HEALTH PHYSICS
RADIATION: Particles emitted by
unstable nuclei during spontaneous transformation into stable nuclei is called
radiation. Three types of radiations are emitted.
1. ALPHA
(α )
2. BETA
(β)
3. GAMMA
(γ)
RADIOACTIVITY: The spontaneous
transformation of unstable nuclei into stable nuclei with emission of fast
moving particles is called radioactivity
ACTIVITY: The activity ‘A’ of a
radioactive element is the number of
transformations taking place in unit time and is expressed in transformation
per second ( tps). The unit of activity is Becquerel(Bq). 1 Bq = 1 tps
The old unit of activity is Curie
(Ci). 1 Ci = 3.7 x 1010 Bq.
EXPOSURE: In general terms, it
refers to the amount of radiation reaching a material. It refers to the amount
of ionization produced in air by ionizing radiation. Unit of Exposure is
roentgen(R). 1R = 2.58 x 10-4 Coulombs/Kg of air.
Exposure of 1 roentgen is frequently
considered approx. equivalent to an absorbed dose of 1 rad (radiation absorbed
dose).
ABSORBED
DOSE:
Energy absorbed per unit mass of a substance to which it is exposed. SI unit is
joule/kg and it is termed as Gray (Gy). The earlier unit is rad. 1 Gy = 100
rad. 1 Gy = 1 J/kg.
DOSE LIMIT:
|
Category
|
Annual
effective Dose limit (mSv)
|
Annual
equivalent Dose limit (mSv)
|
For
consecutive five yrs (mSv)
|
Life
time effective Dose limit (Sv)
|
||
|
Lens
of eye
|
Skin
|
Extremities
|
||||
|
Radiation
worker
|
30
|
150
|
500
|
500
|
100
|
1
|
|
Apprentices
& Trainees
|
6
|
50
|
150
|
150
|
--
|
--
|
|
Temporary
worker
|
15
|
75
|
250
|
250
|
--
|
--
|
|
Member
of Public
|
1
|
15
|
50
|
--
|
--
|
--
|
For Pregnant
woman, 1
mSv effective dose to the embryo/fetus for remainder of pregnancy
EXTERNAL
EXPOSURE CONTROL:
External exposure control can be
achieved by:
A. TIME: Dose (mSv) = Dose rate (mSv/hr) x time(hr). By reducing the
time spent in radioactive areas.
B. DISTANCE: I1D12 = I2D22.
(Where I1 -> Intensity of radiation at a distance d1,
& I2 -> Intensity of radiation at a distance d2.
)Radiation field at a point is inversely proportional to the square of the
distance between the point & source.
C. SHIELDING: Introducing shielding material in between the source and
the target can reduce the intensity of gamma radiation.
DOSE
MEASUREMENT:
1. DIRECT READING
DOSIMETER(DRD): (FOR DAY TO DAY EXPOSURE)
It
works on the principle of gold leaf electroscope. It consists of two
electrodes, one is a fixed metal wire and the other is metal coated quartz
fiber spring. Initially, the electrodes are charged to around 200V, externally
by touching the charging pin to a battery. Both the electrodes will then be
positively charged and the electrostatic repulsive force existing between them
will drive the movable fibre away from the fined wire. When radiation falls on
DRD for a time, ionization of air (app. 2cm3 volume) i.e filled in cavity
(chamber) take place and this ionization discharges the movable fibre to lower
voltage. The difference in voltage gives a measure of the total amount of
radiation which fell on the chamber during irradiation.
Range
of DRD:
0
– 200 mR
0
– 500 mR
0
– 1000 mR
0
– 5 R(5000 mR)
2. THERMO LUMINESCENT DOSIMETERS(TLD): Issued every month and
processed after completion of month material. CaSO4(Calcium Sulphate
deposited in Dysprosium)
3. ZONING:
In
order to restrict spread of contamination to various areas and also to confine
contamination, entire plant area is divided into 4 zones.
