Dose Limits

Radiological Safety and ResponseRPT-243 -2

Learning OutcomesUpon completion of this lesson, the student will be able to:

• Discuss the regulatory dose limits from 10CFR20 and 10 CFR835.

• State the purpose of having plant administrative limits for radiation exposure (such as margin from regulatory limits).

• Describe when a planned special exposure is allowed and the detailed requirements of the planned special exposure.

• Describe exposure control techniques that can be used to control worker and technician radiation exposures.

Outline• Introduction• 10CFR20 Limits• 10 CFR 835 Limits• Administrative Limits• Planned Special Exposures• Exposure Control Techniques• Questions

Introduction

Introduction

• As discussed in the previous lecture, the nuclear industry is regulated through the use of either the 10CFR20 or 10CFR835 codes depending on whether it is NRC or DOE.

• In this lecture, we will look at the various dose limits used in the industry established by these regulations.

• The principle of administrative limits and planned special exposures will also be discussed.

• Finally, we will further explore exposure control techniques.

10CFR20 Dose Limits

Basic Terms• Whole body means, for purposes of external

exposure, head, trunk (including male gonads), arms above the elbow, or legs above the knee.

• Extremity means hand, elbow, arm below the elbow, foot, knee, or leg below the knee.

• Dose or radiation dose is a generic term that means absorbed dose, dose equivalent, effective dose equivalent, committed dose equivalent, committed effective dose equivalent, or total effective dose equivalent (exposure is used as an equivalent term here).

Subpart C – Occupational Dose Limits - Adults

• Occupational Dose is defined as:– the dose received by an individual in the course of

employment in which the individual's assigned duties involve exposure to radiation or to radioactive material from licensed and unlicensed sources of radiation, whether in the possession of the licensee or other person.

Subpart C – Occupational Dose Limits - Adults

• Occupational Dose :– does not include doses received from:

• background radiation, • any medical administration the individual has received, • exposure to individuals administered radioactive

material and released under § 35.75, • from voluntary participation in medical research

programs, • or as a member of the public.

10CFR20.1201

Occupational Dose Limits - Adults• The licensee SHALL control individual occupational

adult doses to the following annual limits:– Total Effective Dose Equivalent (TEDE) of 5

rem/yrOR

– Sum of the deep-dose equivalent (DDE) and the committed dose equivalent (CDE) to any individual organ or tissue (except lens of the eye) being equal to 50 rem/yr

AND

10CFR20.1201

Occupational Dose Limits - Adults– Lens dose equivalent (LDE) (lens of the eye) -

15 rem/yr

AND– Shallow dose equivalent (SDE) (skin of the

whole body or any extremity) - 50 rem/yr

• The most limiting is used to determine compliance.

10CFR20.1201

Occupational Dose Limits - Adults• Derived air concentration (DAC) and annual limit on

intake (ALI) values are presented in table 1 of appendix B to part 20 and may be used to determine the individual's dose and to demonstrate compliance with the occupational dose limits.

• In addition to the annual dose limits, the licensee shall limit the soluble uranium intake by an individual to 10 milligrams in a week in consideration of chemical toxicity (see footnote 3 of appendix B to part 20).

10CFR20.1201

Occupational Dose Limits - Adults• The licensee shall reduce the dose that an

individual may be allowed to receive in the current year by the amount of occupational dose received while employed by any other person

10CFR20.1207

Occupational Dose Limits - Minors• Minor means an individual less than 18 years

of age.• The annual occupational dose limits for

minors are 10 percent of the annual dose limits specified for adult workers in § 20.1201.

10CFR20.1208Occupational Dose Limits

Unborn Child

• Dose equivalent to the embryo/fetus during the entire pregnancy, due to the occupational exposure of a declared pregnant woman, does not exceed 0.5 rem – The dose equivalent to the embryo/fetus is the sum of:

(1) The deep-dose equivalent to the declared pregnant woman; and

(2) The dose equivalent to the embryo/fetus resulting from radionuclides in the embryo/fetus and radionuclides in the declared pregnant woman.

10CFR20.1208Occupational Dose Limits

Unborn Child

• Dose equivalent to the embryo/fetus during the entire pregnancy, due to the occupational exposure of a declared pregnant woman, does not exceed 0.5 rem – The dose equivalent to the embryo/fetus is the sum of:

(1) The deep-dose equivalent to the declared pregnant woman; and

(2) The dose equivalent to the embryo/fetus resulting from radionuclides in the embryo/fetus and radionuclides in the declared pregnant woman.

10CFR20.1208Occupational Dose Limits

Unborn Child

• If the worker has received 0.5 rem at time of declaration, then the limit becomes less than or equal to 0.05 rem during remainder of pregnancy.

Subpart D - Radiation Dose Limits for Individual Members of the Public

• Public dose means the dose received by a member of the public from exposure to radiation or to radioactive material released by a licensee, or to any other source of radiation under the control of a licensee.

• Public dose does not include occupational dose or doses received from background radiation, from any medical administration the individual has received, from exposure to individuals administered radioactive material and released under § 35.75, or from voluntary participation in medical research programs.

