Regulatory Guide 3.32

General Design Guide for Ventilation Systems for Fuel Reprocessing Plants

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Issue date:	09/30/1976
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U.S. NUCLEAR REGULATORY COMMISSION September 1975 REGULATORY GUIDE

OFFICE OF STANDARDS DEVELOPMENT

REGULATORY GUIDE 3.32 GENERAL DESIGN GUIDE FOR VENTILATION SYSTEMS

FOR FUEL REPROCESSING PLANTS

B. DISCUSSION

Section 5034, "Contents of Applications; Technical Ventilation systems for fuel reprocessing plants are Information," of 10 CFR Part 50, "Licensing of designed to supply properly conditioned air to occupied Production and Utilization Facilities," requires, among and unoccupied areas, ensure that airl confined to other things, that each application for a construction prescribed flow paths for discharge _. final filter or permit for a production or utilization facility, including treatment system and stack, an that proper fuel reprocessing plants, include the principal design monitoring and filtration or tmen e provided.

criteria for the facility. At fuel reprocessing plants, a Ventilation systems for tion 61 reproces principal risk to health and safety is the uncontrolled sing plants usuallco st ough air supply and exhaust air syer 'th associated air release and dispersal of airborne radioactive material.

Structures, systems, and components important to filters, fans, dam m m ring equipment, and safety in a fuel reprocessing plant include, among other control instru ten can include medium things, features designed to prevent, limit, or mitigate efficiency*re -efficiency filters such as the release of radioactive material. These features sandfil packs with deep bag polishing include protection by multiple confinement barrierrand unitan -efficiency particulate air) filters.

systems, ventilation systems, and offgas systems.

Regulatory Guide 3.18, "Confinement Barriers and u~pisydrawn into the plant and conditioned by Systems for Fuel Reprocessing Plants," provides u ly system and distributed to various zones mation relative to establishing principal design d by personnel. Part of the air is directed from for confinement barriers and systems that will m e zones into areas of greater potential for contamina the amount of radioactive material rele t. tion but also accessible to personnel, and thence into environment or to areas normally occup by p process zones. Air from process area zones is removed nel. Regulatory Guide 3.20, "Process 0 yste for through a ventilation exhaust and filtration system which discharges through a stack to the environment.

ifor ew Fuelestabl toel Reprocessingsshing Plants,"

Princi provides

'pal videsigncinforn* tive t Provisions may be made for alternative release points to establishing associated with pprincipal Oesoffdesign criteria system

• atment syteqm fr ent fuel downstream of final exhaust air filters in the event that reprocessing plants. The on systems for a fuel flow through a stack is blocked due to structural failure.

reprocessing plant are d fine, channel, and control airborne v taminants and provide Part of the ventilation air for normally occupied zones normal ventilati func s. any acceptable bases for may be recycled to the air supply 'system through the design e e tio stems for fuel reprocessing recirculating air systems. Independent recirculating air plants ar eailve been used. These bases can systems may be used in selected-areas of the plant having differ si tly because there has not been sufficient particular occupancy requirements such as control guidance to standardization. In the interest of rooms or control areas that are designed to permit standardization, this guide describes bases acceptable to occupancy to operate the plant safely under normal the NRC staff for the design of ventilation systems for conditions and to maintain the plant in a safe condition fuel reprocessing plants. under accident or other abnormal conditions.

USNRC REGULATORY GUIDES Comments should be sent to the Secretary of the Commision. U.S. Nuclear the public Regulatory Commission. Washington. D.C. 2065. Attention: Dockieting and Regulatory Guides are issued to describe and make available toparts of the Service Section.

methods acceptable to the NRC staff of Implementing specific Commission's regulations, to delineate techniques used by the staff in evalu The guides are issued in the following tan broad divisions:

