Radiation protection unsealed sources Powerpoint

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					Radiation protection for work
  with unsealed sources
SEMINAR
1.    Legislative control RSA93 & irr99
2.    Management Structure
3.    Duties of Workers – ALARA + red tape
4.    To carry out ALARA – know isotope and hazards, know units
5.    Stochastic & non-stochastic damage. No way of eliminating risk – hence
      ALARA
6.    Maximum Legal Dose
7.    Equivalent risks
8.    Minimise Dose
9.    Minimum Activity – counts 10,000 maximum
10.   Shielding
11.   Common Sense (demo) LOCAL RULES – tray, gloves, care
12.   Monitoring – 2 types of monitor demo
13.   Records – account for waste disposal – 3 routes
14.   Record Sheets
15.   Dealing with spillages
Ionising Radiations Regulations
ALARA – As low as reasonable attainable. Minimising dose by reducing time
  spent in vicinity of isotopes by increasing working distance and by using
  appropriate shielding.

Radioactive Substances Act
BPM – all users are expected to have available for inspection, written assessments
  showing the considerations taken into account in disposal of radioactive waste
  and how that constitutes the use of Best Practicable Means
                The Radioactive Substances Act 1993


The RSA93 is aimed at ensuring the security of radioactive materials in
   industrial/research use, especially with regard to the proper disposal of any
   radioactive waste that may be generated.

Registration of Sources – most radioactive materials are required to be registered
   under the RSA93 act for their safe keeping and use at a specified premises.

A Registration licence is issued under the Act which specifies the number of
   sources and their respective maximum activities which may be brought on to
   the premises.

The keeping of radioactive material and the disposal of radioactive waste are both
   highly regulated by the Environment Agency.
                 Ionising Radiations Regulations 1999

Made under the Health & Safety at Work Act 1974, these regulations apply to all users of
   radioactive materials or radiation generating equipment and are enforced by the health
   & Safety Executive.

In the UK the National Radiological Protection Board advises the Government on standards
     to be adopted and fully endorses the EU recommendations for reducing worker dose
     limit.

IRR99 are concerned with regulation of work with ionising radiation and dose limitation:
• Restriction of exposure
• Dose limits
• Arrangements for the control of Radioactive substances
• Monitoring of ionising radiation
• Designation of controlled and supervised areas
• Local rules, supervision and radiation protection supervisors
• Information, instruction and training
                         Best Practical Means


1.   Can we justify the use of radioactive tracers in all the procedures
     currently using them. Is there a practical non radioactive alternative
     (e.g. fluorescent dyes)?
2.   Are there procedures where a different radionuclide could be used
     that has a lower environmental impact (shorter half life perhaps)
3.   Are the procedures currently followed best practice? Could
     different techniques be employed that would reduce the amount of
     radioactive material used.
4.   Is there scope for reducing waste by ordering radionuclides in
     smaller amounts?
5.   Could we usefully reduce emissions by increased decay storage? (I-
     125 perhaps). Currently only used for 32-P.
Management Structure set up by the University to control work with unsealed
radioactive sources – summarised by flow chart


Registrar                   Ultimately responsible for all work carried out at
                            Keele University
URPS                        Ensures compliance with the Ionising Radiations
                            Regulations 1999 concerning the holding and
                            disposal of radioactive substances
DRPS                        Authorises all work including purchases of
                            radioisotopes, advised on safe handling and
                            disposal of isotopes, keeps records on use and
                            disposal of isotopes
Project Leader              Designs and supervises experiments, ensure all
Laboratory Manager          relevant regulations are observed within laboratory
Radiation workers           Ensure safe working practices by carrying out all
                            laboratory work in accordance with the ALARA
                            principal to ensure any dose of radiation received is
                            As Low As Reasonably Attainable
            Scheme of Responsibility
                     Registrar
                 (Mr Simon Morris)
                        
 University Radiation Protection Supervisor (URPS)
                (Dr David Dugdale)
                        
Departmental Radiation Protection Supervisor (DRPS)
                        
       Project Leaders / Laboratory Managers
                        
                Radiation Workers
Summary of responsibilities of workers using unsealed sources
It is the duty of all workers to take reasonable care for the health and safety of
     themselves and of other persons who may be affected by their acts or
     omissions at work.
Health and Safety at Work Act, 1974 (see University Safety handbook)

