure of 2-RB-30.1 A/B and 2-RB-37.2A/B. The resulting CCW flow is reduced from 2000 gpm (prior to SRAS) to 1600 gpm per CAR cooling unit.
s flow reduction, coupled with the reduction in containment air/steam temperature at the time RAS, results in a reduction in the containment heat removal capability of a CAR cooling unit m 80 million to 60 million Btu/hr. Two containment air recirculation and cooling units in bination with one containment spray pump (see Section 6.4.2.1) provide complete tainment cooling capabilities under post-accident conditions. Each component in this bination is powered from the same emergency power source (Section 8.3) and is provided h cooling water from the same RBCCW header (Figure 9.4-2). This combination is designed removing 280 x 106 Btu/hr. The heat sink for the containment air recirculation and cooling em is shown in Figure 6.4-9.
ile the failure of both trains of the containment spray system requires multiple failures and is ond the licensing design basis of the plant, following a LOCA, containment cooling may be vided by three of the four containment air recirculation and cooling units without the tainment spray system. This combination is designed for removing 240 x 106 Btu/hr under CA conditions. However, following a MSLB accident, the combination of three containment ecirculation and cooling units does not provide adequate containment heat removal. A MSLB dent can result in a dry steam blowdown. With a dry steam blowdown, the potential exists for gnificant increase in and superheating of the containment steam/air temperature above 289°F.
he design basis event/Section 14.8.2), the initiation of the containment sprays quickly reduces 28/18 6.5-2 Rev. 36
m temperature remain above 289°F for extended periods of time, possibly resulting in an essive heatup of structures and equipment inside containment.
containment air recirculation and cooling system is designed to maintain an ambient perature within the containment of 120°F during normal operation. The duct work distribution em is routed to provide cooling air near all major components.
reactor cavity cooling air is supplied by two independent, physically separated air supply ders. These are located on opposite sides of the reactor cavity. The two air supply headers are by a common plenum, which in turn, is fed by the four (4) CAR Fans.
cavity cooling system is designed to supply air at a maximum of 91°F to the bottom of the ity and to the reactor vessel supports and nuclear instruments in the reactor cavity. The imum estimated air temperature at the permanent reactor cavity seal plate is 132°F.
is supplied directly in the vicinity of the steam generators, reactor coolant pumps and motors pressurizer. Additional air is supplied in the lower regions of the steam generator partments. As the air is heated by sensible heat, a stack effect is created within the steam erator compartments.
is supplied directly into the pressurizer skirt assembly to provide a suitable environment for pressurizer heaters. The ambient temperature in this region is limited to 120°F.
is supplied directly to cool the concrete interface where the concrete is in contact with ironment operating above 150°F. In all cases, the concrete does not exceed 150°F the tainment during normal operation.
h of the four containment air recirculation and cooling units consists of a direct drive two-ed vaneaxial fan, eight cooling coil sections and steel housing which forms an integral air dling units.
h coil house is equipped with eight individual coils piped to supply and return manifolds ch connect to the RBCCW system.
four containment air recirculation and cooling units (CARs) are arranged in two groups. Each up includes two CAR units that share an independent RBCCW supply header. Each header nches into two supply lines, one supply line to each of the two CAR units in the group (Refer igure 9.4-5).
h of the four RBCCW supply lines has an air-operated stop valve for its associated CAR unit example: 2-RB-28.1A for one of the four units). Each of these four RBCCW supply stop es is normally open and deenergized. Each of these valves is designed to fail in the open ition.
28/18 6.5-3 Rev. 36
s). Each of the air-operated control valves in the four sets of return line valves can be operated m the control room. One of the two control valves in each return line set (e.g., 2-RB-28.3A in example set) opens automatically on receipt of a safety injection signal (SIAS).
re are twenty air temperature measuring instruments located in the containment. Eight of these sure the containment atmosphere air temperature in different locations in the containment, uding one location within the reactor cavity. By use of an eight position selector switch and a perature indicator located on the main control board, the containment air temperature at the t locations can be monitored in the main control room. In addition, the temperature readings inputted into the computer. The other 12 temperature measuring instruments are associated h the various ventilation systems. These measurements are also inputted into the computer.
alfunction in the cavity cooling system is indicated by an increase in cavity air temperature also by an increase in the containment air temperature since these areas are served by the e air distribution system. The limiting conditions for operation is the primary containment rage temperature of 120°F as described in the Technical Specification 3.6.1.5. During normal t operation the CAR coolers are designed to maintain the cavity concrete temperature below
°F.
2.2 Components twork for the containment air recirculation and cooling system outside the secondary shield l is galvanized steel containing 1.25 oz/square foot of zinc. Inside the steam generator partment duct work is 18-8, ANSI Type 304 stainless steel with a 2B mill finish. Transverse t work joints are welded flange with angle reinforcing. Longitudinal seams are continuously ded.
erials of construction and performance data for system components are listed in Tables 6.5-1 6.5-2, respectively. The fan performance curve is shown in Figure 6.5-1. The coil ormance is shown in Figure 6.5-2.
es and Standards:
Cooling coils ASME Section VIII Fan AMCA 211A Motors IEEE STD-334-1971, NEMA, MG-1 Duct work SMACNA, High Velocity Standards Seismic Class 1 (Ductwork Class 2) 28/18 6.5-4 Rev. 36
3.1 Normal Operations ing normal operation, the 120°F containment air is recirculated through the containment air rculation and cooling system by the vaneaxial fans. The fans operate normally at high speed.
is supplied through the duct work system into the steam generator compartments and reactor ity at approximately 91°F. The cooling air is heated, by the sensible heat, to 120°F as natural ulation occurs.
RBCCW system supplies cooling water at 85°F maximum to the cooling coils of each CAR (Section 9.4). During normal operation, the full sized valve in each of the four sets of two llel RBCCW return valves (e.g., for one CAR unit, 2-RB-28.3A) is positioned according to containment heat load requirements. (Each of these same full sized RBCCW return valves provides service during a LOCA). Additionally, during normal operation, the corresponding ller (6 inch diameter) return line valve in each parallel set is open.
ing normal operation, three of the four containment air recirculation and cooling units are uired to provide sufficient sensible cooling.
loss of the normal containment cooling system is not considered credible.
wever, postulating the above event, the containment temperature and pressure response would inguish this occurrence from the LOCA. The containment conditions following the design s accident (DBA) are described in Section 14.8.2). Assuming the loss of normal cooling nt, the containment temperature would increase approximately 40°F for a one (1) psi increase ontainment pressure. Therefore, for this event there is an elevated containment temperature to latively small increase in containment pressure. Other minor accidents, less severe than the A, would result in the elevated temperature and relatively large increase in pressure since itional mass is being introduced into the containment free volume. Thus, the postulated loss of mal cooling capability could be distinguished from an accident condition.
tion 3.6.1.5 in the Technical Specification states the containment temperature limit. Safety ted instrumentation exposed to the containment atmosphere is capable of withstanding 150°F continuous basis.
he unlikely event that the fusible link plates and blowout plates open during normal operation, containment air distribution system would be out of service. As a result, the cool air from the tainment air recirculation and cooling units would be discharged outside the secondary shield
- l. However, the stack effect created by the temperature gradient within the steam generator partments would induce portions of this cool air inside the compartments. Although partial ling does exist, potential hot spots could be present around major components. Temperature ments located throughout the containment will alarm any elevated temperature condition.
n receipt of a high-temperature alarm on the plant computer, the operator will take action in ordance with plant procedures.
28/18 6.5-5 Rev. 36
operation of the Containment Air recirculation and Cooling systems are not required during Integrated Leak rate test. During the initial containment pressurization, the units may be rated to remove the heat from compression through RBCCW as the cooling medium. The fans motors operate at low speed to reduce horsepower requirements at these elevated pressure ditions.
units may be operated during the test, if required.
units may operate without cooling water during the post-test containment depressurization to vide heating.
