Dose Limits, Biological Effects & Risk Module 3 Dose Limits, Biological Effects & Risk

Objectives Understand exposure limits and control levels Define occupational exposure Understand Navy limits Genetic and Biologic effects Understand Risk

Members of the Public NRC Limits: 2 mrem (0.02 mSv) in any one hour. Radiation Dose Limit for Individual Members of the Public 2 mrem (0.02 mSv) in any one hour. 100 mrem (1 mSv) in a calendar year. External radiation – Directives state that radioactive material and other sources of radiation shall not be used, maintained, or transferred in such a manner as to cause: The dose in any unrestricted area from external sources, to exceed 2 mrem (0.02 mSv) in any one hour. An individual member of the general public to receive a total effective dose equivalent in excess of 100 mrem (1 mSv) in a calendar year. Exposure limits for members of the public shall continue to apply when the member enters a controlled area. Exposure limits for members of the public apply to unrestricted areas and berthing spaces. It must be locally documented, by measurement, calculation, or both, that due to limited occupancy or transient situations: The maximum exposed individual’s total effective dose equivalent (TEDE) from occupancy in all unrestricted areas would not be expected to exceed 100 mrem (1 mSv)per calendar year. 10CFR20.1301 & 1302

Rad Worker limits and control levels NRC Limit for Workers (10CFR20.1201) 5 rem (0.05 Sv) in a calendar year BUMED Limit (NAVEMED P-5055, CH. 4-3) 3 rem (0.03 Sv) per calendar quarter Administrative Control Level NPS control level of 0.1 rem per year RASP control level of 0.5 rem per year

RASP administrative control level is set at 500 mrem per calendar year RASP Control Levels RASP administrative control level is set at 500 mrem per calendar year Provides an administrative review point Only the President, NPS, may authorized exceeding the RASP Control Level of 500 mrem/yr

NPS administrative control level set at 100 mrem per calendar year NPS Control Level NPS administrative control level set at 100 mrem per calendar year Expected dose evaluation performed at 80 mrem/yr 100 mrem/yr requires Radiation Medical Exam

Occupational Exposure The dose received by an individual in the course of employment in which the individual’s assigned duties involve exposure to radiation. Includes Licensed and Machine Sources Personnel exposure Background (Reg. Guide 8.29). Man made sources Occupational exposure - received by individuals who perform radiologically related work. Medical exposure – not considered as occupational exposure and is exempted by the Nuclear Regulatory Commission 1.) Diagnostic – used for identifying medical conditions. 2.) Therapeutic – used in the treatment of certain medical conditions.

Occupational dose does not include: Non Occupational Dose Occupational dose does not include: Dose received from background radiation 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.

Navy Boundaries High Radiation Area 100 mrem/hr Radiation Area STRESS: We post sign at the NRC restricted are not the NRC radiation area. § 20.1302 Compliance with dose limits for individual members of the general public Radiation Area 2 mrem/hr

Navy Radiation Boundaries Radiation Area 2 mrem/hr High Radiation Area 100 mrem/hr Very High Radiation Area 500 rad in any one hour

Embryo/Fetus Exposure Female employees may have dose limited to 50 mrem/month during pregnancy by informing command in writing. Dose calculated from the date of conception. References: P-5055 Art. 5-10, RAD-010 Section 2.1.6 & 10CFR20.1003 Must declare pregnancy on a Chronological Record of Medical Care (SF-600) Signature on the form must be witnessed by someone from Medical. “I hereby make notification I am pregnant. My estimated date of conception is _________. I understand by declaring my pregnancy, my occupational exposure to ionizing radiation will be controlled so that the dose to my unborn child does not exceed the limits prescribed in Ch. 4 of NAVMED P-5055, the Navy Radiation Health Protection Manual.” At the conclusion of the pregnancy the woman must notify the command of the date the pregnancy ended so that the Total Effective Dose Equivalent to the embryo/fetus may can be calculated and her exposure limit can be modified back to her whole body limit. An entry shall be made on the SF-600 documenting the date the declared pregnancy ended.

Special Limits for Embryo/Fetus Federal limit 500 mrem (5 mSv) for gestation period 50 mrem (0.5 mSv) for one month Limits for Declared Pregnant Worker References: P-5055 Art. 4-4, 10CFR20.1208, RAD-010 Section 2.1.6, NRC Regulatory Guide 8.13

Radiation can cause cell damage to Biological Effects Radiation can cause cell damage to Cell structure Chromosomes Damage may result in: Cell death Abnormal cell reproduction Cell repair Effects minimal if repaired faster than additional damage is done Corporate Slide (modified) It is fair to say that there has been more scientific study on the effects of ionizing radiation than on most, if not all, other occupational hazards. National Academy of Sciences Report of the Committee on the Biological Effects of Ionizing Radiations, 1980  

