Regulatory Guide 3.12: Difference between revisions

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{{Adams
{{Adams
| number = ML003740232
| number = ML102730431
| issue date = 08/31/1973
| issue date = 12/31/2010
| title = General Design Guide for Ventilation Systems of Plutonium Processing & Fuel Fabrication Plants
| title = (Draft Was Issued as DG-3034, Dated July 2008), General Design Guide for Ventilation Systems of Plutonium Processing and Fuel Fabrication Plant
| author name =  
| author name =  
| author affiliation = NRC/RES
| author affiliation = NRC/RES
Line 9: Line 9:
| docket =  
| docket =  
| license number =  
| license number =  
| contact person =  
| contact person = Hicks, Angelisa L., 301-251-7448  RES/DE
| document report number = RG-3.12
| case reference number = DG-3034
| document report number = RG 3.12, Rev 1
| package number = ML102730357
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 6
| page count = 9
}}
}}
{{#Wiki_filter:August 1973 U.S. ATOMIC ENERGY COMMISSION
{{#Wiki_filter:The NRC issues regulatory guides to describe and make available to the public methods that the NRC staff considers acceptable for use in implementing specific parts of the agencys regulations, techniques that the staff uses in evaluating specific problems or postulated accidents, and data that the staff needs in reviewing applications for permits and licenses.  Regulatory guides are not substitutes for regulations, and compliance with them is not required.  Methods and solutions that differ from those set forth in regulatory guides will be deemed acceptable if they provide a basis for the findings required for the issuance or continuance of a permit or license by the Commission.
                              REGULATORY
 
                                DIRECTORATE OF REOULATORY STANDARDS
This guide was issued after consideration of comments received from the public.
                                                                                                                                GUIDE
 
                                                                REGULATORY GUIDE 3.12 GENERAL DESIGN GUIDE FOR VENTILATION SYSTEMS
Regulatory guides are issued in 10 broad divisions:  1, Power Reactors; 2, Research and Test Reactors; 3, Fuels and Materials Facilities; 4, Environmental and Siting; 5, Materials and Plant Protection; 6, Products; 7, Transportation; 8, Occupational Health;
                        OF PLUTONIUM PROCESSING AND FUEL FABRICATION PLANTS
9, Antitrust and Financial Review; and 10, General.
 
Electronic copies of this guide and other recently issued guides are available through the NRCs public Web site under the Regulatory Guides document collection of the NRCs Electronic Reading Room at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession No. ML102730431.  The regulatory analysis may be found in ADAMS under Accession No. ML102730449.
 
U.S. NUCLEAR REGULATORY COMMISSION  
December 2010
Revision 1
 
REGULATORY GUIDE
 
OFFICE OF NUCLEAR REGULATORY RESEARCH
 
REGULATORY GUIDE 3.12 (Draft was issued as DG-3034, dated July 2008)
 
GENERAL DESIGN GUIDE FOR VENTILATION SYSTEMS OF
PLUTONIUM PROCESSING AND FUEL FABRICATION  
PLANTS  


==A. INTRODUCTION==
==A. INTRODUCTION==
Ventilation systems are important to safety because they serve as principal confinement barriers in a multiple Each applicant for a license to possess and use                                confinement barrier system which guards against the special nuclear material in a plutonium processing and                               release of radioactive or other potentially dangerous fuel fabrication plant as defined in § 70.4 (r) of 10 CFR                            materials during normal or abnormal conditions.
This guide describes a method that the staff of the U.S. Nuclear Regulatory Commission (NRC)
considers acceptable for use in complying with Title 10, Section 70.23(a)(3), of the Code of Federal Regulations (10 CFR 70.23(a)(3)) (Ref. 1), and 10 CFR 70.23(a)(4) on the design of ventilation systems for plutonium processing and fuel fabrication plants.  At plutonium processing and fuel fabrication plants, a principal risk to health and safety is the release and dispersal of radioactive materials.  The prevention of such release and dispersal is an important function of the ventilation systems.  To meet these objectives, this guide provides recommendations for achieving defense in depth and for minimizing the release of radioactive materials to the environment.


Part 70, "Special Nuclear Material," must satisfy the                                 Ventilation systems will be subject to variations in provisions of § 70.23, "Requirements for the Approval                                 operating temperatures and pressures and to of Applications." Paragraphs (aX3) and (4) of § 70.23                                 environmental conditions associated with normal require that the applicant's proposed equipment and                                  operation, maintenance, plant shutdown, and testing.
Each applicant for a license to possess and use special nuclear material in a plutonium processing and fuel fabrication plant, (as defined in 10 CFR 70.4, Definitions,) must satisfy the provisions of  
10 CFR 70.23, Requirements for the Approval of Applications. The regulations at 10 CFR 70.23(a)(3)  
and 10 CFR 70.23(a)(4) require that the applicants proposed equipment, facility, and procedures be adequate to protect health and minimize danger to life or property.


facilities and proposed procedures be adequate to                                    They may also be subject to effects of natural protect health and minimize danger to'life or property.                               phenomena such as seismic motion and floods, missiles, fire and explosion, and other accidents.
Rev. 1 of RG 3.12, Page 2 This regulatory guide contains information collection requirements covered by 10 CFR Part 70,  
and that the Office of Management and Budget (OMB) approved under OMB control number 3150-0009.


At plutonium processing and fuel fabrication plants, a principal risk to health and safety is the release and                                    The systems must continue to perform their safety dispersal of radioactive materials. The prevention of such                            functions effectively under all conditions by confining release and dispersal is an important function of the                                 radioactive or other potentially dangerous materials. The ventilation systems. This regulatory guide presents                                  systems must assure that the concentration of methods acceptable to the Regulatory staff for                                        radioactive materials in the effluent gases is as low as complying with § § 70.23 (aX3) and (aX4) with respect                                practicable.
The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number. The NRC has determined that this Regulatory Guide is not a major rule as designated by the Congressional Review Act and has verified this determination with the OMB.


to the design of ventilation systems for plutonium processing and fuel fabrication plants.                                                     The continuity of necessary. ventilation can be assured by means such as standby equipment and
==B. DISCUSSION==
Ventilation systems for a plutonium processing and fuel fabrication plant may comprise the air supply, recirculating air, process ventilation, and exhaust air systems together with associated air filters, fans, dampers, ducts, and control instrumentation. The air supply system draws in and conditions fresh air and distributes it throughout the plant.  A portion of the supply air enters the process ventilation system through gloveboxes, hoods, and other components and is removed together with other plant air through the exhaust ventilation system, which discharges through a stack to the environment. A portion of the ventilation air in occupied areas may be recycled to the air supply system through the recirculating air system.


==B. DISCUSSION==
Ventilation systems are important to safety and are crucial to protect workers, the public, and the environment because they serve as principal confinement barriers in a multiple confinement barrier system that guards against the release of radioactive or other potentially dangerous materials during normal or abnormal conditions.  Ventilation systems will be subject to variations in operating temperatures and pressures and to environmental conditions associated with normal operation, maintenance, plant shutdown, and testing.  They may also be subject to the effects of natural phenomena such as seismic motion, floods, tornadoes, hurricanes and other tropical storms, missiles, fires, explosions, and other accidents.
fail-safe control systems. The ability of the systems to perform their safety functions effectively can be assured Ventilation systems for a plutonium processing and                             by periodic testing of safety-related components during fuel fabrication plant may consist of air supply,                                     normal operation of the systems to demonstrate their recirculating air, process ventilation, and exhaust air                              ability to perform at design efficiency andto verify their systems together with associated air filters, fans,                                  availability for emergencies.
 
The systems may be required to continue to perform their safety functions effectively under all conditions by confining radioactive or other potentially dangerous materials.  The systems also contribute to meeting the as low as reasonably achievable criteria in 10 CFR Part 20, Standards for Protection against Radiation (Ref. 2).  


dampers, ducts, and control instrumentation. The air supply system draws in and conditions fresh air and                                                    
The continuity of necessary ventilation can be ensured by such means as standby equipment and fail-safe control systems. The ability of the systems to perform their safety functions effectively can be ensured by periodic testing of safety-related components during normal operation of the systems to demonstrate their ability to perform at the assumed efficiency and to verify their availability and reliability for emergencies.


