1 - PRINCIPLE OF RADN PROTECTION_2018(Oct 1).ppt

Principles of Radiation Protection Norriza Mohd Isa Radiation Safety & Health Division Radiation Safety & Health Division Agensi Nuklear Malaysia (Nuklear Malaysia) E-mail: [email protected] H/p: 019-3877607 1 INTRODUCTION • Radiation: Benefit & Risk • Biological damage: Nonstochastic (Deterministic) & Stochastic effects • Severity depends on: Dose/ dose rate, Age and Parts of the body/cells. To control & limit to acceptable level by; - Adopt Radiation Protection Standards - Establish Regulatory Agency for Enforcement - Ensure Adequate Training 2 Principles of Radiation Protection Objective Protection of man and his environment from unnecessary radiation exposure without eliminating the beneficial application of radiation and radioactive materials Main Aim Prevent deterministic effects and limit the probability of stochastic effect to acceptable level 3 Radiation Protection Systems Three principles used in dose limitation system: - Justification of a practice - Optimization of dose - ALARA - Dose Limitation 4 Radiation Protection Systems JUSTIFICATION No practice involving ionizing radiation shall be adopted unless its introduction produces a net positive benefit and • no other alternative technique or • radiation technique more superior than other techniques E.g.: Screening of school children 5 Radiation Protection Systems Optimization of Dose  A key component of the system is that all necessary exposures be kept As Low As Reasonably Achievable. The concept of 'ALARA' and 'optimization of protection' are identical.  A wide range of techniques is available. Example, QC & maintenance program is to reduce the number of rejected diagnostic films and in turn, to reduce the dose presently incurred by nursing staff, radiographer and patients. 6 Radiation Protection Systems • Other techniques for dose optimization: - Choice of materials and equipments - Choice of specific technique and working procedures - Use of personnel protective equipment (PPE) - Proper monitoring system - Proper engineering & administrative control - etc. 7 Proper engineering control • Selection of radioactive used as a radiation source (half life, energy, activity, radiation type) • Source Housing (tested and comply the regulation) Radionucli Energy de Physical Half-life Radiation Type I-131 364 keV 8 days Gamma, alpha Tc-99m 140.5 keV 6 hrs Gamma Cs-137 662 keV 30 yrs Gamma, Beta F-18 511 keV 109.77 Gamma, 8 Administrative control  Local Rules-device should be installed, used and maintained by authorized persons  Adequate Information-workers should be informed about the potential hazard present in the working area.  Proper Signage- the device should be labeled to indicate the presence of radioactive material (name, activity & S/N)  Leak test-Radioactive source must be tested for possible leakage.  Movement & storage- inform AELB & Proper storage 9 PPE Mobile shielding and leaded aprons play an important protective role in certain applications. 10 Radiation Protection Systems Dose Limit Dose limit is used to apply controls on each individual’s accumulation of dose and is not a line of demarcation between “safe” and “dangerous”, • For occupational exposure only, excluding dose received from natural radiation and medical exposure • Similar for men and women except pregnant women. 11 Radiation Protection Systems: Dose Limit To prevent deterministic effects: equivalent dose to extremity < 500 mSv except eye < 150 mSv To limit the occurrence of stochastic effect: effective dose, E is limited to 20 mSv per year E =  WTHT where: WT - weighting factor; HT – equivalent dose Tissue or organ WT Gonad 0.20 Bone marrow, colon, lung, stomach 0.12 Bladder, breast, liver, oesophagus, thyroid 0.05 Bone surface, skin 0.01 Remainder (5 organs) 0.05 12 Tissue Weighted Factor (Recommendation of ICRP) Tissue ・ Organ Tissue Weighted Factor for 1990 for 2007 Gonad 0.20 0.08 Marrow, Colon, Lung, Stomach 0.12 0.12 Vesica, Liver, Esophagus, Thyroid gland 0.05 0.04 Breast 0.05 0.12 Skin, Surface Bone 0.01 0,01 Brain, Salivary Grand - 0.01 Remained Tissues and Organs 0.05 0.12 Total 1.00 1.00 13 Relation between Absorption Dose (Gy) and Equivalent Dose (Sv) and Effective Dose (Sv) Effective Effective Dose Dose (E) (E) E[Sv] (HT [Sv] x ΣT W ) T H := Equivalent Dose for Each