Regulatory Guide 3.18
| ML003740303 | |
| Person / Time | |
|---|---|
| Issue date: | 02/28/1974 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| References | |
| Reg Guide 3.18 | |
| Download: ML003740303 (3) | |
FEBRUARY 1974 U.S. ATOMIC ENERGY COMMISSION
REGULATORY GUIDE
DIRECTORATE OF REGULATORY STANDARDS
REGULATORY GUIDE 3.18 CONFINEMENT BARRIERS AND SYSTEMS
FOR FUEL REPROCESSING PLANTS
A. INTRODUCTION
commonly provide the first confinement barrier to control releases of radioactive material. Additional Section 50.34 oT IOCFR Part 50, "Licensing of barriers, as necessary for safety, are provided by Production and Utilization Facilities," requires, among ancillary process systems and equipment such as the other things, that each application for a construction process offps system or gloveboxes, by process cell or permit for a production or utilization facility, including vault walls, or by building walls. These additional a fuel reprocessing plant, Include the principal design barriers are designed to work in conjunction with the criteria for the facility. Section 20.1 of 10 CFR Part 20, building ventilation system to limit the spread of
"Standards for Protection Against Radiation," states airborne contamination which could be generated by that licensees should make every reasonable effort to leakage of either gases or liquids from process and maintain radiation exposure, and releases of radioactive storage vessels into process cell or vault air spaces and materials in effluents to unrestricted areas; as far below thence into other areas. Barriers also serve to prevent the the limits specified in that part as practicable. Properly spread of contamination via leakage of contaminated designed confinement, barriers and systems in fuel liauids and solids.
reprocessing plants provide a principal means of reducing such exposures and releases. This regulatory guide In order tp limit the spread of radioactive materials, provides information relative to establishing principal processing facilities are separated by confinement design criteria for confinement systems that will barriers into areas or zones of various levels of minimize the amount of radioactive material released to contaminafion. The building ventilation and process the environment or to areas normally occupied by offgas systems aid in controlling the spread of airborne personnel. contamination through openings In barriers by regulating the direction of air or gas flow between these zones so
B. DISCUSSION
that gas leakage Is successively from zones of low potential for contamination to zones of higher potential A principal objective in the design of fuel for contamination. For example, air flow would be reprocessing plants is to prevent the uncontrolled release successively from the environs to building areas occupied and dispersal of radioactive materials. These materials by personnel, to potentially contaminated process areas, are ingredients of process fluids, process solids, and to the ventilation cleanup system, and thence to blowers building ventilation gases. Release of radioactive for discharge to the atmosphere. "The capacity of materials is controlled by one or more individual ventilation systems must be adequate in relation to confinement barriers and systems which successively confinement system requirements to assure that the restrict releases of radioactive material to the velocity of gas flowing through hny barrier oeni... is environment or into areas normally occupied by plant sufficient to prevent backflow of airborne contaminants personnel. The confinement system design is affected by through such openings and that air flow patterns are not the design and operation of building ventilation and disrupted by winds, movement of equipment or process offgas systems and by fire protection personnel, or temporary opening of passageways through requirements. These items will be subjects of future confinement barriers.
guides.
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materials to the environment. These fluids often prdvided to limit releases of radioactive material to circulate between radioactive and nonradioactive areas restricted areas so that exposures to individuals are as and are subject to contamination by leakae of process low as practicable and that the concentrations are as low solutions through defects which may develop in heat as practicable and do not exceed the limits specified in exchanger components Should these fluids be §20.103 of 10 CFR Part 20.
discharged to the environs, releases of radioactivity may occur. Barriers to release via this pathway are usually 2. Confinement systems and barriers should be provided by intermediate heat exchangers located provided to limit releases of radioactive materials to between the utility system and the process system. This unrestricted areas; they should be capable of serves to form a "closed-loop" (as opposed to a withstanding the effects of design basis accidents,
"once-throughV) heat transfer circuit in which the heat including natural phenomena, so that releases of exchangers function as confinement barriers. radioactive materials are as low as practicable and so that they do not exceed the annual limit prescribed by Piping penetrations through confinement barriers §20.106(a) of 10 CFR Part 20.
