May 1986 U.S. NUCLEAR REGULATORY COMMISSION

CREGULATORY GUIDE 

-*0*O OFFICE OF NUCLEAR REGULATORY RESEARCH 

REGULATORY GUIDE 3.56 

(Task CE 309-4) 

GENERAL GUIDANCE FOR DESIGNING, TESTING, OPERATING, AND MAINTAINING 

EMISSION CONTROL DEVICES AT URANIUM MILLS

A. INTRODUCTION 

Regulations applicable to uranium milling are contained 

in 10 CFR Part 20, "Standards for Protection Against Radi

ation," and in 10 CFR Part 40, "Domestic Licensing of 

Source Material." 

Paragraph 20.1(c) of 10 CFR Part 20 states that licensees 

should make every reasonable effort to keep radiation 

exposures, as well as releases of radioactive material to 

unrestricted areas, as low as is reasonably achievable. 

Paragraph 20.105(c) of 10 CFR Part 20 requires that licens

ees engaged in uranium fuel cycle operations subject to 

the provisions of 40 CFR Part 190, "Environmental Radia

tion Protection Standards for Nuclear Power Operations," 

comply with that part. Part 190 of Title 40 requires that 

the maximum annual radiation dose to individual members 

of the public resulting from fuel cycle operations be lim

ited to 25 millirems to the whole body and to all organs 

except the thyroid, which must be limited to 75 millirems. 

Criterion 8 of Appendix A to 10 CFR Part 40 requires that 

milling operations be conducted so that all airborne efflu

ent releases are reduced to levels as low as is reasonably. 

achievable. 

Air in the immediate vicinity of such uranium milling 

operations as ore crushing, ore grinding, and yellowcake dry

ing and packaging frequently contains radioactive materials 

in excess of that permissible for release to unrestricted 

areas. Emission control devices are installed in ventilation 

systems of uranium mills to limit releases of these radio

active materials to the environment. 

General guidance for filing an application for an NRC 

source material license authorizing uranium milling opera

tions is provided in § 40.31 of 10 CFR Part 40. An appli

cant for a new license or renewal of an existing license for a 

uranium mill is required by § 40.31 to provide detailed

USNRC REGULATORY GUIDES 

Regulatory Guides are issued to describe and make available to the 

public methods acceptable to the NRC staff of Implementing 

specific parts of the Commission's regulations, to delineate tech

niques used by the staff in evaluating specific problems or postu

lated accidents or to provide guidance to applicants. Regulatory 

Guides are not substitutes for regulations, and compliance with 

them is not required. Methods and solutions different from those set 

out in the guides will be acceptable If they provide a basis for the 

.- findings requisite to the issuance or continuance of a permit or 

license by the Commission. 

This guide was issued after consideration of comments received from 

the public. Comments and suggestions for improvements In these 

guides are encouraged at all times, and guides will be revised, as 

appropriate, to accommodate comments and to reflect new Informa

tion or experience. 

Written comments may be submitted to the Rules and Procedures 

Branch, DRR, ADM, U.S. Nuclear Regulatory Commission, 

Washington, DC 20555. _

information on the proposed equipment, facilities, and 

procedures at the installation. This information is used by 

the NRC to determine whether the applicant's proposed 

equipment, facilities, and procedures are adequate to protect 

the health and safety of the public and and to determine if 

they will significantly affect the quality of the environment. 

Calculations by the NRC of the environmental impact from 

the proposed uranium milling operations are based on the 

estimated rate of production of radioactive airborne partic

ulates adjusted to reflect the removal efficiency of the 

emission control devices installed in the plant ventilation 

systems. This requires reliable information on the efficiency 

of these devices. It also requires reliable information on the 

production of airborne radioactive particulates during the 

proposed operations. 