Sting specific problems or postulated accidents. or to provide guidance to appli cants. Regulatory Guides are not substitwles for regulations, and compliance 1. Power Reactors S. Products with them is not required Methods and solutions different from those set out in 2. Research end Test Reactors 7. Transportation the guides will be acceptable if they provide a basis for the findings requisite to &. Fuels and Materials Facilities S. Occupetionat Health the issuance or continuance ol a permit or license by the Commission. 4. Environmental and Siting &.Antitrust Review Comments and suggestions for improvements in these guides are encouraged S Materials and Plant Protection to. General at all times, and guides will be revised, as appropriate, to accommodate com ments and to reflect new information or experience However. comments on Copies of published guides may be obtained by written request indicating the this guide, if received within about two months after its issuance, will be par divisions desired to the U.S. Nucker Regulatory Commission. Washington. D.C.

ticularly useful in eveluating the need for an early revision 20S. Attention: ODrector. Office of Standards Development.

Ventilation systems will be subject to variations in nents should have fail-safe features with provision for operating temperatures and pressures and to environ alarm Indicatioai.

mental conditions associated with normal operation, maintenance, plant shutdown, and testing. They may d. Onsite emergency power should be provided to also be subject to effects of natural phenomena such as operate the ventilation systems and components, includ.

seismic motion and floods and of missiles, fire, explo ing instruments and controls, important to safety.

sion, and other accidents. Ventilation systems should be capable of operating during normal power outage at capacities required to The, systems must continue to perform their safety maintain confinement of contaminants. The onsite functions effectively under all conditions by confining emergency power sources and the electrical distribution radioactive or other potentially dangerous materials. circuits should have independence and testability to They should be designed to ensure that the concentra ensure performance of their safety functions assuming a tion -ofradioactive materials In the effluent gases is as far single failure.

below the limits specified in 10 CFR Part 20 as practicable. e. The ventilation systems should be designed to withstand any credible fire and explosion and continue The continuity of necessary ventilation can be to act as confinement barriers. The ventilation systems ensured by means such as standby equipment and should be constructed of fire-resistant materials of fail-safe control systems. The ability of the systems to construction and should include fire-resistant filters, perform their safety functions effectively can be ensured heat and smoke detectors, alarms, heat removal devices, by periodic testing of safety-related components during fire-suppression equipment,'and fire doors and dampers normal operation of the systems to demonstrate their or other proven devices to restrict the spread of fires.

ability to perform at design efficiency and to verify The design of the fire protection system should include availability for emergencies. provisions to protect against adverse effects in the event of operation or failure of this system. For example, a

C. REGULATORY POSITION

drain system of critically safe geometry should be provided to prevent a criticality Incident in the event of Ventilation systems for a fuel riprocessing plant water discharge on activation of a water spray heat should ensure the confinement of hazardous materials removal system or in the event of water leakage on during normal or abnormal conditions, including natural phenomena, fire, and explosion. The release of radio.

failure of a heat removal system component such as a spray nozzle while the system is not in operatio

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active material to the environment or to an area in which levels of radioactivity are normally sufficiently low to f. Ventilation systems should be capable of operating permit personnel access should be reduced to a level as during a fire in the areas they ventilate and safely handle low as practicable in accordance with 10 CFR Part 20. products. of combustion through appropriate ventilation channels. A supply air system should remain operational;

1. General Safety however, the option to discontinue air supply to the involved space or spaces should be maintained. Any a. Ventilation systems should be designed to confine system that may be shut down should be protected radioactive materials as close to the point of origin as against backflow.

practicable and prevent uncontrolled release of radio active aerosols, noxious fumes, and vapors into rooms g. The materials of construction for the ventilation and areas normally occupied by personnel. systems should be fire-resistant to protect against fires occurring inside or outside the systems. All filters should b. Confinement of radioactive materials should be be of a fire-resistant type and, where applicable, listed provided by multiple-zone confinement barriers and by Underwriters' Laboratories (Ref. 1) or the Factory systems. Negative pressure differentials should be main Mutual Research Corporation (Ref. 2). Filters and tained between building confinement zones and also exhaust fans, especially a final filter plenum and exhaust between the confinement zones and the outside atio fan enclosure, should be so located as not to be exposed sphere to ensure that air flow is from zones of lesser to the direct effects of fire or explosion in the operating potential for contamination to zones of greater potential areas. Smoke and heat detectors listed by the Under.

