Information Notice 1996-18, Compliance with 10 CFR Part 20 for Airborne Thorium

Compliance with 10 CFR Part 20 for Airborne Thorium
	ML031060199
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	03/25/1996
From:	Cool D; NRC/NMSS/IMNS
To:	;
References
	IN-96-018, NUDOCS 9603200218
	Download: ML031060199 (14)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON D.C. 20555 March 25, 1996 NRC INFORMATION NOTICE 96-18: COMPLIANCE WITH 10 CFR PART 20 FOR AIRBORNE

THORIUM

Addressees

All material licensees authorized to possess and use thorium in unsealed form.

Purpose

This notice is provided to alert recipients to radiological problems that may

be encountered in using thorium in unsealed form. These problems were

identified by U.S. Nuclear Regulatory Commission (NRC) inspectors, during

inspections of the approximately 120 licensees authorized to use unsealed

thorium, some of which are engaged in processing and manufacturing activities

that pose a potential for generating significant airborne radioactive

contamination. It is expected that recipients will review the information for

applicability to their facilities and consider actions, as appropriate, to

avoid similar problems. However, suggestions contained in this information

notice are not NRC requirements; therefore, no specific action or written

response is required.

Description of Circumstances

NRC inspections at facilities using thorium in unsealed form revealed a number

of programmatic weaknesses in the control and monitoring of airborne thorium

hazards at an unexpectedly high proportion of these facilities. One of the

areas of weakness frequently encountered was worker intake monitoring programs

that did not appear capable of adequately quanti,-rng intakes for purposes of

demonstrating compliance with the requirements of 10 CFR Part 20, particularly

the annual limits on intake (ALI). A second area of concern was the frequent

lack of adequate licensee efforts to maintain exposures as low as reasonably

achievable (ALARA), as required by 10 CFR 20.1101(c). NRC inspectors

repeatedly observed intakes and resulting organ doses that appeared to be

unnecessary, or avoidable, in view of the potential to reduce them by

implementation of relatively simple ALARA measures. Some of the intakes in

these cases were evaluated and produced organ doses in the 0.2 to 0.3 Sv

(20 - 30 rem) range in a year. Such high doses, representing a substantial

fraction of the maximum permissible organ doses, cannot be viewed as

acceptable unless justified by a thorough ALARA analysis. In most of the

observed cases, however, an adequate ALARA assessment had not been performed.

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IN 96-18 March 25, 1996 Demonstration of compliance with dose limits to members of the public, from

airborne thorium, was also found, in some cases, to have been less than

adequate. In some cases, the licensees were found to have no adequate

monitoring systems for their airborne effluents, and in others the methods

used to quantify these effluents did not possess sufficient sensitivity to

enable demonstration of compliance.

In response to the regulatory violations noted above, NRC issued Confirmatory

Action Letters (CALs) to a number of licensees, confirming commitments to

taking specific actions to correct these deficiencies. Notices of Violation

and other enforcement actions were also taken by NRC, in some cases. These

actions, as well as extensive discussions with licensees, to alert them to the

problems, have resulted in substantial improvements in most licensees'

programs.

Discussion

The programs that licensees should develop for control of airborne hazards

arising from the use of unsealed thorium do not differ in any basic respect

from those needed in the case of programs to control the hazards from any

airborne radioactive material. Facilities using thorium, however, must make

allowances for certain constraints imposed by the nature of the thorium decay

chain. The major constraint is the difficulty of measuring thorium-232 (Th-232) in the body after an intake using bioassay methods, either in vivo, such as whole body counting, or in vitro, such as urine analysis. This is

caused, in part, by the relatively low ALI for Th-232, which is 37 Bq (1 nCi)

for class W. and 111 Bq (3 nCi) for class Y aerosols, as well as the type of

radiation emissions from the thorium decay chain, which are mostly alpha and

beta radiations, with only relatively low-intensity gamma radiations.

The difficulties regarding the use of bioassay methods were increased after

implementation of the revised 10 CFR Part 20, which became mandatory for all

licensees on January 1, 1994. Intakes of Th-232 by inhalation before the

Part 20 revisions were limited to 520 MPC-hours per quarter, where MPC was the

maximum permissible concentration tabulated in the old Appendix B to 10 CFR

Part 20. This was equivalent to an intake of about 700 Bq (19 nCi) per

quarter for both the soluble and insoluble forms of thorium, or about 2800 Bq

(75 nCi) per year. The revised Part 20 lowered that limit to ALIs of about

40 Bq (1 nCi) and 100 Bq (3 nCi) for classes W and Y aerosols, respectively.

Therefore, bioassay methods that may have been capable of detecting intakes

that were a small fraction of the allowable limits in the old Part 20 were no

longer capable of the same performance under the revised Part 20 limits, and

could therefore not serve the same monitoring functions in a routine airborne

radioactivity control program as they did previously.