3.3 Emergency Conditions n receipt of a SIAS, the idle containment air recirculation and cooling unit is automatically ted on the low speed setting. Simultaneously, the running units are switched from their normal rating high speed setting to low-speed operation. The full flow (10 inch diameter) RBCCW es at the outlet of each cooler are also opened upon receipt of the SIAS. (Figure 9.4-2) h off site power available under this mode of operation, three units are switched to low speed the fourth is started on low speed as described above. Each of two emergency buses carries load of two containment air recirculation and cooling units.
h CAR fan coil unit is provided with blowout doors equipped with fusible links downstream he fan discharge. At high temperature in the containment environment after either a LOCA or SLB, these fusible links melt disengaging the doors allowing them to swing open. This allows o circulate through the path of least resistance as described in Section 6.5.4.1.
containment air recirculation and cooling units assist in uniform mixing of combustible gas hin the containment environment as described in Section 6.6.2.1.
3.4 Refueling containment air recirculation and cooling units may be operated at reduced speed during eling operations. The units provide mixing with the containment purge air (see Section 9.9.2) uniform temperatures throughout the containment.
4 AVAILABILITY AND RELIABILITY 4.1 Special Features components of the containment air recirculation and cooling system are designed to the eral requirements including seismic response as described in Section 6.1. Components are ected from missile damage and pipe whip by physical separation of duplicate equipment as cribed in Section 6.1.
28/18 6.5-6 Rev. 36
ure of the normal electrical power supply automatically places all four fans on emergency tric power source. A failure mode analysis is given in Table 6.5-3.
ociated system components, such as piping, valves, and instrumentation are located outside secondary shield to minimize the possibility of missile damage.
ductwork system which is located on the containment air recirculation fan discharge, nstream of the blowout doors, is not required during post-accident operation. To assure an estricted flow path, 4 doors downstream of the discharge of each fan open via the melting of high-temperature fusible links. These doors consist of galvanized steel sheets attached rigidly he duct work system by means of UL rated fusible links.
fusible links are nominally rated at 165°F +/- 7% based on the UL allowable tolerance for ble links. Each containment air recirculation unit is provided with blowout doors equivalent to square feet of flow area. This flow area is greater than the fan outlet area. This assures fan rability and prevents flow restrictions following any possible duct work failure during post-dent conditions. All blowout doors plates are hinged to the ductwork to prevent their oming credible missiles after separation.
post-accident distribution system is designed to discharge the air in four (4) horizontal ctions from each unit through the openings left by the fusible link plates. Under design ditions, it is assumed that the existing duct work is restricted such that all the air is discharged ugh these openings. The throw (distance traveled by the air stream before reaching terminal city) is approximately 100 feet. Under these conditions, the discharge from the upper unit is l beyond the intake region of the lower unit, thus preventing any short circuiting. The air ams drop off toward the end of the throw and tend to settle toward the bottom of containment to the slightly lower temperatures. This creates secondary stack effects throughout these ons of containment.
anticipated, but not necessary, that portions of the ductwork distribution system remains ct. This provides greater air distribution throughout containment. However, the velocity of air, hence the throw, through the fusible link plate openings would be much less. This could te a slight short circuiting effect. Since the units are located one above the other, the bottom may suction portions of the discharge from the upper unit. However, this has negligible effect he performance of the units since, during the short term, the units will be removing latent and sensible heat. That is, the discharge temperature from the units will be only a few degrees er than the inlet temperature. The effect of short circuiting is slightly more pronounced as the tainment post-accident temperature begins to decrease, as the units are removing more sible heat. However, at this time, the containment heat removal requirements are much less the heat removal capabilities of the containment air recirculation and cooling units. Short uiting is not expected to affect the performance of the system.
28/18 6.5-7 Rev. 36
tainment air recirculation and cooling system to provide a uniform containment atmosphere.
ief dampers are provided for the ductwork headers on the side of the main CAR fan discharge um outside of the secondary shield wall. These dampers are provided to prevent a pressure t from reaching the containment air recirculation and cooling units through the ductwork em. The relief dampers are held closed by tension springs of Type 301 stainless steel. The ngs are designed to permit the damper to be fully open (out from the duct) at a three-psi sure differential. Each main ductwork header is provided with 30 square feet of relief area.
condensate leaving the cooling coils is collected in individual drip pans. These pans cascade liquid into the housing drain. The air side coil face velocity is approximately 180 fpm under CA conditions. This low velocity reduces moisture carry-over from the coils.
h housing is equipped with two four-inch drains with loop seals. Clogging of these drains does render the unit inoperable. Under this postulated case, the housing water level rises and rflows through the coil sections before reaching the fan inlet. The curb supporting the cooling s extends approximately six inches above the housing floor and the fan inlet extend roximately 15 inches above the housing floor.
fin pitch is 8.5 fins per inch of cooling coil length. With this pitch, water logging of the coil under post-accident conditions is minimized to avoid any problem.
ouling factor of 0.0005 for the water side is included in the coil ratings. Demineralized water CCW) fouling factor of 0.0005 is recommended by the Tubular Exchangers Manufacturing ociation (TEMA). The water side of the cooling coil tubes is equipped with removable plugs he return bends of the coils to permit cleaning.
cooler housing is designed to ensure no loss of function when subjected to a pressure erential of 2 psi. The housing is open on four sides through the cooling coil sections and ugh the base by the fan barrel. Each of the four sides of the housing is approximately ercent free area through the coil face. This provides ample free paths to minimize differential sure during the post-accident transient-pressure condition.
implified analysis was performed on the containment air recirculation and cooling units to onstrate that the units will not experience a differential pressure greater than 2.0 psi during post-incident conditions. The following is a summary of that analysis:
- 1. It was assumed that a given cooler was pressurized with air to a pressure of 2.0 psig.
- 2. Assuming air to be a perfect gas, the change in mass from atmospheric pressure to 2.0 psig was calculated.
28/18 6.5-8 Rev. 36
- 4. Assuming the pressure drop across the coil banks is proportional to the square of the flow rate, for any given flow rate the corresponding pressure drop across the coil banks, and hence the cooler housing, can be calculated.
ed on the above-simplified analysis, a flow rate less than 7,000 CFM (normal flow rate is 00 CFM) was calculated based on the 2.0 psi per second pressure transient. The drop across coil banks is much less than 0.10 inches w.g., which is negligible. This allows a factor of about inches converting the model from the perfect gas to the post-accident steam-air mixture. The erence in densities between the model assumed (0.075 lb/ft3) and the design post-accident osphere (0.18 lb/ft3) is about a factor of 2. Therefore, there is adequate margin to demonstrate the containment coolers will not experience a pressure gradient across the housing of 2 psi.
h Containment Air Recirculation and Cooling unit is provided with a vibration-sensing tch. In the event of excessive, sustained vibration at the fan assembly, the switch will provide larm in the Control room.
valves in the normal cooling water outlet lines (6 inches) will be open during normal ration and valves in the parallel emergency outlet lines (10 inches) can be opened from the trol room and the flow rate can be monitored at any time.
maximum RBCCW temperature on the discharge side of the containment air recirculation cooling unit coils is 234°F during design post-accident conditions. The RBCCWS operates er pressure, approximately 50 psia in the downstream piping. The saturation temperature esponding to this operating pressure is approximately 280°F. Therefore, the RBCCW perature at the discharge side of the CAR units is approximately 46°F below saturation. In ition, the RBCCW surge tank (Section 9.4.2.1) maintains a minimum static head on the CAR lers, corresponding to about 30 psia. The saturation temperature corresponding to this pressure 50°F.
4.2 Tests and Inspections major components of the containment air recirculation and cooling system are tested for ormance and integrity to assure its ability to operate within the containment post-accident ironment.
cooling coil sections are similar to a coil section which has been previously tested and has onstrated the capability of condensing steam at conditions equal to or greater than the LOCA gn conditions. The coil section performance test results are compared to computed data and comparison is then used to predict the performance of the full-size coil assembly. A topical ort, W-CAP-7336-L, verifying the performance of similar coils for this application was filed Westinghouse with the NRC.
