ML20052G945
| ML20052G945 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/28/1982 |
| From: | Herrick R, Hofkin T FRANKLIN INSTITUTE |
| To: | Brown S NRC |
| Shared Package | |
| ML20052G915 | List: |
| References | |
| CON-NRC-03-79-118, CON-NRC-3-79-118, TASK-09-05, TASK-9-5, TASK-RR TER-C5257-412, TER-C5257-412-DRFT, NUDOCS 8205190176 | |
| Download: ML20052G945 (29) | |
Text
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TECHNICAL EVALUATION REPORT REVIEW OF THE DESIGN AND OPERATION OF VENTILATION SYSTEMS FOR SEP PLANTS NORTHEAST NUCLEAR ENERGY COMPANY (SEP, IX-5)
MILLSTONE NUCLEAR POWER PLANT UNIT 1 NRC DOCKET NO. 50-245 FRC PROJECT C5257 NRC TAC NO. 47069 FRC ASSIGNMENT 15 NRC CONTRACT NO. NRC479-118 FRC TASK 412 Preparedby Franklin Research Center Author:
R. C. Herrick, T. Hofkin 20th and Race Street Philadelphia, PA 19103 FRC Group Leader:
R. C. Herrick Prepared for Nuclear Regulatory Commission Washington, D.C. 20555 Lead NRC Engineer:
S. Brown April 28, 1982 This report was prepared as an account of work sponsored by an agency of the United States Govemment. Neither the United States Govemment nor any agency thereof, or any of their employees, makes any warranty, ex-pressed or implied, or assumes any legal liability or resocnsibility for any third party's use, or the results of such use, of any information, apparatus, product or process disclosed in this report. or represents that its use by such third party would not infringe privately cwned rights.
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TER-C5257-412 CONTENTS Section Title Page 1
INTRODUCTION.
1 2
REVIEW CRITERIA.
2 3
REIATED SAFETY TOPICS 4
4 TECHNICAL EVALUATION.
5 4.1 Control Room Area Ventilation System 5
4.2 Reactor Building Ventilation System.
5 4.3 Spent Fuel Area Ventilation System.
9 4.4 Turbine Building Ventilation System 9
4.5 Radwaste Area Ventilation System 12 4.5.1 Radwaste Building Ventilation System.
13 4.5.2 Radwaste Storage Building Ventilation System.
15 4.6 Engineered Safety Features Ventilation Systems.
16 4.6.1 Engineered Safeguards Systems Ventilation and Cooling.
16 4.6.2 Ventilation for Station Water Systems 18 4.6.3 Diesel Generator Room Ventilation System.
19 4.6.4 Gas Turbine Building Ventilation System.
20 4.6.5 Auxiliary Electrical Equipment Rooms Ventilation.
20 4.6.6 Battery Rooma Ventilation System.
21 5
CDNCLUSIONS.
23 5.1 Availability of Onsite Generated anergency Power 23 5.2 Reactor Building Ventilation Systems 23 5.3 Turbine Building Ventilation Systems 23 5.4 Radwaste Building Ventilation System 24 5.5 Engineered Safety Features Ventilation Systems.
24 6
REFERENCES 26 nklin Research Center A Ohnmen of N Frenseiinsumme
TER-CS257-412 FOREWORD This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Consaiscion (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NRC operating reactor licensing actions. The technical evaluation was conducted in accordance with criteria established by the NRC.
Mr. T. Hofkin contributed to the technical preparation of this report through a subcontract with WESTEC Services, Inc.
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o TER-C5257-412 1.
INTRODUCTION This review of the design and operation of ventilation systems at Millstone Nuclear Power Plant Unit 1 is part of Topic IX-5 of the Systematic Evaluation Program (SEP) and consists of the technical review and assessment of safety systems in light of changes in design conditions and criteria. The purpose of this review is to ascertain whether ventilation systems at the Millstone Unit 1 plant can provide a safe environment for plant personnel under all modes of operation and whether all safety-related equipment can function properly to ensure safe shutdown of the reactor under normal and emergency conditions.
The SEP was established to evaluate the safety of 11 of the older nuclear plants. An important part of the SEP is the evaluation of each plant according to current licensing criteria with regard to 137 selected topics. A wide range of information sources is used, including final safety analysis reports, more recent drawings and system descriptions, and licensee submittals.
Information for this review included the above sources, and elements of related FEP topics already reviewed for the Millstone Unit 1 plant.
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TER-C5257-412 2.
REVIEW CRITETLA In accordance with Nuclear Regulatory Commission (NRC) guidance for this evaluation, a ventilation system or portion thereof is considered essential to safety if it services systems or parts of systems that are necessary to ensure:
o the integrity of the reactor coolant pressure boundary o the capability to shut down the reactor and maintain it in a safe condition the capability to prevent or mitigate the consequences of accidents o
that could result in potential offsite exposures comparable to the guidelines of 10CFR100, "Reautor Site Criteria."
j The criteria and guidelines used to determine if the ventilation systems meet the topic safety objectives are provided in the following sections of the Standard Review Plan:
Section Subiect 9.4.1 Control Room Area Ventilation System 9.4.2 Spent Fuel Pool Area Ventilation System 9.4.3 Auxiliary and Radwaste Area Ventilation System 9.4.4 Turbine Area Ventilation System 9.4.5 Engineered Safety Feature Ventilation System In addition, applicable portions of related safety topic reviews were used where possible.
