Radiation Hazards, Chemistry tutorial

Exposure to Radiation:

Human beings are in constant contact by at least low levels of radiation from natural occurring radioactive isotopes in our office, homes, food, water and air we breathe.

For example, potassium 40 is present in all potassium including food 141C; radion-222, strontium-90 and iodine-181 are in different food and air around man.

Cosmic rays is the other source of background radiation, people which travel frequently in air stands the chance of getting greater amount of cosmic radiation as there are fewer molecules in atmosphere to absorb he radiation. 

Medical source of radiation are the additional source of radiation exposures. These comprise dental, hip, X-ray, spine and mammogram. Contact with radiation throughout research as well comprises the other main source. By the year 1992, around 100 radiologists had died of a result of biological radiation damage. The table below illustrates average annual radiation receives in U.S.A.

Table: Average Annual Radiation receives by a Person in U.S.A

                   Source                                 Dose (mrem)

Natural    The ground                                   20

               Air, water, food                             30

               Cosmic rays                                   40

               Wood, concrete and break            50

Medical   Chest-ray                                       20

               Dental-x ray                                   20

               Mammogram                                  40

               Hip x-ray                                        60

               Lumbar some x-ray                        70

               Upper gastrointestinal X-ray         200

Others     Television                                     20

               Air travel                                       10

                 Radon                                         200m

Mrem = milli radiation equivalent in man

Radiation and Health disorders:

The biological consequence of very large whole body doses leads to the radiation sickness and early death whereas large organ doses leads to local cell destruction and maybe organ death. Exposure to radiation more than 100 rem (that is, rem is the measure of radiation), the person might suffer the symptoms of radiation sickness:  vomiting, nausea, fatigue and reduction in white blood cell count. At dosage more than 300 rem all white blood cells get damaged, the victim suffers hair loss, diarrhea and other infection whereas at 500 rem, half of the population dies; therefore it is termed as LD50  (Lethal dose for one half the population). The table below illustrates function LD50 for different life forms. Dosage above 600 leaves all the humans fatal in a week.

Table: Lethal Dose (LD50) for various Life forms

Life             formD50 (rem)

Insect          100,000

Bacterium    50,000

Rat               800

Human         500

Dog              300

* Radiation equivalent in human

The earth we live is drenched in radiation from the cosmic sources and mineral exploration from the ground. Thus, the effects of the natural radiation background has become a significant health issue specifically radon levels in houses. As well associated closely to this is the effect of man-made sources of identical low levels, like nuclear waste. Fundamentally, whenever it comes to the effect of radiation on human cell, two kinds of cells come into mind: those that directly comprise in functioning of the organ (example: bone marrow, liver or the nervous system) and those which are related with reproductions. Radiation damages in the former provide rise to somatic effect like cancer induction and to later, a genetic effect.

Exposure to large dose radiation can take place by:                                                                          

Accidental exposure example: Japan, Chernobyl: This exposure is stated to be stochastic as the harm caused is statistically distributed over the exposed population. The frequency of tumor induction is noticed to increase linearly with the dose.

Deliberate exposures: These are deterministic as the damage is caused intentionally to some organ or population. Such irradiations are considered to encompass a threshold value, beneath which no effects take place.

Management of Radioactive Waste:

The handling of radiation waste is a main source of radiation in the community. Nuclear power system remains the cheapest, source of power to drive industries and electricity, though, the hazard it produces if the waste is not correctly disposed is overwhelming. Countries which comprise in nuclear power generation dispose the nuclear power waste throughout large water bodies like seas and ocean.

Though, the hazardous effect from those waste only come back to man with time, as illustrated in the figure.

1824_Fate of Hazardous Contaminants in an Ecosystem.jpg

Fig: Fate of Hazardous Contaminants in an Ecosystem 

Early in the year 1990, the Environmental Pollution Agency gave its approval for the storage of radioactive harmful waste in chambers 2150 ft underground. That was implemented in the year 1999 if waste isolation pilot plant (WIPP) marked repository site in New Mexico to get plutonium waste from former U.S. Bomb factories.

Though, in spite of the U.S authority assured the populace the safety of this scheme, the mean of transporting such waste to site has been the other (problem) source of radiation, must the nuclear waste be transported via the rail or by highway truck?

The other safer process of handling harmful nuclear waste as proposed in the wake of different criticism over dumping nuclear waste in either deep sea or buried deep underground, comprise casting the nuclear waste to ceramics  to remove the possibility of waste dissolving in ground water.

The encapsulated waste could then be settled in underground salt drone. Salt drones are positioned in geographically stable regions that has held petroleum and compressed natural gas trapped for millions of years. The other process comprises storing long-lived radionuclide from spent fuel underground in a heavy, shock-resistant container till they have decayed to the point they are no longer biologically dangerous. Illustration comprise strontium - 90 (half-life = 28years) and plutonium - 298 (half-life = 24000 years) should be stored for 280 years and 240,000 years correspondingly before they lose 99.9% activities. Though the problem of corrosion of container is the other point the critics argued for picking holes in the process.

Protective measure from Radiation laboratory work:

The three fundamental principles are recommended for keeping radiations exposure to a minimum level; these are as follows:

  • Shielding
  • Control
  • Distance

Whenever a radiochemical laboratory is designed correctly and the work is performed in such a way that the general background contamination is adequately low so as to avoid the low level tracer, then the health feature of radiation control are satisfied. The common principles are as:

A) Special room or location is employed for the radioactive work.

B) The airborne contamination should be prevented in the lab.

C) The air velocity in the hood must never be beneath 0.5ms-1

D) Limitation of the radioactive work to a minimum area.

E) The room must be equipped with alarm system to monitor the hazards like interrupted water system.

F) Entering and leaving the f laboratory must be via air locked and hand and also feet should be sensored for radioactivity.

G) Shielded cells are employed that assists to keep the pressure low as compare to that for the working pressure.

Control of Radiation protection measure:

In bigger organizations, protection of radiation measure three phases:

a) Prevention: This comprises the use of devices like fume hoods, α box, radiation shielding, tongs and so on.

b) Supervision phase comprises the use of radiation instrument to monitor the radiation level. For example: small TLD, film or pocket pen dosimeter is employed for individual monitoring. For spills and contamination of hand and shoes, special contamination instrument (or counters) is employed that are more sensitive as compare to the monitoring dose instrument.

The after control generally comprises of checking personal dosimeter and a medical assessment. This might be based on the kind and level of work executed. The dosimeter might be checked, two times a week or a month, whereas examination might be once or more than a few times a year.

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