ML20213F724
| ML20213F724 | |
| Person / Time | |
|---|---|
| Site: | 05000601 |
| Issue date: | 10/31/1986 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML19292G244 | List:
|
| References | |
| NUDOCS 8611170064 | |
| Download: ML20213F724 (8) | |
Text
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m) 6.4 CONTROL ROOM HABITABILITY SYSTEM The control room habitability system is designed to maintain the control room in a safe, habitable condition following a postulated accident. The control O room ventilation system is designed as an Engineered Safety Feature to protect plant operators against the effects of accidental releases of toxic and radioactive gases.
6.4.1 Design Bases 6.4.1.1 Safety Design Bases SAFETY DESIGN BASIS ONE - The control room habitability system shall maintain a suitable atmosphere within the control room during all modes of plant operation, including postulated design basis accidents and hazardous chemical releases (Title 10 of the Code of Federal Regulations Part, 50, (10CFR 50)
Appendix A, General Design Criterion 19 (GDC-19)).
SAFETY DESIGN BASIS TWO - The radiation exposure of control room personnel l shall not exceed 5 rem whole body, or its equivalent to any part of the body, during accident conditions (GDC-19).
4 SAFETY DESIGN BASIS THREE - The control room habitability system shall remain functional following a safe shutdown earthquake, and shall withstand the effects of appropriate natural phenomena such as tornadoes, floods, and hurricanes (GDC-2).
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- SAFETY DESIGN BASIS FOUR - The control room habitability system shall be protected against the effects of missiles, pipe' whip, and jet forces (GDC-4).
SAFETY DESIGN BASIS FIVE - The control room habitability zone shall include
. V all critical areas requiring access in the event of an accident. Areas not requiring access shall be excluded from the habitability zone, thereby reducing the probability of zone contamination (Standard Review Plan, 6.4).
h500$og PDR WAPWR-AS 6.4-1 OCTOBER, 1986 5416e:1d i
SAFETY DESIGN BASIS SIX - The control room emergency recirculation filter system shall perform its protective function assuming a single failure of an active component coincident with a loss of off-site power (Regulatory Guide 1.52).
SAFETY DESIGN BASIS SEVEN - The fresh air intake for the control room ventilation system shall be monitored for presence of radioactive and toxic gases. Sufficient redundancy shall be provided to detect contamination and assure isolation of the intake assuming a single failure of an active component.
6.4.2 System Description 6.4.2.1 General Description The control roum ventilation system is shown in Figure 9.4-1 (Sheets 1 through
- 7) of this module. A detailed evaluation of this system is presented in Subsection 9.4-1 of this module. The system is designed to maintain the environment in the habitability zone within acceptable limits during normal operation as well as post-accident conditions.
The control room ventilation system utilizes habitability zone isolation and l filtered recirculation in conjunction with low-leakage building construction l
to achieve protection of personnel. Redundant low-leakage valves in the fresh I air intake and exhaust provide positive isolation when signalled to close.
Adequate self-contained breathing apparatus is provided to maintain l habitability during extended periods of zone isolation.
1 The habitability system also includes the following features and design O
considerations:
- a. The control room is located within the reactor external building to minimize effects of a postulated release of hazard'ous airborne l materials.
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- b. Structural concrete provides shielding for radiological protection and i
, serves as a low-leakage barrier for protection against natural phenomena.
- c. All major deposits of hazardous chemicals listed in Table C-1 of Regulatory Guide 1.78, known or projected to be shipped within a five mile radius of the reactor facility, are ' considered in the evaluation of control room habitability.
O d. The effect of a gaseous chlorine leak from on-site storage facilities is considered in the evaluation of control room habitability based on criteria provided in Regulatory Guide 1.95.
6.4.2.2 Component Description 1
The component description of the control room ventilation system is detailed in Subsection 9.4.1 of.this module. This system is specifically designed with
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the following ' features to assure control room habitability during post-accident conditions:
- a. Redundant emergency circulation filter trains with high-efficiency particulate air (HEPA) fil~ters and carbon adsorber are provided to remove contaminants from the habitability zone atmosphere. The system is automatically actuated upon loss-of-coolant accident or detection of contaminants in the fresh air intake.
- b. Control room zone isolation is initiated in the event of a loss of-coolant accident. Redundant, low-leakage butterfly valves in each intake and exhaust path provide positive shutoff to minimize infiltration during post-accident conditions.
- c. All duct used in the control room ventilation system is seismically designed, and is protected from the effects of tornadoes, including tornado generated missiles. Duct and equipment outside of the
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habitability zone utilize low-leakage construction features to minimize infiltration. Duct and filter housings are designed in accordance with applicable leakage classifications addressed in ANSI N509.
- d. The fresh air intake is monitored for radioactivity in the form of particulates, iodine, and noble gases by redundant monitoring equipment. The isolation valves in intake and exhaust ducts are signalled to close if contaminants are detected. The emergency circulation system is automatically actuated to remove contaminants.
- e. Redundant chlorine detectors and redundant smoke detectors sample the fresh air intake for toxic fumes. The isolation valves in intake and exhaust ducts are signalled to close if contaminants are detected.
The emergency circulation system is automatically actuated to remove contaminants.
6.4.2.3 System Operation O
Operation of the control room ventilation system is evaluated in detail in Subsection 9.4.1 of this module.
During normal operation, fixed portions of recirculated room air and outside air are supplied to the control room by one of the main control room air-handling systems. Each redundant air handling system receives outdoor air from a common fresh air intake. This remote intake is carefully located to reduce the probability of contamination and to prevent debris or dust from entering the system. Normal operation is with the inlet open such that ventilation of the control room is maintained.