In accordance with NRC guidance, the following criteria (expressed in the f
form of questions to be determined) also were used to evaluate those heating, ventilation, and air conditioning (EVAC) systems or portions thereof that are relied upon to ensure the operation of safety-related equipment:
1.
Whether a single active failure cannot result in loss of the system functional performance capability. nklin Research Center
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TER-C5257-412 2.
Whether the failure of a non-safety-related portion of a system will affect the performance of the essential portion of the system or will result in an unacceptable release, as was defined during licensing review, of radioactive contaminants.
- 3.. Whether the capability exists to detect the need for isolation and to isolate safety-related portions of the system in the event of failures or malfunctions, and the capability of the isolated cystem to function under such conditions.
4.
Whether the ventilation systems (except for the control room) have the capability to direct ventilation air from areas of low radio-activity to areas of progressively higher radioactivity.
5.
Whether both control room and engineered safety feature area ventilation systems have the capability to maintain temperature within the design parameters range for safety-related equipment.
6.
Whether the engineered safety feature area ventilation system has the capability to circulate air to prevent accumulation of flammable or explosive fuel vapor mixtures from stored fuel. klin Research Center A Denemen af The Fransen bumene
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REIATED SAFETY TOPICS
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I The scope of review for this topic was limited to avoid duplication of effort, since come aspects of the review are covered under related topics.
These relat.ed topics are identified below. Each related topic report contains acceptance criteria and review guidance for 'its subject matter.
SEP Topic Subiect II-2.A Severe Weather [henomena II-3.B Flooding Potential and Protection Requirements' II-4 Geology and' Seismology III-l Classification of Structures, Components and Systems (Seismic and Quality)
III-2 Wind and Torne.do Ioadings III-3 Hydrodynamic Loads III-4 Missile Gene. ratio'ta' anf Penetration III-5.A Pipe Breaks Inside Containment III-5.B Pipe Breaks Outside Containment *.
III-6 Sei::mic Design Considerations VI-4 Containment Isolation' System VI -7.C.1 Independehce of Cbite Power VII-3 Systems Required for Safe Shutdown 1
IX-3 Station $ervice and Cooling Water IX-6 Fire Protection
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XV-20 Radiological Consequence gf Fuel Damaging ~$ cidents (Inside and Outsid,e Containment)
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TECHNICAL EVALUATION 4.1 CONTROL ROOM AREA VENTILATION SYSTEM The primary function of the control room ventilation system (CRVS) is to l
provide a controlled environment for the safety and comfort of control room personnel and to ensure the operability of control room components during normal operating, anticipated operational trancient, and design basis accident conditions. However, since the CRVS is being reviewed generically under TMI Item III.D.3.4, " Control Room Habitability," to ensure compliance with 10CFR50, Appendix A,
" General Design Criteria for Nuclear Power Plants,"
Criterion 19, " Control Room," it is not evaluated in this report.
l 4 '. 2 REACTOR BUILDING VENTILATION SYSTEM The reactor building ventilation system services all areas of the reactor building, providing ventilation and cooling for such safety-related equipment located in the reactor building as the care spray system, low pressure coolant injection system, and reactor building closed cooling water system, including their pumps, motors, and controla. The ventilation of safety-related equipment is evaluated in later sections of this report. This section considers the overall reactor building system.
The Licensee has described the basic ventilation system as follows (4, p.S]:
"The reactor building is provided with both supply and exhaust ventilation I
to ensure proper air flow direction and remove the heat generated by the equipment. The supply system furnishes approximately 54000 cfm of fresh air to each level in the building.
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The supply system includes two full capacity fans, filters, and steam heating coils to temper the outside air in the winter. Steam unit heaters are f arnished on the operating level to maintain desired temperatures. Supplementary cooling units utilizing water from the secondary closed cooling water system are furnished in areas where high I
heat loads are generated.
Each unit recirculates the air and passes it over a cooling coil to provide cooling for the area served."
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l TER-C5257-412 specifically, the reactor building ventilation system is designed to supply 54,400 cfm of filtered, heated, outside air, to distribute it through all working areas and equipment rooms while maintaining a negative pressure in the building, and, in normal operation, to exhaust this same flow rate of air to the plant stack via the common exhaust plenum for the turbine and reactor buildings.
No provision is made to filter the exhaust air.
Instead, whan radioactivity is detected in the exhaust from the reactor building, the reactor building ventilation system is isolated by redundant pairs of butterfly valves from both the supply and exhaust fan systems, and all exhaust is then directed to the standby gas treatment system.
Note that the 54,400 cfm of air supplied to the reactor building is the total delivered by the reactor building supply air handler, HVS-4, which is equipped with two full capacity fans, one serving as standby. These fans obtain electrical power from motor control centers MCC F6 (480-V bus 2A) and MCC G6 (480-V bas 2) which receive emergency power from the diesel and gas i
turbine, respectively. When effsite power is lost, these fan motor loads drop out and must be reconnected by the operator for operation on emergency generated power.
With respect to the handling of ventilation air within the reactor building and the exhausting of the air, the Licensee provided the following information (4):
"The heating and ventilation system is provided for personnel and equipment protection from airborne radioactive contaminants and excessive thermal conditions. Air flow is controlled in the direction of greater contamination prior to final exhaust through a remote ventilation stack.