University Radiation Protection Supervisor (URPS: Dr David Dugdale)
• Ensure compliance with the Ionising Radiations Regulations 1999.
Departmental radiation Protection Supervisor (DRPS:
• Authorise all work including purchase of radioisotopes
• Advise on safe handling procedures, and disposal of radioactive waste
• To keep all records of all radioactive waste disposal
Project leader (may be delegated to Laboratory Manager)
• Design and supervise experiments
• Training workers in proper handling procedures and local rules
• Ensure that all relevant regulations are observed within the laboratory
• Provide facilities for disposal of radioactive waste
• Arrange removal of radioactive waste to store
• Ensure local records of monitoring and waste disposal are kept
Radiation Workers
• Register with the URPS before beginning any work with ionising
   radiations
• Proceed with work only when reasonably familiar with, and confident in,
   the experimental techniques involved- under close supervision initially.
• Carry out all laboratory work in accordance with the principal of ALARA, i.e.
   to ensure any dose of radiation received is As Low As Reasonable Attainable
• Dispose of all radioactive waste by the appropriate local route
• Keep local records of the generation and disposal of radioactive waste
• Monitor person and work area frequently, including the start and end of each
   working period.
          Important Characteristics of a Radioisotope

                                             Example
1.   Designation                             32P

     (AX)
2.   Activity                                370MBq
     (MBq or mCi)
3.   Radiations emitted                      
     (,  or )
4.   Energies of the Radiations              0.51MeV
     (MeV)
5.   Frequency of emission                   95%
     (% disintegrations)
6.   Half-life                               14 days
                       Common Isotopes

                3H           14C         32P      125I


Type                                            


Energy (MeV)   0.018        0.159        1.71    0.035


Half-life      12 y         5760 y       14 d    60 d


Target organ   Any           Any         Bone   Thyroid
          Physical Properties of Common Unsealed Sources

      Isotope           Half-life          Principal        Energy (MeV)           Abundance (%)
                                          Radiations
         3H               12.3y                                 0.018                   100.0
        14C              5760 y                                  0.16                   100.0
        32P              14.3 d                                  1.70                   100.0
        33P               25 d                                   0.25                   100.0
        35S              87.2 d                                  0.17                   100.0
        36CI            3 x 105 y                               0.l71                   100.0




32-Phosphorus is one of the highest energy beta-emitting radionuclides commonly used in biomedical research
 Hazards represented by different ionising
                radiations
Radiation                  Hazard
                External             Internal


 particle   None              Very serious


 particle   Skin, eyes        Serious



Neutrons     Whole body


 Rays       Whole body        Less serious


X Rays       Whole body
                              Radiological Units
Source strength (Activity)
The quantity of radioactivity, being the strength of a source or its ‘activity’, is
expressed in terms of the disintegration rate of isotopes’ atoms, or becquerels.

1 becquerel          (Bq)                 =   1 dps (1 disintegration per second)
1 Kilo-              (kBq)                =   103 dps
1 mega-              (MBq)                =   106 dps
1 giga-              (GBq)                =   109 dps

1 microcurie         (Ci)                = 3.7 x 104 dps
1 milli-             (mCi)                = 3.7 x 107 dps
1 curie              (Ci)                 = 3.7 x 1010 dps

1 MBq                = 27  Ci            1mCi                 = 37MBq
                                DOSE
Maximum permitted dose           = 10 mSv

Permitted dose at Keele          = 1 mSv

Estimating Dose
• Measure it
   -     dosemeter (accurate)
   -     personal monitor
         -        film badge
         -        thermoluminescence detector
• Calculate it
   -     assumptions (approximate)

Action level: positive film badge/TLD return
        Effect of radiation dose:
non-stochastic effects (acute, short-term)
    0-50 mSv       no visible effect

    500 mSv        reversible blood changes

    1 Sv           mild illness, fever

    3 Sv           vomiting, hair loss

    4.5 Sv         bone marrow destruction
                   (LD 50 (infection)

    6 Sv           1st/2nd degree burns

    10 Sv          diarrhoea; death in 3-5 days
             Effect of radiation dose:
     stochastic effects (statistical, long-term)
mainly cancers       -   leukemia (5-7 years)
                     -   others (>20 years)

difficult to get accurate statistics for low doses

50 mSv               - 1 in 2,000 chance above average
   
                           extrapolating
   
10 mSv               - 1 in 10,000 chance above average

               There is probably no “safe” dose:
                Follow the principle of ALARA
              (As Low As Reasonably Attainable)
Average Annual Dose Equivalent to an Individual (UK)
                                           = 10-6 m = 1-3
•   Natural          cosmic radiation           300 sv
                     Terrestrial               400 sv       87%
                     radon decay                800 sv       of total
                     internal radiation         370 sv
                     (eg. K-40)
                      TOTAL NATURAL            1870 sv