T Tissue WT: Tissue Weighting Factor Systematic Exposure Dose (Whole-body Exposure) DT: Absorption Dose (Gy) 1 J/kg =1 Gy Equivalent Equivalent Dose Dose (H (HTT)) HT[Sv] (DT [Gy] x WR) = DT: Absorption Dose for Each Tissue WR: Radiation Weighting Factor Regional Exposure Dose for γ-ray and β-ray → 1Gy = 1Sv 14 Types of Radiation Quality Factor X-ray and γ-ray 1 β-ray 1 <10keV 5 >10keV>100keV 10 >100keV>2MeV 20 >2MeV>20MeV 10 >20MeV 5 Neutron* (by ICRP 1990’s Counsel≈ 2007’s Counsel) Proton (>2MeV) 5 α-ray, Fission Fragment, Heavy Nucleus 20 Radiological Quality Factor (WR) Radiological Quality Factor (Recommendation of ICRP in 1990) Neutron Energy (MeV) 15 Biological Effect of Radiation • • • • • • • Cataracts Deterministic Effect:PREVENTION of deterministic effect deterministic effect = threshold Erythema Eg: Infertility Stochastic effect:LIMITING the probability of stochastic effect to an acceptable level stochastic effect = no threshold ↑dose ↑ probability Eg: leukimia, skin cancer Cancer Induction Radiation Effects on Human Body Deterministic Effect 18 Stochastic Effect 19 Radiation Protection Systems Annual Dose Limits (ADL) There are different categories of dose limits for:       radiation workers female pregnant workers members of the public trainees of radiation Special planned exposures Derived and Authorized Limits 20 Radiation Protection Systems ADL Radiation Worker/Staff Occupational exposure shall be controlled so that their total dose does not exceed: Effective Dose: 20 mSv/yr for wholebody exposure (BSRP 2010) Equivalent Dose: 150 mSv/yr to the lens of the eye 500 mSv/yr to skin, hands, feet and other organ or tissue 21 Radiation Protection Systems FEMALE STAFF (Occupationally Exposed) Embryo or fetus is radiation sensitive, notify Licensee of a pregnancy ASAP. Fetal dose should be limited to less than 1 mSv/ pregnancy period (by limiting dose to surface of abdomen to about 2 mSv-estimation) If this restriction is achieved, no special administrative arrangement for the worker is necessary. Pregnancy shall not be considered a reason to exclude a female worker from her duties. Special Restriction for Pregnant Radiation Radiation Protection Protection Systems Systems ADL for members of public Application Dose limit for the whole body exposure ADL (mSv) 1 Equivalent dose for lens of the eyes 15 Equivalent dose for the skin 50 Effective dose constraint for supporting personnel (during diagnostic examination or treatment of the patient) <5 Effective dose constraint for visitor (< 16 years old) (of patient undergoing treatment or diagnostic examination) <1 23 Radiation Radiation Protection Protection Systems Systems Dose limit for apperentice and students Apprentices and students in radiation work (in a supervised or controlled areas) must not be less than 16 years old. Application Dose limit for the whole body exposure In a calendar year (mSv) 6 Equivalent dose for lens of the eyes 50 Equivalent dose to the extremities and skin 150 24 Radiation Radiation Protection Protection Systems Systems Dose limit in special circumstances  Refers to voluntary exposure during normal operation whereby the ADL for a worker are likely to be exceeded. Conditions i. Allowed only in situations when alternative techniques, which do not involve such exposure, cannot be used. ii. Shall be carried out when approved by appropriate authority (i.e. AELB or MoH). iii. Temporary and is subjected to review by appropriate authority 25 Special Planned Exposure With a written approval from the authority: a) Extended period - Dose equivalent averaged over 10 consecutive years < 20 mSv/yr - < 50 mSv in one calendar year - Review, when accumulated dose of 100 mSv b) Change of annual Dose limit - Not more than 50 mSv per year for five consecutive years - Voluntarily and temporary in nature Should be review annually No renewal Specific working area and radiation worker Not for pregnant women or student 26 Dose Limit (annual) • Radiation workers  - 20 mSv whole body - 150 mSv (eye) - 500 mSv (others) • Pregnant female worker - 1 mSv (to fetus, within pregnancy) • Public - 1 mSv • Students - 6 mSv • Special Planned Exposure - 50 mSv • Derived Limits • Authorized Limits ALARA : - Special modeling approved by AELB - Special limit by AELB As Low As Reasonably Achievable 27 Radiation Radiation Protection Protection Systems Systems Intervention Intervention is carried out when: • an emergency situation occurred; • a directive issued by appropriate authority in any temporary exposure situation to reduce or avert temporary exposures; • the appropriate authority directs the remedial action to reduce or avert chronic exposure The form, extent and duration of intervention shall be optimized to produce the maximum net benefit in the social and economic circumstances. 