Dose Effect Relationships Acute: Significant exposure over a short period of time. Chronic: Small exposure over a long period of time. Classification of doses Acute: The absorption of a relatively high radiation dose in a short period of time (i. e. in a few hours). Chronic: The absorption of a relatively low radiation doses over a long period of time Fractionated: Doses of radiation delivered incrementally Effects of acute radiation dose: Hematopoetic syndrome (blood and blood forming organs). Occurs after an acute exposure of 1 to 5 gray (100 to 500 rad). 1.) Nausea 2.) Vomiting 3.) Some diarrhea 4.) Transitory 5.) LD 50/60 (50% of exposed die in 60 days) 5 Gy (500 rad) Gastrointestinal syndrome 1.) Occurs after an acute exposure of 5-20 Gy (500 to 2000 rad) 2.) Small intestine is the critical organ. 3.) Nausea and vomiting. 4.) Maximum survivable dose is 10 Gy (1000 rad). 5.) Therapeutic range is 1 - 10 Gy (100 to 1000 rad). Central Nervous Syndrome Occurs after and acute exposure of 20 Gy (2000 rad). 1.) Death within 1-2 days. 2.) Nausea and vomiting almost immediate. 3.) Neurological, psychological trauma. 4.) Tremors, convulsions, coma. 5.) Direct and indirect damage to cells Effects of Chronic radiation doses and late effects Purpose of small doses over extended periods is to reduce or eliminate delayed or genetic (stochastic) effects. Allows the cells of the body to recover and repair any damage. At current dose levels and limits there should be no late or long term effects from occupational exposure to ionizing radiation.

Acute effects 25 rem of acute whole body exposure will cause a change in white blood cell percentage 100 rem of acute whole body exposure will cause radiation sickness Approximately 50% of the people who receive 500 rem acute whole body exposure will die without prompt medical attention 600 rem of acute skin exposure will cause 1st degree burns Somatic: Reduction in the white blood cell count One of the first observed somatic effects is a transient (temporary) reduction in the white blood cell count which results from an exposure of 25,000 mrem (25 rem) received in a period of eight hours or less. Radiation burns: Equivalent to a first degree burn and become evident when the dose to a portion of the body exceeds about 600 rads (6 Gy ) Radiation sickness: Radiation sickness - nausea, vomiting, diarrhea within a few hours after exposure as the dose delivered to the torso increases above 100 rad (1 Gy). Two or three weeks later other symptoms may appear such a loss of hair, loss of appetite, general weakness, a feeling of ill health, and purpura (purple spots on the skin). Delayed effects: Cancer and genetic defects in offspring. Radiosensitivity – susceptibility of cells to radiation damage, Law of Bergonie and Tribondeau: a. Cells which are actively reproducing are more susceptible to radiation damage than cells which are dormant or not actively reproducing b. Cells with high rates of metabolism are more susceptible to radiation damage than cells which have low metabolic rates. c. Cells which are not fully matured or that are undifferentiated are more susceptible to radiation damage than fully matured or fully differentiated cells. Genetic – abnormalities that may occur in the future children of exposed individuals and in subsequent generations Genetic effects exceeding normal incidence have not been observed in any of the studies of human populations. For reference see: (Reg Guide 8.13)

Chronic effects The Navy has always conservatively assumed that radiation exposure, no matter how small, may involve some risk. Therefore radiation exposures should be kept As Low As Reasonably Achievable.

Radiation risk to personnel Is being a radiation worker safe?

Radiation risk to radiation workers In a group of 10,000 workers, about 2000 (20%) will normally die from cancer. If each of the 10,000 received over his or her career an additional 1 rem, then an estimated 4 additional cancer deaths (0.04%) might occur. Therefore, the average worker’s lifetime risk of cancer has been increased nominally from 20% to 20.04%.

Lifetime Occupational Risks Lifetime Risk Percent (Assumes working from 18 to 65 years of age (47 total years) Occupation Agriculture Mining, Quarrying Construction Transportation and Public Utilities All Industries Average Government Services Manufacturing Trade Radiation exposure associated with 1 rem lifetime dose 2.1 2.0 1.5 1.0 0.4 0.2 0.04

Some Commonplace Lifetime Risks Lifetime Risk Percent* Tobacco Poor Diet/Lack of Exercise Infectious Agents Accidents (all) Firearms Motor Vehicle Accidents Falls Accidental Poisoning Drowning Fires Other Land Transport Accidents Radiation exposure associated with 1 rem (risk estimate) 11.1 10.7 3.0 2.7 1.5 1.2 0.42 0.39 0.09 0.08 0.03 0.04 * For tobacco use, the risk assumes the population is at risk from age 18 to 76.5 years (58.5 years). Other risks assume the population is at risk for a lifetime (76.5 years)

Dose to radiation workers A person would get a dose of at least one mrem from: Spending a few days in Atlanta or Denver Spending less than a day in some parts of Brazil An average year of TV watching A year of wearing a luminous dial watch A coast-to-coast airline flight

Is being a radiation worker safe? Any exposure may involve some risk. Exposure to personnel within the accepted limits represents a risk that is small when compared with normal hazards of life. Radiation risk to RASP workers – As with the risks associated with occupational exposure from other types of work involving radiation and radioactive materials, the risk to RASP workers is considered to be smaller than the risk of accidents in many other jobs if work is performed within the limits and guidelines established by the Nuclear Regulatory Commission.