•   Artificial       Medical procedures          250 sv
                     Weapons fall out             10 sv
                     Nuclear discharge to        1.5 sv
                     Environment                             13%
                     Occupational exposure        8 sv      of total
                     Miscellaneous sources       11 sv
                     TOTAL ARTIFICIAL            280 sv

•   Chernobyl estimate (U.K.) 40 sv (May 86 – April 87)
                              20 sv subsequently
Important Dose Equivalents (Annual) relating to occupational exposure


 Annual dose limit for men (radiation works)                 = 10 msv



 Special controls may become necessary if the dose rate exceeds 7.5 sv hr-1
       (wholebody)

 Risk Factors
 1.    The risk factor for radiation induced fatal cancer is :
          1.25 x 10-2 sv -1 (1 in 80 per Sievert)
       The average dose equivalent received by a radiation worker is:
           1.4 msv per year.
       Therefore the annual risk of death for radiation workers due to cancer is:
          1 in 57,000
2.    To put this value into perspective compare it with:
      (a) Average annual risk of death in the U.K. from accidents at work

         Occupation                             Risk of death per year
         Fishing                                1 in 800
         Coal mining                            1 in 6,000
         Construction                           1 in 10,000
         All employment                         1 in 43,500

And (b) Average annual risk of death in the U.K. from some common causes

         Cause                                  Risk of death per year
         Smoking 10 cigarettes per day          1 in 200
         All natural causes for a 40 year old   1 in 850
         Accidents on the road                  1 in 9,500
         Accidents in the home                  1 in 26,000
There are three strategies for dose control

1.    Planning of experiments to reduce dose, mechanical interlocks (As Low
      As Reasonably Achievable (ALARA)).
2.    Retrospective, film badges
3.    Active monitoring, hand-held radiation detectors and swab testing.

Planning
Always plan experiments so that the minimum amount of radioactivity is used.
Always plan experiments with the minimum of sample handling
Do not linger in areas where radioisotopes are being used

Retrospective
Film badges are issued by the DRPS and any reported doses will be invesitigated
immediately
         The Inverse Square Law
• The Inverse Square Law is a very powerful tool for
  practical protection against external radiation.- it describes
  how the intensity of radiation from a radioactive source
  decreases as you move away from it.
• The simple rule to remember is that by doubling the
  distance the radiation level is reduced to one quarter., by
  trebling the distance the radiation level is reduced to one
  ninth, and so on.
                        Minimising Dose
                   Total dose = dose rate x time

• Assess potential hazard – get to know your isotope

• Minimise external hazard:
      - minimise time of exposure- planning
      - keep distance from source
      - use minimum activity necessary for experiment- planning
      - use shielding where appropriate

• Minimise internal hazard
      - good lab hygiene
      - good technique

Apply liberal quantities of common sense!
           Minimum activity considerations
• Statistical counting errors
• Signal/noise (background)
Statistical errors

   error         =                 total counts

  Total counts          Error                  Error(%)
  10                     3.2                  31%

  100                    10.0                 10%

  1000                   32                   3%

  10,000                 100                  1%
  10,000 counts over 5 min at 50% counting efficiency
  = 4,000 dpm = 67 Bq ( 2 nCi)
Alpha particles are very easily absorbed. A thin sheet of paper is sufficient to
stop them so they never present a shielding problem.

Beta particles are more penetrating than alpha. The best shielding for beta
radiation is low density material such as perspex – 6mm thick will stop all beta
radiation up to 1MeV. Whilst relatively easy to shield, however, the dose rates
from beta radiation can be very high. High density material such as lead will
produce the ‘Bremsstrahlung’ effect where energy is emitted as penetrating X
rays.

Gamma radiation is much more penetrating and is attenuated exponentially when
they pass through any material. The most efficient absorbers are highly dense
materials such as lead or steel.
                                   Shielding
The amount of shielding required depends on three things:
1.    The type of radiation
2.    The activity of the source
3.    The dose-rate which is acceptable outside the shielding material
                                      Monitoring

There are 2 categories of monitors and dosemeters:

1. Contamination monitors – read out in cps and very sensitive
2. Dose ratemeters – which can calculate dose to person in Sv – less
      sensitive.
Use correct monitor for the job in hand.