Section 40.65 of 10 CFR Part 40 requires mill operators 

to submit semiannual reports to the NRC specifying the 

quantity of each of the principal radionuclides released to 

unrestricted areas in gaseous effluents. This information 

may be used by the NRC to estimate maximum potential 

annual radiation doses to the public resulting from effluent 

releases and thereby determine compliance with paragraphs 

20.1(c) and 20.105(c) of 10 CFR Part 20 and with Crite

rion 8 of Appendix A to 10 CFR Part 40. The quantity of 

radionuclides released is based on scheduled sampling of 

effluents discharged into exhaust stacks. The reliability of 

these data for estimating radiation exposures depends on 

maintaining uniform operation of the emission control 

devices during the reporting time interval because these 

effluents are not continuously sampled. 

All emission control devices used in uranium mill ventila

tion systems need to perform reliably under expected oper

ating conditions to meet the objectives discussed above. This 

guide describes procedures acceptable to the NRC staff for 

designing, testing, operating, and maintaining these emission 

control devices to ensure the reliability of their performance.

The guides are issued in the following ten broad divisions: 

1. Power Reactors 6. Products 

2. Research and Test Reactors 7. Transportation 

3. Fuels and Materials Facilities 8. Occupational Health 

4. Environmental and Siting 9. Antitrust and Financial Review 

5. Materials and Plant Protection 10. General 

Copies of Issued guides may be purchased from the Government 

Printing Office at the current GPO price. Information on current 

GPO prices may be obtained by contacting the Superintendent of 

Documents, U.S. Government Printing Office, Post Office Box 

37082, Washington, DC 20013-7082, telephone (202)275-2060 or 

(202)275-2171. 

Issued guides may also be purchased from the National Technical 

Information Service on a standing order basis. Details on this 

service may be obtained by writing NTIS, 5285 Port Royal Road, 

Springfield, VA 22161.
Any information collection activities mentioned in 

this regulatory guide are contained as requirements in 

10 CFR Parts 20 or 40, which provide the regulatory basis for this guide. The information collection require

ments in 10 CFR Parts 20 and 40 have been cleared 

under OMB Clearance Nos. 3150-0014 and 3150-0020, 

respectively. 

B. DISCUSSION 

The milling of uranium ores results in the produc tion of airborne particulates containing uranium and its 

daughters in several areas of a typical uranium mill. 

These areas encompass (1) ore storage, handling, and 

crushing; (2) ore grinding, leaching, and concentrating 

processes; (3) yellowcake precipitation, drying, and 

packaging, and (4) miscellaneous mill locations such as maintenance shops, laboratories, and general laundries. 

Milling operations must be conducted so that all airborne 

effluent releases are reduced to levels as low as is 

reasonably achievable (ALARA). The primary means of 

accomplishing this is the control of emissions at the 

source. 

The most significant sources of radioactive airborne 

particulates occur in ore handling and crushing areas and 

in yellowcake drying and packaging areas. These sources are generally controlled by separate ventilation systems in each area that remove these airborne particulates through local hoods, hooded conveyor belts, etc., into 

emission control devices where they are removed from 

the air streams. The cleaned air is then discharged by fans into the atmosphefe through local exhaust stacks. 

Emission control devices are available in a wide range of designs to meet variations in air cleaning requirements. 

Degree of removal required, quantity and characteristics 

of the contaminant to be removed, and conditions of 

the air stream all have a bearing on the device selected 

for any given application. Emission control devices used 

at ore crushing and grinding operations include bag or fiber filters (baghouses), orifice or baffle scrubbers, and 

wet impingement scrubbers. Water spray systems are also used at these operations to minimize the generation of dust. Wet impingement scrubbers or venturi scrubbers are generally employed at yellowcake drying and packag

ing areas. 

All emission control devices used in a uranium mill 

ventilation system need to be designed for reliable 

performance under the expected operating conditions. 

Initial testing and proper maintenance are primary 

factors in ensuring the reliability of these components. Periodic testing during operation to verify the efficiency of these components is another important means of 

ensuring reliability. Built-in features that will facilitate 

convenient in-place testing of these devices are important 

in ventilation system design. 

Emission control devices used in a uranium mill 

ventilation system need to be sufficiently instrumented

to measure and monitor their operating characteristics. 