IN 96-18 March 25, 1996 Although bioassay techniques'are still useful in assessing relatively large

intakes, they are not capable of providing routine monitoring for intakes

substantially below the ALI. The air monitoring program therefore usually

must assume a much greater importance at facilities using unsealed thorium

than for other radionuclides. Facilities using thorium need to rely on

accurate air sampling to estimate intakes that cannot be detected by bioassay

techniques, which, in effect includes all intakes other than those that

approach or exceed the ALI. Because of this reliance on air sampling to show

compliance and assess internal doses, the air sampling program must be

carefully designed to provide accurate intake estimates for all occupationally

exposed workers, as well as members of the public who may be exposed to

airborne thorium as a result of licensed operations. However, appropriate

bioassay procedures should be established and available for use in assessing

accidental or suspected high exposures, and for use in cases where adequate

air sampling was inadvertently not provided. In this latter case, bioassay

would provide an upper limit on the magnitude of any intake that may have

occurred, even though it may not be capable of quantifying intakes below an

ALI.

Air Sampling

The major deficiencies noted in air sampling programs at some of the inspected

facilities included programs that did not provide samples that are representa- tive of the intake by each exposed worker, monitoring frequencies that were

far too low to be capable of detecting changes in air concentrations over

time, and counting techniques that did not possess adequate sensitivity for

their intended purpose.

One of the factors that led to non-representative samples was the excessive

reliance on general area air sampling to monitor worker intakes in that area.

Studies have repeatedly shown that air concentrations in a work area can vary

by several orders of magnitude over distances of only a few feet, and a

general area sample is most likely to grossly underestimate the intake of a

worker involved in activities that generate aerosols. With rare exception, the most reliable method of assessing worker intakes is by use of personal air

samplers. In the case of effluent sampling, the method chosen should be

capable of obtaining a representative sample from the exhaust duct or other

outlet. For aerosols, this usually means use of isokinetic sampling methods, and licensees should determine, for their particular case, whether such

sampling methods are needed.

The choice of method of analysis should also be given careful consideration.

This includes choice of the filter medium to use in the air sampler, air flow

rates, as well as choice of counting techniques. These factors should be

IN 96-18 March 25, 1996 selected to ensure that the desired monitoring sensitivity, expressed as a

lower limit of detection (LLD), is achieved. A good guide as to the appro- priate LLD to use in any application is that it should not exceed 10 percent

of the value to which compliance is to be demonstrated.

ALARA

Licensees are required, by 10 CFR 20.1101(b), to demonstrate that the doses

received by their workers, or by members of the public, as a result of their

activities, are ALARA. The most effective method to maintain internal doses

ALARA is usually to contain the radioactive material and prevent it from

entering the air in the work space. Other methods might be use of wet pro- cesses, which have the effect of preventing or minimizing the generation of

aerosols, or use of other engineering controls, depending on the details of

the aerosol-generating process and the configuration of the workplace.

Regardless of the choice of engineering controls, their use must include

periodic maintenance to ensure continued effectiveness, as well as periodic

checks to ensure that the systems remain effective.

If engineering controls fail to maintain airborne concentrations at suffi- ciently low levels, then other methods may be used, such as limiting stay

times, or restricting access to the contaminated areas. Alternatively, respirators may be used to limit intakes during periods when other measures

are not sufficiently effective. It should be noted, however, that 10 CFR

Part 20 specifies that respirators are to be used only when other methods of

control of intake fail to achieve the desired result or are impractical.

The above discussion on air sampling and ALARA is not exhaustive, and only

highlights some of the most frequently encountered problems. Licensees should

thoroughly evaluate their operations, and design and implement programs that

would properly protect the workers, minimize intakes, and show compliance with

applicable regulations. These evaluations are not one-time efforts, but

should be ongoing and integral parts of the overall radiation protection

program on site.

IN 96-18 March 25, 1996 This information notice requires no specific action or written response. If

you have any questions about this matter, please call one of the technical

contacts listed below or the appropriate regional office.