28/18 6.5-9 Rev. 36
ordance with the Draft IEEE Standard 334-1971. Westinghouse is preparing to file topical ort, W-CAP-7829, on the test results. Topical reports, W-CAP-7343-L and W-CAP-9003, for motor insulation and cable splice were filed with the NRC by Westinghouse. A complete mercial motor test is performed before and after the simulated LOCA tests on the production del motor.
h fan and motor was tested as a unit to assure characteristic performance curves. Fan ratings in accordance with Air Moving and Conditioning Association (AMCA) Standard Test Code
-A.
stators used in qualified Class 1 motors (such as these) are given a voltage test in water before mbly in a motor.
rostatic testing was performed on the cooling coil sections in accordance with ASME Code tion VIII requirements. The cooling coil tubes were nondestructively tested in accordance h ASTM Standard E-243-68.
containment air recirculation and cooling system ductwork is leak tested and balanced in ordance with Sheet Metal and Air Conditioning Contractors National Association (SMACNA) ndards.
visions are incorporated into system design for online testing during normal operation. Each up of two containment air recirculation and cooling units is tested separately. In accordance h applicable Technical Specifications and corresponding procedures, during Modes 1, 2, and 3, R unit emergency RBCCW outlet valves and slow CAR fan speeds are tested. The testing of remotely operated RBCCW valves is performed by operating the corresponding manual trol switch. The testing of slow fan speeds is also performed by use of manual control switches he control room. The positions of the valves and fan speeds are verified by status lights in the trol room.
testing of these components during Modes 1, 2, and 3 does not use any manual initiation of S. Such a manual SIAS actuation would result in unnecessary starting of diesel generators and ecessary RBCCW flow transients.
itionally, in accordance with Technical Specifications required surveillance frequencies, ng outages, manual SIAS actuations are used for testing automatic actuation circuitry for rgency operation of CAR units, as well as other integrated safeguard features.
fusible link blowout doors (plates) were tested as part of the initial plant pre-operational test he containment air recirculation and cooling system. The blowout doors were tested for ngaging to open to allow an air flow path from the ductwork as the local ambient temperature eeded 170°F. The blowout doors are mounted with compressed springs between the blowout rs and the ductwork to provide a spring action for an initial disengaging push to open the wout doors, when the fusible links melt.
28/18 6.5-10 Rev. 36
east partial flow. Should one of the four (4) plates on a given unit fail, there would be only a ial loss of flow due to the increased system resistance.
reoperational test of the containment air recirculation and cooling system was performed prior tart up. The test procedure is described in Section 13.
ipment and associated components located in the containment are accessible for inspection maintenance during shutdown.
ieu of test results under 10 CFR 50, Appendix J. Type C testing, the T-Ring seats on the tainment isolation valves, for the RBCCW supply and return lines for the Containment Air irculation and Cooling heat exchangers, will be replaced based on observed degradation.
se valves are not in the Type C testing program because the valves are open during accident ditions. This eliminates a commitment made under letter A06107 dated 1/16/87 under Docket mber 50-336.
28/18 6.5-11 Rev. 36
TABLE 6.5-1 CONTAINMENT AIR RECIRCULATION AND COOLING UNITS MATERIALS OF CONSTRUCTION s (F-14A/B/C/D)
Type Vaneaxial Standard AMCA 211-A Seismic Class 1 tor Type Induction Standard NEMA Seismic Class 1 ling Coils (X-35A/B/C/D)
Type Water (RBCCW)
Standard ASME Section VIII Seismic Class 1 ctwork Type In Accordance With Specification M-506 Standard SMACNA Seismic Class 1 28/18 6.5-12 Rev. 36
PERFORMANCE DATA Post-incident Per Unit Normal (prior to SRAS) at removal capability (Btu/hr) 2.2 x 106 (nominal rating) 80 x 106 (nominal rating) r flow (cfm) 70,000 (nominal rating) 34,800 (nominal rating) tic pressure (inches wg) 2.98 0.53 ake horsepower (bhp) 70.0 18 tic efficiency (%) 56 50.7 M 1760 875 tor horsepower, (hp) 75 37.5 r temperature, inlet/outlet (°F) 120/90.9 289/281.8 ter temperature, inlet/outlet (°F) 85/94 130/210 ter side pressure drop (feet H20) 3 25 ter flow rate (gpm)
- 500 2000 e:
The cooling water flow through the CAR coolers is maintained at approximately 2000 gpm during normal operation to maintain RBCCW pump flow closer to the normal pump design conditions.
28/18 6.5-13 Rev. 36
DETRIMEN COMPONENT METHOD OF TAL RESULTANT IDENTIFICATION FAILURE DETECTION EFFECT ON CORRECTIVE SYSTEM
& QUANTITY MODE & MONITOR SYSTEM ACTION STATUS REMARK Housing CTMT Housing failure Temperature Loss of Unit taken out of One unit out of Sufficient contain cooling unit (4) (Air bypasses sensing device cooling service service, three cooling provided b cooling coils) if available alternate units units in combinati operable one containment s subsystem or by t containment spray subsystems.
Cooling coils Tube header of Temperature Loss of Same as above Two units on Sufficient contain (Eight (8) per unit) manifold sensing device, cooling RBCCW Header cooling by a comb rupture if available taken out of service of two (2) units wi (1) containment sp subsystem.
Fans (4) Fails to operate Status lights Loss of air Same as above One unit out of Same as Item 1 CRI flow service, three alternate units operable Fusible ink plates (4) Fails to open None Partial loss to None Partial to complete Same as Item 1 complete loss loss of one unit, of air flow three alternate units depending operable upon degree of restriction in ductwork system 06/28/18 6.5-14 Rev. 36
06/28/18 6.5-15 Rev. 36 06/28/18 6.5-16 Rev. 36 hydrogen recombiner portion of the Post-Accident Hydrogen Control System is installed, but used for any mitigating function. The hydrogen recombiners, associated controls and alarms e been isolated awaiting abandonment. The following section describes the recombiners as inally installed and operated.
1 DESIGN BASES 1.1 Functional Requirements post-accident hydrogen control system functions to control the concentration of hydrogen ch may be released within the reactor containment atmosphere following postulated accidents.
1.2 Design Criteria following criteria have been used in the design of the containment post-accident hydrogen trol system:
- a. Each system has two redundant, independent subsystems, each capable of performing the functional requirements.
- b. The system has suitable subsystem and component alignments to assure operation of the complete subsystem with its associated components.
- c. Capabilities are provided to assure the system operation with on site power (assuming off site power is not available) or with off site electrical power.
- d. A single failure of an active component in either subsystem will not affect the functional capability of the other subsystem.
- e. The system is designed to permit periodic inspection of important components such as hydrogen recombination units, fans, filters, valves, piping, ductwork and analyzers to assure the integrity and capability of the system.
- f. The post-accident hydrogen control system is designed to permit appropriate periodic pressure and functional testing to assure (1) the structural and leak-tight integrity of its components; (2) the operability and performance of the active components of the system, and (3) the operability of the system as a whole. Under conditions as close to the design as practical, the performance will be demonstrated of the full operational sequence that brings the system into operation, including operation of applicable portions of the protection system and the transfer between normal and emergency power sources.
- g. The post-accident hydrogen control system is designed to the general criteria as described in Section 6.1.
28/18 6.6-1 Rev. 36
Section 6.1.
- i. The post-accident hydrogen control system is designed in accordance with the conditions given in Regulatory Guide 1.7.