provide another potential pathway for release of radioactive material to the environment. These 3. Pipes penetrating confinement barriers should be penetrations usually serve as conduits for instrument equipped with at least one isolation valve located outside leads or serve to conduct cold chemical or utility fluids of and as dose to the confinement barrier as is between zones formed by the barriers. During practicable.
maintenance or remodeling activities, it may be necessary to isolate selected equipment items to assure confinement. In such penetrating lines an isolation valve 4. Confinement zones should be established and located close to the confinement barrier can function as should be bounded by confinement barriers. Generally, a confinement barrier by being dosed during such zones should be established on the basis of their activities. function(s) which may include confinement of process fluids, process equipment, maintenance areas, operating In this guide, barriers are arbitrarily classified as areas, and process control area
s. Zones should be
"'total" or "selective." Total barriers are those fabricated arranged in order of contamination potential. The zones of impermeable materials which can be expected to with the highest contamination potential should be prevent penetration of all confined material without situated adacent to contaminated process areas and the regard to that material's physical or chemical nature. zones with the lowest contamination potential at the Examples of total barriers are pipe and vessel walls and outer areas of the process building.
walls of buildings and structures. Total barriers may also function as radiation shields. Information on design for 5. Barriers should be designed with regard to the this function may be found in Regulatory Guide 3.9. capabilities of the process .offgas and the building Selective barriers are mass transfer devices or filters and ventilation systems. Barriers should be designed to are usually employed to remove selected chemicals or withstand loadings due to pressure differentials imposed particulate matter from a process or ventilation stream by these systems. Openings through barriers should be while allowing the bulk amount of the stream to pass limited in size to preclude disruption of confinement or through. Examples of selective barriers are adsorbers, disruption of air flow patterns due to lost of pressure scrubbers, distillation units, and particulate filters. differential.
To verify continued integrity of barriers, monitoring 6. Barriers should be provided to prevent leakage of devices are necessary. Where a total barrier is used for contaminated fluids into heat transfer fluids circulated gas confinement, integrity may reasonably be inferred into unrestricted areas. A preferred method for this is by by monitoring the difference in pressure across the use of closed primary and independent secondary heat barrier and noting any deviation from normal. Where a transfer circuits.
total barrier is used for liquid confinement, leakage may be indicated by a liquid high-level alarm in a specially 7. To monitor the integrity of total confimement designated leakage collection sump or by analytical barriers for gases, devices should be provided to control devices which measure and alarm. contaiminant intrusion and indicate pressure differentials between confinement into normally uncontaminated tanks or process streams. zones. Alarms should be provided to indicate when Continuous air monitors are used to indicate any breach pressure differentials are not maintained within a in integrity of a total barrier or any loss of function of a prescribed range. In addition, radiation monitoring selective barrier which would release radioactivity from a devices with local alarms should be provided to indicate designated confinement area into a monitored area. leakage of radioactive material through confinement barriers into normally inhabited areas.
C. REGULATORY POSITION
8. To monitor the integrity of total confinement I. Confinement systems and barriers should be barriers for liquids, devices should be provided to
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Indicate and alarm upon "aqu4 hakap throuAh a other zones or to the envtro%.. Devices such as CAMs confifemant barier. (continuous air monitors) and stack monitors are acceptable.
9. To monitor the function of selective barrier s, 10. Confinement systems should be constructed of devices should be provided to indicate and alarm ar,y nonflammable materials except where this is not possible deterioration or Jon of function which may relai le because of Special fun*tional requitements, for example, radiactivity from duipated conemmnt zones tat o glves in gloveboxes.
3.18.3