• 1895 - Wilhem Conrad Roentgen discovered X-rays and in 1901 he received the first Nobel Prize for physics. • 1903 - Marie Curie and Pierre Curie, along with Henri Becquerel were awarded the Nobel Prize in physics for their contributions to understanding radioactivity, including the properties of uranium. • 1942 - Enrico Fermi and others started the first sustained nuclear chain reaction in a laboratory beneath the University of Chicago football stadium. • 1945 – Nuclear bombs dropped on Japan. Historical Awareness
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1895 - Wilhem Conrad Roentgen discovered X-rays and in 1901 he received the first Nobel Prize for physics. 1903 - Marie Curie and Pierre Curie, along with.
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• 1895 - Wilhem Conrad Roentgen discovered X-rays and in 1901 he received the first Nobel Prize for physics.
• 1903 - Marie Curie and Pierre Curie, along with Henri Becquerel were awarded the Nobel Prize in physics for their contributions to understanding radioactivity, including the properties of uranium.
• 1942 - Enrico Fermi and others started the first sustained nuclear chain reaction in a laboratory beneath the University of Chicago football stadium.
Gamma-raysGamma can be a problem in nuclear wars,and in using gamma for treatment. In hospitals you need very thick walls in gamma-rooms to stop them from penetrating to outsideShield is usually made from LeadThere is a massive wall in tel aviv, in case of a nuclear war, everyone will go inside the walls, completely isolated from outside.
There can be a psychological problem because of having so many people in such a small area for very long.
X-rays• Overlap with gamma-rays• Electromagnetic photons or radiation • Produced from orbiting electrons or free
electrons – usually machine produced outside nucleus
• Produced when electrons strike a target material inside x-ray tube
• Emitted with various energies & wavelengths• Highly penetrating – extensive shielding
required (usually lead, stronger than concrete, so u need a less thick wall)
• External radiation hazard• Discovered in 1895 by Roentgen
X-rays• Soft x-ray:• When a patient takes an X-ray, some particles
will reflect from the patient, those reflected radiations have low energy, but they’re still a little harmful, so theses soft X-rays (reflected) can be a hazard to other people around the patient (doctors and nurses)
• Sometimes with an old/very young patient, a person will help the patient to position himself correctly for the X-ray, this person is in danger of soft X-rays, even if they stay away from the primary radiation
Ionizing Radiation Health Effects
We evolved with a certain level of naturally occurring ionizing radiation from cosmic radiation, radioactive materials in the earth.
We have mechanisms to repair damage. Sometimes the damage may skip the repair mechanism, so you have a mutation
Radiation Units
Older units:
Curie (Ci): was used to measure activity of a source, to know if a source is more active than others
It is the number of disintegrated atoms per unit time
It does not measure health effects
Radiation UnitsOlder units:
Roentgen:
Measures ionization power.
when a radioactive material hits a medium, changing it to the ionized form, then measure how many ions are produced
Joul/KG
Doesn’t show health effects.
Radiation UnitsOlder units:
Rad: (Radiation absorbed dose)
When a radiation hits a body/tissue, it’ll give it energy, how much of radiation energy is absorbed into the medium is rad.
Still, not health effects
Radiation UnitsOlder units:
REM: Radiation equivalent man (wiki says its Roentgen equivilent man)
Measures the amount of damage that occurred in a tissue after it absorbs energy
Radiation UnitsOlder units:
There’s a relationship between rad and rem, they decided that X-ray should be standard, which means for X-ray radiation, REM = rad
Means that REM is amount of damage that occurred in a tissue that absorbed one rad of X-ray
Radiation UnitsOlder units:
Every radiation has a Coefficient, called quality factor.
Quality Factor X rad = REM
Example:
If beta was given with the same energy as an X-ray, it will deal more damage than the X-ray. Alpha even more damage. (10 times more Damage; quality factor = 10)
Radiation UnitsOlder units:
So to know REM from rad, you need to know the type of radiation and the quality factor of that radiation.
New Radiation Units
Exposure – X (joul/kg)
(Related to energy)
Absorbed Dose – Gray (Gy) (amount of energy absorbed) instead of
rad
Equivalent Dose – Sievert (Sv) (makes different sources of radiation
equivalent) instead of REM
Standards
Occupational Exposure Guidelines
100 mSv over 5 years (average 20 mSv/year) with a maximum of 50 mSv in any one year
General public – back ground about 3 mSv/year – Guideline 1 mSv/year
If someone’s exposed to radiation above the standard exposure, they get a break to reduce the exposure
Standards
Notice how occupational is 20, general public is 3.
Remember, workers are 20~60 years old, with usually a better health than the general public.
The general public contains elderly, young children, sick people ..etc so their exposure has to be lower
That is why occupational health is different from public health
Dose Response Tissue
Examples of tissue Sensitivity
Very HighHighest mitotic activity
White blood cells (bone marrow)Intestinal epitheliumReproductive cells
High Optic lens epitheliumEsophageal epitheliumMucous membranes
Medium Brain – Glial cellsLung, kidney, liver, thyroid, pancreatic epithelium
Lowlowest mitotic activity
Mature red blood cellsMuscle cellsMature bone and cartilage
Dose Response Issues
Dose(Sv)
Effects / organ Time to death
Death(%)
1-2 Bone marrow Months 0-10
2-10 Bone marrow Weeks 0-90
10-15 Diarrhea, fever
2 weeks
90-100
>50 Neurological 1- 4 hrs 100
Dose Response IssuesNotice how its 100% death if it involves the brain. Anywhere else, there’s a possibility that they survive if they’re provided excellent support. Which is expensive
once an accident inside a hospital in france resulted in a few workers getting a rapid very high exposure of radiation, in the hospital, they isolated them completely.
They had to give them huge amounts of blood, up to 500 units of blood. That is unaffordable.
Dose Response IssuesThe first 14 days are the most crucial ones, if you survive for the first 14 days there’s a good chance you’ll recover completely..
The doctor read the 2 tables in slides 37, 38, focusing on neurological effects.
The closer you are to the radiation source, the more your dose will be. Meaning those closest so the source of radiation are in the most danger.
• Rate of decay of radioisotope• How long it takes to lose half their
strength
• Can range from very short to billions of years
• Carbon – 5730 years, which makes it valuable for dating (fossils)
Half-life
TimeReduce the spent near the source of radiation.
DistanceIncrease the distance from the source of radiation.
Its actually distance squared, so if you move away 2 meters, you’ll get ¼ of the radiation.
ShieldingPlace shielding material between you and the source of
radiation.
Remember if there’s a nuclear war, its not just about the initial effect, the after-effect is also important, and just as dangerous.
Remember that Bone morrow radiation exposure causes weak immunity
Reducing Exposure
• Occupational exposure guidlines are 100 mSv in 5 years (average, 20 mSv per year) with a limit of 50 mSv in any single year.
• General public the standard is 1 mSv per year. (Natural background radiation is approximately 3 mSv/year.)
Recommended exposure limits are set by the US National Council on Radiation Protection (NCRP) and world wide by International Council on Radiation Protection (ICRP).