2 SYSTEM DESCRIPTION 2.1 System post-accident hydrogen control system is shown schematically in Figure 9.9-2.
post-accident hydrogen control system includes independent, fully redundant subsystems to and monitor the hydrogen concentration in the containment following a loss-of-coolant dent.
uniform mixing of the containment post-accident atmosphere is provided by the post-dent recirculation (PIR) system. This (PIR) system is provided inside the containment to mix hydrogen accumulated in the upper portion of the containment with the rest of the tainment atmosphere.
post-accident recirculation system takes suction from the highest points in the containment discharges air to the minus 3 foot elevation area of containment. Two CAR fans and coolers ove air from the minus 3 foot elevation area, and dilute this mixture with additional tainment air and discharges it into the lower elevations of containment. Each PIR system is gned for one air change per hour from the upper 20 percent of the containment volume.
o full capacity, completely redundant, hydrogen concentration monitoring systems are vided outside the containment for periodic or continuous analysis of hydrogen concentration he containment atmosphere.
h train of the hydrogen monitoring system consists of a sensor module located in the east trical penetration room elevation 14 feet 6 inches, a remote calibration module located in the oad and truck access bay elevation 14 feet 6 inches, and a control room module located in trol room panel C101. Recorders in control room panel C101 provide indication and a manent record of the hydrogen concentration.
main control room and the remote calibration module are accessible at all times. Access to sensor modules under post-accident conditions is not necessary. Control of all system ctions including performing calibrations is available from the remote calibration modules. In ition, the control room module provides system power status indication, system alarms and em start control to the control room personnel. Since the two trains of the hydrogen nitoring system are completely independent, no single failure can prevent operating personnel m initiating hydrogen sampling or reading hydrogen concentration from the control room.
28/18 6.6-2 Rev. 36
volume percent.
h hydrogen monitoring system draws containment gases through a small diameter sample line ch limits the flow rate and reduces the sample transit time. From the analyzer, the sample is rned to the system from which it is drawn.
active means for reducing the hydrogen concentration in the containment following a tulated accident are provided by hydrogen recombination subsystems. The recombiners have mitigating function.
h of the recombiners is capable of 100 SCFM.
hydrogen recombiners are located within the containment and consist of two completely ependent, full capacity thermal type recombiner units.
recombiner unit is located on the operating floor at Elevation 38 feet 6 inches. The second is at Elevation 14 feet 6 inches.
containment hydrogen-air atmosphere is circulated across electric heating elements. The uent is heated to approximately 1100°F at which temperature the recombination reaction takes
- e. Containment air is induced into the recombiner unit by the natural draft created by the perature differential between influent and effluent. Additional driving forces are not required.
ethod for hydrogen reduction in the containment following a LOCA is the hydrogen purge em. The hydrogen purge operation, is not credited in accident analysis. During purging rations, the hydrogen concentration is reduced by providing makeup air from the instrument or station air compressors using containment atmosphere sample return line penetrations into containment, and by remotely opening the containment isolation valves (2-EB-91 & 2-EB-92,
-EB-99 & 2-EB-100) to their respective 6 inch line connecting with the Enclosure Building ration System (EBFS) common plenum.
h purge train includes a passive flow control station, consisting of a manual valve (in the open ition) in the 6-inch line (valve 2-EB-193 Train A or valve 2-EB-194 Train B), and a small inch bypass line equipped with a flow element and a remote flow indicator.
containment purge flow is mixed with the enclosure building filtration system and is passed ugh the EBFS charcoal filters discharging through the Millstone Stack.
hydrogen purge system does not need to be redundant or be designed Seismic Category I, sistent with the recommendations of Regulatory Guide 1.7, Rev. 2, except insofar as portions he system constituting part of the primary containment boundary or containment filters.
instrument air, used for purging, ties into line 1"-HCD-118 upstream of valve 2-AC-20 and rs the containment through penetration 87, (Figure 9.11-1). The station air used for purging 28/18 6.6-3 Rev. 36
es 2-AC-20 and 2-AC-15 for a temporary emergency air supply.
e air compressors are not available after a LOCA, there is adequate time to restore the system ervice. Portable air compressors can be connected to the capped connections provided for rgencies.
ce the purging of containment atmosphere could increase the radiological dose to the public, system is initiated only when hydrogen concentration must be reduced due to a threat to tainment integrity as the result of a beyond design basis accident.
2.2 Components components of the hydrogen purge system are described with the EBFS in Section 6.7.2.2.
major components with associated fabrication and performance data are listed in Table 6.6-1.
Hydrogen Recombiner units supplied by Westinghouse, consist of two 100 percent capacity mbiners, thermal (electric) type, of completely passive design with no moving parts and with rating controls mounted on control boards located in the Main Control Room. Environment s under simulated conditions have been performed by Westinghouse with results verifying the grity and reliability of their units.
hydrogen monitoring system is supplied by Whittaker Safety Systems. Two redundant trains supplied each consisting of a sensor module, a remote calibration module, and a control room dule.
h sensor module contains valves, sensors, heat trace and a sample pump. Connections to the ple stream supply and return, calibration gases and Containment Air Post Accident Sampling tem are provided. The hydrogen sensors use electrochemical gas measurement technology.
sensor modules are located in the east electrical penetration room elevation 14 feet 6 inches.
maximum air temperature in this room will be 140°F and maximum relative humidity will be percent after a LOCA. Access to the sensor modules is not required for system operation or to orm system calibrations.
sensor module will take a sample from the containment atmosphere and return it to tainment after measuring the hydrogen concentration. Provisions to divert the sample stream he Containment Air Post Accident Sampling System prior to returning it to containment are vided. Operation of the Containment Air Post Accident Sampling System with the hydrogen nitoring system discharge will not interrupt the ability to monitor hydrogen concentration.
h remote calibration module contains a microprocessor, controls and relays necessary for ration, self-monitoring, performing calibrations and interfacing with the control room. Control m annunciation is provided for high hydrogen, system trouble and low ambient temperature l to the remote calibration modules. The system range is 0 to 10 percent hydrogen. Calibration he system is performed using calibration gases with 1 percent and 4 percent hydrogen. The 28/18 6.6-4 Rev. 36
h train has a control room module located in control room panel C101 which interfaces with remote calibration module. Each control room module has system 120 VAC and 480 VAC us lights, alarms for loss of power, system trouble and high hydrogen, and a control switch for ating hydrogen monitoring from the control room. Control room display of hydrogen centration is provided on a recorder also located on control room panel C101.
hydrogen monitoring system is QA Category 1. Two redundant trains of equipment meet the gn and separation requirements for Class 1E and are powered from separate Class 1E power rces. Piping, tubing and other equipment is Seismic Class 1. The monitor system must be rable following, but not necessarily during a SSE. Pressure boundaries which are an extension he containment building atmosphere are designed to maintain their integrity during a SSE.
lification tests for the hydrogen monitoring equipment include seismic testing, pressure ing and performance testing.
3 SYSTEM OPERATION 3.1 Emergency Conditions he unlikely event of a LOCA, the post-accident hydrogen control system is manually initiated peration action. All subsystems are initiated and monitored in the control room.
PIR system is initiated within the first few hours following the LOCA. The system takes ion from the dome region where the initial local concentration of hydrogen is anticipated.
s potential hydrogen-air mixture is conveyed through carbon steel piping headers and austed near the inlet of the containment air recirculation and cooling units located on the us three foot level of containment (Section 6.5) where it is diluted with the containment ironment from lower elevations.
operation of the PIR system can be monitored in the control room by indicating lights and or trip alarms.
o redundant, independent hydrogen monitors are provided for sampling during post-accident ration. Continuous sampling is manually initiated from the Control Room. Recorders provide operators with visual indications of the measured hydrogen concentration between zero to ten ume percent. Grab sampling of containment atmosphere can be taken from the post-accident ple system (PASS) containment air remote operator modules C102A & B located at elevation eet 6 inches of the auxiliary building.
ccordance with Regulatory Guide 1.7 Rev. 3, within 90 minutes following the initiation of ty injection, the hydrogen monitors are required to be fully functional.