Frequent checks of all significant operating parameters are necessary to determine whether or not conditions are within a range prescribed to ensure that this equipment is operating consistently near peak efficiency. When 

checks indicate that the equipment is not operating with

in this range, it is necessary to take action to restore 

parameters to the prescribed range. To ensure that 

timely actions are taken, instrumentation is often supple mented by audible alarms that are preset to signal when prescribed operating range limits are exceeded. 

When the required actions cannot be taken without shut

down and repair of this equipment, it will be necessary 

to suspend milling operations that are the source of the 

emissions until corrective actions have been taken. Crite

rion 8 of Appendix A to 10 CFR Part 40 requires suspen sion of yellowcake drying and packaging operations as soon as practicable when shutdown and repair of the 

emission control system is necessary. The installation of 

automatic shutdown instrumentation on processes and 

systems at which operating parameters on emission con trol devices may exceed acceptable limits could prevent excessive releases that may result from continuous oper ations under these circumstances, e.g., those associated 

with the production of yellowcake. The installation of 

backup or redundant emission control systems would per mit continuous operation during repair and maintenance 

of the primary system. 

A preventive maintenance program is important for 

emission control devices used in uranium mill ventilation 

systems. A program designed to identify deficiencies in 

operation of these devices so that corrective action can be taken to reduce the frequency of off-normal opera tion can provide a measure of confidence in the operat ing characteristics of these devices. This program may require periodic updating to reflect actual in-plant experience, equipment manufacturers' guidelines, and 

NRC guidance. For example, a preventive maintenance 

program can consist of the equipment supplier's recom mendations supplemented by provisions derived from the 

licensee's own routine inspection and maintenance 

records. 

The key to proper maintenance of emission control 

devices is frequent inspection. It is important that a regular program of inspection be established and followed 

and records be kept of all inspections and the resulting maintenance. Inspection intervals will depend on the 

type of emission control device, the manufacturer's 

recommendation, and the process area where the unit is 

installed. These inspections need to be performed as frequently as experience shows to be necessary but not 

less than annually. 

Considerable maintenance time can be expended on trouble shooting and correction of malfunctions of emis

sion control devices. The ability to locate and correct 

malfunctioning components of these devices requires a thorough understanding of the system.

3.56-2
Throughout the manufacturing industry, there are 

many models of each type emission control device used 

at uranium mills. These models range in size in order 

to meet the different air capacity needs at the mills. In 

addition, some design features of each manufacturer are 

unique. Accordingly, the specific design and the testing, 

operating, and maintenance procedures for each model 

are beyond the scope of this guide. General guidance is 

presented, however, for each type of emission control 

device based on typical models in present-day use. 

Background information for this guidance can be found 

in the Bibliography. The licensee may substitute proce

dures based on specific operating parameters of the 

model in use at the facility for those described in this 

guide. 

1. DESIGN AND OPERATION 

1.1 Bag or Fabric Filters (Baghouses) 

Bag or fabric filters, usually in the form of baghouses, 

remove particulates from a gas stream by filtering the 

airborne particulates (by impaction or diffusion) through 

a porous flexible fabric made of a woven or felted 

material. These collected particles form a structure of 

their own, supported by the filter, and have the ability 

to intercept and retain other particles. The increase in 

retention efficiency is accompanied by an increase in 

pressure drop through the filter. The baghouses are 

equipped with one of several automatic cleaning mecha

nisms for periodically dislodging collected material from 

filter components to prevent excessive resistance to the 

gas flow (i.e., excessive pressure drop) that would 

otherwise develop. The dislodged material settles in 

storage hoppers before the filter components are placed 

back on stream. The automatic cleaning cycle can be 

initiated by either a differential pressure switch or a 

timer, which may be interlocked with the main fan 

motor for the baghouse. 

The cleaning mechanisms employed in baghouses are 

based on either mechanical shaking of the filter compo

nents or pneumatic vibration of these components 

by high-pressure air applied in reverse flow, reverse jet, 

or reverse pulse modes. The effectiveness of these 

compressed air systems depends on maintaining a suffi

cient reservoir of compressed air at the pressure speci

fied by the baghouse manufacturer. Higher pressures 

than specified could cause failure of the filter fabric, 

while lower pressures can result in poor filter cleaning. 