for contamination. Features of confinement barriers and writers' Laboratories (Ref. 3) or the Factory Mutual systems, including pressure monitoring and alarm Research Corporation (Ref. 2) should be provided in the requirements, are discussed in Regulatory Guide 3.18. ventilation systems.

c. Ventilation systems should be designed so that the h. Fire- and smoke-suppression equipment should be failure of any one component (equipment or control so located as to ensure that the integrity of final device) will not affect the continuous operation of the high-efficiency filters or filter systems is not degraded.

ventilation systems. Ventilation systems and compo- Spark and flame arresters and isolation valves may be

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used at filter installations in intermediate -stages of d. Part of the air in normally occupied areas may be effluent cleaning. Where appropriate, a heat removal recirculated to reduce thermal loads. Air containing system should precede a high-efficiency filtration system noxious, toxic, or corrosive gases and vapors should not serving as a final means of effluent cleaning (see be recirculated. Recirculating air systems should be regulatory position CA.a(6)). equipped with adequate air-cleaning equipment to ensure the maintenance of air quality in occupied areas.

I. Normally, plant design and operating procedures Provisions should be made for monitoring the recircu should limit quantities of combustibles. Where sources lated air. Upon any Indication that the limits for of combustible solvents, gases, and vapors are Identified radioactivity in occupied areas specified in 10 CFR Part or postulated to be present in a ventilation system under 20 or in the technical specifications have been reached, normal or abnormal conditions, suitable continuous the air in the recirculating system should be diverted to monitoring systems should be employed. These monito the once-through exhaust ventilation system for dis ring systems should sound audible alarms and display charge through a final filtration system.

visual alarm indications to operating personnel when the prescribed safe limits for combustible gas and vapor e. Recirculating air systems independent of ventila mixtures are reached. The monitoring and alarm system tion systems may be used in selected areas of the plant itself should not introduce an ignition source and should having particular occupancy requirements such as con not affect the confinement integrity of the ventilation trol rooms or control areas.

system. The monitoring and alarm system should be designed for in-place calibration and testing. f.- Air locks should be provided where frequent entry between personnel occupancy and limited access areas is J. The ventilation systems should be designed to necessary and where air flow must be maintained in one withstand tornado conditions without loss of confine direction.

ment capability resulting from mechanical damage to the system or components or from the reduced ambient 3. Process Area Ventilation Systems pressure at the intake and exhaust openings of the building. Protection against missiles should be provided a. Fire-resistant medium-efficiency prefilters should for the intake and exhaust openings, as well as for any be used in process area ventilation systems to remove the exposed (outdoor) ductwork or equipment between the bulk of particulate matter in the air streams and thus intakes and exhaust filters. limit the loading of the high-efficiency filters installed in the exhaust air systems. Each prefilter should have an k. Components of the ventilation systems should be atmosphere dust spot efficiency rating (Ref. 4) of designed to withstand the effects of earthquakes and approximately 80% or better.

remain functional to the extent that they will prevent the uncontrolled release of radioactive materials to the b. Where necessary, appropriate means and proce environment. dures should be provided in addition to the process offgas treatment systems (see Regulatory Guide 3.20) to

2. Occupied Area Ventilation Systems protect final HEPA filter systems from exposure to wetting or deleterious chemical attack.

a. Supply air should be properly conditioned and distributed, where practical, in a downward flow pattern c. The ventilation systems should maintain minimum to the potentially contaminated areas of the facility. air velocities of 120 linear feet per minute (design velocity should be %,150linear feet per minute) through b. Outside makeup air supply units should be protec all process area openings such as fume hood doors and ted from the weather and should be so located as to process cell covers to prevent significant reverse flow of minimize potential for intake of stack discharge gases. contaminated air.