28/18 6.6-5 Rev. 36
uent temperature. Performance of the recombiners is monitored by measurements of the local centration of hydrogen in the containment by the monitoring system.
rating at rated capacity of 100 scfm of hydrogen-air mixture, each recombiner removes two m of free hydrogen from the containment atmosphere when the hydrogen concentration is at t two percent by volume.
hydrogen purge system is provided as an active means for reducing the local buildup of rogen. This operation is initiated manually.
overall performance of the containment post-accident hydrogen control system is monitored he recorders located in the control room. Each hydrogen monitoring system is set to alarm at volume percent containment hydrogen concentration.
4 AVAILABILITY AND RELIABILITY 4.1 Special Features components of the containment post-accident hydrogen control system are designed to the eral requirements, including seismic response, as described in Section 6.1. All components are ected from missile damage and pipe whip by physical separation of duplicate equipment, as cribed in Section 6.1.
assure availability, all components located within containment are designed to withstand the sure and temperature transients conditions resulting from a LOCA. Each PIR subsystem is vided with carbon steel suction headers to assure system integrity following the LOCA.
twork is not used in the PIR system. The motors associated with the PIR fans are designed to rate in a containment post-accident environment.
PIR fans are located outside the secondary shield wall, below the operating floor, at an ation well above the post-accident water level. In this location the fans are protected against ible missiles and flooding.
PIR fans are completely redundant, are powered from independent emergency sources and physically separated in the containment. A failure mode analysis of the PIR system is given in le 6.6-4.
hydrogen monitoring system includes two independent, fully redundant monitoring systems. Both are physically separated and located outside the containment. Independent rgency power sources are provided for each subsystem.
e normally aligned Instrument Air System is unavailable, a safety related backup bottled air ply subsystem provides the source of air required to open the Containment Isolation Valves uired to establish a flow path for the Hydrogen Monitoring System post-accident. The backup 28/18 6.6-6 Rev. 36
he inside valves and one supply header to the outside valves), however, it is designed to meet gle Failure Criteria.
hydrogen recombiner systems are completely redundant, are supplied from independently rgency power supplies and are physically separated. Each recombiner unit is designed to hstand the temperature and pressure transient following a LOCA and to operate under t-accident conditions. Both units are located well above the flood level in the containment and sically separated for missile protection.
containment has redundant penetrations and pipe headers for the hydrogen purge systems and physically separated for protection from credible missiles. Each hydrogen purge system is vided with independent valving and instrumentation and powered from independent rgency sources. Prior to initiation of the hydrogen purge system, the EBFS electric heaters, 1A/B, are manually taken out of service. The EBFS is described in Section 6.7. Ductwork is zed outside the containment only, under atmospheric pressure conditions.
h hydrogen purge valve is provided with an auxiliary air accumulator to assure an air supply post-accident operation. The cylinder air-operated valves if open, are closed by the umulator air assuming a failure of the normal instrument air system (Section 9.11). Air is ilable in the accumulator for opening the purge valves, if required, for hydrogen control. Each umulator is sized for four open or close operations.
hydrogen purge containment isolation valves inside containment are designed to fail in their position. These valves are normally closed and are therefore, expected to be closed during the CA condition.
rmittent system operation or system isolation can be controlled by the outside containment ation valve. These valves are provided with handwheels for manual operation should rument air be unavailable.
cautions have been taken in the design of the equipment, their support structures and building ctures in the containment to avoid probable pockets or enclosures where hydrogen build-up ld occur locally. Provisions have been incorporated for ventilation holes, sloping concrete r slabs, openings and other means of allowing locally generated hydrogen to flow upward in containment.
major source of hydrogen generation following the accident is the containment sump. Since sump region will be at a higher temperature than the dome region due to the cool containment y water (Section 6.4) entering the containment, a stack effect will be created. Therefore, it is med that the higher energy hydrogen-air mixture from the containment sump region will tend se toward the dome. Vent areas, such as the floor grating outside of the secondary shield wall, und the steam generators and over the reactor coolant pump motors, offer negligible resistance his induced flow. Taking a cross-section of the containment at the operating floor (elevation 38 6 inches), the ratio of the free area created by the grating and other openings to the cross-28/18 6.6-7 Rev. 36
(1) day after the accident. Although this flow rate decreases with containment post-incident perature and pressure, the mechanism of transport is established.
hough the hydrogen concentration will tend to equalize itself, the PIR system accelerates this cess by maintaining a slight negative pressure in the containment dome region, thereby plementing the natural buoyancy forces, and by mixing the dome hydrogen-air mixture ugh the containment air recirculation and cooling units with lower level mixtures, thereby ring a uniform mixture throughout the containment.
h hydrogen recombiner unit is capable of 100 scfm to assure the reduction of hydrogen centration and to shorten the duration of operation. The backup hydrogen purge system cesses the containment effluent through the EBFS charcoal filters prior to discharge through 375 foot Millstone stack.
ficient emergency electrical power is available to operate the post-accident hydrogen control ponents.
4.2 Tests and Inspection post-accident recirculation fans and motors are similar to those which are tested for starting operating within the containment post-accident environment. Engineering data are provided ubstantiate the extrapolation of environmental tests which are conducted at Joy Manufacturing mpany on nuclear containment motors (Section 6.5.4.2) which are similar to the motors vided for the PIR fans. Components, materials, standards, method of manufacture and design eria of the PIR fan motors are of identical origin and application to those motors tested by Joy.
only variation is in the motor size with relative horsepower and RPM. The tests performed by are in accordance with the Draft IEEE Standard 334-1971. Identical QA records and reports maintained on both the motors.
motors used in the postincident recirculation units are made by Reliance Electric Company.
totype motors have been successfully tested in a steam-air environment, hence the ufacturer does not consider a production test as described above to be necessary.
totype testing included a four hour run followed by four two-hour runs in a 300°F ambient.
ord bearing temperatures were of the order of 300°F, and winding temperatures were of the er of 360-400°F. Each of the above cycles were separated by two, two hour runs in an ambient 00-220°F.
ce this is a totally enclosed motor, no boric acid crystals can enter the internal air passages. All rnal air is directed along the ribbed motor enclosure.
qualification test can insure that a motor has a service life greater than that demonstrated by ice experience to date. It demonstrates that the equipment, in an aged condition, is capable of rating in a post design basis event environment for a period at least as long as the test cycles.
28/18 6.6-8 Rev. 36
PIR system is incorporated with provisions for on-line testing. Each subsystem is tested vidually. The PIR fan is manually initiated from the control room and is monitored for ration by motor trip alarms.
system tests are conducted during shutdown.
PIR system is located within containment. The PIR fans are located near the operating floor ermit access for inspection and maintenance during shutdown.
hydrogen monitoring system design has provisions for performing calibrations without essing the sensor module in the east electrical penetration room elevation 14 feet 6 inches. The bration process is initiated and controlled from the remote calibration module in the railroad truck access bay elevation 14 feet 6 inches. The calibration process utilizes calibration gases percent hydrogen in nitrogen and 4 percent hydrogen in nitrogen. The gas cylinders with the bration gases are located in the railroad and truck access bay near the remote calibration dules.
hydrogen purge system is incorporated with provisions for on-line testing. The hydrogen ge valves are tested with the EBFS as described in Section 6.7.4.2. Purge valves 2-EB-91, 92, and 100 opening is monitored by position indication in the control room.
h purge valve is tested periodically to assure the operability of the accumulator tank. The mal air supply is isolated and operation is provided by the accumulator.
ge valve elastomers and shaft packing are adjusted and/or replaced based on 10 CFR 50, endix J, Type C test results.
