2005 Radiation Safety Refresher Training

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2005 Radiation Safety Refresher Training

• Sue Dupre, Radiation Safety Officer
• Stephen Elwood, Health Safety Specialist

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Refresher Training Topics

• The results of the intensive audits of six labs
  conducted in 2004 by the Radiation Safety
  Committee
• A couple of minor contamination incidents
• Some general reminders about good practice and
  policies
• Policy and administrative changes
• The NRC inspection expected this spring

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Audit Survey Records

• Some of the labs audited were inconsistent or
  seriously deficient in maintaining survey logs.
• Remember to record every postoperational survey!
• Wipe surveys for H-3 use must also be noted on
  the Survey Log.

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Audit Protective Clothing

• The audit team observed a person performing
  radioisotope
• work without a lab coat, while wearing sandals
• Protective clothing requirement for work with any
  open source
• Lab coat
• Gloves
• Closed-toe shoes. No sandals permitted!

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Audit Liquid Waste Issues
The audit team found several problems relating to
liquid waste disposal

• Inadequately labeled bottles of wastes. Label
  liquid wastes with isotope, activity, dates and
  chemical content
• Disposal of acidic wastes. The allowable pH
  range for sink disposal is 5-9.
• Some labs were storing bottles of liquid wastes
  due to concerns that the wastes contained too
  much activity or due to other uncertainties.
• The monthly disposal limit for P-32 is 300 µCi
  and for S-35 is 3 mCi but EHS can give special
  permission to dispose of larger amounts.
• Take advantage of the sink disposal option!

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Contamination Incidents

• Two interesting contamination incidents
• occurred in 2004. Although contamination
• did occur, in both cases there were no
• serious consequences, and the incidents
• illustrate that many aspects of good
• practice were being followed.

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Incident 1

• Following H-3 use, a researcher conducted a
  postoperational wipe survey, put the wipes into
  the liquid scintillation counter to count and
  then left for the day without waiting to see the
  results. The researcher checked the wipe results
  the next morning and found that the wipe taken on
  her face contained low-level H-3 contamination.
• EHS responded and found no contamination on skin,
  the lab coat or the work area (the researcher had
  taken a shower the previous evening). EHS also
  conducted a urine bioassay and verified that
  there was no internal uptake of H-3.

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Lessons from Incident 1

• Always count wipes as soon as possible after the
  survey and check the results before leaving the
  lab.
• If youre in a hurry, do 1 minute counts to
  screen the critical wipes and then set the wipes
  up to count again for longer counts.
• Remember to record the results in the Survey Log.

Note H-3 poses a hazard only if taken up
internally in large amounts (it takes 80 mCi of
H-3 taken up internally to reach the annual dose
limit of 5000 millirems.)
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Incident 2

• A researcher used P-32 on a Saturday, conducted a
  post-operational survey immediately afterwards,
  and found substantial P-32 contamination on his
  shoes and on the floor between the hood and the
  sink. No contamination had been tracked to the
  hallway outside the room.
• A post- operational survey had been conducted
  (and recorded) on the previous day and had found
  no contamination, so the contamination found on
  Saturday was attributed to the work done on
  Saturday.
• Public Safety was notified and responded
  appropriately by contacting EHS.
• EHS agreed that it was OK to lock the room and to
  put warning signs on the door so that the
  clean-up could be done on Monday.

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Lessons from Incident 2

• Doing the postoperational survey immediately
  afterwards can prevent the spread of
  contamination to other areas
• Be sure to survey the path between the work area
  and the waste disposal area.
• Survey shoes, clothing, hands and face.
• Post-operational surveys are required but we also
  highly recommend that you perform a
  preoperational survey before you begin working to
  be sure that your work area is clean at the start
  of work.

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Review of Incident Procedures

• Incidents include
• Spill of radioactive materials
• Widespread or unusual contamination
• Any case of contamination on
• skin or clothing
• Missing radioactive materials
• Exposure to an x-ray machine

Be sure you know where to find the Emergency
Response book for your lab!
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Radiation Incident Notification

• Call EHS during work hours
• Call Public Safety at 8-3134 after work hours

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Radiation Safety Reminders
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Count Rate and Activity

• A survey meter typically detects only a small
  of what is actually being emitted by a spot of
  radioactive material, so counts per minutes are
  not equal to disintegrations per minutes (cpm ?
  dpm)
• Instrument Efficiency (?) cpm/dpm
• What affects efficiency?
• Shielding (even air acts as a shield for lower
  energy beta emitters such as C-14 or S-35 or
  P-33)
• Geometry (the radiations are emitted in a 4p
  geometry but a detector placed directly over the
  radioactivity is only seeing half of the sphere
  of emissions, or a 2 p geometry)
• Distance of the detector from the contamination
• For a G-M meter, under the best circumstances, ?
  25 for P-32 and is lt5 for S-35.