Air pressure in controlled areas of the reactor building is at a slight negative pressure (about 0.1 to 0.25 inches water) to prevent out-leakage of airborne radioactive contaminaton. Supplementary fans in the reactor building, excluding the pipe tunnel, are used to ensure proper air flow direction and maintain negative pressures in enclosed areas housing equipment. The supplementary fans are used as transfer fans from the reactor building to the main exhaust system."
4 E
Air flow through the plant is augmented by the use of a number of transfer fans, identified in pairs, each pair of which receives electrical )
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TER-C5257-412 power from separate motor control centers of 480-V buses 2 and 2A.
Since these buses receive emergency gas turbine and diesel power, respectively, they make fully-redundant emergency power available to these fans.
Exhaust air is collected by a network of ducts and directed to the common turbine building and reactor building exhaust plenum where it is exhausted to the plant stack by fans HVE-1A, HVE-1B, and HVE-lC.
For this ccabined turbine and reactor buildings exhaust system, three half-capacity exhaust fans are useo, each rated at 80,750 cfm, two operating and one on standby.
While mechanical redundancy is provided by the three half-capacity exhaust fans, only two of these fans, HVE-1A and HVE-lC, have access to onsite emergency generated power following a loss of offsite power. The third fan, HVE-18, is powered from 480-V bus 12D (lA), which is reportedly not normally connected to onsite diesel-or gas-turbine-generated power [6]. Note, also, that fans HVE-1A and HVE-1B both drop from their respective essential buses upon loss of offsite power and must be restored to operation by the operator.
Thus, with a single active failure, the operator can restore only half the exhaust fan capacity following a loss of offsite power.
Air flow through the plant, at least for operation with the normal supply and exhaust, appears to satisfy the acceptance criterion for flow from areas of lower radioactivity to areas of higher radioactivity. However, this condition holds only as long as no significant level of radioactivity is detected in the exhaust air. With the detection of radioactivity in the reactor building exhaust effluent, the reactor building is automatically isolated from the supply and exhaust systems by the redundant pairs of butterfly valves and the reactor building is connected to the standby gas treatment system.
I with a flow rate of only 1100 cfa, the standby gas treatment system draws of fluent from the reactor building and passes it through one of two redundant gas treatment systems and then to the atmosphere through the vent stack. The standby gas treatment system is redundant in that the effluent can ce directed l
into either of two gas treatacnt paths by either of two parallel fans. The fans are supplied with electric power separately through MCC F6 (480-V bus 2A) 000 Franidin Research Center Aonesaern.numeo en.
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1 TER-C5257-412 and MCC G6 (480-V bus 2), which are connected to onsite diesel and gas turbine emergency generated power, respectively. Both fans remain connected to their power sources following a loss of offsite power.
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The low flow rate of 1100 cfm for the standby gas treatment system causes i
concern. While it may be sufficient to sustain a negative pressure in the reactor building to prevent leakage of radioactive effluent out of the plant, it is insufficient to prevent its spread inside the reactor building by local convective currents. Therefore, it does not satisfy the acceptance criterion that requires air flow from areas of lower to higher radioactivity. The question is whether personnel must have access to areas in the reactor building following the building's isolation upon detection of radioactive effluent. The Licensee should comment on this point and assure that the spread of radioactivity would not constitute a personnel hazard.
A second question concerning the venting of the reactor building by the standby gas treatment system is whether the reactor building ventilation transfer fans would continue to operate. These fans are designed to operate with the larger air volumes of the normal ventilation system. Their continued operation after the reactor building is isolated and being vented by the standby gas treatment system could possibly cause spreading of the radioactive effluent by leakaga from ducts now pressurized by one or more of the transfer fans.
The Licensee has described a separate air supply and exhaust system for the reactor building pipe tunnel as follows [41:
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" Ventilation in the pipe tunnel area is provided by redundant full supply fans of approximately 2000 cfm capacity and exhaust fans of approximately 2500 cfm which discharge to the stack."
The supply and exhaust systems are identified as HVS-7 and HVE-16, respectively. Since this separate ventilation system is not considered essential to safe shutdown, it is not discussed further in this report.
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In summary, the reactor building ventilation system features redundancy of equipment and emergency power to prevent the loss of functional performance capability from a single active failure. All other acceptability criteria are rankun'Research Center A Dennen af The Presuen bushan
e TER-C5257-412 satisfied except for questions about the adequacy of the flow rates during venting by the standby gas treatment system. Those flow rates may not satisfy the acceptability criterion for movement of ventilation air frem areas of lower radioactivity to areas of progressively higher radioactivity.
4.3 SPENT FUEL AREA VENTILATION SYSTEM The Licensee's description and conclusion with respect to the spent fuel pool area ventilation system are as follows:
"The spent fuel pool area ventilation system is contained within the reactor building ventilation system. The function of the reactor building ventilation is to provide for personnel and equipment protection from airborne radioactive contaminants and excessive thermal conditions during normal operation, anticipated operational transients, and postulated fuel handling accidents.
Based on our review of the reactor building ventilation system and our fuel handling accident analysis provided in SEP Topic XV, it has been determined that the reactor building ventilation system can maintain ventilation in the spent fuel pool equipment areas to permit personnel access and control airborne radioactivity during normal operation, anticipated operational transients, and following postulated fuel handling accidents."
