04. Safety of sources and design of facilities (2,935 KB)Presentation Transcript
Part 4 Safety of Sources Design of facilities IAEA Training Material on Radiation Protection in Nuclear Medicine
OBJECTIVE To become familiar with the types of sources used in nuclear medicine. To become aware of how the basic principles of defence in depth, safety of sources and optimization are applied to the design of a nuclear medicine facility. To get basic information about shielding calculations.
Work with sources
Security of sources
Defense in depth
Categorization of hazard
Part 4. Design of facilities Safety of Sources Module 4.1. Sources IAEA Training Material on Radiation Protection in Nuclear Medicine
Sealed sources in nuclear medicine Sealed sources used for calibration and quality control of equipment (Na-22, Mn-54, Co57, Co-60, Cs137, Cd-109, I-129, Ba-133, Am-241). Point sources and anatomical markers (Co-57, Au-195). The activities are in the range 1 kBq-1GBq .
Unsealed sources in nuclear medicine
Unsealed sources in nuclear medicine
Unsealed sources in nuclear medicine
RADIOTOXICITY Class A. Very high e.g. Am-241, Cf-252 Class B. High e.g. Na-22, Ca-45, Mn-54, Co-60, Sr-89, I-125, I-131 Class C. Medium e.g. C-14, F-18, P-32, Cr-51, Co-57, Ga-67, Se-75, Mo-99, In-111, I-123, Au-198, Tl-201 Class D. Low e.g. H-3, C-11, N-13, O-15, Tc-99m, Xe-133
Nuclear medicine application according to type of radionuclide Radionuclide
e.g. 99m Tc-MDP, 99m Tc-MAA, 99m Tc-HIDA, 111 In-Octreotide
kits requiring heating
e.g. 99m Tc-MAG3, 99m Tc-MIBI
products requiring significant manipulation
e.g. labelling of blood cells, synthesis and labelling of radiopharmaceuticals produced in house
Radiopharmaceutical labeling must be performed in accordance with :
Radiation safety regulations
Requirements of these respective regulations are sometimes conflicting :
Manipulation of radioactive material must be performed in closed area under negative air pressure
Manufacturing of sterile injectable preparation must be performed under filtered positive air pressure (laminar flow)
Part 4. Design of facilities Safety of Sources Module 4.2. Work with sources IAEA Training Material on Radiation Protection in Nuclear Medicine
Production of radionuclides Medical cyclotron Industrial cyclotron
Preparation and dispensation of radiopharmaceuticals
Laboratory work with radionuclides
Administration of radiopharmaceuticals
CARE OF RADIOACTIVE PATIENTS
Storage of radionuclides
Part 4. Design of facilities Safety of Sources Module 4.3. Security of sources IAEA Training Material on Radiation Protection in Nuclear Medicine
LOCATION AND SITING OF SOURCES (BSS)
“ IV.13. Account shall be taken in choosing the location for any small
source within installations and facilities such as hospitals and
manufacturing plants of:
Factors that could affect the safety and security of the source;
Factors that could affect occupational exposure and public
exposure caused by the source, including features such as
ventilation, shielding and distance from occupied areas; and
The feasibility in engineering design of taking into account the
Requirements for the Safety of Sources
Licensees shall ensure safety of the sources
A multilevel system of provisions for
restoring sources to safe conditions
Use of sound engineering practice on all operations with sources
Security of sources
BSS 2.34: “Sources shall be kept secure so as to prevent theft or damage and to prevent any unauthorized legal person from carrying out any of the actions specified in the General Obligations for practices of the Standards (see para’s 2.7-2.9),
Accountability and security of sources
Records of source inventory (source characteristics, locations)
Periodic inventory of sources
Records of receipt, transfer and disposal
Transfers only to receiver holding a license
Prompt communication of information to the Regulatory Authority regarding decontrolled, lost, stolen or missing sources
SECURITY OF SOURCES Use Storage of waste Transport (in house) Storage before use Receipt The security of sources shall be taken into account in the different steps of the lifetime of a source in a hospital
Local rules should specify
Persons authorized to order radionuclides
Routines for delivering radioactive material to the department
Routines for check and unpacking of shipment
Routines in case of damaged package
Routines for check of radionuclide and activity
Records to be kept
Source stores must:
provide protection against environmental conditions
be only for radioactive materials
provide sufficient shielding
be resistant to fire
STORAGE OF SOURCES
locked to prevent unauthorized use
shielded to <2 µ Sv/h at 1m
(permanently occupied areas)
alternatively <20 µ Sv/h at 1 m
(temporarily occupied areas)
In house transport, according to local rules.
External transport, according to international standards and requirements.
Radioactive waste should be handled, stored and disposed of according to local rules that are based on national regulations.