==C. REGULATORY POSITION==
==C. REGULATORY POSITION==
distributes it throughout the plant. A portion of supply air enters the process ventilation system through glove                                    The ventilation systems of a plutonium processing boxes, hoods, and other components and is removed                                    and fuel fabrication plant should assure the confinement together with other plant air through the exhaust                                    of hazardous materials during normal or abnormal ventilation system which discharges through a stack to                                conditions including natural phenomena, fire, and the environment. Part of the occupied-area ventilation                               explosion. The release of radioactive material to the air may be recycled to the air supply system through the                              environment, or to an area in which levels of recirculating air system.                                                             radioactivity are normally sufficiently low to permit USAEC REGULATORY GUIDES                                        copie of published guides nay be WAined by request indiating ft division desired to the US. Atomic Energy Commission, Weshington, Dr.. 20645.
Subpart H, Additional Requirements for Certain Licensees Authorized To Possess a Critical Mass of Special Nuclear Material, of 10 CFR Part 70, Domestic Licensing of Special Nuclear Material, requires the applicant to conduct an integrated safety analysis (ISA). Based on the ISA, the ventilation system may be designated as an item relied on for safety (IROFS) needed to ensure the confinement of hazardous materials during normal and abnormal conditions, including natural phenomena, fires, and explosions.  In addition, the release of radioactive material to the environment or to areas occupied by facility workers must meet the requirements of 10 CFR Part 20 and should be reduced to levels as low as reasonably achievable in accordance with 10 CFR Part 20.
 
Rev. 1 of RG 3.12, Page 3
1.
 
General Safety
 
a.
 
Consistent with the applicants ISA, the ventilation systems should have the general safety attributes described in this section.
 
b.
 
The ventilation systems should confine radioactive materials within the process areas as close to the point of origin as practicable.
 
c.
 
Confinement of radioactive materials should be provided by multiple zones.  Each zone should be bounded by barriers such as vessel and glovebox walls, building walls, and internal room walls.
 
The primary confinement zone should be the process ventilation system for gloveboxes, conveyors, transfer boxes, and other spaces that may contain dispersible plutonium or other radioactive materials during normal operations.  A secondary confinement zone should be the operating and other potentially contaminated areas surrounding the process equipment and gloveboxes.  A tertiary confinement zone should be provided in areas outside the secondary confinement zone to provide defense in depth between potentially contaminated areas and the environment.
 
d.
 
Pressure differentials should be maintained between building confinement zones and also between the building confinement zones and the outside atmosphere to ensure that airflow is from zones of lesser potential for contamination to zones of greater potential for contamination (i.e., from the environment into the building, to tertiary, secondary, and primary confinement zones). Devices should be provided to control and indicate pressure differentials between confinement zones.
 
Alarms should be provided to indicate when pressure differentials are not maintained in a prescribed range.
 
e.
 
Based on the results of the ISA, ventilation systems may be designated as IROFS and require that the failure of any one component (equipment or control device) will not affect the continuous operation of the ventilation system.  Ventilation systems and components designated as IROFS
may require fail-safe features with provision for alarm indication.


Regulatory Guide we Issued to describe and meks v41able to the public              Attention: Director of Regulatory Standards. Comments end egestlon for methods acceptable to the AEC Regulatory staff of kIplementing egecific parts of    Improvemnents In these guide amnd    encouraged    should be sent to die Secetay No Commission's reguletions, to delineate technklues used by the staff in          of the Commission. U.S. Atomic Enerny Commisin Wedhlno, D.C. 20M45.
f.


seifc problems or postulated eccidents, or to provide guidance to
Based on the results of the ISA, one or more onsite emergency power supply systems may be needed to operate the ventilation systems designated as IROFS.
      ,mlustinil                                                                    Attention: Chief. Public Proceedings Staff.


aplicents. Regulatory Guides ae not substitutes for reguletlons nd  Wcompliance wIth e is not equird. etods end solutions different from th              let out in The guids we Issued in the followig ten b        d    ons:
g.
the guides will be ecceptable If they provide a basis for the findings nequiste to goe Iuenc or continuerm of epermit or loiar by the Commission.                        1. Power Reactors                            . Products
                                                                                      2. Resserch md Test Reactors               


===7. Transportation===
Based on the results of the ISA, ventilation systems designated as IROFS may need to be designed to withstand the effects of fires and to maintain confinement during these events.  Such ventilation systems should have fire protection features such as fire doors and dampers or other proven devices to restrict the spread of fires, fire-resistant construction materials, fire-resistant filters, heat and smoke detectors, alarms, heat removal devices, and fire suppression equipment. The design of the fire protection systems should include provisions to protect against adverse effects in the event of the inadvertent operation or failure of the fire suppression system.
                                                                                      3. Fuels And Materials Facilities          L OccuptiOnal Health Published uides will be evised periodically. as appropriate, so accommodate          4. Enronmental end SIting                  9. Antitrust Review eonmients end to reflect new informaton or experIence.                              "S. Materials and Plant Protection          1


===0. General===
h.


personnel access, should be reduced to a level as low as        fires, fire-resistant materials of construction, practicable in accordance with the provisions of 10 CFR        fire-resistant filters, heat and smoke detectors, alarms, Part 20.                                                        heat removal devices, and fire-suppression equipment.
Based on the results of the ISA, air supply systems designated as IROFS may need to remain operational during fires.  Such systems should have the capability to shut off air supply to involved fire areas and should be designed to protect systems that are shut down from backflow.


The design of the fire protection system should include
i.
1.  General Safety                                            provisions to protect against adverse effects in the event of operation or failure of this system. For example, a a. The ventilation systems should confine                  drain system should be provided to prevent a criticality radioactive materials within the process areas as close to      incident in the event of water discharge on activation of the point of origin as practicable. They should also            a water spray heat removal system or in the event of confine and prevent uncontrolled release of radioactive        water leakage on failure of a heat removal system aerosols, noxious fumes, and vapors into rooms and              component, such as a spray nozzle, while the system is areas normally occupied by personnel.                          not in operation.


b. Confinement of radioactive materials should be                g. All ventilation systems should be capable of provided by multiple zones. Each zone is bounded by            operating during a fire in the areas they ventilate and barriers such as vessel and glove box walls, building          safely handle products of combustion through walls, and internal room walls. The primary confinement        appropriate ventilation channels. A supply air system zone (Zone I) should be the process ventilation system          should. remain operational; however, the option to for glove boxes, conveyors, transfer boxes, and other            discontinue air supply to the involved space or spaces spaces that may contain plutonium or other radioactive          should be maintained. Any system shut down should be materials during normal operations. A secondary                  protected from backflow.
Based on the results of the ISA, components in ventilation systems designated as IROFS should be fire resistant to protect against fires that occur within or outside the system. Such ventilation system components should meet the requirements in American Society of Mechanical Engineers (ASME) AG-1, Code on Nuclear Air and Gas Treatment, issued 2003 (Ref. 3).  


confinement zone (Zone III) should be the operating and other potentially contaminated areas surrounding                  h. The materials of construction i for the the process ventilation system. Areas inside the building,      ventilation systems should be fire resistant. to protect potentially free of 6ontamination and surrounding the          against fires occurring within or without the systems. All primary confinement zone, but interposed between                filters should be of a fire resistant type and, where Zones I and III, would constitute an additional                applicable, approved by Underwriters' Laboratories, secondary confinement zone (Zone II).
Rev. 1 of RG 3.12, Page 4 j.
                                                                Incorporated (UL). 1 Filters and exhaust fans, especially a final filter plenum and exhaust fan enclosure, should c. Pressure differentials should be maintained              be located where they are not exposed to the direct between building confinement zones and also between              effects of fire or explosion in the operating areas. Smoke the building confinement zones and the outside                  detectors and thermostats for fire detection, approved K
atmosphere to assure that aii flow is from zones of lesser      by UL,2 should be provided in the ventilation systems.


potential for contamination to zones of greater potential for contamination, i.e., from the environs into the                  i. Fire- and smoke-suppression equipment should building, thence to secondary and primary confinement            be so located as to assure that the integrity of final zones. Devices should be provided to control and                high-efficiency filters or filter systems is not degraded.
Based on the results of the ISA, ventilation systems designated as IROFS should have fire and smoke suppression equipment to ensure that the integrity of high-efficiency particulate air (HEPA)
filters or filter systems are not degraded during fires.  Spark and flame arresters and isolation valves or dampers may be necessary to protect final HEPA filters from contact with hot particles and excessive soot loading beyond their design capacity.  (Final HEPA filters are those HEPA
filter banks located immediately upstream of the discharge stack and represent the final stages of particulate removal for the ventilation system.)  HEPA filters should meet the requirements in ASME AG-1.