The spent fuel pool ventilation area system is not essential for safe shutdown and was reviewed here only with respect to personnel safety as reflected in the criterion that air must be directed from areas of lower radioactivity to areas of progressively higher radioactivity. This ventilation system, in conjunction with the reactor building ventilation system of which it is a part, and which was reviewed in Section 4.2, satisfies that criterion.
4.4 TURBINE BUIIIING VENTILATION SYSTEM The Licensee's SAR [4] provided the following overall description of the turbine building ventilation systems "The turbine building ventilation system services all areas within the turbine building, which includes ventilation for the following equipment which is considered safety related; feedwater coolant injection system (condensate pumps, condensate booster pumps, and reactor feedwater 4
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l TER-C5257-412 pumps), switchgear rooms, emergency diesel generator, battery room, secondary closed cooling water pumps, and related piping valves and controls.
As a result of the environmental qualification program for safety related electrical equipment Millstone Unit 1, extensive modifications were made to the turbine building ventilation system to ensure adequate ventilation can be provided during accident conditions for the switchgear rooms, battery rooms, and emergency diesel generator room..These modifications included installation of redundant safety grade fans and associated dampers and duct work. The heating / cooling systems associated with this system are not required to ensure reliable operation of the associated equipment, therefore, is not safety grade.
The turbine ventilation system consists of approximately 46,000 cfm redundant supply fans and associated dust filtration and heating / cooling elements, which supplies ventilation to the majority of the turbine building including the areas which contain the condensate pumps, condensate booster pumps, reactor feedwater pumps, and component cooling water pumps. The remainder of the building which includes ventilation to the switchgear rooms, battery room and emergency generator room, is serviced by approximately 30,000 cfm supply fans and dust filtration and heating / cooling elements.
The building exhaust system discharges into a plenum which also receives air from the reactor containment building. Three 50% capacity, approximately 80,000 cfa, f ans are furnished to handle the combined exhaust from the turbine and reactor buildings.
Two fans operate with the third fan serving as a standby. The fans discharge to the common header that is run out to the stack.
Potentially contaminated areas in the turbine building are maintained at a negative pressure by exhausting from these areas. The exhaust air is drawn from adjacent spaces. This arrangement controls the air flow pattern and prevents out-leakage."
A review confirms the Licensee's statement that the turbine building ventilation system services safety-related systems and equipment and is therefore essential to safe shutdown. This section of this technical evaluation report reviews the turbine building ventilation system as a whole regarding its overall ability to service the safety-related equipment.
Specific ventilation and cooling requirements of the safety-related equipment are considered below in the review of engineered safety features ventilation systems.
Three systems, EVS-1, EVS-2, and EVS-6, supply ventilation for safety-related r.quipment in the turbine building.
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reviewed separately below in relation to the safety-related equipment it services. The exhaust system, as described by the Licensee, picks up exhaust air at appropriate distributed points and ducts it to the common plenum where i
the combined exhaust of the turbine and reactor buildings is directed to the stack.
HVS-1 supplies ventilation to the condensate booster pumps, which are part of the safety-related feedwater coolant injection system, as well as to non-saf ety-related areas of the condenser bay. Two full-capacity fans, HVS-1A and HVS-1B, are employed, electrically powered from motor control centers MCC-F6 (2A-6) and MCC-G6(2-6), respectively. As noted below in the discussion of electric power, all sets of turbine building ventilation fans have redundant electric power supplies, but must be reconnected by the operator if they are to be used after loss of offaite power.
HVS-2 supplies filtered, tempered ventilation air to the area of the reactor feedwater pumps, which are part of the safety-related feedwater coolant injection system, as well as to non-safety-related areas. Two parallel, full-capacity supply fans are used, one operating and one standby.
HVS-2 is powered 'oy the same motor control centers that supply HVS-1 (see discussion of power supply redundancy below).
Ventilation supply system HVS-6 also employs two full-capacity fans, one as standby, to supply filtered, heated air to safety-related areas including the diesel generator room, the battery rooms, the 4-kV switchgear #3 room, and the room housing essential 480-V switchgear 2 and 2A and 4-kV switchgear 1, 2, 5, and 6.
While redundant, essential 480-V electric service is supplied to these fans through MCC-F6 (bus 2A) and MCC-G6 (bus 2), the fans must be reconnected by the operator after loss of offsite power, as discussed below.
Thus, portions of air supplied by all turbine building ventilation systems are directed to safety-related equipment areas. Mechanical redundancy l
is provided by the use of two parallel, full-capacity fans (one as standby) in l
each ventilation supply system and by the use of three fans (one as standby) in the combined turbine and reactor buildings exhaust system. Although redundancy of essential electrical power for the ventilation supply systems is rankun Research Center A Ohemen of The Presumi humane
TER-C5257-412 provided by connection of one fan of each supply system to gas-turbine-generated emergency power through MCC(2-6) and essential 480-V bus 2, and connection of the other fan to diesel-generated emergency power through MCC(2A-6) and 480-V bus 2A, a circuit review indicated that under-voltage circuit breakers automatically disconnect all the supply fans upon loss of j
offsite power. Restoration of power to these fans following a loss of offsite power requires the operator to reset the tripped breakers.