28 Internal Dose Intake - the amount of activity taken into the body. Entry into the body can occur via: • Inhalation (dust, gas or volatile materials) • Ingestion (contaminated food or water) • Wound (dust, solid or liquid materials) • Direct absorption (tritium)  The limit of internal exposure resulting from the intake of radionuclide is based on the Annual Limit of Intake (ALI).  The ALI is the intake by inhalation, ingestion or through the skin of a given radionuclide in a year by the reference man which would result in a committed dose equal to the relevant dose limit. The ALI is expressed in units of activity. 29 Application of the annual dose limits - by comparing the total effective dose with the relevant dose limit where Hp(d) is the personal dose equivalent during the year; e(g)j,ing and e(g)j,inh are the committed effective dose per ingested or inhaled unit intake for radionuclide j by the group of age g; and Ij,ing and Ij,inh are the intake via ingestion or inhalation of radionuclide during the same period 30 Application of the annual dose limits - by satisfying the following condition ADL where ADL is the relevant limit on effective dose, and Ij,ingL and Ij,inh,L are the ALI via ingestion or inhalation of radionuclide j 31 ADL Q2. If in a year, a radiation worker was exposed to 106 Bq natrium-22 through ingestion and 102 Bq plutonium oxide-239 through inhalation. What is the maximum equivalent dose received by the worker if the DL is not exceeded? ALINa-22=107 Bq ALIPuO2-239=5 x 102 Bq Note DL= ADL Answer: 33 The values of Ij,L Limit of intake for radionuclide j, Ij,L A where ADL is the relevant annual dose limit on effective dose and ej is the relevant value of dose per unit intake for radionuclide j 34 Protection Against Radiation Hazards Types Types of of Radiation Radiation Hazard Hazard Internal Radiation Exposure External Radiation Exposure Contamination Protection Against Radiation Hazards One method of control against radiation hazard employing both engineering and administrative controls is through the classification of areas. Working areas may be classified according to : clean area, supervised area & controlled areas. Classification of areas take into account the likelihood and magnitude of potential exposures (risk) and the nature and extent of the required protection and safety procedure. 36 Classification of Areas • Clean Areas “Work area where the annual dose received by a worker is not likely to exceed the dose limit for a member of the public” No special arrangements are necessary. • Supervised Areas “Work area for which the occupational exposure conditions are kept under review even though specific protective measures and safety provisions are not normally needed” 37 Classification of Areas • Controlled Areas “Work area where specific protection measures and safety provisions could be required for controlling normal exposures or preventing the spread of contamination during normal working condition and preventing or limiting the extent of potential exposures” and Annual dose to a worker is likely to exceed 3/10 ADL. – Entry limited to authorized personnel. – Area is clearly demarcated with radiation warning signs and legible notices clearly posted – Subjected to regular medical examination, routine monitoring and training. 38 Protection Against External Radiation Exposures Shielding Source • Appropriate Shielding • Shortest Time • Maximum Distance Distance Time SHIELDING The shielding materials & thickness depend on: i. Type of radiation ii. Activity of the radioactive source iii. Energy of radiation Alpha lose energy rapidly in passage through matter and hence do not penetrate far. No shielding is required. Beta radiation requires shielding of low atomic number (Z) materials such as perspex, aluminum and thick rubber are most appropriate for the absorbance of beta particles. Gamma and x-ray, the high density materials such as lead and concrete are good and normally used for shielding this type of radiations. 