indicate pressure differentials between confinement            Spark and flame arresters and isolation valves may be zones. Alarms should be provided to indicate when              used at filter installations in intermediate stages of pressure differentials are not maintained in a prescribed      effluent cleaning. A heat removal system should precede range.                                                          the first stage of a high-efficiency filtration system d. All ventilation systems should be designed so          serving as a final means of effluent cleaning (see that the failure of any one component (equipment or            regulatory position C.8.e).
k.
control device) will not affect the continuous operation            j. If sources of combustible solvents, gases, and      .1 of the ventilation systems. Ventilation systems and            vapors are identified or postulated to be present in a components should have fail-safe features with provision        ventilation system under normal or abnormal conditions, for alarm indication.                                          they should be monitored by suitable continuous e. Onsite emergency power supply systems should            monitoring systems as specified in Regulatory Guide be provided to operate the ventilation systems and              3.7.3 components as well as other systems and components                    k. The ventilation systems should be designed to important to safety. Ventilation systems should be              withstand tornado conditions without loss of capable of operating, during normal power outage, at            confimement capability due to mechanical damage to the capacities required to maintain confinement of                  system or components or due to the reduced ambient contaminants. The onsite emergency power sources and            pressure at the intake and exhaust openings of the the electrical distribution circuits should have                building. Protection against missiles should be provided independence and testability to assure performance of          for the intake and exhaust openings.


their safety functions assuming a single failure.
Based on the results of the ISA, the design of ventilation systems designated as IROFS may need to consider combustible or explosive solvents, gases, or vapors.  The applicant should consider the continuous monitoring of such materials with suitable monitoring systems that can function under normal and abnormal conditions as dictated by the ISA.


f. The ventilation systems should be designed to                1. Components of the ventilation systems should withstand any credible fire and explosion and continue          be designed to withstand the effects of earthquakes and to act as confinement barriers. Fire protection features        remain functional to the extent that they will prevent    K
l.
of the ventilation systems should include fire doors and        the uncontrolled release of radioactive materials to the dampers or other proven devices to restrict the spread of environment.


3.12-2
Based on the results of the ISA, ventilation systems designated as IROFS should be designed to withstand tornado, hurricane, and other tropical storm conditions without the loss of confinement capability because of mechanical damage to the system or components or because of reduced ambient pressure at the intake and exhaust openings.  Protection against missiles generated by tornadoes may also be needed at the intake and exhaust openings.


2.  Occupied-Area Ventilation Systems                            3 Process Ventilation Systems
m.
                                                                          3.


a. Supply air should be properly conditioned and                  a. Air or inert gas should enter each ventilated distributed at or near the ceiling to the potentially            glove box or process enclosure through at least one contaminated areas of the facility.                              fire-resistant HEPA filter and be discharged through at b. Outdoor makeup air supply units should be                least one fire-resistant HEPA filter to exhaust ductwork protected from the weather. For example, intakes                  leading to a final filter system (see regulatory position should be arranged so as to minimize the effects of high          C.8.e). The inlet filter prevents any backflow of winds, rain, snow, ift, and debris on the operation of the        contaminants into the work areas, and the outlet filter system. Heaters may be necessary in areas where icing              minimizes contamination of the exhaust ductwork.
Based on the results of the ISA, ventilation systems designated as IROFS may need to be designed to withstand the effects of seismic conditions without the loss of confinement or system function to prevent an uncontrolled release of radioactive materials to the environment.


can cause significant supply filter damage. Screens should be provided over supply air inlets to protect                    b. All process ventilation systems should have moisture separators and filters from wind-blown debris.            adequate capacity and appropriate controls to maintain at least 125 linear feet per minute inward air flow c. Air from each Zone II or Zone III area should            through the maximum credible breach and thereby be removed near the floor through, individual area grills          prevent the escape of particulates.
2.


or registers, each equipped with a fire-resistant                        c.  Air or inert gas from glove boxes or other medium-efficiency filter. The filter should have an                process enclosures where wet chemical operations take atmospheric dust spot efficiency 4 rating of                      place should be treated to protect the ventilation approximately 90% or better. Filtered air can be                    ductwork, final filters, and filter plenums from exposure recirculated or can be discharged through an exhaust              to wetting or deleterious chemical attack.
Ventilation Systems in Occupied Areas


ventilation system.                                                      d. Consideration should be given to recirculation d. Part of the Zone II ot Zone Ill filtered air may of exhaust air or inert gas to glove boxes and other be recirculated to reduce thermal loads. The point of            process enclosures to minimize release of radionuclides Zone II or Zone III air withdrawal should be selected so          to the biosphere. If recirculation is used, the exhaust gas that Zone I air streams cannot be drawn into the Zone 11          from these enclosures should be filtered through two or Zone Ill air supply. Local exhaust effluent that may            stage's of fire-resistant HEPA filters in series before being contain noxious, toxic, or corrosive gases and vapors              recirculated.
a.


should not be recirculated into a Zone 11or Zone IIl area. Recirculated air should be passed through two
Based on the results of the ISA, supply air systems designated as IROFS should be provided to ensure the adequate control and proper functioning of each confinement zone.  Supply air should be conditioned to maintain the design control parameters of temperatures and humidity. Supply air systems should be provided with filters to remove incoming particulate matter for controlling contamination within the confinement zones and for reducing the dust loading on filters in the final filtration assemblies.
+,,  stages of fire-resistant high-efficiency particulate air           4.    Fans (HEPA) filters in series'before it is returned to Zone I]
    or Zone I11 areas.                                                      a. Installed spare fans and isolation dampers e. Provision should be made for continuous                  should be provided for the supply air and exhaust air monitoring of recirculated air prior to the second stage          systems. When any one fan is inoperative in a system, a of' HEPA filtration. Upon an indication that the limits            backflow damper should automatically isolate the idle for soluble isotopes of plutonium specified in Table 1,            fan from the system. Standby fans should automatically Column I of Appendix B to 10 CFR Part 20 or in the                start and have sufficient capacity to maintain minimum license conditions have been exceeded, the air in the             system air flow.


recirculating system should be diverted to a                            b. Alarms should be provided to indicate once-through exhaust ventilation system for discharge              malfunction of each ventilation fan (see regulatory through a final filter plenum. The point of diversion of          position C5.f).
b.
    Zone I1 or Zone Ill filtered air into the once-through                    c. Supply air fans should be interlocked with an exhaust ventilation system should be prior to the heat            exhaust air plenum pressure sensor to prevent supply fan removal system preceding the final filter plenum.                  operation unless the exhaust fans are running. This will Recirculation of Zone I1or Zone Ill air may be resumed            prevent pressurization of any process room or area on correction of offending operations and/or equipment            should exhaust ventilation fail.


deticicncies.                                                            d. Emergency power should be supplied to fans in f. A final filter plenum should have at least two            the, event of failure of the normal power supply (see stages of fire-resistant HEPA filters in series. HEPA            regulatory position C.le).
Air in the secondary and tertiary confinement zones may be recirculated. Based on the results of the ISA, the ventilation system design should consider the need for HEPA filtration and removal of radioactive and chemical contaminants in recirculated air streams before the air is returned to secondary and tertiary confinement zones. The design should also consider the continuous monitoring of recirculated air streams and the capability to exhaust the recirculated air directly to the final filtration assemblies in the event that contaminant levels exceed safe occupational levels.
    filters should be designed to military specifications MIL-F-51068Cs and MIL-F-51079A6 and should satisfy                S. Ventilation System Construction and Layout the requirements of UL-586. 7 Final filtration systems incorporating high-efficiency filters other than HEPA                    a. The material of construction for the ventilation filters and having equivalent efficiency and resistance to        systems should be carefully selected according to such fire are also acceptable (see regulatory, positions C.8.e.        safety considerations as strength to withstand accident and C.8.g).                                                      conditions; corrosion resistance, particularly when g. The filtered ait should be discharged to the             associated with chemical processes; fire resistance; long environs through a stack of sufficient height to reduce          operating life 'to avoid frequent replacement of close-in ground-level concentrations of radioactive or            contaminated equipment; and smooth surface finish to other potintially dangerous contaminants.                        aid in decontamination.