A similar situation exists for the fans of the combined turbine and reactor buildings exhaust system as discussed in Section 4.2.
Two of the three exhaust fans are powered by essential 480-V buses 12F(2A) and 12 E (2),
but both fan motor loads drop out upon loss of offsite power and must be reconnected by the operator to restore operation. The third fan, HVE-1B, receives power from non-essential 480-V bus 12D (lA), reportedly not normally supplied with emergency power (6).
Thus, the turbine building ventilation system that supplies ventilation and cooling to safety-related areas is redundant so that a single active failure would only reduce the capacity of the system, that is, one of two exhaust fans with available emergency power could fail, leaving only one half-capacity fan in service. All other acceptance criteria are satisfied.
Further discussion of the relationship of this ventilation system to each safety-related system serviced is included below under the topic of that specific safety-related system.
4.5 RADWASTE AREA VENTILATION SYSTEM The following introduction was made in the Licensee's review of the radwaste area ventilation systems (4):
"The radwaste area ventilation systems consist of the radwaste building ventilation system and the radwaste storage building ventilation system.
Neither of these buildings house any safety-related components or systems. A description and evaluation of each system is provided herein."
A review confirms the Licensee's statement that these buildings do not house essential safety-related systems.
Rather, the objective of the review and evaluation of the radwaste areas is to ensure that the systems provide a rankun Research Center A Denman of The huneen busasse
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I TER-C5257-412 safe environment, under all modes of operation, for plant personnel and prevent offsite exposures comparable to the guidelines of 10CFR100, " Reactor Site Criteria."
4.5.1 Radwaste Building Ventilation System In Reference 4, the Licensee provides the following description of the radwaste building ventilation system:
"The heating and ventilating system is designed to supply filtered and heated air at approximately 9,000 cubic feet per minute and exhaust it af ter filtration. This corresponds to about one change of air per hour.
No air is discharged from the building except through the stack.
The supply fans, exhaust fans, and exhaust filters are provided in full-capacity duplicates. Either supply fan and either exhaust fan can then be used to operate the system while the other members of the pair are on standby.
Outside air is drawn into the system through a fixed louver housed above i
the roof of the building. The air is drawn through a filter designed to remove dust, and an electric heater of 200 KW capacity. The heater is thermostatically controlled to warm the air to maintain at least 70*F in accessible areas, and 50*F in inaccessible areas. Beyond the heater section the supply duct is split with each half routed through its section of duct by a butterfly valve damper on both inlet and discharge i
sides. Beyond the fan discharge control dampers, the ducts rejoin into a common manifold from which supply ducts convey fresh air to various areas of the building. At or near the discharge point of each of these ducts, a manually set damper determines the fraction of air delivered at that particular point.
The fresh air supply points are located where the rate of air contamination is lowest while the inlets to the exhaust ducts are located where the rate of contamination is likely to be the highest.
An air outlet is located in each room and at each piece of equipment or other place where radioactive contamination in the foran of dust, gas, or vapor could be released. Ducts from these areas lead to an exhaust air manifold with each duct having a manually set control damper.
A shunt circuit draws air from the exhaust manifold and monitors its airborne radioactivity. The circuit is located so that it monitors building air conditions and not the axhaust from individual equipment areas. High activity is alarmed in both the radwaste building control room and the main control room, providing the ability to isolate the building in a timely manner, if required.
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TER-C5257-412 Beyond the manifold, the exhaust duct divides into two full sized parts, each of which contains a roughing filter followed by a high efficiency filter and an exhaust fan. Butterfly valves in the ducts, before the filters, between filters, and fans, and following the fans, are used to control which of the alternate routes the exhaust will take and to regulate the amount of air exhausted. Beyond the last valves, the ducts are reunited and discharge to the plenum leading to the stack. Backflow from other systems is prevented by interlocks which require valves to be closed if the exhaust fans are not in operation.
Each high efficiency particulate filter in the exhaust system has a minimum removal efficiency of 99.974 based on the 0.3 micron "DOP" (diotylphthalate smoke) test.
As previously stated, the radwaste building does not house any safety related equipment.
In addition, it has been determined that the radwaste building ventilation system can maintain ventilation in subject areas to permit personnel access, control airborne activity, and provide adequate cooling and heating for equipment contained within the building during normal operation and anticipated operational transients. Also, as a result of the majority of all radioactive waste contained within this building being below site grade level, any failure of equipment which could result in spillage would be contained below grade thus minimizing any spillage outside the building perimeter."
A review confirmed the Licensee's foregoing assessment and added the following summarizing comments.
The use of two full-capacity fans on both ventilation supply and exhaust provides mechanical redundancy.
Information supplied for this review indicates that both fans of the supply system are on one motor control center and both fans of the exhaust system are on another motor control center. This would make both the supply and exhaust fan systems vulnerable to a single failure of the respective motor control centers. While such a failure would not affect safe shutdown, a failure of both exhaust fans that allowed the supply fans to continue to operate could pressurize the building and promote the escape of radioactive effluent that is not first drawn through the HEPA e
filters.
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i The method of detecting the need for isolation or other method of handling this possibility was not addressed in the Licensee's assessment [4 ].
However, the assessment does indicate the presence of redundant isolation dampers on both the ventilation supply and exhaust.