te:
ORNZ-4749, VC4-Chemistry, Analytical Chem. Div. Annual Progress Report, September 30, 1971 28/18 6.6-9 Rev. 36
COMPONENT DESCRIPTION Fan (F-18A/B)
Type Vaneaxial Flow (CFM) 7,000 (nominal rating)
Standard AMCA 211-A Seismic Class 1 Fan Motor Type Squirrel Cage Induction Horsepower rating, (hp) 25 Code NEMA mic Class 1 drogen Monitoring System Manufacturer Whitaker Safety Systems Model Containment Atmosphere Monitoring System Accuracy +/- 0.2% Hydrogen Ambient Temperature 40 to 140°F (Analyzer and Remote Cabinets)
Sample Temperature 300°F Sample Pressure -5 to 65 psig drogen Recombiner Manufacturer Westinghouse Quantity 2 Type Thermal (electric)
Capacity 100 SCFRM Power Input 75 kW Housing Material Stainless Steel 300 series Inner Structure Inconel 600 Heater Element Sheath Incoloy 800 Maximum Sheath Temperature 1550°F Temperature at Heater Outlet 1150°F to 1400°F Exhaust Temperature 100°F above ambient 28/18 6.6-10 Rev. 36
28/18 6.6-11 Rev. 36 28/18 6.6-12 Rev. 36 COMPONENT METHOD OF DETRIMENTAL RESULTANT IDENTIFICATION FAILURE DETECTION & EFFECT ON CORRECTIVE SYSTEM
& QUANTITY MODE MONITOR SYSTEM ACTION STATUS REMAR PIR Fan (2) Fails to start Status light Loss of one None One subsystem Redundant subsystem taken out of PIR service Subsystem available.
Pipe header Rupture None Partial loss of None One subsystem Same as suction from does not perform above.
containment dome the intended region function 06/28/18 6.6-13 Rev. 36
CHARACTERISTICS 28/18 6.6-14 Rev. 36
1 DESIGN BASES 1.1 Functional Requirements functions of the enclosure building filtration system (EBFS) are to collect and process ential containment leakage, to minimize environmental activity levels resulting from sources ontainment leakage following a loss-of-coolant accident (LOCA). The enclosure building ation region (EBFR) contains potential containment leakage. Throughline leakage that can ass the EBFR is discussed in Section 5.3.4. The EBFS is also designed to reduce the centration of combustible gas built up in the containment following a LOCA in conjunction h the Hydrogen Purge System (Section 6.6). Although not credited in the fuel handling dent and cask drop analyses, EBFS is capable of being automatically or manually aligned to imize the consequences of those accidents.
1.2 Design Criteria following criteria have been used in the design of the EBFS:
- a. The system has two redundant, independent subsystems, each fully capable of the functional requirement.
- b. The system has suitable subsystem and component alignments to assure operation of the complete subsystem and with its associated components.
- c. Capabilities are provided to assure the system operation with either on-site power (assuming off site power is not available) or with off site electrical power.
- d. A single failure of an active component in either subsystem will not affect the functional capability of the other subsystem.
- e. The EBFS is designed to permit periodic inspection of important components such as fans, motors, filters, filter frames, ductwork, dampers, piping and valves to assure the integrity and capability of the system.
- f. The EBFS is designed to permit appropriate periodic pressure and functional testing to assure (1) the structural and leak tight integrity of its components, (2) the operability and performance of the active components of the system, and (3) the operability of the system as a whole. Under conditions as close to the design as practical, the performance is demonstrated of the full operational sequence that brings the system into operation, including operation of applicable portions of the protection system and the transfer between normal and emergency power sources.
- g. The EBFS is designed to the general requirements as described in Section 6.1.
28/18 6.7-1 Rev. 36
heaters, X-6/A/B.
- i. The EBFS is designed to support the Hydrogen Purge System (Section 6.6) in accordance with the conditions given in Safety Guide 7. However, consistent with Regulatory Guide 1.7, Rev. 2, a backup hydrogen purge system is not required to satisfy the safety-related function to control post-accident containment hydrogen.
Therefore, the backup hydrogen purge system is no longer credited for hydrogen control.
2 SYSTEM DESCRIPTION 2.1 System EBFS is shown schematically in Figures 9.9-1 and 9.9-2. The EBFR includes the region ween the containment and the enclosure building, the penetrations rooms and the engineered ty feature equipment rooms.
EBFS is designed to establish and maintain a negative pressure of 0.25 inches w.g. within the FR immediately following a LOCA and to reduce airborne radioactive products to the ironment by filtration prior to release of air through the Millstone Stack. Neglecting wind and k effects, each EBFS train has the capability to maintain the EBFR under the minimum ative pressure of 0.25 inches w.g. The required minimum negative pressure can be achieved g both trains or either train of the redundant filtration systems.
EBFS is located external to the containment in an enclosed area adjacent to the enclosure ding. The EBFS exhausts air from all areas of the EBFR. Makeup air is induced into the FR by infiltration through building cracks, doors, and penetrations between the EBFR and ide or surrounding structures, as well as from potential containment leakage. The entire em is designed to operate under negative pressure up to the fan discharge. In all cases, the rate from this region exceeds the total maximum containment leakage rate.
in-leakage into the EBFR was originally estimated using analytical and experimental leakage (Reference 6.7-1). This leakage rate included a conservative containment leakage rate of 0.03 tainment volumes per day. The design in-leakage rate was established at a factor of 3.0 greater the estimated in-leakage rate. The leak tightness of the containment is independent of the ration of the EBFS and is established through Integrated Leak Rate Testing (ILRT) ction 5.2.8.1).
original Bechtel building specification for the enclosure building (Reference 6.7-2), required all metal siding and metal roof decking be designed to withstand the pressure created by a d load of 140 mph (Section 5.3) at the girt spacing shown on the design drawings, and with a imum deflection of L/180 of span under load. In addition to the wind pressure, the metal ng and roof decking shall also withstand a differential pressure equivalent to 2 inches water ge and maintain air tightness for the completed installation. On May 25, 1972, a test 28/18 6.7-2 Rev. 36
.75 inches w.g. was used and the leak-tightness capability was established at this pressure.
calculated maximum negative pressure (Reference 6.7-1) demonstrates that during two llel fans operation, the EBFR negative pressure is less than the tested limit of 9.75 inches w.g.
EBFS consists of independent, full redundant fans, filter banks, heating elements, isolation pers, and ductwork with the exception of common plenums. Charcoal filters installed are onstrated by tests to have a bypass leakage efficiency above 99 percent, and by a laboratory to have an iodine removal efficiency above or equal to 95 percent in accordance with hnical Specification requirements.
prefilters are provided to remove coarse airborne particles to prolong high efficiency iculate air (HEPA) filter life. The HEPA filters are provided to remove fine airborne particles penetrate the prefilters. The activated coconut shell charcoal filters are impregnated to ove methyl iodine as well as elemental iodine contaminates resulting from a LOCA or a spent handling accident in the spent fuel pool.
ctric heaters (X-61A/B), rated at 25 kW each, are provided to maintain the entering air stream tive humidity (RH) to the charcoal filters below 90 percent. They are also required to be rated per Technical Specification surveillance requirements. These heaters may not be ilable throughout a LOCA due to high radiation. However, analyses considering the maximum sible relative humidity within the Enclosure Building Filtration Region during a LOCA, or a A, or within the Fuel Handling area during a Fuel Handling Accident, determined that the ring EBFS air stream remains below 90 percent RH without the heaters. The electric heaters energized when the fan is on and deactivated manually prior to initiation of Hydrogen purge.
EBFS fans are belt driven centrifugal fans capable of operating singly or in parallel with the undant system. EBFS fan operating parameters are shown in Table 6.7-1. A failure mode lysis for the EBFS is given in Table 6.7-2.
twork for that portion of the EBFS located outside the enclosure building is round and/or angular. Longitudinal seams are continuously welded air tight.
EBFS may be used for containment cleanup during cold shutdown and refueling (Modes 5 6). The EBFS can be operated in combination with the containment purge system ction 9.9.2) for containment cleanup of minor releases of radioactivity. These interconnections ween the two systems are shown in Figures 9.9-1 and 9.9-2. This process may be initiated to uce activity levels prior to purging the containment.
en using the EBFS to purge containment, either train or both trains may be used to perform activity. The incoming flow path is provided by opening the following dampers: 2-AC-1, 3, 4, and the exhaust flow path is provided by opening 2-AC-6 and 2-AC-7. Since the purge supply F-23, is not activated, the purge rate is a function of the EBFS train(s) capacity.