3,12-3
3.


b. Ducts and housings should be designed,                given to locating continuously operating exhaust fabricated, and erected with a minimum of ledges,              samplers after each stage of HEPA filtration.
Process Ventilation Systems


protrusions, and crevices that could collect dust -and                e. In addition to a local station alarm, the CAMS
a.
moisture or that could impede personnel or create a            and stack monitoring systems should have readout and hazard in performance of their work. Duct runs and flow        alarm panels in the central control area(s).
distributors should assure uniform, representative air flow past monitoring and sampling stations as well as          7.    Glove Boxes and Other Process Enclosures through filter installations.


a. Glove boxes. should be constructed using the c. The design should permit convenient                  highest quality of materials and workmanship to assure inspection, maintenance, decontamination, and/or              total containment and minimize leakage. Combustible replacement of critical components such as filters, fans,      materials that are an integral part of the glove box and dampers.                                                  should be held to a minimum.
Based on the results of the ISA and process control specifications, the supply air and inert gases to gloveboxes and process equipment may require conditioning to control temperature and humidity.


d. Housings, filter mounting frames, and ducts                b. The design of enclosures should be based on should be designed to withstand system pressure changes        downdraft ventilation flow to minimize the spread of without distortion, fatigue, or yielding of such              fire. Heat detectors and combustible gas and vapor magnitude that inleakage or bypassing of the filters          detection meters should be provided on glove boxes or results.                                                        enclosures where fire or explosion hazards exist.
Humidity control may also be necessary for criticality safety. Supply air should be provided consistent with the recommendations in Regulatory Position 2.a of this guide.


e. Supply, recirculation, process ventilation, and      Automatic fire suppression equipment should be exhaust ducting should incorporate manual and                  provided in these boxes or enclosures. Where automatic automatic dampers and controls to distribute and                systems are not required, fire detectors should be regulate the movement of air in each room, area, and            installed and provisions made for manual fire ventilation system and to prevent possible backflow in          suppression.
b.


case of pressure reversal.                                            c. Small glove box or enclosure systems supplied f. The ventilation systems should be appropriately        with gases under positive pressure should have instrumented to read out and alarm in one or more              positive-acting pressure-relief devices (discharging into an central control areas. These areas should be designed to       exhaust system) to prevent overpressurization. Further, permit occupancy and actions to be taken to operate the         should these systems be recirculating, all necessary ventilation systems safely during normal or abnormal            cleanup and detection equipment for noxious, corrosive, conditions.                                                    or explosive vapors or gases.should be considered.
Based on the results of the ISA, supply air and inert gases may need to be introduced into primary confinement zones through at least one HEPA filter and be discharged through at least one HEPA
filter to the exhaust duct leading to the final filtration assemblies. (Final filtration assemblies are


d. The glove box or enclosure design should
Rev. 1 of RG 3.12, Page 5 those filter assemblies located immediately upstream of the discharge stack and represent the final stages of contaminant removal for the ventilation system.)  The inlet HEPA filters should be designed to prevent the backflow of contaminants into supply ducts, and the outlet HEPA filters should provide contamination and criticality control in the exhaust ductwork.
6. Ventilation System Testing and Monitoring                    permit filter replacement with minimum exposure to
                                                                "personnel performing this task and with minimum a. Provisions should be made so that components          release of contaminants to the environment outside of of ventilation systems can be tested periodically for          the glove box or enclosure.


operability and required functional performance. They                e. The minimum instrumentation for a glove box should include capability for periodic measurement of          or enclosure ventilation system should include devices to air flows in exhaust ducts and in or at equipment, hoods,      indicate the pressure differential between the box or and glove boxes.                                                enclosure and the surrounding work area, the filter b. The capability should be provided to test,            resistance, and the exhaust flow rate from the box or under conditions as close to design as practicable, the        enclosure. When box operations are not in full-time operating sequence that wotild briig ventilation systems        attendance for a continuous process, a sensor should be into action, including the transfer to alternate power          provided to monitor abnormal pressure or temperature sources and the design air flow delivery capability.            and alarm at a point where cognizant personnel are c. All exhausting ducts and stacks which may              stationed.
c.


contain plutonium contaminants should be provided with two monitoring systems: a continuous monitor             
Based on the results of the ISA, gloveboxes designated as IROFS should be designed to minimize contaminant releases in the event of credible breaches.  Such designs should provide adequate capacity and controls to maintain an inward airflow of at least 125 linear feet per minute through the maximum credible breach.


===8. Filtration Systems===
d.
  [Continuous Air Monitoring System (CAMS)) and a fixed sampler. The probes for sampling purposes should                a. Each exhaust filter housing should have a rigid be designed for isokinetic sampling and located to obtain      mounting frame for the filter. The complete housing representative samples. Each system should be                  structure should have minimum leakage from outside to connected to an emergency power supply (see regulatory        inside, inside to outside, or across the filter sealing position C.l.e). The continuous stack sampler should          barrier (exclusive of the filter).
  alert cognizant personnel through an audible and visual              b. The filter access opening in these housings annunciator if the airborne radioactive effluents reach        should permit filter removal and replacement with prescribed limits.                                            minimum exposure to personnel performing this task d. Air monitoring and warning systems (including        and with minimum release of contaminants outside of CAMS) should be installed in areas where radioactive            the housing.


material is handled. Air sampling heads should provide a            c. The filter housings should be equipped with represrntative sample of the potential airborne                necessary test ports to permit reliable in-place testing of radioactivity being breathed. Consideration should be         all filter stages with dioctyl phthalate (DOP).
Based on the results of the ISA, the exhaust flow from gloveboxes and process equipment, which are designated as IROFS and are associated with wet chemical operations, should be treated to protect exhaust ductwork and downstream filtration units from wetting and chemical attack.
                                                          3.12-4


d. Damper valves should be so located that a bank                  f. HEPA filter systems should be tested after filter of filters can be completely isolated from the ventilation          installation using a !'cold DOP" test. Acceptance should systems during filter replacement operations.                        be based on an efficiency. of 99.95% or better for DOP
e.
      e. A HEPA filtration system serving as a final                having a light-scattering mean 'diameter of approximately means of effluent cleaning should have at least two                  0.7 microns. Regular in-place testing of both on-line and stages of fire-resistant filters in series in a filter plenum.      standby filter installations should be performed because A heat removal system and a spark arrester should                    of system deterioration that can take place even when precede the first stage of filters. If a cooling spray such          the installations are not being used. Test procedures used as a water spray system is used for heat removal, it                should comply with the recommendations contained in should be followed by a combination spark                            ORNL-NSIC-65, "Design, Construction and Testing of arrester/demister screen to also remove entrained                    High-Efficiency Air Filtration Systems for Nuclear droplets, thereby protecting filters from plugging and              Application"s and in Regulatory Guide 3.2.'
damage. A roughing filter should be mounted behind                        g. Final filtration systems Incorporating these components to -remove the bulk- of the                        high-efficiency filters other than HEPA filters and having draft-carried debris so as to avoid loading the HEPA                  equivalent efficiency and resistance to fire are also filters installed downstream.                                        acceptable.


The cooling spray system should operate automatically (with a manual override) upon abnormal heat rise in the cooling chamber inlet indicated by                  9.  Quality Assurance Program detectors in exhaust ducts feeding the filter plenum. A
Based on the results of the ISA, if exhaust air or inert gases from gloveboxes and process equipment are recirculated, ventilation system designs should provide for HEPA filtration and the removal of chemical contaminants in recirculated air streams before the air is returned to the gloveboxes and process equipment. The design should also consider the continuous monitoring of recirculated air and inert gas streams and the capability to exhaust the recirculated air and inert gases directly to the final filtration assemblies in the event that contaminant levels exceed process and contamination control objectives.
manually operated valve actuating the spray system                        A quality assurance program should be established should also be provided as a backup. If a drain system is            for the design, construction, testing, operation, and installed to prevent accumulation of liquid in the                   maintenance of all structures, systems, and components plenum, the collection tanks should be of favorable                  addressed in this guide in accordance with the criteria in geometry.                                                            Appendix B of 10 CFR Part 50.