Contamination monitors – 2 types

1.  Geiger Muller detector used to detect beta particles, has very thin end window which
    lets particles through easily. Not very sensitive to gamma rays as they pass straight
    through it and do not react.
2.  Scintillation detector (900 series) has crystal in it with denser medium to stop gamma
    and react. Beta particles cannot penetrate thick end window, so not detected.
   Type E has a grill at the end and is most suitable for measuring low levels of leakage
    radiation.
   Different types of monitor for different types and energies of radiation.
NB 3H (Tritium) emits low energy beta which cannot penetrate the detector and is not
    detected by either monitor. Monitor contamination by swabbing surface and liquid
    scintillation counting of swab.
Active Monitoring

Types of emission


Radioactive decay              Type of active monitoring Emission
process
                              Swab testing              Helium nucleus

Soft                          Mini-instrument type EL   electrons
                               probe and swab testing
Hard                          Mini-instrument type EL   electrons
                               probe
 + X ray                      Mini-instrument type 44   electromagnetic
                               A, B or X probe



Each radioisotope has a specific emission spectrum
Monitoring and dose control theory
The hazard to the worker associated with various types of emission can be divided
into two groups.


Emission                    Hazard
                            External radiation         Internal contamination
                           None                       Very serious
                           Skin and eyes              Serious
                           Whole body (including      Minor (except if target
                            internal organs)           organ is small)
X ray                       Very serious
                          The use of mini-monitors

NB the monitor is not tropicalised or ruggedised and will not work if it is dropped
     into a pond or run over by a tank!

Operation

•         Select the correct type of monitor
•         Switch the battery check for at least 2 minutes
•         Check the monitor is working with a radioactive source

Areas where work with ionising radiation is used are divided into three types:

Controlled > 1 mCi
Supervised > 100 Ci
Registered +/- 10 Ci
Various types of probes are available but commonly they are Geiger Muller eg mini-
      monitor type EL and scintillation eg type 44A. The response of both probes varies
      with the energy of the source as shown in Fig 1 and 2.

So it can be seen that the response of a monitor will vary with
a)     The amount of radiation
b)     Its energy

c)    Monitoring: Radioactivity is measured in KBq or Ci but the monitors give c.p.s.

The interpretation of c.p.s. must take into account the type of emission, the distance from
      the source and the response of the probe to the energy of the emission, eg using a
      type 44A probe with a 1ci sample at 20mm:

     Radionuclide                 c.p.s.                          Principal emission
     125I                         1610                            35 keV and 27-32 keV
     51Cr                         73                              0.32 mev and 5 kev
                CONTAMINATION MONITORING

Levels of radiation have to be routinely monitored both within and around all
   controlled and supervised areas to check for:

•   Presence of enhanced levels of radiation exposure
•   Leakage from source housings, waste storage containers etc.
•   Presence of contamination on surfaces from use of unsealed radioactive
    material
•   Presence of airborne contamination resulting from the release of gaseous
    materials
                    Master Sheet Waste Disposal Section
Each time some isotope is removed from the stock bottle, its fate should be
recorded in the disposal section as follows:
•   NB the Department isotope code (e.g. B10/09) must be marked on the
   stock container
• DATE:               When the isotope was removed from stock

•   AMOUNT USED: Record the amount removed from stock and amount
                  remaining in stock. It is essential that the master sheet
                  completely account for ALL of the isotope originally
                  delivered. For long-lived isotopes, this account must be in
                  activities. For isotopes that significantly decay with time
                  accounting procedures can be in volumes.

•   PURPOSE:           Indicate type of equipment (optional)

•   DISPOSAL ROUTE: If the activity is all used up in one experiment, then the
                    amount used should be accounted for in the first three
                    waste disposal route columns. NB. The disposal limited
                    for liquid organic waste is only 20 Ci/month so be
                    accurate. If the procedure involves preparation of a
                    derivative source to be used in several experiments (eg a
                    radiolabelling prep, make sure you keep track of all the
                    radioactivity.
                             Master Sheet Header Section
                (A new sheet every time some isotope arrives in the School)
This should be filled in as soon as possible after delivery, as follows:

DEPT CODE:              a unique code from STORES identifying the delivery (e.g.B10/09)- this
                        code must be marked on the outside of the radioisotope container.
•
SUB-CODE:               mark this as MASTER on all master sheets
•
DATE RECVD:             date received by stores
•
ACTIVITY REF.
DATE:                   as supplied by Amersham for short-lived isotopes
•
COMPOUND:               chemical composition of the isotope source

ISOTOPE:                radionuclide (I-125, P-32, C-14 etc.)
•
LOCATION:               laboratory where isotope is to be kept
•
TOTAL ACTIVITY:         as delivered from Amersham (eg 5mCi)
•
TOTAL VOLUME:           volume of isotope delivered