40 SHIELDING Continue ... • Neutrons are uncharged particles and can penetrate matter considerably. Shields use on neutron is directed towards reducing the energy of the neutrons to levels that can easily be absorbed  Neutron (< 1 MeV) A reduction of the energy of neutron is best accomplished by collisions with atoms of light elements, e.g. hydrogen.  Neutrons (> 1 MeV) Energy of fast neutrons is best reduced using water and paraffin wax. 20 cm of paraffin wax will attenuates 1 MeV fast neutrons by a factor of 10 SHIELDING CONCEPT For X and -rays: Xo XT  μT  e XT Xo Thickness, T Xo = Doserate before shielding XT = Doserate after shielding T  = Shielding thickness = linear attenuation coefficient Half Value Layer, HVL HVL: Thickness of a shielding material required to reduce the intensity of the beam to the half of its initial value. TVL?43 SHIELDING Half-value layer (HVL) Thickness of shielding material that reduces the dose rate to half of original 0.33 R/h 1.32 R/h Iron (2 HVL = 4.2 cm) 1m 1.32 R/h Radiation Source, 60 Co, 1 Ci Concrete (1 HVL = 6.2 cm) 1m 1m 0.66 R/h 1.32 R/h 0.165 R/h Pb (3 HVL = 3.6 cm) 44 TIME Dose = Dose rate x Time Doserate = 2.0 mSv/hr 2.0 mSv/hr x 3 hr = 6.0 mSv 2.0 mSv/hr x 6 hr = 12.0 mSv Exposure starts at 12:00 am 2.0 mSv/hr x 9 hr = 18.0 mSv 45 1. A radiation survey meter reads 200 Sv/hr. How long it takes before a dose of 5 mSv achieved 2. A radiation survey meter reads 20 mR/hr. How long it takes before a dose of 15 mSv is achieved ? (note: 100R≈ 1Sv) 46 1. Dose Rate= Dose , Time = 5 mSv Time 200 uSv/hr = 5000 uSv 200 uSv/hr = 25 hrs 47 2. Dose rate = Dose , Time = 15 mSv Time 20 mR/hr = 15 mSv 2x10-4 Sv/hr = 15 mSv 2x 10-1 mSv/hr = 75 hrs 48 Relationship of D and d (Inverse Square Law) Radiation dose inversely proportional the square of the distance X1 X1d12 = X2d22 d1 d2 X2 = (X1d12) d22 Source Where: X1 : dose rate at a distance d1 from the source X2 : dose rate at a distance d2 from the source 49 Example 1 Dose rate at a distance of 2 meter from a source is 100 Sv/hr. What is the dose rate at a distance of 1 meter from source? X1 d1 2 = X2d22 100 Sv/hr x 2 m x 2 m = I2 x 1 m x 1 m I2 = 100 Sv/hr x 4 m2 1m2 = 400 Sv/hr 50 Example 2: The dose rate at 2 meter from an X-ray machine is 400 Sv/hr. At what distance will it give a dose rate of 25 Sv/hr? Solution Inverse square law: X1d12 = X2d22 Given: X1 = 400 Sv/hr d1 = 2 meter X2 = 25 Sv/hr Therefore 400 x (22) = 25 x d22 d2 2 = (400 x 4) / 25 = 64 d2 = 8 meter 51 Protection Against Internal Radiation Exposures Internal exposure is attributed to radiation exposures from radionuclides inside the body. There are three modes of entry of radionuclides into the body; i.e. inhalation, ingestion and penetration through the skin. Protection against such radiation hazards may be overcome through:  the use of personal protective equipment (PPE),  having proper equipment and facilities to handle unsealed sources  having proper procedures and surveillance to safely handle them. 52 Personal Protective Equipment (PPE) • worn to reduce the risk of radiation exposure from internal radiation exposure and radioactive contamination. • the last line of defense in controlling risk and should only be used to complement other means of radiation hazard control already in place. Examples of PPE/clothing include:       Laboratory coat Overall or boiler suit Rubber gloves Overshoes Rubber boots Breathing apparatus [example - Pressurized clothing, SCABA + whole body suit (Self Contained Breathing Apparatus)] 53 Personal Protective Equipment (PPE) Rubber glove Lab Coat Mask Shoes Cover Coveralls Half-face Respirator Full-face Respirator Self-contained breathing apparatus (SCBA) Safety Equipment and Facilities These equipments are used to reduce exposure and contamination. Safety facilities include building design incorporating safety features to handle radiation and radioactivity. Examples of such equipment and facilities are: • • • • • Remote-handling tongs Lead brick Liquid transfer system Radioactive containers Ventilated facility 55 Protection from unsealed sources  Minimum quantity of radioactive material  Use fume hood, glove boxes, controlled areas  