These problems are minimized by pressure-regulating 

devices used in the compressed air systems. 

The most critical parameter to be observed during 

baghouse operation is the pressure drop. Proper operation 

of the baghouse requires, at a minimum, maintaining the 

differential pressure of this device in the correct range 

specified by the manufacturer. A manometer or a 

differential-pressure gauge and transmitter are usually 

provided for this purpose. This instrumentation is often 

supplemented by an audible alarm system designed to

signal and alert mill operators when prescribed differential

pressure ranges are exceeded. Lower differential pressures 

indicate potential deficiencies such as damaged filters or 

other air bypass channels that should be corrected. 

Higher differential pressures indicate that cleaning opera

tions are inadequate. This can be corrected by increasing 

the frequency of the automatic cleaning cycle through 

adjustment of the differential-pressure switch or timer of 

the baghouse installation. 

1.2 Wet Scrubbers 

Wet scrubbers remove particulates from a gas stream 

by effecting intimate contact between the gas stream 

and a scrubbing liquor, usually water. The basic opera

tions that take place within a wet scrubber are (1) 

saturation of the incoming gas, (2) contacting and 

capture of the particulates in the scrubbing liquor, and 

(3) separating the entrained particulate-laden liquid from 

the gas stream. The basic types of wet scrubbers are 

distinguished by the mechanisms used for transfer of 

particulates from the gas stream to the liquid stream. 

Most scrubber systems require some type of treatment 

and disposal of the particulate-laden scrubbing liquor. 

Several water spray systems may be used in wet 

scrubber operations. Water from the main water spray 

system is directed either into a screen or throat to 

contact the particulate-laden gas stream. In applications 

where inlet gas temperatures are inordinately high, pre

conditioning of the incoming gas to the scrubber may 

be necessary to provide adequate humidity and thereby 

maintain particulate collection efficiency. This may be 

accomplished by use of an auxiliary water spray system 

upstream of the scrubber particulate scavenging area. 

Where particulate . buildup is likely to occur in the 

entrainment separator, a wash system may be necessary 

to avoid this condition. The wash system is usually 

composed of low-pressure spray nozzles using recycled 

scrubbing liquor or fresh water for cleansing. 

Orifice, wet impingement, or venturi wet scrubbers 

are generally used in uranium mill ventilation systems. 

In orifice-type wet scrubbers, the gas stream is made to 

impinge upon a surface of scrubbing water and is then 

passed through various constrictions where its velocity 

may be increased and where greater liquid-particulate 

interaction may occur. -The gas stream finally discharges 

through a chamber section where entrained droplets are 

disengaged. In wet impingement scrubbers, the gas 

stream is wetted with water from low-pressure spray 

nozzles in the scrubber inlet and then passed through 

perforated plates at high velocity to impinge on baffle 

plates or vanes where liquid droplets containing partic

ulate matter coalesce and drain to a sump. Solid particles 

are washed to the sump by either intermittent or con

tinuous sprays. Prior to exiting from the scrubber, the 

gas stream passes through an entrainment separator to 

remove entrained liquid droplets. In a venturi scrubber, 

the gas stream flows through a throatlike passage where 

the gas is accelerated in velocity. The scrubbing liquor is

3.5 6-3
added at or ahead of the venturi throat and is sheared 

into fine droplets by the high-velocity gas stream, 

resulting in liquid-particulate interaction. The gas and 

liquor droplets then pass through a cyclone separator 

where entrained droplets containing particulate matter 

are removed from the gas stream. 

Although each type of scrubber discussed above has 

unique design features, their collection efficiencies are 

influenced in similar ways by incremental changes in 

certain common operating parameters, principally gas 

and liquid flow as well as pressure drop. A decrease in 

either the gas or liquid flow rate could result in insuffi

cient gas cleaning. Collection efficiency can also dimin

ish if the liquid-to-gas flow rate ratio falls below design 

values. An increase in pressure drop across the scrubber 

will enhance the collection efficiency for the same size 

distribution and concentration of particulates in the gas 

stream. Proper operation of these wet scrubbers requires 

monitoring of these parameters to determine that they 

are within ranges prescribed to ensure equipment perform

ance consistently near optimum collection efficiency. 