1. WHITE ZONE: This zone will be free from contamination at all times and
will contain no radioactive equipment. (Ex. Control room building, all offices,
canteen etc)
2. GREEN ZONE: This zone should not normally become contaminated and will
not contain any radioactive equipment. With movement of person from amber zone
some contamination may spread into this area. To prevent spread of
contamination to white areas, contamination in green areas will be cleared as
soon as it is detected. (Ex. All corridors, Lobby, Make up areas, solution make
up & pumping areas, Change room). External radiation field less than 0.25
mR/hr. Air borne contamination = 0.1 DAC.
3. AMBER ZONE: This zone includes the service areas for entire equipment
and materials that are potential sources of contamination. Hence this zone is
likely to get contaminated at times. Work procedures shall be planned to keep
contamination localized and loose contamination shall be cleaned up whenever it
occurs. (Ex. All access galleries, Sampling gallery etc. External radiation
field less than 1 mR/hr. Air borne contamination = 1 DAC.
4. RED ZONE: This zone contains
sources of contamination and also radioactive equipment. (Ex. Dissolver cell,
all cells, Hot cell storage area, Pu enclosure A & B in Pu lab, all LEWA
pumps located at 1st south side, 2nd north & south
side.
A person moving from a higher zone to
a lower should always check fro contamination at each inter zonal monitors.
4.
CONTAMINATION: Unit -> Bq/cm3.
§ Contamination is the
presence of a radioactive substance in or on a material or on the human body or
on any other place where they are undesirable or could lead to unwanted
exposures.
§ Contamination which can be removed by simple
means, is called loose contamination.
§ Contamination which
requires either mechanical or chemical methods for removal, is called fixed
contamination.
§
5.
DECONTAMINATION: It is the process of
removal of contamination from any surface or material.
§ Personal Decontamination:
1.
First find out the precise location of contamination.
2.
Special emphasis should be placed on the location of any hot
spots on the individual.
§ Decontamination methods:
1.
Flush the location with water
2.
Wash with liquid soap/detergent for 2-3 minutes.
3.
Check for contamination. If contamination persists then
4.
Use compelling agent like EDTA(Ethylene diamante tetra acetic
acid) solution.
5.
Check for contamination. If contamination persists then use
mild organic acid like citric acid.
6.
Check for contamination. If contamination persists then refer
to medical officer.
6.
ANNUAL LIMIT OF INTAKE(ALI): It is the quantity
of radionuclide that, when taken in a year by the by the reference man, would
result in a committed effective dose not exceeding the annual dose limit of 20
mSv of occupational exposure.
7.
DERIVED AIR CONCENTRATION
(DAC): It
is that concentration of a radionuclide in air (Bq/m3) which when
breathed by reference person for working year of 2000 hrs under the condition
of light activity (no any heavy work) which would result in intake of one ALI.
The breathing rate for light activity is 1.2 m3/hr.
1.2m3/hr
x 2000 hr = 2400 m3.
ALI
DAC
= --------------- 2400 m3.
2400
If
a person works in one DAC environment for one hour, the dose received is
1mrem(1 mR). 1DAC-hr = 1mrem
For
Pu-239 : 1 DAC = 0.26 Bq/m3
For
Sr-90; 1DAC = 110 Bq/m3.
8.
SOLID WASTE CATEGORIES:
Category
I -> < 200 mR/hr
Category
II -> 200 – 2000 mR/hr
Category
III -> 2000 mR/hr(2R/hr) – 50 R/hr
Category
IV -> > 50 R/hr.
RADIATION EMERGENCY CLASSIFICATION
1. Personal Emergency
2. Emergency Alert
3. Plant Emergency
4. Site Emergency
5. Off Site Emergency
EMERGENCY ALARM
1. STAY IN: Off side: Short Intermittent Siren. 5 sec. on, 5 sec, off
up to 2 minutes External Hazards. After 1.6 Km
Safe shutdown, normal route, assembly area
2. EVACUATION: Inside plant. Long Intermittent Siren. 15 sec on, 5 sec off
up to 2 minutes. Internal Hazards (Criticality). Safe shutdown, normal route,
assembly area. Avoid affected area, shortest route, assembly area
3. ALL CLEAR : Continuous Uninterrupted Siren for the period of 2
minutes.