Good housekeeping  Spill is confined and decontaminated ASAP  Periodic surveys  Practice first for new operation with dummy  Hand and foot must be monitored before exit the area Safety Procedures and Surveillance Safety procedures must stress the importance of preventing inhalation, ingestion and penetration of radionuclides through the skin, and contamination of personnel and working areas in normal routine procedure and emergency situations. Having a safe working procedure does not guarantee its compliance. Surveillance of compliance and monitoring of radiation levels must be carried out periodically. Both visual surveillance and those using radiation monitoring and detectors must be used. 57 Routes of Exposures Atmosphere Vegetation Soil (Pastures,cereals, vegetables) Rain Direct Contamination Animals Meat Milk Man 58 DESIGN AND CALCULATION OF SHIELDING FOR EXPOSURE AND CONTROL ROOMS Contents Contents  Introduction  Design of Exposure Room  Shielding Calculation For Exposure and Control Rooms  Details Design of Exposure Room Introduction Application of Radiation Education Medicine Industry Agriculture Introduction Radiation hazards relates to different types and characteristics of the radiation source Types Types of of Radiation Radiation Sources Sources Nuclear Reactor X-ray Machine Irradiating Apparatus Sealed Radioactive Sources Linear Accelerator Unsealed Radioactive Sources Design Design of of Exposure Exposure Room Room Different design of exposure room for different types of sources, hazards & characteristic of radiations Design Design of of Exposure Exposure Room Room  External Radiation Exposure o Related to high penetrating radiation source outside the body [sealed source, irradiating apparatus & unsealed source]. o Radiation penetrates the skin and organ to cause harm to the body system. o Highly penetrative radiation include X- and rays, high-energy  (> 70 keV) and neutron. Design Design of of Exposure Exposure Room Room  Require a specially built shielded room.  General requirements for the shielded rooms include: o designed and built according to the standards required for its purpose; o classified and demarcated appropriately; o all necessary control measures and procedures in accordance to its classification must be enforced.  Besides safety, the overall work place design must provide for comfort of work and security of the facility. Design Design of of Exposure Exposure Room Room General GeneralAspects: Aspects:Materials Materials Factors that should be considered: • Required thickness & weight of material • Uniformity of shielding • Permanence/stability of shielding • Optical transparency • Possibility of multiple use • Cost of material Normally used material: Pb, Concrete, Ba Plaster, Pb glass, UHPC Barrier Design Design of of Exposure Exposure Room Room Primary PrimaryProtective Protective Barrier: Barrier: Any wall on which the useful (primary x-ray) beam is directed. Wall A in the diagram is the primary barrier Secondary Secondary Protective ProtectiveBarrier: Barrier: C Toilet Service D Dark Room Dark Room B X-Ray Room CONTROL A A Any wall (e.g B,C and D) on which the secondary or scattered radiation is directed. Secondary (stray) radiation the sum of scatter & leakage radiation. Design Design of of Exposure Exposure Room Room a - Useful beam radiation Radiation which passes through the window, aperture, cone or other collimating device of the source housing. Sometimes called primary beam. c a b - Scattered radiation Radiation that, during passage through matter, has been deviated in direction c - Leakage radiation All radiation coming from the source or tube housing except the useful beam. b Exponential Attenuation of Radiation Xo XT  μT  e X T Xo Thickness, T Where Xo and XT are doserate before and after shielding respectively, T is shielding thickness and  is linear attenuation coefficient • No barrier will completely eliminate the radiation dose outside an exposure room • What is safe? 69 Doserate Doserate After After Shielding Shielding Design Goal Controlled Area Uncontrolled Areas NCRP-49 50 mGy/y = 1 mGy/wk 5 mGy/y = 0.1 mGy/wk NCRP-147 5 mGy/yr = 0.1 mGy/wk 1 mGy/y = 0.02 mGy/wk 70 Shielding Calculation for Exposure and Control Rooms Doserate Before Shielding No. of HVL, 2n = Doserate After Shielding No. of TVL, 10n = Doserate