Instrumentation used to monitor these parameters is 

often supplemented by audible alarm systems designed 

to signal and alert mill operators of the need for correc

tive action when prescribed operating ranges are exceeded. 

In some cases automatic control systems with interlocks 

may be necessary. For example, the scrubber fan could 

be interlocked to shut down in the event of an indica

tion of water flow failure. These circumstances would 

require suspending particulate-producing processes in the 

ventilation zone serviced by the scrubber until corrective 

action could be taken or switching to a redundant 

scrubber unit. 

Daily operational data summaries on baghouse and 

wet scrubber performance are useful in providing a con

tinuous record of performance of these devices. Other 

formats that contain equivalent information such as 

recorder charts can also be used for this purpose. 

Criterion 8 of Appendix A to 10 CFR Part 40 requires 

that checks of all parameters that determine the effi

ciency of yellowcake stack emission control equipment 

operation be made and logged hourly. In addition, data 

from checks made of all operating parameters necessary 

to enable timely identification of malfunctions can be 

of value in ensuring proper operation of baghouses and 

wet scrubbers and in updating preventive maintenance 

programs for these devices to reflect actual operating 

experience. 

2. MAINTENANCE 

2.1 Bag or Fabric Filters (Baghouses) 

The frequency of needed maintenance for baghouses 

can be determined from manufacturers' recommendations 

and operating experience. In order of decreasing frequen

cy, the principal baghouse components requiring mainte

nance are (1) filter bags, (2) flow controls, (3) hoppers, 

and (4) cleaning mechanisms. Symptoms of potential

operating problems requiring corrective maintenance are 

almost always one of the following: (1) excessive emis

sions, (2) short filter bag life, and (3) high pressure 

drop. These symptoms may indicate malfunctioning in 

more than one component. For example, high pressure 

drop may be attributable to difficulties with the filter 

bag cleaning mechanism, low compressed air pressure, 

high humidity, weak shaking action, loose filter bag 

tension or excessive reentrainment of dust. Many other 

factors can cause excessive pressure drop, and several 

options are usually available for appropriate corrective 

action. 

2.2 Wet Scrubbers 

The major maintenance problems with wet scrubbers 

are (1) excessive buildup of solids in the wet/dry zones 

and entrainment separator, (2) plugged water spray noz

zles, (3) abrasion in areas of high velocity such as 

throats and orifices, and (4) corrosion on. scrubber vessel 

internal surfaces. A buildup of solids often occurs 

around the wet/dry interfaces of ducts where the gas 

stream contacts the wetted scrubber housing. Instrumen

tation such as liquid and gas pressure indicators can 

exhibit rapid solids buildup and therefore require regular 

cleaning to ensure proper system operation and perform

ance. Increased pressure drop, reduced gas flow, and 

subsequent system malfunction are all possible conse

quences of a buildup -of solids in the entrainment 

separator. Water spray nozzles frequently wear or clog, 

which produces an uneven liquid pattern and requires 

their replacement. Venturi and impingement scrubbers 

tend to show signs of abrasion in areas downstream of 

gas and liquid acceleration. Corrosion can occur from 

the high moisture and airborne liquid incident on 

components, in particular where protective liners may 

have deteriorated. 

A regular schedule of routine inspection of key com

ponents and operating parameters is an essential ingredi

ent of a maintenance program for ensuring the reliabil

ity of performance of typical baghouses and wet scrub

bers. Examples of some typical maintenance activities 

for baghouses and wet scrubbers used at uranium mills 

are presented in Appendices A and B, respectively. 

These activities are in addition to those procedures 

recommended by manufacturers for routine lubrication, 

inspection, and replacement of component parts. 

3. TESTING 

To ensure proper selection of emission control de

vices, it is necessary for potential users to supply manu

facturers with a list of specifications for the given appli

cation, including gas flow rates, liquid flow rates (where 

scrubbers are under consideration), temperature, pressure, 

pressure drop, concentration of particulates, particle size 

distribution, emission levels, and collection efficiency. 