10CFR20.1301Limits Members of the Public

• 0.1 rem in a year - TEDEAND• Dose received in unrestricted areas shall be controlled

below 0.002 rem in any one hour

10CFR835Dose Limits

Subpart C - Standards for Internal and External Exposure

10CFR835.202Occupational Dose Limit for General Employees

General employee means an individual who is either:• a DOE or DOE contractor employee; • an employee of a subcontractor to a DOE contractor; • or an individual who performs work for or in conjunction

with DOE or utilizes DOE facilities.

10CFR835.202Occupational Dose Limit for General Employees

Doses shall be controlled such that the following limits are not exceeded in a year:• Total Effective Dose of 5 rem• Sum of the equivalent dose to the whole

body and the committed equivalent dose to any individual organ or tissue (except the skin or lens of the eye) being equal to 50 rem

10CFR835.202Occupational Dose Limit for General Employees

– An equivalent dose to the lens of the eye of 15 rems

– The sum of the equivalent dose to the skin or to any extremity for external exposures and the committed equivalent dose to the skin or to any extremity of 50 rems

10CFR835.207

Limits for the Unborn Child• The equivalent dose limit for the embryo/fetus from the

period of conception to birth, as a result of occupational exposure of a declared pregnant worker, is 0.5 rem

10CFR835.207

Limits for the Unborn Child• If the equivalent dose to the embryo/fetus is determined to

have already exceeded 0.5 rem by the time a worker declares her pregnancy, the declared pregnant worker shall not be assigned to tasks where additional occupational exposure is likely during the remaining gestation period.

10CFR835.207

Occupational Dose Limits - Minors• Minor means an individual less than 18 years

of age.• The dose limits for minors occupationally

exposed to radiation and/or radioactive materials at a DOE activity are:– 0.1 rem total effective dose in a year and – 10 percent of the occupational dose limits .

• Member of the public means an individual who is not a general employee. An individual is not a “member of the public” during any period in which the individual receives an occupational dose.

• Controlled area means any area to which access is managed by or for DOE to protect individuals from exposure to radiation and/or radioactive material.

10CFR835.208Limits Members of the Public Entering A Controlled

Area

10CFR835.208Limits Members of the Public Entering A Controlled

Area• The total effective dose limit for members of the public

exposed to radiation and/or radioactive material during access to a controlled area is 0.1 rem in a year.

Administrative Dose Limts

Administrative Margin

• The regulatory limits just discussed have been established based on various studies and research.

• The level at which they have been set ensure the absence of any discernably adverse effects either in the person receiving the dose or in their progeny.

• Failure to maintain dose received below the limits in any of the categories is a violation of the federal law; therefore, very serious.

Administrative Margin

• Because of that, every organization establishes administrative limts which are significantly less than the federal limit- creating a “margin of safety”.

• The administrative limits are usually stipulated in administrative and implementing level procedures.

• Typically, exceeding administrative limits is also viewed very seriously and is investigated through the organization’s incident reporting process.

Planned Special Exposure

In Both Regulations

• Defined in 10CFR20 - Planned special exposure (PSE) means an infrequent exposure to radiation, separate from and in addition to the annual dose limits. Addressed in 10CFR20.1206.

• Although not specifically defined in 10CFR835, PSE is addressed in 10CFR835.204 and is the same principle as in 10CFR20.

In Both Regulations

• Basically, the doses received in a PSE are not counted against the annual limits.

• However, a PSE follows a stringent process which involves detailed planning and prior authorization from upper management.

• The PSE dose received is limited to no more than the normal annual limits in each case

AND• No more than 5 times the annual limits when summed over

a lifetime.• Not often used and then only with great care and kept

ALARA.

Exposure Control Techniques

Remember

• The last lecture introduced the main means by which dose is reduced:– Annual Collective and Individual Dose Goals– ALARA Job Planning Group– ALARA Committee Formation and Operation– RWP– “The Big Three” – TDS

• Here will look in a little more detail at some select areas.

In the Field

• As an RP Technician you are viewed as the “expert” in the field.

• If there is a question in the field, you will be sought out for assistance.

• Often, you are placed “in charge” of the radiological aspect of the job.

• You provide job coverage.• Job overage may be classified as:

– part time (initial and intermittent)– full coverage (continuous coverage)

Job Coverage

• Part Time Coverage (Initial and Intermittent) – will be for jobs that have a potential for impacting the radiological conditions of the area. – The technician will do an initial radiological

assessment (dose rates, air sample possibly, maybe some contamination surveys)

– Additional assessments will performed based on the specifics of the task.

– Aside for that the technician is not required to be in the area.

– Typically not a dose issue.

Job Coverage

• Full Coverage (Continuous Coverage) – is required when the radiological conditions warrant the presence of the “expert” at all times that workers are in the area.– The technician does an initial radiological

assessment and informs the workers of the conditions.

– The tech provides on-site instructions needed to maintain dose ALARA and to protect the worker.

– The tech will often assign local stay times and will keep time on the workers.

Job Coverage

• Full Coverage (cont’d) –– Direct workers away from hot spots or areas of

higher dose– Look for shadow shielding to take advantage of – The idea is, the tech serves as an objective

monitor of the radiological conditions in the area, of the workers’ accumulating dose, or as a time keeper.

– Do not get side-tracked or involved in the task you are covering

– Maintain your objectivity

What Are Your Questions?