If toxic or radioactive gases are detected, the inlet and exhaust isolation valves are closed, and operation of the emergency circulation system is automatically actuated. Sampling locations are situated near the fresh air intake. Isolation valves are located as far downstream as possible to 6.4-4 OCTOBER, 1986 O
WAPWR-AS 5416e:1d
minimize the quantity of contaminants that reach the habitability zone during the detection and isolation sequence.
In the event of a loss of-coolant accident, the control room habitability zone O', is sutomatically isolated, and the emergency circulation system is actuated.
The main control room air-handling system operates in a recirculation mode with a portion of return air passing through the emergency circulation filter m system. This mode of operation minimizes infiltration of contaminants and affords maximum protection for control room occupants.
After the effects of a potential release have diminished, as determined by remote sampling or control at the source, ventilation air may be restored by opening the inlet isolation valves from the control room. In the event of a component failure, the valves may be manually repositioned through use of a local override. Short-term release effects may last only a few hours, but long-term effects may require zone isolation for several days. The air volume ,
of the isolated habitability zone is sufficient to support at least five j people for severi days. Breathing apparatus capable of being refilled or replenished are available to supplement this period as required.
6.4.3 Codes and Standards -
The work, equipment, and materials conform to the requirements and recommendations of the following codes and standards:
- a. Fan ratings conform to standards of the Air Moving and Conditioning Association (AMCA).
b; Ventilation ductwork conform to applicable standards of the Sheet Metal and Air-Conditioning Contractors National Association (SMACNA) and ANSI N509, Design of Nuclear Air Cleaning Systems.
- c. Fan motors conform to applicable standards of the Nation'al Electrical Manufacturer's Association (NEMA).
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- d. HEPA filters and carbon adsorbers conform to ORNL-NSIC-65, " Design, Construction, and Testing of High-Efficiency Air Filtration Systems for Nuclear Applications" and ANSI N509.
6.4.4 Safety Evaluation Safety evaluations are numbered to correspond with safety design bases of Subsection 6.4.1.1.
SAFETY EVALUATION ONE - The control room ventilation system consists of completely redundant and independent air-handling systems. Each train is powered from independent, Class 1E power sources and served from separate essential chilled water systems. The control room emergency circulation systems consist of completely redundant, full capacity emergency circulation fan, HEPA filter, and carbon adsorber units. Each system is powered from independent Class 1E power sources.
SAFETY EVALUATION TWO - Control room dose assessment is present in Subsection 15A.3 of RESAR-SP/90 PDA Module 6/8, " Secondary Side Safeguards System / Steam and Power Conversion". Radiation exposure will be within the guideline values presentea in GDC-19. -
SAFETY EVALUATION THREE - The control room habitability system is designed to Seismic Category I requirements, and will remain functional following a design basis earthquake. Those portions of the habitability system having direct connections with the outside are provided with isolation valves designed to withstand the differential pressure associated with extreme wind and tornado conditions. The control room habitability zone is protected against flooding by virtue of location. Major equipment in the control room ventilation system trains are physically separated.
SAFETY EVALUATION FOUR - All equipment and piping near the habitability system are evaluated for pipe breaks and equipment failure. Shielding to protect against missiles, pipe whip, and jet forces is provided where required.
O I WAPWR-AS 6.4-6 OCTOBER, 1986 5416e:1d
SAFETY EVALUATION FIVE -
The control room habitability zone includes the following areas which require access in the event of an accident: control room, kitchen facilities, and operator waiting room. Other areas are not required for frequent access during post-accident conditions.
. SAFETY EVALUATION SIX - The control room emergency recirculation filtration systems are designed mechanically and electrically to assure system performance. A single-failure analysis is presented in Tables 9.4-1 and 9.4-2 O
V of this module.
SAFETY EVALUATION SEVEN - Protection of control room personnel is provided by habitability zone isolation and filtered recirculation of the zone atmosphere. A single fresh air intake provides normal ventilation air for the
, control room ventilation system. The intake is monitored by redundant radiation monitors, redundant chlorine detectors, and redundant smoke detectors. Upon detection of a contaminant, redundant isolation valves in the intake duct and in each exhaust path are closed. Redundant trains of monitoring equirpment and isolation valves are served from separate independent power supplies such that detection and isolation will occur in the event of a single failure of an active component.
6.4.5 Inspection and Testing Requirements A program of tests and inspections is performed to demonstrate the capability of components and the overall system to perform the intended functions.
Emphasis is placed on tests and inspections essential to a determination that performance criteria and operations capability are achieved and maintained.
Test and inspection requirements are given in Subsection 9.4.1.5 of this module.
The following is verified by testing:
- a. Carbon filters are tested for iodine removal and' collection capability, leak-tightness, and flow resistance.
i WAPWR-AS 6.4-7 OCTOBER, 1986 5416e:Id
- b. HEPA filters are tested prior to installation in accordance with MIL-F-51068.
- c. Fan flow and head characteristics are tested in accordance with AMCA.
- d. Heating and cooling coils are leak-tested and rated in accordance with O
ARI standards.
The control room isolation capability is periodically verified. The performance cf the control room emergency circulation units is periodically tested.
6.4.6 Instrumentation Application Instrumentation required for the control room ventilation system is discussed in Subsection 9.4.1.6 of this module. Sufficient instrumentation is included with the system to assure satisfactory operation.
The following equipment is monitored with status displayed in the control room: O
- a. Fan Status
- b. Filter Load j c. System Air Flow l
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O WAPWR-AS 6.4-8 OCTOBER, 1986 5416e:1d