Accountability of sources
Receipt, storage, use and all movements of a source must be recorded
Accountability of Sources
Source accountancy records should contain:
radionuclide and activity of sources
location and description of sources
The records should be updated regularly, and the location of the sources checked.
Identification of the mechanisms for exposure (both routine and accidents)
Realistic estimate of doses and likelihood of occurring
Identification of possible safety system failures
Identification of protection measures needed
Safe use of sources
classification of areas
individual monitoring arrangements
workplace monitoring arrangements
How do we transfer the requirements of BSS regarding safety and security of sources into the design of a nuclear medicine facility? ??
The role of RPO The radiation protection officer (RPO) should be consulted as soon as the planning process commences for construction or renovation of a nuclear medicine facility or other hospital radioisotope laboratory.
Facilities The design of the facility should take into consideration the type of work and the radionuclides and their activities intended to be used. The concept of ‘categorization of hazard’ should be used in order to determine the special needs concerning ventilation, plumbing, materials used in walls, floors and work benches.
Part 4. Safety of Sources Design of facilities Module 4.4. Defense in depth IAEA Training Material on Radiation Protection in Nuclear Medicine
DEFENSE IN DEPTH (BSS)
“ 2.35. A multilayer (defense in depth) system of provisions for protection and safety commensurate with the magnitude and likelihood of the potential exposures involved should be applied to sources such that a failure at one layer is compensated for or corrected by subsequent layers, for the purposes of:
(a) preventing accidents that may cause exposure;
mitigating the consequences of any such accident that does
(c) restoring sources to safe conditions after any such accident.”
Defense in depth
Part 4. Design of facilities Safety of Sources Module 4.5. Categorisation of hazard IAEA Training Material on Radiation Protection in Nuclear Medicine
Categorization of hazard Based on calculation of a weighted activity using weighting factors according to radionuclide used and the type of operation performed. Weighted activity Category < 50 MBq Low hazard 50-50000 MBq Medium hazard >50000 MBq High hazard
Categorization of hazard Weighting factors according to radionuclide Class Radionuclide Weighting factor A 75 Se, 89 Sr, 125 I, 131 I 100 B 11 C, 13 N, 15 O, 18 F, 51 Cr, 67 Ga, 99m Tc, 111 In, 113m In, 123 I, 201 Tl 1.00 C 3 H, 14 C, 81m Kr 127 Xe, 133 Xe 0.01
Categorization of hazard Weighting factors according to type of operation Type of operation or area Weighting factor Storage 0.01 Waste handling, imaging room (no inj), waiting area, patient bed area (diagnostic) 0.10 Local dispensing, radionuclide administration, imaging room (inj.), simple preparation, patient bed area (therapy) 1.00 Complex preparation 10.0
Categorization of hazard Administration of 11 GBq I-131 Weighting factor, radionuclide 100 Weighting factor, operation 1 Total weighted activity 1100 GBq Weighted activity Category < 50 MBq Low hazard 50-50000 MBq Medium hazard >50000 MBq High hazard
Categorization of hazard Patient examination, 400 MBq Tc-99m Weighting factor, radionuclide 1 Weighting factor, operation 1 Total weighted activity 400 MBq Weighted activity Category < 50 MBq Low hazard 50-50000 MBq Medium hazard >50000 MBq High hazard
Categorization of hazard Patients waiting, 8 patients, 400 MBq Tc-99m per patient Weighting factor, radionuclide 1 Weighting factor, operation 0.1 Total weighted activity 320 MBq Weighted activity Category < 50 MBq Low hazard 50-50000 MBq Medium hazard >50000 MBq High hazard
Category of hazard (premises not frequented by patients) Typical results of hazard calculations High hazard Room for preparation and dispensing radiopharmaceuticals Temporary storage of waste Medium hazard Room for storage of radionuclides Low hazard Room for measuring samples Radiochemical work (RIA) Offices
Category of hazard ( premises frequented by patients) Typical results of hazard calculations High hazard Room for administration of radiopharmaceuticals Examination room Isolation ward Medium hazard Waiting room Patient toilet Low hazard Reception
Building requirements Category Structural shielding Floors Worktop surfaces of hazard walls, ceiling Low no cleanable cleanable Medium no continuous cleanable sheet High possibly continuous cleanable one sheet folded to walls What the room is used for should be taken into account e.g. waiting room
Building requirements Category Fume hood Ventilation Plumbing First aid of hazard Low no normal standard washing Medium yes good standard washing & decontamination facilities High yes may need may need washing & special forced special decontamination ventilation plumbing facilities facilities facilities
Safety of sources
Optimize exposure of staff, patients and general public
Maintain low background where most needed
Fulfil requirements regarding pharmaceutical work
Prevent uncontrolled spread of contamination
Part 4. Design of facilities Safety of Sources Module 4.6. Building requirements IAEA Training Material on Radiation Protection in Nuclear Medicine
Curved to the walls
All joints sealed
Glued to the floor
Walls and ceiling Should be finished in a smooth and washable surface with joints being sealed, wherever practicable. Walls should be painted with washable, non-porous paint (e.g. gloss paint). What the room is used for should be taken into account e.g. waiting room
Worktop surfaces must be finished in a smooth, washable and chemical-resistant surface with all joints sealed. Some laminates do not resist certain chemicals, and the supplier should be consulted with regard to the specific chemicals to be used in the laboratory.