3.12-5
4.


REFERENCES
Fans
1. Underwriters' Laboratories Building Materials List            Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, Pa. 19120.


(latest edition). Copies may be obtained from Underwriters' Laboratories, Inc.,.207 -East Ohio
a.
                                                              6.  MIL-F-51079A, "Filter Medium, Fire-Resistant, Street, Chicago, IlI. 60611.


High-Efficiency," Military Specification. Copies may be obtained fropt Commanding Officer, Naval
Based on the results of the ISA, ventilation systems designated as IROFS should have redundant fans and isolation dampers for the supply and exhaust air systems. (Supply air systems include filters and fans that supply fresh outside air into the facility.  Exhaust air systems include filters and fans that discharge ventilation air and process gases from the facility.) Controls should be provided to automatically start redundant fans and automatically isolate idle fans with backflow dampers.
2.  Underwriters' Laboratories Fire Protection Publications and Forms Center;. .5801 Tabor Equipment List (latest edition). Copies may be                 Avenue, Philadelphia, Pa. 19120.


obtained from Underwriters' Laboratories, Inc., 207 East Ohio Street, Chicago, Ill. 60611.
b.


7.  Underwriters' Laboratories' Standard UL-586,
Based on the results of the ISA, fans designated as IROFS should be provided with alarms to indicate fan malfunctions.
                                                                  "High-Efficiency    Air Filtration Units," (also
3.  Regulatory Guide 3.7, "Monitoring of Combustible designated ANSI B 132.1-1971). Copies may be Gases and Vapors in Plutonium Processing and Fuel obtained from Underwriters' Laboratories, Inc., 207 Fabrication Plants," Directorate of Regulatory Standards, USAEC,.                                            East Ohio Street, Chicago, Il. 60611.


4.  ASHRAE (American Society of Heating,                      8.  C. A. Burchsted and A. B. Fuller, "Design, Refrigerating and Air Conditioning Engineers)                Construction, and Testing of High-Efficiency Air Standard 52-68, "Method of Testing Air Cleaning              Filtration Systems for Nuclear Application,"
c.
    Devices Used in General Ventilation for Removing              ORNL-NSIC-65, Oak Ridge National Laboratory, Particulate Matter," Section 9. Copies may be                January 1970. Copies may be obtained from obtained from American Society of Heating,                    National Technical Inf6rmation Service, U.S.


Refrigerating and Air Conditioning Engineers, Inc.,           Department of Commerce, Springfield, Va. 2215 1.
Supply air fans, including those designated as IROFS based on the results of the ISA, should be interlocked with exhaust fans to prevent supply air fan operations unless the exhaust fans are in operation. This will prevent the pressurization of confinement zones in the event that the exhaust fans fail.
 
d.
 
Based on the results of the ISA, emergency power supplies may be needed for the operation of fans that are designated as IROFS.


United Engineering Center, 345 East 47th Street, New York, N.Y. 10017.                                      9.  Regulatory Guide 3.2, "Efficiency Testing of MIL-F-51068C, "Filter, Particulate, High.                      Air-Cleaning Systems Containing Devices for
5.
5.


Removal of Particles," Directorate of Regulatory Efficiency, .Fire-Resistant,' Military Specification.
Ventilation System Construction and Layout
 
a.
 
Based on the results of the ISA, ventilation systems designated as IROFS should use construction materials that are selected based on their strength to withstand accident conditions, corrosion resistance, fire resistance, and ease of decommissioning.
 
b.
 
Based on the results of the ISA, ventilation systems designated as IROFS should be designed and constructed in accordance with ASME AG-1.
 
Rev. 1 of RG 3.12, Page 6
6.
 
Ventilation System Inspection, Testing, and Monitoring
 
a.
 
Based on the results of the ISA, ventilation systems and components designated as IROFS should be designed so that they can be initially and periodically inspected and tested to ensure that they will be available and will perform reliably when they are needed to perform their functions.  Based on the results of the ISA, ventilation systems and components, including the ductwork and pressure boundaries, should be inspected and tested in accordance with the applicable provisions of ASME AG-1.
 
b.
 
Based on the results of the ISA, ventilations systems designated as IROFS should have a continuous air monitoring system (CAMS) to continuously obtain representative samples and monitor effluent releases.  The CAMS should have alarms at appropriate control rooms or areas.
 
Designation of the CAMS as an IROFS should be based on the results of the ISA.  Air monitoring and sampling systems should also be provided in occupied areas to alert workers of hazardous concentrations of radioactive or chemical materials.
 
7.
 
Gloveboxes and Other Process Enclosures
 
a.
 
Based on the results of the ISA, gloveboxes designated as IROFS should be designed, fabricated, tested, installed, operated, and inspected in accordance with American Glovebox Society (AGS)-G001, Guideline for Gloveboxes, issued 2007 (Ref. 4).
 
b.
 
Based on the results of the ISA, gloveboxes and process enclosures designated as IROFS should use materials that are selected based on their strength to withstand accident conditions, corrosion resistance, fire resistance, and ease of decommissioning.  This equipment should use fire detectors, combustible gas and vapor detection, pressure relief devices, and fire suppression designed for the materials and processes used within the gloveboxes and enclosures.  Downdraft ventilation should be considered to minimize the spread of fires.
 
c.
 
Based on the results of the ISA, gloveboxes and process enclosures designated as IROFS should have differential pressure sensors and alarms to ensure that pressure differentials between confinement zones are maintained.
 
d.
 
Based on the results of the ISA, gloveboxes and process enclosures designated as IROFS should be tested for leaks, containment integrity, and ventilation flow in accordance with the provisions in AGS-G001.
 
8.
 
Filtration Systems
 
a.
 
Based on the results of the ISA, filter components and assemblies designated as IROFS should be designed, fabricated, inspected, tested, stored, handled, packaged, shipped, and received in accordance with ASME AG-1.
 
b.
 
Based on the results of the ISA, filter assemblies designated as IROFS should have at least two banks of HEPA filtration.  In addition, filter assemblies should have prefilters and roughing filters to reduce HEPA filter dust loadings and to protect HEPA filters from hot particles.  Other filtration systems with removal efficiencies equivalent to HEPA filters may also be used.
 
c.
 
If credit is taken for HEPA filters in the ISA, those HEPA filters should be tested in place in accordance with ASME AG-1 initially when placed into service and periodically thereafter to
 
Rev. 1 of RG 3.12, Page 7 ensure that they will be available and reliable to perform their intended function.  HEPA filter banks should demonstrate an efficiency of at least 99.95 percent using a polydisperse dioctylphthalate penetrant that has a light-scattering mean diameter of approximately 0.7 microns.
 
Penetrants equivalent to polydisperse dioctylphthalate may also be used.
 
9.
 
Management Measures
 
Management measures should be established for the design, fabrication, installation, testing, inspection, operation, and maintenance of ventilation systems designated as IROFS consistent with the results of the ISA, the quality assurance requirements in 10 CFR 70.22(f) and the requirements in Subpart H of 10 CFR Part 70.
 
==D. IMPLEMENTATION==
The purpose of this section is to provide information on how applicants and licensees may use this guide and information regarding the NRCs plans for using this Regulatory Guide.  In addition, it describes how the NRC staff has complied with the Backfit Rule in 10 CFR 70.76.
 
Applicant and Licensees Use
 
Applicants and licensees may (i.e., voluntarily) use the information in this regulatory guide to develop applications for initial licenses, amendments to licenses, or other requests for NRC regulatory approval (e.g., exemptions).  Licensees may use the information in this regulatory guide for actions which do not require prior NRC review and approval.  Licensees may use the information in this Regulatory Guide or applicable parts to resolve regulatory or inspection issues (e.g., by committing to comply with provisions in the regulatory guide).
 
Current licensees may continue to use the guidance that was found acceptable for complying with specific portions of the regulations as part of their license approval process, which may be a previous version of this Regulatory Guide.
 
A licensee who believes that the NRC staff is inappropriately imposing this Regulatory Guide as part of a request for a license amendment or request for a change to a previously issued NRC regulatory approval may file a backfitting appeal with the NRC in accordance with applicable procedures.
 