Inlets should be so arranged as to minimize the effects of high winds, rain, snow, ice, and debris on the operation d. Air or inert gas should enter each ventilated glove of the system. Heaters may be necessary in areas where box through at least one fire-resistant HEPA filter and icing can cause significant supply filter damage. Trash be discharged through at least one fire-resistant HEPA

screens or other proven devices should be provided over filter to exhaust ductwork leading to a final filter system supply air inlets to protect air treatment equipment and (see regulatory position C.4A(6)). The Inlet filter pre filters from debris. vents any backflow of contaminants into the work areas, and the outlet filter minimizes contamination of the C. Where air from occupied areas is directed to exhaust ductwork.

contaminated or potentially contaminated areas, con sideration should be given to passing this air through e. Consideration should be given to recirculation of suitable filters to prevent backflow of particulate con exhaust air or inert gas in glove boxes to miirmize taminants. release of radioactive particulates to the biosphere. If

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recirculation is used, the exhaust gas from these enclo abnormal heat rise in the cooling chamber inlet is sumes should be filtered through at least one fire-resistant indicated by detectors in exhaust ducts feeding the filter HEPA filter before being recirculated. plenum. A manually operated valve actuating the spray system should also be provided as a backup. If a drain f. The features described In regulatory position C.7 system is installed to prevent accumulation of liquid in of Regulatory Guide 3.12, "General Design Guide for the plenum, the collection tanks should be of critically Ventilation Systems of Plutonium Processing and. Fuel safe geometry.

Fabrication Plants," addressed specifically to glove boxei for plutonium processing and fuel fabrication (7) The filtered air should be discharged to the plants are also generally applicable to glove boxes for environs through a stack of sufficient height to reduce fuel reprocessing plants. close-in ground-level concentrations of radioactive or other potentially dangerous contaminants. Provisions should be made for an alternative release point in the

4. Exhaust Ventilation and Filtration Systems event that flow through the stack is blocked because of structural failure.

a. HEPA Filter Systems

(8) The stack should be located sufficiently

(1) Each exhaust filter housing should have a distant from other facilities that structural failure would rigid mounting frame for the filter. The leakage of the not result in damage to any process systems or structures complete housing structure should be as low as possible important to safety.

from outside to inside and zero from inside to outside or across the filter-sealing barrier (exclusive of the filter). (9) HEPA filters used in intermediate and final The filter-sealing barrier should be made leaktight filtration systems should be designed to military specifi withoui resorting to sealing tapes or caulking. cations MIL-F-51068D (Ref. 5) and MIL-F-51079B

(Ref. 6) and should satisfy the requirements of UL-586

(2) Where filter access openings in these housings (Ref. 7).

are provided for filter removal, the configurations should permit filter removal and replacement with minimum (10) HEPA filter systems should be tested after exposure to personnel performing this task and with filter installation using a "cold DOP" test. Acceptance minimum release of contaminants outside of the hous should be based on an efficiency of 99.95% or better for ing. DOP having a light-scattering mean diameter of approxi K

mately 0.7 micron. Regular. in-place testing of both

(3) The filter housings should be equipped with on-line and standby filter installations should be per necessary test ports to permit reliable in-place testing of formed because system deterioration can take place even all filter stages with dioctyl phthalate (DOP). when the installations are not being used. Test proce dures used should comply with the recommendations

(4) The minimum instrumentation for each filter contained in ORNL-NSIC-65, "Design, Construction and housing should include a device or multiple devices to Testing of 1igh-Efficiency Air Filtration Systems for Indicate filter resistance and airflow rate. Nuclear Application," (Ref. 8) and in Regulatory Guide

3.2, "Efficiency Testing of Air-Cleaning Systems Con

(5) Where filter systems are designed for replace taining Devices for Removal of Particles."

ment, isolation valves should be so located that a bank of filters can be completely isolated from the ventilation systems during filter replacement operations.