Donald A. Cool, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Sheri Arredondo, Region I

(610) 337-5342 Internet:saal@nrc.gov

Sami Sherbini, NMSS

(301) 415-7902 Internet:sxs2@nrc.gov

Attachments:

1. List of Recently Issued NMSS Information Notices

2. List of Recently Issued NRC Information Notices

d/-4- e 4 Is XiX,4 >SC

Attachment 1 IN 96-18 March 25, 1996 LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-04 Incident Reporting 01/10/96 All Radiography Licensees

Requirements for and Manufacturers of

Radiography Licensees Radiography Equipment

95-58 10 CFR 34.20; Final 12/18/95 Industrial Radiography

Effective Date Licensees.

95-55 Handling Uncontained 12/6/95 All Uranium Recovery

Yellowcake Outside of a Licensees.

Facility Processing Circuit

95-51 Recent Incidents Involving 10/27/95 All material and fuel cycle

Potential Loss of Control licensees.

of Licensed Material

95-50 Safety Defect in Gammamed 10/30/95 All High Dose Rate

12i Bronchial Catheter Afterloader (HDR) Licensees.

Clamping Adapters

95-44 Ensuring Combatible Use of 09/26/95 All Radiography Licensees.

Drive Cables Incorporating

Industrial Nuclear Company

Ball-type Male Connectors

95-39 Brachytherapy Incidents 09/19/95 All U.S. Nuclear Regulatory

Involving Treatment Commission Medical

Planning Errors Licensees.

95-29 Oversight of Design and 06/07/95 All holders of OLs or CPs

and Fabrication Activities for nuclear power reactors.

for Metal Components Used

in Spent Fuel Dry Storage Independent spent fuel

Systems storage installation

designers and fabricators.

Attachment 2 IN 96-18 March 25, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

95-03 Loss of Reactor Coolant 03/25/96 All holders of OLs or CPs

Supp. 1 Inventory and Potential for PWR power plants

Loss of Emergency Mitiga- tion Functions While in a

Shutdown Condition

96-17 Reactor Operation Incon- 03/18/96 All holders of OLs or CPs

sistent with the Updated for nuclear power reactors

Final Safety Analysis

Report

96-16 BWR Operation with 03/14/96 All holders of OLs or CPs

Indicated Flow Less Than for boiling-water reactors

Natural Circulation

96-15 Unexpected Plant Perform- 03/08/96 All holders of OLs or CPs

ance During Performance for nuclear power reactors

of New Surveillance Tests

96-14 Degradation of Radwaste 03/01/96 All holders of OLs or CPs

Facility Equipment at for nuclear power reactors

Millstone Nuclear Power

Station, Unit 1

96-13 Potential Containment 02/26/96 All holders of OLs or CPs

Leak Paths Through for nuclear power reactors

Hydrogen Analyzers

96-12 Control Rod Insertion 02/15/96 All holders of OLs or CPs

Problems for nuclear power reactors

96-11 Ingress of Demineralizer 02/14/96 All holders of OLs or CPs

Resins Increases Potential for pressurized water

Stress Corrosion Cracking nuclear power reactors

of Control Rod Drive

Mechanism Penetrations

OL = Operating License

CP = Construction Permit

IN 96-18 March 25, 1996 This information notice requires no specific action or written response. If

you have any questions about this matter, please call one of the technical

contacts listed below or the appropriate regional office.

Donald A. Cool, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Sheri Arredondo, Region I

(610) 337-5342 Internet:saal@nrc.gov

Sami Sherbini, NMSS

(301) 415-7902 Internet:sxs2@nrc.gov

Attachments:

1. List of Recently Issued NMSS Information Notices

2. List of Recently Issued NRC Information Notices

Document: 96-18.IN INITIALS: __

KMR CXH FCC CLE

NMSS/EDITOR EKRAUS [TICKET - IKNS-5083]

2/14/96 OFC IINS* L REGION I* I REGION I* REGION I*

NAME SSherbini/ss/ll SArredondo MShanbaky RBellamy

DATE 10/25/95 11/14/95 1 11/14/95 11/14/95 OFC INNS* I INNS* I IMN, I

NAME LCamper GPangburn

DATE 2/09/96 12/05/95 03/Z6/96 Tv14id So 3 CE46 cP

IN 96-XX

March XX, 1996 If engineering controls fail to maintain airborne concentrations at

sufficiently low levels, then other methods may be used, such as limiting stay