NRC Staff Use
 
The NRC staff does not intend or approve any imposition or backfitting of the guidance in this Regulatory Guide.  The staff does not expect any existing licensee to use or commit to using the guidance in this Regulatory Guide in the absence of a licensee-initiated change to its licensing basis.  The NRC staff does not expect or plan to request licensees to voluntarily adopt this Regulatory Guide to resolve a generic regulatory issue.  The NRC staff does not expect or plan to initiate NRC regulatory action which would require the use of this regulatory guide without further back-fit consideration.
 
During inspections of specific facilities, the staff may suggest or recommend that licensees consider various actions consistent with staff positions in this regulatory guide.  Such suggestions and recommendations would not ordinarily be considered backfitting even if prior versions of this Regulatory Guide are part of the licensing basis of the facility with respect to the subject matter of the inspection.
 
However, the staff may not represent to the licensee that: (i) the licensees failure to comply with the positions in this Regulatory Guide constitutes a violation; (ii) the licensee may avoid the violation by
 
Rev. 1 of RG 3.12, Page 8 agreeing to comply with this Regulatory Guide; or (iii) the only acceptable way for the licensee to address the NRC-identified non-compliance or violation is to commit to this Regulatory Guide (i.e., including this Regulatory Guide in the facilitys licensing basis).
 
If an existing licensee seeks a license amendment or change to an existing regulatory approval, and the staffs consideration of the request involves a regulatory issue which is directly relevant to this Regulatory Guide and the specific subject matter of the new or revised guidance is an essential consideration in the NRC staffs determination of the acceptability of the licensees request, the staff may require the licensee to use this Regulatory Guide or its equivalent as a prerequisite for NRC approval.  This is not considered backfitting as defined in 70.76(a)(1).
 
Conclusion
 
This regulatory guide is not being imposed upon current licensees and may be voluntarily used by existing licensees.  In addition, this Regulatory Guide is issued in conformance with all applicable internal NRC policies and procedures governing backfitting.  Accordingly, the NRCs staff issuance of this regulatory guide is not considered backfitting, as defined in 70.76(a)(1).
 
Rev. 1 of RG 3.12, Page 9 REFERENCES1 
 
1.
 
10 CFR Part 70, Domestic Licensing of Special Nuclear Material, U.S. Nuclear Regulatory Commission, Washington, DC.
 
2.
 
10 CFR Part 20, Standards for Protection against Radiation, U.S. Nuclear Regulatory Commission, Washington, DC.
 
3.
 
ASME AG-1, Code on Nuclear Air and Gas Treatment, American Society of Mechanical Engineers, New York, NY, 2003, and applicable addenda.2
 
4.
 
AGS-G001, Guideline for Gloveboxes, American Glovebox Society, Santa Rosa, CA, 2007.


Standards, USAEC.
1 Publicly available NRC published documents are available electronically through the Electronic Reading Room on the NRCs public Web site at: http://www.nrc.gov/reading-rm/doc-collections/.  The documents can also be viewed online or printed for a fee in the NRCs Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD; the mailing address is USNRC PDR, Washington, DC 20555; telephone 301-415-4737 or (800) 397-4209; fax (301) 415-3548;
and e-mail pdr.resource@nrc.gov.


Copies may be obtained from Commanding Officer, K
2 Copies of American Society of Mechanical Engineers (ASME) standards may be purchased from ASME, Three Park Avenue, New York, NY 10016-5990; telephone (800) 843-2763.  Purchase information is available through the ASME
                                                          3.12-6}}
Web-based store at http://www.asme.org/Codes/Publications/.}}


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Revision as of 02:43, 14 January 2025

(Draft Was Issued as DG-3034, Dated July 2008), General Design Guide for Ventilation Systems of Plutonium Processing and Fuel Fabrication Plant
ML102730431
Person / Time
Issue date: 12/31/2010
From:
Office of Nuclear Regulatory Research
To:
Hicks, Angelisa L., 301-251-7448 RES/DE
Shared Package
ML102730357 List:
References
DG-3034 RG 3.12, Rev 1
Download: ML102730431 (9)
v • d • e


The NRC issues regulatory guides to describe and make available to the public methods that the NRC staff considers acceptable for use in implementing specific parts of the agencys regulations, techniques that the staff uses in evaluating specific problems or postulated accidents, and data that the staff needs in reviewing applications for permits and licenses. Regulatory guides are not substitutes for regulations, and compliance with them is not required. Methods and solutions that differ from those set forth in regulatory guides will be deemed acceptable if they provide a basis for the findings required for the issuance or continuance of a permit or license by the Commission.

This guide was issued after consideration of comments received from the public.

Regulatory guides are issued in 10 broad divisions: 1, Power Reactors; 2, Research and Test Reactors; 3, Fuels and Materials Facilities; 4, Environmental and Siting; 5, Materials and Plant Protection; 6, Products; 7, Transportation; 8, Occupational Health;

9, Antitrust and Financial Review; and 10, General.

Electronic copies of this guide and other recently issued guides are available through the NRCs public Web site under the Regulatory Guides document collection of the NRCs Electronic Reading Room at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession No. ML102730431. The regulatory analysis may be found in ADAMS under Accession No. ML102730449.

U.S. NUCLEAR REGULATORY COMMISSION

December 2010

Revision 1

REGULATORY GUIDE

OFFICE OF NUCLEAR REGULATORY RESEARCH

REGULATORY GUIDE 3.12 (Draft was issued as DG-3034, dated July 2008)

GENERAL DESIGN GUIDE FOR VENTILATION SYSTEMS OF

PLUTONIUM PROCESSING AND FUEL FABRICATION

PLANTS

A. INTRODUCTION

This guide describes a method that the staff of the U.S. Nuclear Regulatory Commission (NRC)

considers acceptable for use in complying with Title 10, Section 70.23(a)(3), of the Code of Federal Regulations (10 CFR 70.23(a)(3)) (Ref. 1), and 10 CFR 70.23(a)(4) on the design of ventilation systems for plutonium processing and fuel fabrication plants. At plutonium processing and fuel fabrication plants, a principal risk to health and safety is the release and dispersal of radioactive materials. The prevention of such release and dispersal is an important function of the ventilation systems. To meet these objectives, this guide provides recommendations for achieving defense in depth and for minimizing the release of radioactive materials to the environment.

Each applicant for a license to possess and use special nuclear material in a plutonium processing and fuel fabrication plant, (as defined in 10 CFR 70.4, Definitions,) must satisfy the provisions of

10 CFR 70.23, Requirements for the Approval of Applications. The regulations at 10 CFR 70.23(a)(3)

and 10 CFR 70.23(a)(4) require that the applicants proposed equipment, facility, and procedures be adequate to protect health and minimize danger to life or property.

Rev. 1 of RG 3.12, Page 2 This regulatory guide contains information collection requirements covered by 10 CFR Part 70,

and that the Office of Management and Budget (OMB) approved under OMB control number 3150-0009.

The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number. The NRC has determined that this Regulatory Guide is not a major rule as designated by the Congressional Review Act and has verified this determination with the OMB.

B. DISCUSSION

Ventilation systems for a plutonium processing and fuel fabrication plant may comprise the air supply, recirculating air, process ventilation, and exhaust air systems together with associated air filters, fans, dampers, ducts, and control instrumentation. The air supply system draws in and conditions fresh air and distributes it throughout the plant. A portion of the supply air enters the process ventilation system through gloveboxes, hoods, and other components and is removed together with other plant air through the exhaust ventilation system, which discharges through a stack to the environment. A portion of the ventilation air in occupied areas may be recycled to the air supply system through the recirculating air system.

Ventilation systems are important to safety and are crucial to protect workers, the public, and the environment because they serve as principal confinement barriers in a multiple confinement barrier system that guards against the release of radioactive or other potentially dangerous materials during normal or abnormal conditions. Ventilation systems will be subject to variations in operating temperatures and pressures and to environmental conditions associated with normal operation, maintenance, plant shutdown, and testing. They may also be subject to the effects of natural phenomena such as seismic motion, floods, tornadoes, hurricanes and other tropical storms, missiles, fires, explosions, and other accidents.

The systems may be required to continue to perform their safety functions effectively under all conditions by confining radioactive or other potentially dangerous materials. The systems also contribute to meeting the as low as reasonably achievable criteria in 10 CFR Part 20, Standards for Protection against Radiation (Ref. 2).