ASSIGNED TO:            person ordering the isotope and who is then responsible for ensuring that
                        proper records are kept of its disposal
•   (Continued below)
                        Waste Disposal Routes
                                          Mixed with normal refuse 400 kBq
Very Low Level Waste                      per 0.1m3 (e.g. cube 46x46x46cm.)
                                          paper, gloves in unlabelled sacks

                                          Designated sink 400 MBq per
Aqueous                                   month all isotopes

                                          Incinerators 200 MBq per month
Solid Waste                               includes sample tubes
                                          14C, 3H and 1251 only designated

                                          bins
                                          Incinerators 400 kBq per month
Liquid organic                            includes scintillation vials 14C, 3H
                                          only 4 litre plastic containers

Note that short-lived isotopes, eg 32P, are often best disposed of by storing in
shielded areas until decay has reduced the radioactivity to negligible levels-
e.g. 6 months storage for less than 1 mCi 32P, then, unlabelled, into very low
level waste
 KEY FEATURES CONCERNING RADIATION PROTECTION FOR
        TWO COMMONLY USED RADIONUCLIDES

Feature                     P-32             I-125
Radiation type                              
Energy                      1.7 MeV          35 keV
Proection afforded by       Inverse Square   Inverse
distance                    Law              Square Law
Easily air borne            NO               YES
Radiological half life      14.3 days        60 days
Finger dose problems        YES              NO
Critical organ              BONE             THYROID
Biological stability if     HIGH             MOD
absorbed
Concentration in critical   LOW              HIGH
organ
Disposal problems           NO               YES
                                 Eleven Golden Rules
1. Understand the nature of the hazard and get practical training.

2. Plan ahead to minimise time spent handling radioactivity.

3. Distance yourself appropriately from sources of radiation and use appropriate shielding
       for the radiation

4. Always get detailed instruction and advice from supervisor and/or other experienced
      radiation workers before starting work- do initial work under direct supervision.

5. Contain radioactive materials in defined work areas.

6. Wear appropriate protective clothing and dosimeters.

7. Monitor the work area frequently for contamination control.

8. Follow the local rules and safe ways of working.

9. Minimise accumulation of waste and dispose of it by appropriate routes.

10.    After completion of work monitor yourself, wash and monitor again

11.    Always discuss work procedures and get detailed advice from experienced radiation
       workers.
                        If Radioactive Material is Spilled:
Before starting work with any unsealed radioisotope, make sure a supply of absorbent
tissues is nearby, and that wherever possible all work is performed within trays which
will contain any spillage.

In any accident involving the spillage of radioactive material priority should be given to
the treatment of any personal injury or personal contamination.

      Personal Decontamination
          o Persons carrying out decontamination of a colleague should use gloves and
             take care to avoid contaminating themselves or transferring contamination
             to other areas- i.e. phone for assistance rather than leaving the laboratory.
          o Use appropriate radiation monitors to determine the extent of any
             contamination. For contamination by soft beta emitters (eg H-3) an initial
             judgement based on visual examination may be needed before the results
             of swab tests are available.
          o Remove clothing as necessary and place them in plastic bag in a suitable
             shielded waste receptacle. Those areas of skin where contamination is
             indicated should be washed with soap and water or Decon solution. Use a
             shower if one is available but take care not to wash contamination into the
             eyes or mouth
          o If necessary irrigate the eyes using an eye wash bottle and wash the mouth
             several times.
          o Monitor again. If contamination persists wash again .
          o Continue this process until no contamination can be detected.
          o Report the incident immediately to RPS and research group leaders.
          o If ingestion of radioactive material is suspected then a medical examination
             should be sought
      Area Decontamination
          o For personal protection use gloves and forceps. If dry powder spills are
             involved an appropriate face mask should also be used.
          o For minor spills ( < 1mCi ; likely conditions within Life Sciences
             biochemical and molecular biological laboratories) use absorbent paper
             tissues or other absorbent material to mop up the spill, working inwards
             towards the centre of the spill. Place contaminated swabbing material in
             plastic bags and store in a suitable shielded enclosure for latter disposal.
          o For larger spills ( > 1 mCi) it may be necessary to set up radiation shields
             to give protection to those carrying out the decontamination procedure.
             Advice should be sought from the RPS or URPS
          o Wash the affected area with water or Decon solution until monitoring
             shows that all traces of contamination have been removed.
          Please ask Radiation Protection Supervisor about training if required.

				
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