b. Other Filter Systems

(6) A heat removal system and a spark arrester (1) Final filtration systems incorporating high should precede each HEPA filtration system serving as a efficiency filters other than, HEPA filters, such as packed final means of effluent cleaning. If a cooling spray such glass wool or packed sand units, should have equivalent as a water spray system is used for heat removal, it efficiency and resistance to fire.

should be followed by a combination spark arrester/

moisture separator screen to also remove entrained (2) Packed glass wool and packed sand filter droplets, thereby protecting filters from plugging and systems should be tested prior to operation using a "hot damage. A roughing filter and a wire mesh protective DOP" test and provisions should be incorporated in the screen should be mounted behind these components to installations for periodic in-place "cold DOP" testing remove the bulk of any draft-carried debris and thus (see Regulatory Guide 3.2).

avoid loading the HEPA filters installed downstream.

(3) HEPA filter systems used in combination with The cooling spray system should operate other filter systems should meet the recommendations automatically (with a manual override) when an of paragraph 4.a(l 0) above.

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S. Fans to distribute and regulate the movement of air in each room, area, and ventilation system and to prevent

"a.Installed spare fans and isolation dampers should possible backflow in case of pressure reversal.

be provided for the ventilation systems. When any one fan Is Inoperative in a system, a backflow damper should f. The ventilation systems should be appropriately automatically isolate the idle fan from the system. instrumented to read out and alarm in one or more Standby fans should automatically start and have suffi continuously occupied control areas. These areas should cient capacity to maintain minimum system air flow. be designed to permit occupancy and to permit actions to be taken to operate the ventilation systems safely b. Alarms should be provided in one or more during normal or abnormal conditions.

continuously occupied control areas to indicate malfunc tion of each ventilation fan (see regulatory position C.61). 7. Ventilation System Testing and Monitoring c. Supply air fans should be interlocked with an exhaust air plenum pressure sensor to prevent supply fan a. Provisions should be made so that components of operation unless the-exhaust fans are running. This will ventilation systems can be tested periodically for oper prevent pressurization of any potentially contaminated ability and required functional performance. They area should exhaust ventilation fail. should include capability for periodic measurement of air flows in exhaust ducts and in or at equipment, hoods, d. Emergency power should .be supplied automat and glove boxes.

ically to fans in the event of failure of the normal power supply (see regulatory position C..d).

b. The capability should be provided to test, under conditions as close to design as practicable, the operating

6. Ventilation System Construction and Layout sequence that would bring ventilation systems into action, including the transfer to alternative power sources, and the capability for delivering design air flow.

a. The materials of construction for the ventilation Regulatory Ouide 3.22, "Periodic Testing of Fuel Repro.

systems should be carefully selected according to such cessing Plant Protection System Actuation Functions,"

safety considerations as strength to withstand accident provides information relative to periodic testing of conditions; corrosion resistance, particularly when protection system actuation functions.

associated with chemical processes; fire resistance; long operating life to avoid frequent replacement of contami.

nated equipment; and smooth surface finish to aid in c. Exhaust ducts and stacks that may contain radio decontamination. active contaminants should be provided with a fixed sampler and a continuous monitor [Continuous Air b. Ducts and housings should be designed, fabricated, Monitoring System (CAMS)] that provides a record of and erected with a minimum of ledges, protrusions, and plant effluents. The probes for sampling purposes should crevices that can collect dust and moisture or that could be designed for isokinetic sampling and located to obtain impede personnel or create a hazard in performance of representative samples. Each monitoring system should their work. Duct runs and flow distributors should be connected to an emergency power supply (see ensure uniform, representative air flow past monitoring regulatory position C.I .d). The continuous stack sampler and sampling stations as well as through filter installa should alert cognizant personnel in continuously tions. occupied control rooms or areas through an audible and visual annunciator if the airborne radioactive effluents c. The design and construction should provide for reach prescribed limits. Features of sampling and moni convenient inspection, maintenance, decontamination, toring equipment for process offgases are discussed in and replacement of critical components such as filters, Regulatory Guide 3.20.

fans, and system controls.

d. Housings, filter mounting frames, and ducts d. Air-monitoring and warning systems (including should be designed to withstand system pressure changes CAMS) should be installed in areas where radioactive without distortion, vibration, fatigue, or yielding of such material is handled. Air-sampling heads should provide a magnitude that inleahage or bypassing of the filters representative sample of the potential airborne radio activity being breathed. Consideration should be given to results.

locating continuously operating exhaust samplers after each stage of high-efficiency filtration or, as a minimum, e. Supply, recirculation, and exhaust ducting should providing special connections to allow probes to be j incorporate manual and automatic dampers and controls inserted for sampling.