The manufacturers, in turn, should design and supply 

these devices based on test data already available for 

prototype equipment used under similar circumstances.

3.56-4
If relevant test data are not available, it is generally 

advisable for the manufacturer and potential user to run 

mutually agreed-upon pilot plant or prototype tests with 

a gas stream typical of the gas stream to be cleansed to 

ensure that proper equipment is supplied to meet the 

desired collection efficiency. After installation of the 

device, it may be tested in place to confirm its particu

late removal efficiency. Periodic in-place testing will 

ensure continued effectiveness of the device. In this 

way, reliable data will be available to the licensee for 

estimating the environmental impact of uranium milling 

operations before and after the commencement of 

operations. 

Collection efficiency for baghouses and wet scrubbers 

used in uranium mills is usually based on inlet and out

let particulate concentrations in a dry gas corrected to 

standard temperature and pressure. Inlet and outlet par

ticulate concentrations are preferably sampled simultane

ously if practicable. The procedure of choice for deter

mination of particulate concentrations is described in 

Method 5, "Determination of Particulate Emissions 

From Stationary Sources," of Appendix A to 40 CFR 

Part 60, "Standards of Performance for New Stationary 

Sources." In -this procedure, particulate matter is with

drawn isokinetically from the gas stream and collected 

on a glass fiber filter maintained in a prescribed elevated 

temperature range. The particulate mass, which includes 

any material that condenses at or above the filtration 

temperature, is determined gravimetrically after removal 

of uncombined water. If a preoperational in-place 

determination of collection efficiency is desired, a 

procedure mutually acceptable to the user and manufac

turer may be used. 

4. QUALITY ASSURANCE 

Components of uranium mills do not require a 

formal quality assurance program; however, particular 

quality assurance requirements may be imposed by the 

NRC as license conditions if deemed necessary to 

protect health. A quality assurance program for emission 

control devices need only be an extension of the overall 

quality assurance program usually submitted by an 

applicant for a license to ensure that the emission 

control devices are designed and the testing, operating, 

and maintenance procedures are implemented to main

tain uniform operation of these devices within prescribed 

ranges under expected operating conditions. 

C. REGULATORY POSITION 

Emissions from milling operations must be controlled 

so that all airborne effluent releases are reduced to 

levels as low as is reasonably achievable. An important 

means of accomplishing this is by means of emission 

control devices in mill ventilation systems. The design 

and the testing, operating, and maintenance procedures 

for these emission control devices should ensure that 

these devices are operating consistently near peak opera

-' tional efficiency.

1. DESIGN AND OPERATION 

In addition to the requirement in Criterion 8 of 

Appendix A to 10 CFR Part 40 that requires checks to 

be made and logged hourly of all parameters that 

determine the efficiency of yellowcake stack emission 

control equipment operation, other emission control 

devices should be sufficiently instrumented to monitor 

all operating parameters necessary to enable timely 

identification of malfunctions. Consideration should be 

given to centralizing equipment instrumentation and 

controls, where feasible, to facilitate ease of changing 

and evaluating operating parameters. 

Instrumentation may be supplemented by audible 

alarms that are preset to signal when prescribed operat

ing range limits are exceeded. 

Consideration should be given to installation of auto

matic shutdown instrumentation on processes and sys

tems so that, when operating parameters on emission 

control devices exceed preset limits, operations would 

cease. 

Equipment used in the emission control system 

should be clearly marked to allow easy identification. 

Up-to-date system drawings should be available to 

identify the location of valves and instruments. A rec

ord of system modification or changes should also be 

available. 

Consideration should be given to keeping records of 

operating data in order to evaluate system performance 

and to provide a basis for establishing or modifying a 

preventive maintenance program. 

Written procedures should be available for equipment 

operation and for operator actions if malfunctions 

occur. Checkoff lists should be considered for complex 

or infrequent modes of operation. Some operational 

procedures that may be considered for typical baghouses 

and wet scrubbers used at uranium mills are presented 

in Appendix C. 

Equipment operators should be instructed in the 

function of each device and its operating characteristics. 