·
If the gamma radiation field at 1 meter & above the
ground at any Off site location exceeds 1mR/hr then Off site emergency is
declared.
·
RESPIRATORY PROTECTIVE EQUIPMENTS:
PF
= Protection Factor
= Inhalation(contamination)
without protection
Inhalation(contamination) with protection
MASKS
·
Half Face Mask: 1 to 10 DAC
·
Full Mask: 10 to 50 DAC
·
FAL (Fresh Air Line) half face: 50 to 1000 DAC (20 psi)
·
FAL (Fresh Air Line) full face: 1000 to 2000 DAC (20 psi)
·
Self Contain Breathing: 200 to 1000 DAC
·
Positive pressure self contained breathing apparatus kit
(SCBA) = 2000 to 10000 DAC
DOSE ALLOWED
1. Monthly : 200 mR
2. Quarterly: 1.5 R/15 mSV
3. Yearly: 2 R (20 mSv)
averaged over period of 5 block(successive) yrs or 30 mSv for single year
4. Life time: 1 Sv
DOSE AUTHORISATION
Up to 200 mR -> no
authorization
200 mR to 400 mR ->
Section Superintendent
Up to 1500 mR -> Plant
Superintendent
Ø In ROP, different area
monitors such as AGM(area gamma monitor), SGM(Special purpose gamma monitor),
WGM(wide range gamma monitor), LGM(low range gamma monitors), CAM( continuous
air monitor) such as AMA(air monitor alpha) and AMB(air monitor beta) are
placed in all access gallery, sampling gallery, all Labs & other areas of
plant.
Ø WGMs are placed in one Pu
Lab (WGM-1) off gas heap room & near deep bed filters.
Ø SGMs are placed in PCW,
Steam trap area and Hold up tank area
Ø LGM are placed near TLD
rack area near Pu storage and Control Lab.
Ø AGMs & CAMs are placed
in all access galleries, sampling galleries, all Labs, cell top area etc.
|
Monitor
|
Alarm Level
|
Range
|
|
AGM
|
5mR/hr
|
0 – 100 mR/hr
|
|
LGM
|
50 mR.hr
|
|
|
SGM
|
2 mR/hr
|
0 – 100 mR/hr
|
|
WGM(off gas
HEPA room)
|
20 mR/hr
|
|
|
WGM(deep bed
filter)
|
1 R/hr
|
|
|
AMA
|
360 cpm
|
|
|
AMB
|
2400 cpm
|
|
Ø STACK MONITORS – 2 UNITS. Each unit contain 3 monitors
|
SN
|
MONITOR
|
ALARM LEVEL
|
|
1
|
AMA
|
1200 cpm
|
|
2
|
AMB
|
9000 cpm
|
|
3
|
AMKr
|
2000 cps
|
Ø CRITICALLITY ALARM
SYSTEM(CAS)
PREFRE – II PREFRE
- I
CAS-1
: CELL – 3 Display is kept at 2nd,/N/Corridor CAS-1 : CELL – 3
CAS-2:
CELL – 4 Display is kept at 2nd,/N/Corridor CAS-2: Pu Lab
CAS-3:
Pu LAB CAS-3:
Pu store
CAS-4:
Pu STORE
CAS
AT NMSF Pu STORE IS COMMON TO BOTH
Ø ALARM INDICATION OF CAS
-
Dose rate : 4 R/hr then it will give alarm
-
Dose : 3 mRad in 500 mille sec then it will give alarm
PLANT
EMERGENCY PROCEDURE
TYPE ‘A’ EMERGENCY: Minor accidents, Power failure,
Ventilation failure etc
TYPE ‘B’ EMERGENCY: Heavy Fire, Spillage of radioactive solutions and
Explosion.
SRVO (
SAFETY RELATED UNUSUAL OCCURANCE)
SERVILLANCE
To ensure, the trouble
free availability of the equipment during the plant operations and to define
its frequency.