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S. Quality Assurance Program to applicants and licensees regarding the NRC staff's plans for utilizing this regulatory guide.

a. A quality assurance program should be established for the design, construction, testing, operation, and maintenance of all structures, systems, and components Except in those cases in which the applicant proposes addressed in this guide in accordance with the criteria in to use an acceptable alternative method for complying Appendix B to 10 CFR Part 50. Regulatory Guides 3.3, with specific portions of the Commission's regulations.

"Quality Assurance Program Requirements for Fuel the method described herein will be used in the Reprocessing Plants and for Plutonium Processing and evaluation of submittals for construction permit or Fuel Fabrication Plants," and 3.21, "Quality Assurance operating license applications docketed after May 31, Requirements for Protective Coatingi Applied to Fuel 1976.

Reprocessing and to Plutonium Processing and Fuel Fabrication Plants," describe, respectively, acceptable methods of complying with Appendix B with regard to overall program requirements and to requirements for If an applicant wishes to use this regulatory guide in protective coatings. developing submittals for an application docketed prior

D. IMPLEMENTATION

to May 31, 1976, the pertinent portions of the applica.

The purpose of-this section is to provide information tion will be evaluated on the basis of this guide.

REFERENCES

1. Underwriters' Laboratories Building Materials List 5. MIL-F-51068D, "Filter, Particulate, High-Efficiency, (latest edition). Copies may be obtained from Under Fire-Restant," Military Specification. Copies may be writers' Laboratories, Inc., 207 East Ohio Street, obtained from Commanding Officer, Naval Publications Chicago, Illincis 60611. and Forms Center, 5801 Tabor Avenue, Philadelphia, Pennsylvania 19120.

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2. Factory Mutual Approval Guide (latest edition). 6. MIL-F-51079B, "Filter Medium, Fire-Resistant, High Copies may be obtained from Factory Mutual Research Efficiency," Military Specification. Copies may be Corporation, 1151 Boston-Providence Turnpike, obtained from Commanding Officer, Naval Publications Norwood, Massachusetts 02062. and Forms Center,'5801 Tabor Avenue, Philadelphia, Pennsylvania 19120.

3. Underwriters' Laboratories Fire Protection Equip 7. Underwriters' Laboratories Standard UL-586, "High ment List (latest edition). Copies may be obtained from Efficiency Air Filtration Units," (also designated ANSI

Underwriters' Laboratories, Inc., 207 East Ohio Street, B132.1-1971). Copies may be obtained from Under Chicago, Illinois 60611. writers' Laboratories, Inc., 207 East Ohio Street, Chi cago, Illinois 60611.

4. ASHRAE (American Society of Heating, Refrigera ting and Air-Conditioning Engineers) Standard 52-68, 8. C. A. Burchsted and A. B. Fuller, "Design, Construc

"Method of Testing Air Cleaning Devices Used in tion, and Testing of High.Efficiency Air Filtration General Ventilation for Removing Particulate Matter," Systems for Nuclear Application," ORNL-NSIC-65,Oak Section 9. 'Copies may be obtained from American Ridge National Laboratory, January 1970. Copies may Society of Heating, Refrigerating and Air.Conditioning be obtained from National Technical Information Engineers, Inc., United Engineering Center, 345 East Service, U. S. Department of Commerce, Springfield,

47th Street, New York, New York 10017. Virginia 2215 1.

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OFFICIAL BUSINESS NEOULATOXV COMMISSION

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