They should also be made aware of consequences of 

malfunctions and misoperation as well as of corrective 

measures that may be taken by the operator. 

Equipment operators should be made aware of modi

fications to the equipment, changes in procedures, and 

problems encountered during system operation. 

2. MAINTENANCE 

A preventive maintenance program should be devel

oped and implemented to sustain proper equipment 

performance and to reduce unscheduled repairs. Inspec

tions should be performed at least annually, more 

frequently if necessary, on all components.

3.56-5
In the development of the maintenance program, con

sideration should be given to the type of emission 

control device, the manufacturer's recommendations, and 

the process at which the unit is installed. This program 

may require periodic updating to reflect onsite mainte

nance experience. 

Schedules and written procedures should be available 

for maintenance work. Maintenance personnel should 

be trained in the implementation of maintenance pro

cedures. They should be trained to recognize the symp

toms that indicate potential problems, to determine the 

cause of the difficulty, and to remedy it with the help, 

if necessary, of the manufacturer or other outside 

resource. 

3. TESTING 

Emission control devices should be tested in place 

at least annually to verify collection efficiency. Collec

tion efficiency for baghouses and wet scrubbers used in 

uranium mills should be based on inlet and outlet 

radioactive particulate concentrations in a dry gas cor

rected to standard temperature and pressure. Inlet and 

outlet (radioactive or uranium) particulate concentrations 

should be sampled simultaneously, if practicable. 

The test should be performed in accordance with 

Method 5 of Appendix A to 40 CFR Part 60 or an 

acceptable equivalent.

If a preoperational in-place determination of collec

tion efficiency is desired, a procedure mutually accept

able to the user and manufacturer may be used. 

4. QUALITY ASSURANCE 

The overall quality assurance program submitted by 

an applicant for a license should include provisions for 

(1) documentation, review, and evaluation of design, 

testing, operating, and maintenance data for emission 

control devices and (2) timely initiation of corrective 

actions necessary to maintain uniform operation of these 

devices within prescribed ranges under expected operat

ing conditions. 

D. IMPLEMENTATION 

The purpose of this section is to provide information 

to applicants and licensees regarding the NRC staff's 

plans for using this regulatory guide. 

Except in those cases in which an applicant or 

licensee proposes an acceptable alternative method for 

complying with specified portions of the Commission's 

regulations, the methods described in this guide will be 

used by the NRC staff in evaluating procedures for 

designing, testing, operating, and. maintaining emission 

control devices used at uranium mills.

3.56-6
BIBLIOGRAPHY

American Industrial Hygiene Association, Air Pollution 

Manual, Part II-Control Equipment, American Industrial 

Hygiene Association, Detroit, Mich., pp. 16-18, 46-56, 

70-75, 129-135, 1968. 

American National Standards Institute, "Fundamentals 

Governing the Design and Operation of Local Exhaust 

Systems," American National Standard ANSI Z9.2-1979, 

Sections 6 and 9, New York, NY, 1980. 

Cross, F. L., and H. E. Hesketh, Handbook for the 

Operation and Maintenance of Air Pollution Control 

Equipment, Technomic Publishing Co., Inc., Westport, 

Conn., Chapters 2 and 6, 1975. 

Industrial Gas Cleaning Institute, "Operation and Main

tenance of Fabric Collectors," Publication No. F-3, 

1972.*

Industrial Gas Cleaning Institute, "Basic Types of Wet 

Scrubbers," Publication No. WS-3, 1980.* 

Theodore, L., and A. J. Buonicore, Air Pollution Con

trol Equipment: Selection, Design, Operation and Main

tenance, Prentice-Hall, Inc., Englewood Cliffs, N.J., 

Chapters 8 and 9, 1983. 

U.S. Environmental Protection Agency, "Handbook

Industrial Guide for Air Pollution Control," EPA-625/ 

6-78-004, Chapter 7, 1978. 

U.S. Environmental Protection Agency, "Management 

and Technical Procedures for Operation and Maintenance 

of Air Pollution Control Equipment," EPA-905/ 

2-79-002, Sections 3 and 5, 1979. 

