Regulatory Guide 3.7

Monitoring of Combustible Gases & Vapors in Plutonium Processing & Fuel Fabrication Plants

ML003740201
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Issue date:	03/31/1973
From:	Office of Nuclear Regulatory Research
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RG-3.7
Download: ML003740201 (2)

3/21/73 U.S. ATOMIC ENERGY COMMISSION

REGULATORY

DIRECTORATE OF REGULATORY STANDARDS

GUIDE

REGULATORY GUIDE 3.7 MONITORING OF COMBUSTIBLE GASES AND VAPORS IN

PLUTONIUM PROCESSING AND FUEL FABRICATION PLANTS

A. INTRODUCTION

Combustible gases and vapors and their limits of flammability in various oxidizing atmospheres have been Each applicant for a license to possess and use studied by the Bureau of Mines.' 7 Flammability has special nuclear material in a plutonium processing and been found to be a function of the type of combustible fuel fabrication plant as defined in § 70.4(r) of 10 CFR gas, oxidant concentration, temperature, humidity, Part 70, "Special Nuclear Material," must fulfill the vessel characteristics, and direction of flame provisions of § 70.23, "Requirements for the Approval propagation, among other things. Within the of Applications." Subparagraphs § 70.23(a)(3) and (4) confinement barriers of a plutonium processing and fuel require that the applicant's proposed equipment and fabrication plant, flammable mixtures must be facilities and proposed procedures be adequate to precluded, and therefore the maximum allowable protect health and to minimize danger to life or concentration of any combustible gas or vapor in a property. Where combustible gases and solvents are used mixture should always be below the lower limit of within the confinement barriers of a plutonium flammability as given for that particular mixture.

processing and fuel fabrication plant, measures are needed to protect against the possibility of the Some common sources of combustible gases and formation of flammable mixtures with these gases and vapors that have led to fires and explosions within vapors. The presence of such a flammable mixture confinement barriers have been (1) solvents or coolants within the multiple confinement barriers of the plant used in chemical processing, surface finishing, or

"could result in a fire or explosion which might breach equipment maintenance, (2) reducing atmospheres used one or more of the confinement barriers and allow in conversion and sintering furnaces, and (3)

radioactive material to be dispersed within regions of the decomposition products formed during waste plant and possibly the environs. This regulatory guide incineration and chemical processing. Measures have describes an acceptable program for complying with the been developed to prevent the recurrence of Commission's regulations with regard to protecting flammability conditions and have been based on one or against the possibility of the formation of flammable more of the following concepts: (I) prohibiting or mixtures with combustible gases and vapors. restricting the use of the combustible material, (2) inert gas purging within the confinement barriers where

B. DISCUSSION

combustible gases or vapors are expected, thus reducing or eliminating the oxidant content, or increasing the air Within a plutonium processing and fuel fabrication flow within these confinement barriers, thus diluting the plant, a postulated fire or explosion is an accident that combustible concentration below the lower limit for can furnish sufficient energy for the release and dispersal flammability, and (3) establishing other procedural of radioactive material from the confinement barriers to changes based upon the results of the accident the regions occupied by working personnel and, investigation.

depending upon the severity of the accident, to the environs. Therefore, conditions that can lead to these 'Bureau of Mines Bulletin 503, "Limits of Flammability of hazardous events must be precluded. One such event is Gases and Vapors," H. F. Coward and G. W. Jones.

the uncontrolled or undetected formation of a I Bureau of Mines Bulletin 627, "Flammability flammable mixture of a combustible gas or vapor and an Characteristics of Combustible Gases and Vapors," M. G.

oxidant followed by its deflagration or detonation. Zabetakis.

USAEC REGULATORY GUIDES Copie of published guild may be obtained by request indicating the divisions desired to the US. Atomic Energy Commission, Wiahington. D.C. 20645, Regulatory Guides Ie issued to desclrae and make available to the public Attention: Director of Regulatory Standards. Comments and suggestions for met' od- acpteble to the AEC Regulatory staff of Implementing specific parts of Inpo4 enuats in thee guidos we encouraged end should be sent to the Secretary the Commbelonm' regulations, to delineate schnslque. used by the ptaff In of the Commnilon. US. Atomic Energy Commission. Washington. D.C. 20545.

eowluating specific problems or postulated aciklents, or to provide giuldnc to Attenition: Chief. Public Proceedings Staff.

spalisents. Regulatory Guides ae not substitutes for regulations and complance with them Is not required. Methods and Solutlons different from those sat out In The guids am issued in the following ten broad divisions:

tie guides will be cceptebhl If they provide a balei for the findings requisite to to isuanrc or coatinuarce of a permit or lioense by the Commisslon. I. Power eavctors

6. Products

2. Research end Test Reactort

7. Transportation

3. Fuels end Materials Facilities 8. Occupational Health Pub#visold guides will be revised periodically, a appropriate. to accommodate 4. Environmental and Siting 9. Antitrust Review comments and to reflact .sw information or ixperlence. 5. Matarias and Plant Protection 1

0. General

While this arrangement has for the most part been abnormal conditions, the formation of a flammable or effective in preventing the recurrence of fires and explosive mixture within the confinement barriers explosions for specific processes within an individual should be precluded by establishing suitable process facility, such procedures usually have been initiated parameters and plant operating procedures.

and/or emphasized only after an accident and may suffer with time from relaxation of vigilance, process 3. Assurance that the established processing and modifications, and the formation of unexpected operating procedures are maintaining safe conditions combustible products. The monitoring and alarm system should be provided by suitable continuous monitoring for combustible gases and vapors discussed in this systems appropriately placed within those confinement regulatory guide is expected to contribute to the safe barriers that were identified in C. 1. above. These systems operation of the plant in many ways, especially in the should give an audible and visual local alarm indication following aspects: (1) an initial fire or explosion to operating personnel when the prescribed safe limits accident is unlikely to happen since an alarm will for combustible gas and vapor mixtures have been indicate when the flammable limit is being approached, achieved or exceeded.

(2) the need for administrative involvement should be minimal since the system can provide continuous 4. The procedure for remedial action to be taken automatic surveillance, and (3) unexpected combustible in the event of an alarm signal should be established.

products will have a high probability of being detected.

5. The absence of an evident ignition source

C. REGULATORY POSITION

within those confinement barriers postulated to contain combustible gases, solvents, or vapors does not relieve I. All processes and plant operations carried out the requirement for a monitoring and alarm system.

in or associated with the confinement barriers of a plutonium processing and fuel fabrication plant should 6. The monitoring and alarm system itself should be evaluated as potential sources of combustible not introduce an ignition source and should not affect solvents, gases, or vapors. the confinement integrity.

2. Where sources of combustible solvents, gases, or 7. The monitoring and alarm system should be vapors can be identified or postulated under normal or designed for in-place calibration and testing.

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