28/18 6.7-3 Rev. 36
EBFS discharges to the Millstone stack. Containment cleanup is initiated manually by rator action. The connections to the EBFS are automatically closed by an EBFAS to assure em integrity for post-accident operations.
2.2 Components major components with their associated fabrication and performance data are listed in le 6.7-1.
3 SYSTEM OPERATION 3.1 Emergency Conditions he unlikely event of a LOCA, the EBFS is automatically initiated by the EBFAS as described ection 7.3. Air is exhausted from the EBFR, processed through the filter banks and discharged ugh underground piping to the Millstone 375 foot stack. Redundant on site emergency power rovided by the diesel generators as described in Section 8.3.
tem performance is monitored in the control room. Differential pressure across the filter units cates filter dust loading and replacement requirements. Low flow conditions are alarmed in control room and local flow indication is provided upstream of each filter unit. A temperature sor is located within each enclosure filter unit in the vicinity of the charcoal elements to alarm essive temperature.
pneumatically operated dampers are normally closed to isolate the filter unit. These dampers n automatically upon the EBFAS and are designed to fail in the open position. The positions of ower operated dampers are indicated in the control room.
EBFS is designed to reduce the concentration of combustible gas buildup in the containment owing a LOCA by controlled purging operations. This operation is described in Section 6.6.3.
r to initiation of the hydrogen purge system, the electric heaters in the EBFS filter units are ually taken out of service by tripping electric heater supply breaker. The backup purge ration is described in Section 6.6.2.1.
4 AVAILABILITY AND RELIABILITY 4.1 Special Features enclosure building structure is designed to retain structural integrity subsequent to a seismic nt. However, the EBFS is not designed to be functional subsequent to a safe shutdown hquake (SSE). All components are protected from missile damage and pipe whip by 28/18 6.7-4 Rev. 36
reliability of the EBFS is assured by providing two independent, with the exception of mon ductwork plenums, full capacity subsystems. Each subsystem is capable of maintaining design negative pressure within the EBFR and of discharging into the 375 foot stack.
erential pressure is measured from various locations within the EBFR including four locations hin the enclosure building proper. The acceptance criteria is that each EBFS train individually blish a minimum negative pressure of greater than or equal to 0.25 inches w.g. in the EBFR hin one minute after an enclosure building filtration actuation signal (EBFAS). Neglecting d and stack effects, each EBFS train has the capability to maintain the EBFR under the imum negative pressure of 0.25 inches w.g. The acceptance criteria of 0.25 inches w.g. assures the EBFR will be maintained at a negative or neutral pressure precluding exfiltration under t meteorological conditions. With one EBFS train exhausting the EBFR, the combined effects ertain wind and stack pressures may cause positive pressures in the upper regions of the losure building. The potential exfiltration and radiological consequences due to positive sure in the upper regions of the enclosure building, were analyzed and determined to be fully nded by the radiological consequences of the low wind speed LOCA case presented in tion 14.8.4.
EBFR is constructed to limit leakage as described in Section 5.3. Piping, cable tray and twork penetrations through the EBFR boundary are sealed with foam or insulation to decrease age. All doors into the EBFR are designed to minimize leakage. Containment penetrations the EBFR are described in Section 5.2.6 and Section 5.3. The metal siding is constructed to t leakage as described in Section 6.7.2.1.
EBFS fans F25A/B are fully redundant and are powered from separate emergency sources.
EBFS fans are connected on the suction side by cross-tie ductwork which is provided with a llel arrangement of electric motor-operated dampers which are likewise powered from arate emergency sources. These dampers are normally closed but can be opened by operator on following a fan failure. The design of the EBFS is such that it renders a loss of cooling air he filters due to fan failure as incredible. The EBFS requires no additional decay heat removal em. Cooling air is always available, but not necessary (Section 6.7.4.1.1), to prevent iodine orption and, therefore, ignition of the charcoal elements.
h subsystem has a nominal design flow of 9,000 CFM. The fan performance curve is shown in ure 6.7-1.
ailure mode analysis for the EBFS is given in Table 6.7-2. Although there are common ums, all ductwork is considered a passive component whose failure is not credible.
4.1.1 Minimum Air Flow Required to Prevent Desorption of Radionuclides charcoal filter elements within the EBFS are analyzed to ensure adequate iodine removal acity, and residual heat removal capabilities following any single failure. The analysis med iodine loading is limited to one EBFS unit, and concluded:
28/18 6.7-5 Rev. 36
1.52 design loading.
No minimum flow is necessary to maintain the charcoal temperature below 200°F.
wever, a temperature sensor is mounted within each filter unit, in the vicinity of the charcoal
- s. This sensor provides alarm capability in the control room at 200°F or less.
4.1.2 Single Failure Evaluation containment and enclosure building purge system functions to maintain a suitable ironment in the containment building (during Modes 5 and 6) or the enclosure building during mode of operation (see Section 9.9.2).
noted in Table 9.9-2 of the FSAR, the containment and enclosure building purge system is a safety-related system. Purge system isolation dampers 2-AC-1 and 2-AC-11, including trol circuits, are safety related since they receive a containment isolation actuation signal AS) to close to isolate the enclosure building in the event of a LOCA. For the same reason, the trols for purge fan F23 are also safety related.
ultaneous occurrence of a LOCA and a seismic event is not a design basis for Millstone Unit lthough the enclosure building structure is designed to retain structural integrity subsequent to ismic event, the EBFS is not designed to be functional subsequent to an SSE. Maintaining a ative pressure in the enclosure building after an SSE is not assured mainly because the sheet al siding may not remain intact. The original design for the purge supply and exhaust twork is nonsafety related and nonseismic.
R Question 6.15.4 addressed single failure (failure to close on CIAS) for dampers 2-AC-1 ge supply) and 2-AC-11 (purge exhaust). The response to Question 6.15.4 documented the s for concluding that with an assumed single failure of 2-AC-1 to close, the minimum ative pressure of 0.25 inches w.g. can be maintained within the EBFR. The response noted that evaluation was conservative for a postulated single failure of the exhaust damper 2-AC-11.
ce the installation of damper 2-AC-130 eliminates the 2-AC-1 damper single failure, there is rance that the EBFS can maintain an adequate negative pressure within the EBFR as cribed in Section 6.7.2.
containment and enclosure building purge inlet was modified with the installation of a nterbalanced gravity damper (2-AC-130) to provide redundancy for isolation damper 2-AC-1.
s design change was a system upgrade to mitigate a postulated single failure of the Facility 1 S signal to 2-AC-1.
Main Exhaust System (MES) fans will trip on a CIAS actuation signal as described in tion 9.9.9.4.1, to mitigate the consequences of the 2-AC-11 single failure vulnerability. If the tulated single failure of 2-AC-11 occurred the MES fans will automatically trip. The enclosure 28/18 6.7-6 Rev. 36
R Question 6.17 addressed single failure (failure to open on CIAS) of enclosure building ge isolation dampers 2-AC-3 and 2-AC-8. The response stated that the assumed single failure ither damper was acceptable.
design basis review of enclosure building isolation dampers 2-AC-1 and 2-AC-11 is umented in Millstone Unit 2 Nuclear Engineering Design and Program Services Department rds.
4.2 Tests and Inspections vidual components of the EBFS are tested to assure performance.
ilters are of the throwaway type to be replaced as necessary.