*Available from the Industrial Gas Cleaning Institute, Inc., 700 N. Fairfax Street, Alexandria, VA 22314.

3.56-7
APPENDIX A 

TYPICAL MAINTENANCE ACTIVITIES FOR BAGHOUSES

COMPONENT 

Baghouse Housing 0 

0

Compressed Air System

S

Dust Collection Hopper

Manometer 

Filter Bags

ACTIVITIES 

Inspect exhaust from filters for visible dust. 

Inspect gasketing on filter housing to ensure 

against leakage. 

Inspect for air leakage (low pressure) and check 

valves.* 

Check alignment of air pulse holes with center 

of bag filters.* 

Inspect for dust and debris buildup in ducts to 

hopper. 

Rod out dust buildup on all accessible hopper 

surfaces. 

Check operation of the discharge mechanism. 

Inspect for blockage. 

Inspect individual filter bags and attachment 

hardware.

S 

S 

S 

S 

S

*Activities applicable to pulse or jet baghouses. The remainder are applicable to all baghouses.

3.56-8
APPENDIX B 

TYPICAL MAINTENANCE ACTIVITIES FOR WET SCRUBBERS

COMPONENT 

Scrubber Body 0 

S 

S

Nozzles 

Entrainment Separator

S 

S 

S 

S 

S

Pumps 

Instruments

ACTIVITIES 

Inspect for wear, particularly in areas downstream 

of gas and liquid acceleration. 

Inspect for corrosion on all scrubber internal surfaces. 

Inspect for excessive buildup, in particular in the 

wet/dry zone. 

Inspect for buildup and damage. 

Check operation. 

Inspect structural supports for integrity. 

Inspect pumps for wear, seal water, packing, and 

smooth operation. 

Inspect the condition of all instruments with regard 

to solids buildup.

3.56-9
APPENDIX C 

TYPICAL OPERATIONAL SURVEILLANCE PROGRAM 

FOR EMISSION CONTROL DEVICES

EMISSION 

CONTROL DEVICE 

Baghouses

Wet Scrubbers

SURVEILLANCE ACTIVITY 

"* Monitoring differential pressure. Adjusting timer or 

differential-pressure switch to adjust frequency of 

automatic cleaning cycle as needed. 

"* Monitoring differential-pressure alarm lights in control 

area. 

"* Monitoring compressed air pressure gauge on high

pressure air system. 

"* Monitoring air flow instrumentation in control area. 

"* Monitoring differential pressure. 

"* Monitoring differential-pressure alarm lights in control 

area. 

"* Monitoring air flow instrumentation and alarm lights 

in control area. 

"* Monitoring water flowmeters. 

"* Monitoring water pressure alarm lights in control area. 

"* Monitoring control area process control indicator 

lights for possible process shutdown in the event 

of water flow failures at preconditioning sprays 

or at the scrubber.

3.56-10
VALUE/IMPACT STATEMENT

The NRC staff performed a value/impact assessment 

to determine the proper procedural approach for pro

viding guidance on designing, testing, operating, and 

maintaining emission control devices at uranium mills. 

The assessment resulted in a decision to develop a 

regulatory guide describing procedures for designing, 

testing, operating, and maintaining emission control 

devices at uranium mills. The results of this assessment 

were included in a draft regulatory guide on this sub

ject, CE. 309-4, that was issued for public comment in

May 1985. Comments received from the public and 

additional NRC staff review have shown no need to 

change the value/impact statement published with the 

proposed regulatory guide. Therefore, the value/impact 

statement published with the proposed guide is still 

applicable. A copy of the draft regulatory guide (identi

fied by its task number, CE 309-4) and its associated 

value/impact statement is available for inspection and 

copying for a fee at the NRC Public Document Room 

at 1717 H Street NW., Washington, DC.

3.56-11
UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

WASHINGTON, D.C. 20555

FIRST CLASS MAIL 

POSTAGE Er FEES PAID 

USNRC 

WASH. O.C. 

PERMIT No. G-67

OFFICIAL BUSINESS 

PENALTY FOR PRIVATE USE, $300