Before Shielding Doserate After Shielding 71 Shielding Calculation of X-ray Room HVL and TVL for Lead and Concrete: HVL (mm) TVL (mm) Tube Potential (kVp) Lead Concrete Lead Concrete 40 0.03 3.3 0.06 10.16 60 0.11 6.4 0.34 22.1 80 0.19 10.7 0.64 35.6 100 0.24 15.24 0.80 50.8 125 0.27 19.30 0.90 63.5 150 0.28 21.8 0.95 71.1 Example Shielding Calculation: HVL for Cs-137 is 6.5 mm. of lead. What is the thickness of lead needed to reduce the dose rate from 40 mR/hr to 2.5 mR/hr ? Doserate before shielding No. of HVL, 2n = Doserate after shielding = 40 / 2.5 = 16 n ln 2 = ln 16  n = ln 16 / ln 2 = 4 Therefore, thickness required = n x No. of HVL = 4 x 6.5 = 26 mm. of lead Example Shielding Calculation: A lead shield is used to block 60Co radiation field of 96 Sv/hr. Calculate the final dose rate after passing through 6.2 cm lead. Given, HVL for lead in 60Co is 1.24 cm. Answer: Given 1 HVL for lead is 1.24 cm, therefore 6.2 cm of lead is equivalent to 5 HVL Xo 2  XT n 96 96 2  , therefore X T   3 Sv / hr XT 32 5 Example Shielding Calculation: If dose rate at a particular distance from 192Ir radioactive source is 1000 Sv/hr, calculate the thickness of lead required to reduce the dose rate to 1 Sv/hr. Given for 192Ir, TVL is 1.62 cm of lead. Answer: Using a formula: Xo 10  XT n 1000  10 3 , therefore, n  3 1 Given 1 TVL for Ir  192 is 1.62 cm, 10 n  Therefore, 3 TVL is equal to 3 x 1.62 cm  4.86 cm Details Details Design Design of of Exposure Exposure Room Room (High (High Energy Energy LINAC) LINAC) For details refer NCRP 151 Details Design Exposure Rooms For medical use of X-rays and gamma-rays Shielding models in NCRP-147, extension of NCRP-49 For Non-Medical X-ay and Sealed Gamma Rays- Refer American National Standard (ANSI-HPS) Details Design of Exposure Room • Data required include consideration of: – Type of X-Ray equipment or Gamma Source – Usage (workload) – Positioning – Primary beam access (versus scatter only) – Operator location – Surrounding areas Layout: Exposure Room 79 Example of Details Shielding Calculation for X-ray Room Method for calculating primary barrier: Depends on: -Permissible weekly exposure,P (e.g: 0.1R) Kux = P (dpri)2 ______ WUT - Maximum kV, mA; - Workload(W) (mA.min/wk); - Occupancy factor, T (T=1 for offices, labs, shops, living quarters, occupied space, control space; and T = 0.25 for Corridor, rest rooms, elevators using operators, unattended lots) The thickness x is determined from a calibration curve for the corresponding material and energy K = mSv / mA . min - Use factor, U; * kVp * * required thickness * * * * Thickness x (mm) Occupancy Factor, T N0. 1 2 3 Location Office, lab, shop, ward, nurse station, living quarters, Children’s play area Corridor, Rest Room, elevator, unattended parking load Waiting room, toilet, unattended elevator, outside area used only for pedestrian or vehicular Occupancy Factor 1 Full 1/4 Partial 1/16 Occasional Use Factor, U Barrier Radiographic Installation Therapy Installation Floor 1 1 Wall ¼ ¼ Ceiling 0 <¼ Example of Details Shielding Calculation for X-ray Room The thickness x is determined from a calibration curve for the corresponding material and energy K = mSv / mA . min Method For Calculating Secondary Barrier * kVp * * required thickness * * Thickness x (mm) * Continue….. • a = Ratio of scattered to incident exposure for certain scattered angles from Central Ray (x-ray or gamma ray) • F = Field area at the irradiated phantom (e.g:-surface = 400 cm2 based on phantom area used in determining a ratio value) • dsca = distance where the scattered located (e.g patient) from the radiation source • dsec = distance from the scattered object (e.g patient) to the point of interest Example of Details Shielding Calculation for X-ray Room Other Method For Calculating Secondary Barrier Leakage radiation, P for a diagnostic radiology tube housing is limited to 1 mSv in 1 hr at 1 m. BLX = P I = Max rated continous tube current, mA (dsec)2 (600 I) W T SL = (HVL) ln (BLX) 0.693 The thickness is SL = N (HVL) or n (TVL) N, n -from NCRP 49 for computed BLX Summary Summary  Design of Exposure Room  Shielding Calculation For Exposure and Control Rooms  Details Design of Exposure Room Thank You for your attention

1 - PRINCIPLE OF RADN PROTECTION_2018(Oct 1).ppt

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