Open shelving should be kept to a minimum to prevent dust accumulation.
Services (e.g. gas, electricity, vacuum) should not be mounted on top of the bench, but on walls or upstands.
Light fixtures should be easy to clean and of an enclosed type in order to minimize dust accumulation.
Structural reinforcement may be necessary, since a considerable weight of lead shielding may be placed on counter tops.
Worktop surfaces Cover the surface with absorbing paper
Laboratories in which unsealed sources, especially radioactive aerosols or gases, may be produced or handled should have an appropriate ventilation system that includes a fume hood, laminar air flow cabinet or glove box.
The ventilation system should be designed such
that the laboratory is at negative pressure relative to surrounding areas. The airflow should be from areas
of minimal likelihood of airborne contamination to areas where such contamination is likely.
All air from the laboratory should be vented through a fume hood and must not be recirculated either directly,
in combination with incoming fresh air in a mixing system, or indirectly, as a result of proximity of the exhaust to a fresh air intake.
VENTILATION Sterile room negative pressure filtered air Dispensation negative pressure Corridor Injection room Fume hood Laminar air flow cabinets Passage Work bench
Continuous monitoring of air pressure gradients Alarm system
Fume hood The fume hood must be constructed of smooth, impervious, washable and chemical-resistant material. The working surface should have a slightly raised lip to contain any spills and must be strong enough to bear the weight of any lead shielding that may be required. The air-handling capacity of the fume hood should be such that the linear face velocity is between 0.5 and 1.0 metres/second with the sash in the normal working position. This should be checked regularly.
If the Regulatory Authority allows the release of aqueous waste to the sewer a special sink shall be used. Local rules for the discharge shall be available. The sink shall be easy to decontaminate. Special flushing units are available for diluting the waste and minimizing contamination of the sink.
The wash-up sink should be located in a low-traffic area adjacent to the work area.
Taps should be operable without direct hand contact and disposable towels or hot air dryer should be available.
An emergency eye-wash should be installed near the hand-washing sink and there should be access to an emergency shower in or near the laboratory.
A separate toilet room for the exclusive use of injected patients is recommended.
A sign requesting patients to flush the toilet well and wash their hands should be displayed to ensure adequate dilution of excreted radioactive materials and minimise contamination.
The facilities shall include a wash-up sink as a normal hygiene measure.
Washrooms designated for use by nuclear medicine patients should be finished in materials that are easily decontaminated.
The patient washing facilities should not be used by hospital staff as it is likely that the floor, toilet seat and sink faucet handles will be contaminated frequently.
Drain-pipes from the radioisotope laboratory sink should go as directly as possible to the main building sewer, and should not connect with other drains within the building, unless those other drains also carry radioactive material. This is to minimize the possibility of a "back up" contaminating other, non-controlled areas. and the final plans of the drainage system which are supplied to maintenance personnel must show which drains are from radioisotope laboratories.
Note: Some countries require that drain-pipes from the nuclear medicine department and especially from isolation wards for patients undergoing radionuclide therapy shall end up in a delay tank.
Shielding Much cheaper and more convenient to shield the source, where possible, rather than the room or the person. Structural shielding is generally not necessary in a nuclear medicine department. However, the need for wall shielding should be assessed e.g. in the design of a therapy ward (to protect other patients and staff) and in the design of a laboratory housing sensitive instruments (to keep a low background in a well counter, gamma camera, etc)
Layout of a nuclear medicine department From high to low activity
Part 4. Design of facilities Safety of Sources Module 4.7. Safety equipment IAEA Training Material on Radiation Protection in Nuclear Medicine
Tools for remote handling
of radioactive material
Containers for radioactive waste
Dose rate monitor with alarm
Signs, labels and records
SHIELDING Bench top shield Vial shields Syringe shields Structural shielding
FORCEPS AND TONGS
Containers for radioactive waste Several containers should be available in order to segregate the waste at the point of origin (radionuclides, half-lives, glass, paper, syringes etc.)