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TER-C5257-412 Thus, the only condition that does not satisfy acceptance criteria is the vulnerability to a single failure that would cause both exhaust fans to fail while the supply fans continue to operate, pressurize the building, and consequently promote the escape of radioactive effluent.
4.5.2 Radwaste Storage Building Ventilation System j
In Reference 4, the Licensee has provided the following description and assessment of the radwaste storage building ventilation system:
"The heating and ventilation system is designed to supply filtered and heated air at approximately 3000 cfm and exhaust it after filtration.
Outside air is drawn into the system through fixed louvers. The air is drawn through a filter designed to remove dust and particulate matter.
The air is then distributed throughout various areas of the building.
The fresh air supply points are located where the rate of contamination is lowest while the inlets to the exhaust ducts are located where the rate of contamination is likely to be the highest.
The exhaust contains duplicate roughing filters, high efficiency filters, and exhaust fans.thus ensuring system availability. Each high efficiency particulate filter in the exhaust has minimum removal efficiency of 99.974 based on the 0.3 micron "DOP" (diotylphthalate smoke) test.
Supplementing this exnaust system is a 200 cfm capacity auxiliary system which exhausts air directly from the hydraulic baler through a roughing filter and a high efficiency filter by means of a small exhaust fan and discharges directly into the main exhaust system.
In addition, a 300 cfm hood exhaust from the drum filling area is provided which discharges to the exhaust duct of the building ventilation system.
As previously discussed, the radwaste storage building,does not contain any safety related equipment.
In addition, based upon our review of the radwaste storage building ventilation system, it has been determined that i
the subject ventilation can suitably maintain the building environment to permit personnel access, control airborne activity, and provide adequate cooling and heating for equipment contained within the building during normal as well as anticipated abnormal operation of equipment in the area. As a result of the types, quantities, and frequency of radioactive storage in the building any anticipated failure of equipment which could result in spillage will be minimum consequence."
In addition to the above, information provided for this review indicates that the exhaust fans discharge the effluent to the vent stack through gravity
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TER-C5257-412 dampers that prevent backflow. All applicable acceptance criteria are satisfied.
4.6 ENGINEERED SAFETY FEATURES VENTILATION SYSTEMS 4.6.1 Engineered Safeguards Systems Ventilation and Cooling The emergency core cooling system (ECCS) is the one engineered safeguard system essential for safe shutdown that is ventilated and cooled by ventilation systems within the scope of this review. The review includes the emergency core spray, low pressure coolant injection (LPCI), and feedwater coolant injection (FWCI) subsystems of the ECCS.
4.6.1.1 Emergency Core Spray Subsystem Ventilation The emergency core spray pumps are the only components of the emergency core spray subsystem serviced by ventilation systems within the scope of this review. Since they are located with the LPCI pumps and heat exchanger, they are discussed together with LPCI subsystem ventilation in the following section.
4.6.1.2 Low Pressure Coolant Injection Subsystem Ventilation The LPCI and emergency core spray pumps are located in corner rooms on the basement level of the reactor building ventilated by the reactor building ventilation system. Since the reactor building ventilation system can be supplied with emergency diesel power through operator action following a loss of offsite power, ventilation can be maintained so long as detected radiation does not isolate the reactor building and vent the building through the standby gas treatment system.
In addition to the reactor building ventilation system, each of the two LPCI rooms contains a room space cooler (HVH-15 or HVH-16) that contains a fan and a water-cooled heat exchanger. Water cooling is provided by means of the turbine building secondary cooling water system which, in turn, is cooled by l
the service water system. Both cooling water systems are essential systems i
supplied by diesel-generated emergency power (as stated in the FSAR). The
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fans of room coolers HVH-15 and HVH-16 are powered by motor control centers MCC 2-3 and MCC 2A-3, respectively, from separate essential electrical buses.
Note that while this implies mechanical and electrical redundancy, the LPCI pumps are divided between two rooms with one cooler in each. Therefore, a single active failure of a fan or a motor control center would interrupt 1
space cooling in the room being serviced. Environmental conditions in these f
.>ons, according to Section VI of the FSAR, indicate the need for cooling.
Since the core spray system uses one 100% pump in each room and the LPCI/ containment spray system uses two 33% pumps in each room, the failure of all pumps in a room would remove all backup for the core spray system and reduce the LPCI/ containment spray system to 66% ptnaping capacity.
4.6.1.3 Feedwater Coolant Injection Subsystem Ventilation The feedwater coolant injection system (FWCI) for the Millstone 1 plant serves the purpose of high pressure coolant injection.
The FWCI equipment is located in the turbine building and is serviced by the turbine building ventilation system. The PWCI system is composed of the three condensate pumps, tnree condensate booster pumps, and two feedwater pumps. The condensate pumps and the condensate booster pumps are ventilated by turbine building ventilation supply system HVS-1.
The feedwater pumps are ventilated by HVS-2.
Discussion of turbine building ventilation in Section 4.4 disclosed that these ventilation supply and exhaust systems may be connected to emergency onsite generated power by operator action following a loss of offsite power.
However, it is not known whether procedures are in place for such operator action.
The Licensee has described space cooling of these areas as follows in Reference 4:
" Water cooled heat exchanger cooling units are provided in the areas surrounding the reactor feedwater pumps, condensate pumps, condensate i
booster pumps, and emergency diesel generator to supply supplementary cooling to these areas during normal operation. The cooling water is supplied from the turbine building secondary closed cooling water system."
