Q182.  What is the effect of single phasing?

A.       1. Motor slow down, some time vibrates, 2. motor will draw more current and heat up. If not isolated motor conductors will melt and motor will burn.

Q183.  What is the cause of motor tripping?

A.        Two types of causes -  1. External, 2. Internal

           External – Ambient temperature, furnace heat, steam heat, welding, loose earthing.

           Internal – Electrical, Ventilation,  Mechanical.

           Electrical – O/L, SPP, U/V, O/V, Loose connections, frequency variation.

           Ventilation – Less air flow, duct blocked due to dust particles.

           Mechanical – Bearing heating, rotor rubbing, loose foundation, misalignment.

Q184. Why breaking capacity of ACB & OCB is less than the making capacity?

A.    Closing on faults, doubling effect of switching, residual magnetism of inductive ckt., to have mechanical stability as breaker will vibrate.

Q185. What is the use of auto transformer starter?

A.      Starter gives reduced voltage at start and after definite interval, it is transferred to full voltage. Initial starting current depends upon the tapping selected.

Q186.  What is radiation?

A.        Spontaneous emission of energy or charged or uncharged particles from an unstable nucleus.

Q187.  What are the different types of radiations?

A.        Alpha, Beta, Gamma and Neutrons, X rays.

Q188. What is the common instrument used to detect the Alpha, Beta & Gamma radiation?

A.       Geiger-Muller counter.

Q189. Which radiation is more penetrating?

A.       Gamma rays are more penetrating.

Q190. What are the fission products encountered in the reprocessing plant?

A.        Sr⁹⁰, Kr⁸⁵, Sr⁸⁹, Yt⁹¹, Zr⁹⁵, Nb95, Cs¹³⁷, Ce¹⁴⁴, Ce¹⁴¹, Ba¹⁴⁰, Pm¹⁴⁷, I¹³¹

Q191. Why the process cells are provided with concrete walls?

A.       These walls provide biological shield to reduce the radioactivity to acceptable level.

Q192. Why Br ⁹⁰ is considered more hazardous as compared to other fission products?

A.       It is an energetic Beta emitter and bone seeker and having half-life (28 years).

Q193. Why Pu is considered highly toxic?

A.       Long lived Alpha emitter and bone seeker.

Q194. What is the type of radiation that Pu emits?

A.       Alpha (Pu²⁺¹ –Beta)

Q195. What is a dosimeter? Why is is carried on person?

A.       It is an instantaneous personnel radiation monitoring device used in high radiation fields. It is carried on person because it indicates the amount of radiation has receivd on the spot, so that the exposure can be controlled.

Q196. What are the methods by which radiation exposure is controlled?

A.       Time, distance, shielding, decay.

Q197. What is the function of TLD badge?

A.      It is a personnel monitoring device which gives the dose a person has received during a particular interval a record of this is kept.

Q198. What is SWP? When it is required? Who prepared these documents?

A.       It is a special work permit. It is required when a ;job has to be undertaken in active area involving 1) more than 50 mR/hr field, 2) High air-borne activity, 3) working for long time in active area, 20 mR/hr, 4) Job in contaminated area. It is issued for co-ordination between different agencies for safe working practice. It is prepared by Area In-Charge.

Q199.  How much radiation dose is allowed in a year?

A.        3 Rem/yr, or 30 milli Sieverts/yr, or 300 milli Rem/month.

Q200.  What is Central Radiation Protection Console(CRPC)? Where is it located in plant?

A.       CRPC is a Health Physics panel installed in Control Room of the plant, where all readings of monitors installed in various radiation areas are recorded and displays alarm conditions or otherwise continuously. It makes possible to assess radiation stsatus of any active area of the plant at any time without going to the area.

Q201.  What is contamination?

A.       Undesired presence of unwanted material emitting radiation on the body, floor, air on equipment is called contamination.

Q.202. How contaminated items and waste materials are handled?

A.      Contaminated items are handled by wearing gloves, waste is packed in double polythene bags and sent as waste with tags. High active wastes should be handled remotely.

Q203.  What is a contamination monitor? How is it use?

A.        It is a device to check contamination. It has two probes, one for Alpha and other for Beta, Gamma.

Q204.  How Alpha contamination is different from Beta contamination?

A.       Alpha has no external radiation dose, can be cut off by the skin. It is harmful in case of internal dose, Beta is harmful even in case of external dose.

Q205. How contamination of hand is prevented while doing radioactive jobs?

A.       By wearing clean hand gloves.

Q206.  What is the de-contamination agent used for Alpha contamination removal?

A.       EDTA – Ethyl dia tetra acetic acid. If contamination persists KMnO4 (potassium permanganate) and dilute H2SO4 (Sulphuric acid) mixture is used.

Q207. Why the plant is divided into various zones?

A.        To isolate different radiation zones according to their radiation potential in order to prevent spread of contamination, white, Green, Amber and Red are the different zones in the ascending order with respect to radiation and contamination.

Q208.  Why barrier is necessary between zones?

A.      To avoid spread of contamination from high active areas to low active areas in day to day work. Normally barrier is there at the boundary of green and amber zones only. In case of emergency a temporary barrier can be set up at the boundary of white and green zones.

Q209.  What are Derived Air Concentration (DAC) limits for long lived Alpha and Beta activity?

A.        0.08/Bq/m³  - Alpha (Pu), 300 Bq/m³  -  Beta (Sr⁹⁰)

Q210.  Why are the air samples taken from areas.?

A.        To asses air activity of the area

Q211.  Why a respirator is worn while working in a radioactive area?

A.       To filter radioactive particles from breathing zone of the working atmosphere, to reduce inhalation of radioactivity.

Q212.  Why an air line respirator is used? How do they differ from an ordinary respirator?

A.       Air respirator is worn while working in high air borne active area, where an ordinary respirator is not sufficient. It differs from ordinary respirator in two respects. 1) Breathing zone has +ve pressure w.r.t. working area, 2) It supplies fresh air instead of filtering active air.

Q213.  What type of protective equipment is used against fumes or radioactive gases?

A.        Gas masks.

Q214.  Why a plastic suit is worn for carrying out certain jobs in certain areas?

A.       It gives protection from splashing liquids etc. It also gives complete protection to all parts of the body against contamination.

Q215.  What is the course of action followed if a radioactive spill occurs at the place of work?

A.       1. Confine the spill using cotton waste etc, 2. Inform HP, 3. Cordon off the area using red tape, 4. Survey the spill, 5. Decontaminate the area under HP supervision.

Q216.  What action is to be taken if an area Gamma monitor gives an alarm?

A.        Vacate the area and inform HP.

Q217.  Where are the criticality monitors located? What action is to e taken in case of criticality alarm?

A.     Criticality monitors are located at Pu lab, Pu store, NMSF and CSell-3. Evacuate the area and assemble in the low block lobby. Follow instruction from HP.

Q218.  Why urine samples are required to be submitted periodically?

A.         To find out the extent of internal contamination and assess the body burden.

Q219.  What are the SI units of radiation?

A.         Activity                             - Bacquerel           (1 cps)

             Dose                                  - Gray                   (1 joule/Kg)