The continuity of necessary ventilation can be ensured by such means as standby equipment and fail-safe control systems. The ability of the systems to perform their safety functions effectively can be ensured by periodic testing of safety-related components during normal operation of the systems to demonstrate their ability to perform at the assumed efficiency and to verify their availability and reliability for emergencies.

C. REGULATORY POSITION

Subpart H, Additional Requirements for Certain Licensees Authorized To Possess a Critical Mass of Special Nuclear Material, of 10 CFR Part 70, Domestic Licensing of Special Nuclear Material, requires the applicant to conduct an integrated safety analysis (ISA). Based on the ISA, the ventilation system may be designated as an item relied on for safety (IROFS) needed to ensure the confinement of hazardous materials during normal and abnormal conditions, including natural phenomena, fires, and explosions. In addition, the release of radioactive material to the environment or to areas occupied by facility workers must meet the requirements of 10 CFR Part 20 and should be reduced to levels as low as reasonably achievable in accordance with 10 CFR Part 20.

Rev. 1 of RG 3.12, Page 3

1.

General Safety

a.

Consistent with the applicants ISA, the ventilation systems should have the general safety attributes described in this section.

b.

The ventilation systems should confine radioactive materials within the process areas as close to the point of origin as practicable.

c.

Confinement of radioactive materials should be provided by multiple zones. Each zone should be bounded by barriers such as vessel and glovebox walls, building walls, and internal room walls.

The primary confinement zone should be the process ventilation system for gloveboxes, conveyors, transfer boxes, and other spaces that may contain dispersible plutonium or other radioactive materials during normal operations. A secondary confinement zone should be the operating and other potentially contaminated areas surrounding the process equipment and gloveboxes. A tertiary confinement zone should be provided in areas outside the secondary confinement zone to provide defense in depth between potentially contaminated areas and the environment.

d.

Pressure differentials should be maintained between building confinement zones and also between the building confinement zones and the outside atmosphere to ensure that airflow is from zones of lesser potential for contamination to zones of greater potential for contamination (i.e., from the environment into the building, to tertiary, secondary, and primary confinement zones). Devices should be provided to control and indicate pressure differentials between confinement zones.

Alarms should be provided to indicate when pressure differentials are not maintained in a prescribed range.

e.

Based on the results of the ISA, ventilation systems may be designated as IROFS and require that the failure of any one component (equipment or control device) will not affect the continuous operation of the ventilation system. Ventilation systems and components designated as IROFS

may require fail-safe features with provision for alarm indication.

f.

Based on the results of the ISA, one or more onsite emergency power supply systems may be needed to operate the ventilation systems designated as IROFS.

g.

Based on the results of the ISA, ventilation systems designated as IROFS may need to be designed to withstand the effects of fires and to maintain confinement during these events. Such ventilation systems should have fire protection features such as fire doors and dampers or other proven devices to restrict the spread of fires, fire-resistant construction materials, fire-resistant filters, heat and smoke detectors, alarms, heat removal devices, and fire suppression equipment. The design of the fire protection systems should include provisions to protect against adverse effects in the event of the inadvertent operation or failure of the fire suppression system.

h.

Based on the results of the ISA, air supply systems designated as IROFS may need to remain operational during fires. Such systems should have the capability to shut off air supply to involved fire areas and should be designed to protect systems that are shut down from backflow.

i.

Based on the results of the ISA, components in ventilation systems designated as IROFS should be fire resistant to protect against fires that occur within or outside the system. Such ventilation system components should meet the requirements in American Society of Mechanical Engineers (ASME) AG-1, Code on Nuclear Air and Gas Treatment, issued 2003 (Ref. 3).

Rev. 1 of RG 3.12, Page 4 j.

Based on the results of the ISA, ventilation systems designated as IROFS should have fire and smoke suppression equipment to ensure that the integrity of high-efficiency particulate air (HEPA)

filters or filter systems are not degraded during fires. Spark and flame arresters and isolation valves or dampers may be necessary to protect final HEPA filters from contact with hot particles and excessive soot loading beyond their design capacity. (Final HEPA filters are those HEPA

filter banks located immediately upstream of the discharge stack and represent the final stages of particulate removal for the ventilation system.) HEPA filters should meet the requirements in ASME AG-1.

k.

Based on the results of the ISA, the design of ventilation systems designated as IROFS may need to consider combustible or explosive solvents, gases, or vapors. The applicant should consider the continuous monitoring of such materials with suitable monitoring systems that can function under normal and abnormal conditions as dictated by the ISA.

l.

Based on the results of the ISA, ventilation systems designated as IROFS should be designed to withstand tornado, hurricane, and other tropical storm conditions without the loss of confinement capability because of mechanical damage to the system or components or because of reduced ambient pressure at the intake and exhaust openings. Protection against missiles generated by tornadoes may also be needed at the intake and exhaust openings.

m.

Based on the results of the ISA, ventilation systems designated as IROFS may need to be designed to withstand the effects of seismic conditions without the loss of confinement or system function to prevent an uncontrolled release of radioactive materials to the environment.

2.

Ventilation Systems in Occupied Areas

a.

Based on the results of the ISA, supply air systems designated as IROFS should be provided to ensure the adequate control and proper functioning of each confinement zone. Supply air should be conditioned to maintain the design control parameters of temperatures and humidity. Supply air systems should be provided with filters to remove incoming particulate matter for controlling contamination within the confinement zones and for reducing the dust loading on filters in the final filtration assemblies.

b.

Air in the secondary and tertiary confinement zones may be recirculated. Based on the results of the ISA, the ventilation system design should consider the need for HEPA filtration and removal of radioactive and chemical contaminants in recirculated air streams before the air is returned to secondary and tertiary confinement zones. The design should also consider the continuous monitoring of recirculated air streams and the capability to exhaust the recirculated air directly to the final filtration assemblies in the event that contaminant levels exceed safe occupational levels.

3.

Process Ventilation Systems

a.

Based on the results of the ISA and process control specifications, the supply air and inert gases to gloveboxes and process equipment may require conditioning to control temperature and humidity.

Humidity control may also be necessary for criticality safety. Supply air should be provided consistent with the recommendations in Regulatory Position 2.a of this guide.

b.

Based on the results of the ISA, supply air and inert gases may need to be introduced into primary confinement zones through at least one HEPA filter and be discharged through at least one HEPA

filter to the exhaust duct leading to the final filtration assemblies. (Final filtration assemblies are

Rev. 1 of RG 3.12, Page 5 those filter assemblies located immediately upstream of the discharge stack and represent the final stages of contaminant removal for the ventilation system.) The inlet HEPA filters should be designed to prevent the backflow of contaminants into supply ducts, and the outlet HEPA filters should provide contamination and criticality control in the exhaust ductwork.

c.

Based on the results of the ISA, gloveboxes designated as IROFS should be designed to minimize contaminant releases in the event of credible breaches. Such designs should provide adequate capacity and controls to maintain an inward airflow of at least 125 linear feet per minute through the maximum credible breach.

d.

Based on the results of the ISA, the exhaust flow from gloveboxes and process equipment, which are designated as IROFS and are associated with wet chemical operations, should be treated to protect exhaust ductwork and downstream filtration units from wetting and chemical attack.

e.

Based on the results of the ISA, if exhaust air or inert gases from gloveboxes and process equipment are recirculated, ventilation system designs should provide for HEPA filtration and the removal of chemical contaminants in recirculated air streams before the air is returned to the gloveboxes and process equipment. The design should also consider the continuous monitoring of recirculated air and inert gas streams and the capability to exhaust the recirculated air and inert gases directly to the final filtration assemblies in the event that contaminant levels exceed process and contamination control objectives.

4.

Fans

a.

Based on the results of the ISA, ventilation systems designated as IROFS should have redundant fans and isolation dampers for the supply and exhaust air systems. (Supply air systems include filters and fans that supply fresh outside air into the facility. Exhaust air systems include filters and fans that discharge ventilation air and process gases from the facility.) Controls should be provided to automatically start redundant fans and automatically isolate idle fans with backflow dampers.

b.

Based on the results of the ISA, fans designated as IROFS should be provided with alarms to indicate fan malfunctions.

c.

