Q220.  What is dose equivalent? What is the dose equivalent limit for an occupational worker per annum?

A.         Dose Equivalent = Absorbed dose  X Quality factor

            Dose Equivalent = 50 milli Seivert (5 Rem)

Q221.  What is the DAC value for Pu²³⁹?

A.        2 micro micro curie/m³ or 80 mBq/m³.

Q222.  Which international body is responsible for laying down standards for radiation protection?

A.         International Commission of Radiological Protection (ICRP).

Q223.  How a whole body counter is used to detect Pu inside the human body eveh though Pu is Alpha emitter?

A.        Whole body counter counts as X-rays (1¹⁷ kev) emitted by Pu, not Alpha.

Q224.  How are the biological effects of radiation classified?

A.        There are two types of classifications:

           1. Somatic Effects : Effects contributed to exposed person only

           2. Genetic Effects : Are continued in generations.

           3. Stochastic & Non-stochastic.

Q225. What is the difference between X-ray and Alpha rays?

A.      When Alpha & Beta particles are emitted the nucleus is in an excited starter, while coming back to ground state gamma rays are emitted.

When electrons from inner orbital get excited and de-excited X-rays are emitted.

Gamma rays are a nuclear phenomena, X-rays are an extra nuclear phenomenon.

Q226. What are the common shielding materials in the plant?

A.       Concrete, lead brsicks, lead glass, lead wool, water, M.S. and earth.

Q227.  What is the planning required prior to commencement of radioactive job? What are the important considerations?

A.      Feasibility of job, radiation field, time required, chances of air borne activity spread of contamination.

Q228.  What are the considerations of man-rem budgeting?

A.       1. All exposures should be kept as low as possible.

           2. Remote operation to be undertaken to the extent possible.

           3. Source of radiation, unwanted should be removed and shielded.

           4. Distribution of dose/exposure among personnel. The shield personnel, required to work in

               radiation area repeatedly should be exposed to activity to minimum possible extent in a single

               event.

Q229. What is the cause of action in the event of an alarm at the CRPC in the control room?

A.        Let the alarm sound for 2 minutes. It is acknowledged which silences the audio-alarm but retains the visual indication. Inform HP, push the reset button. If the alarm is false, due to instrument error the indication will go off. Also reading recorded in the chart can be cross-checked.

Q230.  What are the different type of protective equipments generally used for carrying out a job in a highly contaminated are?

A.        Plastic suit, hood, gloves, fresh air line, respirator, gum-boots.

Q231. A continuous air monitor gives an alarm. An air sample taken from the area shows normal air activity. How the cause is explained?

A.     Sudden release of activity for short time causes air monitor to cause alarm. By the time actual sampling is done, the area might have got cleared due to good ventilation. There is always a time lag between monitor alarm and actual sampling.

Q232.  What is radioactive substance?

A.        Radioactive substance is that which emits nuclear radiations such as Alpha, Beta and Gamma Rays

Q233.  What are the different types of radiations encountered at the Plutonium plant? What is the difference between their properties?

A.       1. Alpha particles are nuclei of helium. Hence they are positively charged. An alpha particle has got two protons and two neutrons, it has two positive charge.

          2. Beta particles are negatively charged. It has one negative charge. These are many times lighter than alpha particles.

          3. Gamma rays have no charge and no mass. Therefore these rays can penetrate through many materials.

          4. Neutrons: These we encounter in Pu lab. These are particles without any electric charge but are heavy

Q234. What is the unit of radioactivity? Define what is meant by specific activity?

A.     The unit of radioactivity is Curie. The curie is defined as the activity of a radioactive substance disintegrating at the rate of 3.7 x  10¹⁰ disintegration/sec.

The specific activity is defined as the activity of one gram of a substance. It is generally expressed as 0/gm of the radio-element.

Q235. What is meant by ‘half-life’ of a radioactive substance? A radioactive substance has a half-life of 20 days. What is the fraction of activity remaining after 100 days?

A.     The half-life of a radioactive substance is defined as the time required for a given radioactive substance to decay to one-half of its initial value.

Half-life                            : 20 days

100 days are equivalent to 5 half-lives.

After one half-life fraction remaining ½ .

After two half-life fraction remaining 2^1/2.

After five half-life fraction remaining 2^1/5 =1/32

Q236.  What is an isotope?

A.       The word isotope refers to the same specie of nuclide but with different mass numbers. For example Net uranium has three isotopes: U²³⁸, U²³⁵, U²³⁴. All are having atomic number 92 but they have different mass number. 

Q237.  What is the unit of radiation dose? What is the unit of radiation dose rate?

A.         The unit of radiation dose is Rem. The unit of dose rate is Rad/hr.

Q238.  What are the three methods used in reducing external radiation?

A.        External exposure can be reduced by: Time limit, distance & shielding.