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Activity Count Rate (contd)

• Example A G-M meter with pancake probe reads
  10,000 cpm on
• a flat surface. If the lab uses both P-32 and
  S-35, how can you
• tell which isotope it is?
• Hold a piece of paper over the contaminated area
  and make another reading with the detector.
• If its S-35, the paper will absorb all of the
  betas, and the count rate will decrease to
  approximately background.
• If its P-32, many of the higher energy betas
  will pass through the paper, and there will be
  little change from the initial count rate.

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Activity Count Rate (contd)

• Example A G-M meter with pancake probe reads
  10,000 cpm on
• a flat surface, and you have determined that the
  contamination is
• P-32.
• The activity is approximately 40,000 dpm
  (assuming 25 efficiency)
• Since 1 µCi 2.22 x 106 dpm, the activity
  present is 0.02 µCi
• For P-32, the dose rate on contact with 1 µCi
  spread over 1 cm2 is 7030 mrem/hr. In our
  example in which 10,000 cpm of P-32 is discovered
  on a surface, the dose rate directly on contact
  is 140 mrem/hr (annual skin dose limit is 50,000
  mrem).
• Although this is a substantial dose rate, the
  dose rate will quickly decrease by orders of
  magnitude as you move a few centimeters away from
  the contamination.

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Activity Count Rate (contd)

• Example A lab wants to estimate the activity in
  a 1 liter container of
• P-32 liquid waste and places a G-M detector on
  contact. The count
• rate is 1500 cpm. How much activity does the
  bottle contain?
• Impossible to estimate, due to uncertainties in
  detector efficiency (e.g., wall thickness, width
  of the bottle, how curved the container is, the
  height of the liquid in the bottle, etc.)
• In this case, you must determine the activity
  empirically Take a sample and count in a liquid
  scintillation counter (if needed, ask EHS or Mike
  Fredericks for help)
• Suppose you determine that a count rate of 1500
  cpm corresponds to an activity of 0.1 µCi/ml. In
  the future, you could use the relationship of
  1500 cpm 0.1 µCi/ml, as long as you have the
  same geometry (same bottle type, same volume of
  liquid, etc.)

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Reminder Security

• Keep stock vials locked away except when in use
  and when youre present
• Dont leave empty labs unlocked for more than a
  few minutes.
• Acknowledge people who enter your lab

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Reminder Declared Pregnant Worker Program

• A pregnant woman may choose to formally declare
  her pregnancy.
• Fetal dose limit is 500 mrem for a Declared
  Pregnant Worker (instead of the 5000 mrem limit
  applied to other radiation workers)
• If you become pregnant, consider consulting with
  Sue Dupre for additional information and to
  determine if it makes sense to declare your
  pregnancy.
• More details are available at the EHS website.

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Policy and Procedural Reminders
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Shipping Hazardous Materials

• All hazardous materials must be shipped in
  compliance with U.S. DOT regulations
• Check with EHS if you are not certain whether
  your material is classified as hazardous or
  biohazardous under DOT regs
• Even dry ice in amounts gt 2 kg is regarded as
  hazardous)
• EHS will assist you with the shipment

Complete the online Shipping Hazardous Materials
form
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Transferring Radioactive Materialsbetween
University Labs

• RSC approved a new policy this past year
• If you loan radioactive materials to another lab,
  you must go to the EHS website to check whether
  the recipient lab is authorized to possess the
  radioisotope in question.
• If authorization exists, you will send a
  notification e-mail to EHS via the website and
  may proceed to make the transfer.
• EHS will follow up to adjust inventories and send
  out a new Vial Use Log if necessary.

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Quarterly Inventory Review

• Once a quarter EHS asks each lab manager to use
  the RITA database to look at the RITA record of
  the labs radioisotope inventory
• The lab manager reviews the actual inventory
  against the RITA record and contacts EHS to
  confirm the inventory or to request adjustments.
• Be sure to return Vial Use Logs to EHS promptly
  after disposal of vials to keep inventory current.

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NRC Inspection

• Due in March or April 2005 (according to the NRC
  website)
• Can you answer the sample NRC Interview questions
  which EHS sent to each lab manager? Check with
  your lab manager if you havent received a copy
  of the sample questions.
• Check lab conditions and records and follow good
  practices
• Make sure training for all lab personnel is
  up-to-date
• Pay attention to security matters

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Radiation Safety Website
Accessible through www.princeton.edu/ehs
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Radiation Safety Program Feedback

• Your questions, comments, suggestions and
  feedback are welcome.