1. STACK MONITORS
2. CONTAMINATION MONITORS
3. CRABES
4. D,G, SETS
5. P.A SYSTEM
6. DIESEL/OIL RELATED PUMPS.
MONITORS
1. Plain Monitor/Single hand monitor/Alcin:
Contamination of Alpha (10 cm range)
2. Gamma Area Monitor: 2mr/hr
3. Pu in air monitor(aerosol
monitor): 1DAC/1Bq/m3.
4. CRITICALITY Monitor: 4R/hr
or 3mr/inch<500 milli sec.
5. Alcin: Alpha ventilation
monitor
6. DRD: Direct reading
dosimeter
7. TLD: Thermo Luminous
Dosimeter
8. Neutron Badge: Neutron
counting
HALF LIFE LIMIT
Uranium Oxide – 14 days
Biological: PuO2 – 50
years
Radiological: U238
=7 x 109 yrs
Pu239 =
24360 yrs
CLASSIFICATION OF FIRE
A. Carbon contain fuel ie
wood, paper, cotton etc
B. Petroleum products ie
Petrol, Diesel, kerosene
C. Glass & chemical
D. Combustible metal. Pu, U
E. Electrical fire.
FIRE EXTINGUISHERS
|
SN
|
Fire/Extinguisher
|
Color code
|
Class of fire
|
|
1
|
SODA ACID
|
BLUE
|
B & C
|
|
2
|
CO2. (Carbon Di Oxide)
|
YELLOW
|
A,B, C & E
|
|
3
|
DCP (Dry Chemical Powder)
|
BLACK
|
D
|
|
4
|
HALLON
|
NO COLOR
|
D & E
|
|
5
|
FOAM
|
BROWN
|
B
|
|
6
|
WATER SPRINKLER/HOSE
|
RED
|
A
|
ABBRAVIATIONS
|
PREFRE
|
Power Reactor Fuel Reprocessing Plat
|
|
AWTF
|
Additional Waste Tank Form
|
|
AFFF
|
Advance Fuel Fabrication Facility
|
|
CFS
|
Centralized Fire Station
|
|
ROP
|
Revamping Of PREFRE
|
|
DRP
|
Driven Reading Process
|
|
WIP
|
West Immobilization Plant
|
|
EMC
|
Estate Management Cell
|
|
WMD
|
Waste Management Division
|
|
FRLS
|
Fire Retardant Lower Smoke
|
|
TWMF
|
Tarapur Waste Management Facility
|
|
GSO
|
General Services Organization
|
|
TRAP
|
Tarapur Radwaste Augmentation Plant
|
|
NMSF
|
Nuclear Material Storage Facility
|
|
AFR
|
Away From Reactor
|
|
PLC
|
Programmable Logic Controller
|
|
AWSS
|
Augmented Water Storage Supply
|
|
SFSF
|
Spent Fuel Storage Facility
|
|
SF6
|
Sulphar Hexa Floride
|
|
ASSR
|
Aluminum Conductor Steel Rainforced
|
|
SSSF
|
Solid Storage Surveillance Facility
|
|
PILCA
|
Paper
Insulated Lead Covered Armored
|
|
VFD
|
Variable Frequency Drive
|
|
HRPVC
|
High
Rapchering Poly vinyl Chloride
|
|
WTA
|
Waste Tank Annex
|
|
APFCR
|
Automatic
Power Factor Control Relay
|
|
WTF
|
Waste Tank Form
|
|
FRLS
|
Fire
Retardant Low Smoke Cable
|
|
XLPE
|
Cross Link Polly Ethylene
|
|
ABCB
|
Air
Blast Circuit Breaker
|
|
MOCB
|
Minimum
Oil Circuit Breaker
|
|
VCB
|
Vacuum
Circuit Breaker
|
|
ACB
|
Air
Circuit Breaker
|
|
BOCB
|
Bulk
Oil Circuit Breaker
|
|
ESL
|
Environmental Survey Laboratory
|
|
AVS
|
Advance
Verification System
|
|
|
|
|
|
|
|
|
|
|
|
|
--------**********---------
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