Supply air fans, including those designated as IROFS based on the results of the ISA, should be interlocked with exhaust fans to prevent supply air fan operations unless the exhaust fans are in operation. This will prevent the pressurization of confinement zones in the event that the exhaust fans fail.

d.

Based on the results of the ISA, emergency power supplies may be needed for the operation of fans that are designated as IROFS.

5.

Ventilation System Construction and Layout

a.

Based on the results of the ISA, ventilation systems designated as IROFS should use construction materials that are selected based on their strength to withstand accident conditions, corrosion resistance, fire resistance, and ease of decommissioning.

b.

Based on the results of the ISA, ventilation systems designated as IROFS should be designed and constructed in accordance with ASME AG-1.

Rev. 1 of RG 3.12, Page 6

6.

Ventilation System Inspection, Testing, and Monitoring

a.

Based on the results of the ISA, ventilation systems and components designated as IROFS should be designed so that they can be initially and periodically inspected and tested to ensure that they will be available and will perform reliably when they are needed to perform their functions. Based on the results of the ISA, ventilation systems and components, including the ductwork and pressure boundaries, should be inspected and tested in accordance with the applicable provisions of ASME AG-1.

b.

Based on the results of the ISA, ventilations systems designated as IROFS should have a continuous air monitoring system (CAMS) to continuously obtain representative samples and monitor effluent releases. The CAMS should have alarms at appropriate control rooms or areas.

Designation of the CAMS as an IROFS should be based on the results of the ISA. Air monitoring and sampling systems should also be provided in occupied areas to alert workers of hazardous concentrations of radioactive or chemical materials.

7.

Gloveboxes and Other Process Enclosures

a.

Based on the results of the ISA, gloveboxes designated as IROFS should be designed, fabricated, tested, installed, operated, and inspected in accordance with American Glovebox Society (AGS)-G001, Guideline for Gloveboxes, issued 2007 (Ref. 4).

b.

Based on the results of the ISA, gloveboxes and process enclosures designated as IROFS should use materials that are selected based on their strength to withstand accident conditions, corrosion resistance, fire resistance, and ease of decommissioning. This equipment should use fire detectors, combustible gas and vapor detection, pressure relief devices, and fire suppression designed for the materials and processes used within the gloveboxes and enclosures. Downdraft ventilation should be considered to minimize the spread of fires.

c.

Based on the results of the ISA, gloveboxes and process enclosures designated as IROFS should have differential pressure sensors and alarms to ensure that pressure differentials between confinement zones are maintained.

d.

Based on the results of the ISA, gloveboxes and process enclosures designated as IROFS should be tested for leaks, containment integrity, and ventilation flow in accordance with the provisions in AGS-G001.

8.

Filtration Systems

a.

Based on the results of the ISA, filter components and assemblies designated as IROFS should be designed, fabricated, inspected, tested, stored, handled, packaged, shipped, and received in accordance with ASME AG-1.

b.

Based on the results of the ISA, filter assemblies designated as IROFS should have at least two banks of HEPA filtration. In addition, filter assemblies should have prefilters and roughing filters to reduce HEPA filter dust loadings and to protect HEPA filters from hot particles. Other filtration systems with removal efficiencies equivalent to HEPA filters may also be used.

c.

If credit is taken for HEPA filters in the ISA, those HEPA filters should be tested in place in accordance with ASME AG-1 initially when placed into service and periodically thereafter to

Rev. 1 of RG 3.12, Page 7 ensure that they will be available and reliable to perform their intended function. HEPA filter banks should demonstrate an efficiency of at least 99.95 percent using a polydisperse dioctylphthalate penetrant that has a light-scattering mean diameter of approximately 0.7 microns.

Penetrants equivalent to polydisperse dioctylphthalate may also be used.

9.

Management Measures

Management measures should be established for the design, fabrication, installation, testing, inspection, operation, and maintenance of ventilation systems designated as IROFS consistent with the results of the ISA, the quality assurance requirements in 10 CFR 70.22(f) and the requirements in Subpart H of 10 CFR Part 70.

D. IMPLEMENTATION

The purpose of this section is to provide information on how applicants and licensees may use this guide and information regarding the NRCs plans for using this Regulatory Guide. In addition, it describes how the NRC staff has complied with the Backfit Rule in 10 CFR 70.76.

Applicant and Licensees Use

Applicants and licensees may (i.e., voluntarily) use the information in this regulatory guide to develop applications for initial licenses, amendments to licenses, or other requests for NRC regulatory approval (e.g., exemptions). Licensees may use the information in this regulatory guide for actions which do not require prior NRC review and approval. Licensees may use the information in this Regulatory Guide or applicable parts to resolve regulatory or inspection issues (e.g., by committing to comply with provisions in the regulatory guide).

Current licensees may continue to use the guidance that was found acceptable for complying with specific portions of the regulations as part of their license approval process, which may be a previous version of this Regulatory Guide.

A licensee who believes that the NRC staff is inappropriately imposing this Regulatory Guide as part of a request for a license amendment or request for a change to a previously issued NRC regulatory approval may file a backfitting appeal with the NRC in accordance with applicable procedures.

NRC Staff Use

The NRC staff does not intend or approve any imposition or backfitting of the guidance in this Regulatory Guide. The staff does not expect any existing licensee to use or commit to using the guidance in this Regulatory Guide in the absence of a licensee-initiated change to its licensing basis. The NRC staff does not expect or plan to request licensees to voluntarily adopt this Regulatory Guide to resolve a generic regulatory issue. The NRC staff does not expect or plan to initiate NRC regulatory action which would require the use of this regulatory guide without further back-fit consideration.

During inspections of specific facilities, the staff may suggest or recommend that licensees consider various actions consistent with staff positions in this regulatory guide. Such suggestions and recommendations would not ordinarily be considered backfitting even if prior versions of this Regulatory Guide are part of the licensing basis of the facility with respect to the subject matter of the inspection.

However, the staff may not represent to the licensee that: (i) the licensees failure to comply with the positions in this Regulatory Guide constitutes a violation; (ii) the licensee may avoid the violation by

Rev. 1 of RG 3.12, Page 8 agreeing to comply with this Regulatory Guide; or (iii) the only acceptable way for the licensee to address the NRC-identified non-compliance or violation is to commit to this Regulatory Guide (i.e., including this Regulatory Guide in the facilitys licensing basis).

If an existing licensee seeks a license amendment or change to an existing regulatory approval, and the staffs consideration of the request involves a regulatory issue which is directly relevant to this Regulatory Guide and the specific subject matter of the new or revised guidance is an essential consideration in the NRC staffs determination of the acceptability of the licensees request, the staff may require the licensee to use this Regulatory Guide or its equivalent as a prerequisite for NRC approval. This is not considered backfitting as defined in 70.76(a)(1).

Conclusion

This regulatory guide is not being imposed upon current licensees and may be voluntarily used by existing licensees. In addition, this Regulatory Guide is issued in conformance with all applicable internal NRC policies and procedures governing backfitting. Accordingly, the NRCs staff issuance of this regulatory guide is not considered backfitting, as defined in 70.76(a)(1).

Rev. 1 of RG 3.12, Page 9 REFERENCES1

1.

10 CFR Part 70, Domestic Licensing of Special Nuclear Material, U.S. Nuclear Regulatory Commission, Washington, DC.

2.

10 CFR Part 20, Standards for Protection against Radiation, U.S. Nuclear Regulatory Commission, Washington, DC.

3.

ASME AG-1, Code on Nuclear Air and Gas Treatment, American Society of Mechanical Engineers, New York, NY, 2003, and applicable addenda.2

4.

AGS-G001, Guideline for Gloveboxes, American Glovebox Society, Santa Rosa, CA, 2007.

1 Publicly available NRC published documents are available electronically through the Electronic Reading Room on the NRCs public Web site at: http://www.nrc.gov/reading-rm/doc-collections/. The documents can also be viewed online or printed for a fee in the NRCs Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD; the mailing address is USNRC PDR, Washington, DC 20555; telephone 301-415-4737 or (800) 397-4209; fax (301) 415-3548;

and e-mail pdr.resource@nrc.gov.

2 Copies of American Society of Mechanical Engineers (ASME) standards may be purchased from ASME, Three Park Avenue, New York, NY 10016-5990; telephone (800) 843-2763. Purchase information is available through the ASME

Web-based store at http://www.asme.org/Codes/Publications/.


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