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TER-C5257-412 While this indicates that space cooling is provided to the PWCI components, insufficient review material was available to identify these units and their source of electrical power.
Except for these detailed questions regarding the supply of essential power to the turbine building ventilation system and to the space coolers, all l
acceptance criteria are satisfied.
4.6.2 ventilation for Station Water Systems Three station water systems are essential. Ventilation and cooling of these systems are described in the following sections.
4 ti.2.1 Station Cooling Water System Ventilation The station cooling water system supplies service water to the diesel generator cooling heat exchangers and the turbine building secondary cooling water heat exchangers, and also supplies other, non-essential needs.
The intake structure ventilation system servic'es the station cooling water pianps, and was assessed by the Licensee in Reference 4 as follows:
"The intake structure ventilation system is addressed as a result of this i
building containing the service water and emergency service water pumps which are considered safety related. The ventilation rystem consists of two roof mounted 20,000 cfm exhaust fans and a 600 cfm fan to provide ventilation in the chlorination area, which exhausts directly outside on the roof. The intake air for the various areas is provided through an outside air intake penthouse located on the roof of the intake structure. Also heaters are provided for operation during cold weather.
-The mecnanisms which act to preclude any rapid heat build up are as follows; the service water and emergency service water pipes will contain cool ocean water which act as heat sinks, the room is not airtight thus allowing for cooling as a result of infiltration and if a system failure should occur, doors opening to the outside are available which will provide a sufficient flow of air to ensure adequate equipment cooling.
Bases upon the above review, the system as designed will ensure reliable i
operation of the safety equipment in this area as well as personnel access during design basis accidents."
Information about the electrical power sources for the roof fans was not available and so cannot be reviewed in this report. This review agrees that J
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the buildup of heat in the intake structure would be gradual and could very well be alleviated by the opening of doors, especially if large overhead truck entrance doors are available.
If sufficient ventilation by door openings and other infiltration can be provided, then all acceptance criteria are satisfied.
4.6.2.2 Baergency Station Service Water System ventilation The emergency service water system supplies cooling water to the essential LPCI system and is therefore considered essential. These service water pumps are located in the water intake structure and are ventilated and cooled by the intake structure ventilation system.
(See the discussion of daat system in Section 4.6.2.1 above.) All conclusions drawn there apply to this system as well.
4.6.2.3 Turbine Building Secondary Cooling Water System Ventilation The turbine building secondary cooling water system supplies cooling water to a wide ranga of equipment essential to safe shutdown, including the diesel and diesel generator, provides space cooling of these same equipment areas, and discharges its heat load to the service water system. The pumps, located in the turbine building and ventilated by the turbine building ventilation system, are the only components in this system requiring ventilation and cooling.
Since the specific cooling means are not defined, other than that the turbine building ventilation system is used, the Licensee should identify how these pumps are cooled following a loss of offsite power and whether the cooling means are connected to redundant essential power sources.
4.6.3 Diesel Generator Room Ventilation System Millstone I employs only one diesel generator. Redundant emergency power is provided by a gas turbine generator located in a separate building.
The diesel generator and its associated electrical switchgear are located in a separate room of the turbine building. Ventilation is provided as part of t a output of turbine building ventilation supply system EVS-6, which was evaluated in Section 4.4 above.
Exhaust air is vented through roof vent HVR-7.
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i TER-C5257-412 Turbine building ventilation supply HVS-6 was shown in Section 4.4 to be redundant in power and equipment and to be supplied by essential onsite generated power through operator action following a loss of offsite power.
The source of electrical power or its redundancy could not be traced in the i
available review material. Also, the heat loads to the turbine building secondary cooling water system from diesel generator space coolers, as described in Section X-4.5 of the PSAR, could not be correlated with existing equipment using available review materials.
It is suggested that the Licensee comment on the recent changes made at Millstone I and identify and evaluate tne ventilating and cooling equipment being used for the diesel room.
Ceaunents should mention the existence of alternate discharge paths (e.g.,
doors and windows) for the ventilation air provided.
r 4.6.4 Gas Turbine Buildinq Ventilation System The Licensee provided the following assessment of the gas turbine building ventilation in Reference 4:
"The gas turbine provides a backup to the Millstone Unit No.1 emergency diesel generator thus is considered safety related. The ventilation system for building consists of building louvers and a roof mounted fan along with necessary space heaters for cold weather operation. This is not required for operation of the gas turbine, however, provides personnel access as well as equipment protection during adverse weather cunditions. As a result of this system not being required for operation of the gas turbine, it is our judgement that a safety grade ventilation is not required."
This review concurs that the operation of the gas turbine is not i
l dependent upon operation of the building ventilation system.
All acceptance criteria relating to this ventilation are satisfied.
I 4.6.5 Auxiliary Electrical Equipment Rooms Ventilation Auxiliary electrical equipment necessary for safe shutdown includes the essential 4160-V and 480-V switchgear, motor-generators, and the reactor protection system. This was covered lightly in the Licensee's assessment [4]
in conjunction with the turbine building ventilation system review.
