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LLE Safety Zone

Radiological Safety

Radiological Controls Manual (LLE INST 6610) pdf: 4.2 MB
Radiological Materials Shipment (LLE INST 6680) pdf: 1.6 MB
UR Medical Center Radiation Safety Unit (Requires UR HRMS login to access)
Radiation Safety Training for General Radiation Workers pdf: 1.1 MB
Dosimetric Calculations pdf: 153 KB

Federal and State regulations govern the UR/LLE Radiation Safety Program

  • Requirements come from the Nuclear Regulatory Commission (NRC), Environmental Protection Agency, and Department of Transportation
  • New York State has accepted regulatory authority from the NRC.
    • NYS Department of Health (DOH) governs the use of radioactive material and radiation-producing devices in NYS
    • Department of Environmental Conservation governs the release of radioactive material to the general public
  • University of Rochester is licensed by the NYS DOH
    • UR’s Radiation Safety Unit (RSU) administers the University’s radiation safety program.
    • UR’s Radiation Safety Committee establishes the procedures for the RSU and oversees their operations.
    • LLE operates under a permit issued by the RSU

Types of radiation governed by the radiation safety program 

Type Mass Charge Penetrating ability Shielding
Alpha 4 +2 Very low Skin, paper
Beta ~0.0003 ±1 Low Clothing, plastic
Gamma 0 0 High Lead, water
Neutron 1 0 High Water, plastic

Units of activity and measurements of radiation

  • Activity: number of transformations per unit time
  • Curie: 3.7 x 1010 disintegrations per second
  • Dose: the energy imparted to matter by radiation
  • Rad: unit of dose equal to absorption of 100 ergs/gram of material
  • Dose equivalent: biological damage caused by absorbed dose
    DE = dose x quality factor,
    Where: QF = 1 for gamma and beta
    = 20 for alpha
    = 3 to 10 for neutrons
  • rem – roentgen equivalent man, a unit of dose equivalent
    1 rem = 100 erg/gram of biological equivalent damage
  • Half-life: time required for activity of a substance to decrease by half

Principal OMEGA facility radiation sources 

  • Neutron radiation from fusion
    • Maximum credible yield shot of 3 x 1015 neutrons yields 516 rem at surface of the OMEGA target chamber (OMEGA EP maximum is ~1012neutrons)
  • Gamma radiation from neutron activation of structural components
    • Principal sources are Na24 (15 d) and Mn54 (312 d)
    • Maximum radiation after ten years not expected to exceed 5 mr/hr shortly after a target shot
  • Beta radiation from tritium
    • Up to 15,000 Ci in Tritium Fill Station
  • High-energy x-ray radiation (up to 10 Mev) via bremsstrahlung from fast electrons produced by high-intensity photon bombardment of high-Z target (primary radiation source for OMEGA EP)

Radiation exposure limits and natural sources

To protect people from any harmful effects, radiation exposure from other than natural sources is limited by law to the following:

Radiation worker exposure limit 5,000 mrem/year
General public exposure 100 mrem/year

Surface contamination, airborne, and annual limit on intake tritium limits and basis

  • Surface contamination
    • Limit: 1,000 DPM/100 cm2
      Basis: Control spread of radioactive material, not exposure (continuous exposure to 108 DPM/100cm2 ⇒ 5 rem/yr)
  • Airborne limit
    • Limit for radiation workers: 20 µCi/m3
      Basis: Exposure to this level for 2000 h/yr gives a dose of 5 rem
    • Limit for general public: 0.1 µCi/m3
      Basis: Continuous exposure to this level will give an individual one half of their yearly limit of 100 mrem
  • Annual limit on intake (ALI):
    • Limit: 80 mCi
      Basis: 5 rem

Natural radiation sources and exposure levels are as follows:

Cosmic rays (from outer space) 45 mrem/year/person
Terrestrial (from natural minerals) 65 mrem/year/person
Internal (from elements in the body) 25 mrem/year/person

Biological effects of radiation

  • Radiation can damage individual cells by (if damage occurs slowly, it can be repaired as it happens)
    • ionization of atoms within the cell
    • free-radical formation within cell (e.g, H+ and OH )
    • hydrogen peroxide poisoning of cell
    • breakage of DNA strands
  • Genetic effects (studies indicate that the increased mutation rate due to most radiation doses is statistically insignificant)
    • Damage to ova in ovaries
    • Damage to sperm-forming cells
    • Mutations of genetic material in ova or sperm
  • Effects on the organism
    • Increased risk of ~2 cancers per 10,000 person rem of exposure assuming the linear model (less under threshold model) – compared to risk of 1,600 cancers per 10,000 from all other factors

Typical radiation doses from other activities

Dose (mR/yr) Source
4 Reading glossy magazines for 1 h/d from U and K
25 to 4,000 Wearing enameled jewery 10 h/wk from U
100 to 200 Radon gas inhalation
100 to 200 Foods and fertilizers from K and U
100 Flying 5,000 miles per month
2,000 to 5,000 Smoking 1 pack of cigarettes/day
From Po and Pb for U decay series

Effects of large acute exposures

Dose (rem) Effect
0 to 50 rem No obvious effects, some blood chemistry changes
100 rem Minor radiation sickness in about 10% of population
150 rem Minor radiation sickness in about 25% of population
200 rem Radiation sickness in about 50% of population
300 rem Radiation sickness in all exposed, about 20% death rate within one month
450 rem About 50% death rate without medical treatment
500 rem Radiation sickness within 4 h, over 50% death rate
1000 rem Radiation sickness in 1 to 2 h, 100% death rate

Radiation protection measures

  • Time
  • Distance
  • Shielding
  • Personnel protective equipment
  • No eating, smoking, or drinking
  • Personnel monitoring
  • Contamination surveys
  • Airborne surveys
  • Radiation and shield surveys
  • Waste handling and disposal
  • Emergency actions for spills, suspected personnel contamination

Operating procedures to ensure radiation safety

  • Neutron shield monitoring
  • Monitoring of neutron activation of target bay structures
  • Airborne tritium surveys when opening components exposed to tritium
  • Surface contamination surveys of components exposed to tritium
  • Sampling of decontamination water
  • Establishment of “controlled surface contamination” areas
  • Target chamber entry
  • Decontamination
  • Internal transfer of tritium targets
  • Radioactive material accountability
  • Personnel monitoring

Immediate actions must be taken after a radioactive material “spill” to prevent spreading contamination and minimize exposure. 

SWIMS

  • Stop the spill if possible without risk of personnel contamination.
  • Warn others in the area and notify Radiation Safety Office.
  • Isolate the affected areas by closing doors, establishing barriers, etc.
  • Minimize your exposure.
  • Stop local fans if radioactive material can be spread.

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