HEPA filters characteristics are in accordance with MIL-STD-282 standard.
h HEPA filter bank is tested, in place, periodically. The testing media will be Dioctyl-halate (DOP).
rcoal filters are initially shop performance-tested and methyl iodide tracers for efficiency and on for leakage. After installation the charcoal filter banks were tested in place with Freon to ure that there is no leakage across the filter bank and that the charcoal elements are not aged. Each charcoal filter housing is provided with test canisters which contain a sample cimen of the charcoal used in the filter elements. These test canisters are analyzed periodically an independent laboratory to determine remaining charcoal filter life and replacement uirements.
h fan and motor is tested as a unit to assure characteristic performance curves. Fan ratings are ccordance with AMCA Standard Test Code 211-A.
EBFS ductwork is leak tested and balanced in accordance with SMACNA Standards.
visions are incorporated to test the entire system for performance during normal operation.
h EBFS fan is tested simultaneously with the associated power operated valves and rumentation, but independently from the redundant subsystem.
EBFAS is initiated to start the fan and open the filter unit isolation dampers. The fan is tested ome point on the fan performance curve other than shutoff. Fan flow is verified by measuring pressure differential across the filter elements. Opening of the power-operated dampers is nitored by the damper position indication in the control room. Since the containment purge ts are vented back into the enclosure building by fail open dampers, additional testing is not essary.
28/18 6.7-7 Rev. 36
FR.
EBFS undergoes a preoperational test prior to startup. The test procedure is described in tion 13.
system equipment is fully accessible during all normal operation for maintenance and ormance testing, including replacement of filter elements. The equipment is accessible for ection and maintenance on components outside of the air stream during accident conditions.
5 REFERENCES 1 Conventional Buildings for Reactor Containment, NAA-SR-10100, dated May 1965, issued by Atomics International, a Division of North American Aviation Incorporated.
2 Bechtel Specification Number 7604-A-16A, Section 12.0, Design Criteria.
3 Pittsburgh Testing Laboratory witnessed an Air Infiltration Test, on Siding and Roof Deck Mock-up, of the enclosure building, for Elwin G. Smith Division, Cyclops Corporation.
28/18 6.7-8 Rev. 36
DESCRIPTION ns F-25A & F-25B Type Belt driven Capacity (nominal each) 9,000 cfm Standard AMCA-211-A Seismic Class 1 tors Horsepower rating, hp 25 Code Nema, MG-1 Seismic Class 1 ctric Heaters X-61A & X-61B Power rating, kW 25 Code UL approved Seismic Class 1 rticulate Filters (Non-QA)
Quantity per unit 9 Type (prefilter) Throwaway PA Filters Quantity per unit 9 Type High capacity Rated air flow per filter at 1.30 inches wg 1,500 cfm at 0.87 inches wg 1,000 cfm Standard MIL-STD-282 28/18 6.7-9 Rev. 36
arcoal Filters Quantity per unit (Trays) 27 Charcoal type CNN-816 Activated coconut shell Rated nominal air flow per unit 9,000 cfm Standard ANSI N-509 ctwork Material/Type IAW Specification M-506 Standard SMACNA Seismic Class 1 ing, valves and fittings A. Suction Pipe sizes Wall thickness 2.5 to 10 inches SCH40 12 to 48 inches 0.375 inches wall Material Seamless ASTM A-53B (containment)
Seamless ASTM A-333 (penetration)
Design pressure (psi) 60 Design temperature (°F) 289 Code ANSI B-31.1.0 (containment)
ANSI B-31.7 Class II (penetration)
Seismic Class I Construction Piping 2.5 inches and larger: butt-welded except at flanged equipment Valves 2.5 inches and larger: butt-welded (except Butterfly Valves) 150 lb ANSI rating carbon steel B. Discharge Pipe sizes Wall thickness 28/18 6.7-10 Rev. 36
2 inches and smaller Schedule 80 2.5 inches to 10 inches Schedule 40 12 inches and larger 0.274 wall Material Seamless ASTM A-53A or B Design Pressure (psi) 50 Design Temperature (°F) 120 Standard ANSI B-31.1.0 Seismic Class I Construction Piping 2.5 inches and larger: butt-welded except at flanged equipment 2 inches and smaller: 300 lb M.I. Screwed Valves 2 inches and smaller: 125 lb WSP, screwed bronze ctwork Seismic Class 1 28/18 6.7-11 Rev. 36
Component Method of Detrimental Identification & Failure Detection & Effect On Corrective Resultant System Quantity Mode Monitor System Action Status Remarks EBFS/AES Filtration Fails to Status lights on Loss of one Monitor Redundant system Both trains are automati Fan operate C01 Low flow subsystem charcoal operable started upon EBFAS/AE F-25A/25B alarm on RC 22 heatup and signal. Each unit has 10 utilize capacity. Utilize cross c opposite train line for charcoal temper control if needed.
Electric Heater Fails to None None None See remarks ** Both trains are automati X-61A/61B operate See remarks* See remarks** started upon EBFAS/AE signal. Each unit has 10 capacity.
- There is a local statu the unit, which may be o to personnel during LOC Spent Fuel Pool Acciden
- Analyses determine entering air stream rema below 90% R.H. withou 06/28/18 6.7-12 Rev. 36
Component Method of Detrimental Identification & Failure Detection & Effect On Corrective Resultant System Quantity Mode Monitor System Action Status Remarks Filter Unit L-29A/ N/A Charcoal beds Possible Opposite train Redundant system The filter unit itself and 29B See remarks temperature charcoal bed available. operable components, HEPA filte computer alarm heating Utilize cross- charcoal filters are passi points: AD8772 country line to components. However, i
& AD8776 maintain flow over the charcoal b charcoal off (i.e., fan fails), charc temperature if could heat up due to dec required iodine.
EBFS Plenum FD N/A N/A N/A N/A N/A Fire damper is deemed a 2-HV-37A/37B See remarks component.
EBFS Isolation Fails as is Status lights on None None Redundant system Open on EBFAS. Close Damper to Filter See remark C01 operable AEAS if EBFSAS not p Unit 2-EB-40/50 EBFS/AES Common FO Fails Status lights on None None Redundant system Open on EBFAS or on A Isolation Damper to open C01 operable Filter Unit 2-EB-41/ See remarks 51 Filter Fan F-25A/ FO Fails Status lights on None None Redundant system Open on EBFAS or on A 25B Isolation open C01 operable Discharge Damper 2- See remarks EB-42/52 06/28/18 6.7-13 Rev. 36
Component Method of Detrimental Identification & Failure Detection & Effect On Corrective Resultant System Quantity Mode Monitor System Action Status Remarks Filter Fan F-25A/ Fails as is None None None Redundant system This damper function is 25B Discharge See remarks operable prevent gross recirculati Damper (Backdraft/ idle train if damper 2-EB weighted) 2-EB-43/ fails open.
54 AES Isolation Fails closed Status lights on None None Redundant system Open on AEAS if EBFA Damper to Filter NC C01 operable present.
Unit 2-EB-60/61 Normally closed See remarks Charcoal Beds Fails as is Status lights on None None Redundant If the air flow over the c Bypass Cooling Line NC C01 Cooling Path beds is cut off (i.e. fan f Damper Normally Available charcoal beds could heat 2-EB-76/77 Closed to decaying iodine.
See remarks Purge Plenum Fire N/A N/A N/A N/A N/A Fire damper is deemed a Damper 2-EB-131 See remarks component.
Hydrogen 6 inch N/A None See remarks See remarks See remarks Hydrogen Purge mode i Purge Line from See remarks manually controlled. Th Containment valves are normally ope Penetration number valves are passive comp 82 to EBFS Plenum Valve 2-EB-193 06/28/18 6.7-14 Rev. 36
Component Method of Detrimental Identification & Failure Detection & Effect On Corrective Resultant System Quantity Mode Monitor System Action Status Remarks Hydrogen 6 inch Purge Line from Containment Penetration number 83 to EBFS Plenum Valve 2-EB-194 All EBFS/AES vital N/A N/A N/A N/A N/A Ductwork is deemed a p ductwork See remarks component.
06/28/18 6.7-15 Rev. 36
PERFORMANCE CURVE 28/18 6.7-16 Rev. 36