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TER-C5257-412 Drawings shawing recent revisions of the turbine building ventilation a
systems indicate that turbine building ventilation supply system HVS-6 provides ventilation air to the following switchgear areas o 480-V switchgear 2 and 2A 4-kV switchgear 1, 2, 5, and 6 e
o 480-V switchgear 1 and 1A dc switchgear o 4-kV switchgear 3 Exhaust air transport from these areas is augmented by two parallel exhaust fans, HVE 15A and HVE-15B, which discharge to the common turbine-reactor buildings exhaust plenum discussed for the overall turbine building ventilation system in Section 4.4.
This previous discussion indicated that both HVS-6 and at least two exhaust fans of the common exhaust plenum may be connected to emergency onsite generated power by operator action. The Licensee should evaluate the redundancy and power sources for fans HVE-15A and HVE-15B.
These were not on the submitted list of electrical loads and may be part of the revised system.
The use cf space coolers in these areas was neither mentioned in the Licensee's assessment (4] nor could the coolers be discerned among space coolers in the electrical bus loadings list. The Licensee should comment upon their need, since space coolers operating with cooling water as the cooling mediuir are often used to augment the heat removal capability of ventilation systems.
All acceptance criteria are satisfied except for possible vulnerability to a single active failure.
4.6.6 Battery Rooms Ventilation System The battery rooms are supplied with air by turbine building ventilation supply system HVS-6 and are part of the general flow path described above for the switchgear rooms. The main concern regarding the battery rooms is that ventilation be maintained during shutdown to prevent a buildup of hydrogen gas.
l Hydrogen is given off by the batteries during charging and at times during heavy discharging.
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TER-C5257-412 Evaluation of the battery rooms ventilation system is the same as given above for the switchgear areas. All acceptance criteria are satisfied except for possible vulnerability to a single active failure. Additional information and clarification of the system are needed to assess such vulnerability.
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Q NCLUSIONS l
l The Millstone Unit i ventilation systems satisfied all NRC acceptance criteria except as indicated below.
5.1 AVAILABILITY OF ONSITE GENERATED EMERGENCY POWER With respect to the reactor and turbine buildings ventilation systems, it was determined from the documentation that emergency power is available through 480-V buses 2 and 2A to the supply and exhaust fans following a loss of offsite power. While these fan loads could be connected by the reactor operator, it is not clear that they would be so connected because, together, they constitute a fairly large load. This unresolved question applies to the reactor and turbine buildings systems and to much of the safety-related equipment they contain.
5.2 REAC'IOR BUILDING VENTILATION SYSTDiS If all ventilation loads can be connected to onsite emergency power by the reactor operator following a loss of offsite power, then it is concluded that a single failure in one exnaust fan would halve the exhaust capacity. This conclusion is based upon a telephone conference statement [6] that a third fan is powered by a non-essential electrical bus.
Conclusions regarding the standby gas treatment system are that the flow rate is so low that satisfaction of the acceptance criterion requiring flow from areas of low potential radioactivity to areas of progressively higher levels of radioactivity cannot be ensured. This condition could be made worse t
if the transfer fans continued to operate. Clarification is needed on these points.
5.3 TURBINE BUILDING VENTILATION SYSTDtS The overall turbine building ventilation system is subject to the same concern discussed above in Section 5.1.
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TER-C5257-412 5.4 RADWASTE BUIIDING VENTIIATION SYSTEM It is concluded that this system is vulnerable to a single active failure (motor control center) that would cause both exhaust fans to fail while the supply fans could continue to operate. Thus, the building could be pressurized, which would promote the escape of radioactive effluent outside the building and prevent the flow of air from areas of low radioactivity to areas of higher radioactivity.
5.5 ENGINEERED SAFETY FEATURES VENTILATION SYSTEMS Conclusions are as follows:
LPCI System l
A single active failure in a room cooler could promote the failure of both LPCI pumps in that room and reduce the LPCI pumping system to 66 percent capacity.
FWCI System The FWCI system is dependent upon the turbine building ventilation system (see concluding concern of Section 5.1) and also on space coolers said to be present but not identified sufficiently for evaluation.
l Turbine Building Secondary Cooling Water Pumps Ventilation System The available review material was insufficient to define the cooling means other than that one of the turbine building ventilation supply systems is used. Therefore, the evaluation could not be completed.
Diesel Room Ventilation System Insufficient information was available to enable a determination and evaluation of the full range of diesel room cooling and ventilation exhaust.
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r Battery and Switchgear Rooms l
While the battery and switchgear rooms are ventilated by the turbine building ventilation systems, there is not sufficient information to evaluate these systems for operation during shutdown following a loss of offsite
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power. The role of fans HVE-15A and HVE-15B was not given.
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REFERENCES 1.
Millstone Unit No. 1 FSAR 2.
W. G. Counsil Letter to D. G. Eisenhut (NRC)
Oc tober 31, 1980 3.
W. G. Counsil Letter to D. G. Eisenhut (NRC)
September 14, 1981 4.
Safety Assessment Report, SEP Topic IX-5, Ventilation Systems, Millstone Nuclear Power Station Unit No. 1 November 19, 1981 5.
Telephone Conference, Brown (NRC), Herrick (FRC), and McMullen and Blasioli (Millstone 1)
April 15, 1982 6.
Telephone Conference, Persinko (NRC), Herrick (FRC), and Regan (Millstone 1)
April 21,1982 A Demmen of The Fransen houswee
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