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Radiation Safety Training LSC USE Washington State University Radiation Safety Office. What is an LSC?. LSC stands for L iquid S cintillation C ounter.
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Radiation Safety TrainingLSC USEWashington State UniversityRadiation Safety Office
What is an LSC? LSC stands for Liquid Scintillation Counter. • It is a device for detecting and measuring radiation by means of tiny visible flashes produced by the radiation when it strikes a sensitive substance known as a phosphor or scintillator.
How Does it Work? • The principle of this method is to convert the radioactive emissions from a sample to photons of visible light that a photomultiplier tube can detect. • To do this, we place the radioactive sample (swipe), into a vial with scintillation fluid. This liquid contains a fluor, a compound that fluoresces when it is bombarded with radioactivity.
How Does it Work? The scintillation fluid (preferably Ecoscint only the original, order # LS-271 from National Diagnostics or Optifluor from Perkin Elmer) converts the invisible radioactivity into visible light (photons). The liquid scintillation counter takes the vial and places it in a dark chamber with photomultiplier tubes.
F A block diagram of a scintillation counter. There, the tubes detect the light resulting from the radioactive emissions exciting the fluor.
How Does it Work? • The instrument counts these bursts of light, or scintillations, (photons) and records them as counts per minute (cpm).
CHANNELS • The scintillation counter classifies each pulse of photons according to the number of photons in the pulse, which corresponds to the energy of the individual β emission event.
CHANNELS • Pulses are collated into channels, and the counts per minute (CPM) in each channel is recorded. Each channel corresponds to a specific range of β energies (channels are also known as counting windows), and counts with energies above or below set limits are excluded from a particular channel. H-3 C-14 P-32
CHANNELS And just like with your TV, if the LSC is not set to see the correct channel, you will not see what you are looking for.
CHANNELS A scintillation counter collating the energy spectrum of beta emissions into three channels would read the majority of H-3 emissions in the low energy channel, C-14 in the intermediate channel, and P-32 in the high energy channel.
CHANNELS You will never see any contamination from your swipe surveys. • But if the LSC is set to read only the low energy channel of H-3 and you are using P-32.
CHANNELS • You must set the channels on the LSC to read the energy of the isotope you are looking for and to print them out. So they can be saved for your survey records. Read the manual that came with your LSC to determine how to do this.
CHANNELS • For general surveys the typical set up would be 3 windows; one for low energy isotopes, one for mid-energy and one for high energy isotopes, or a full open window. After your windows or channels are setup. Save them and assign a protocol or flag to the saved setup. Use this flag or protocol when you are counting swipes for contamination surveys.
LSC Quality Assurance notebook. • Each LSC will have a Quality Assurance Notebook. • Be sure to fill in the cover of the notebook. Supervisory Authorized user or equipment coordinator. Plus an alternate and their contact information.
LSC Quality Assurance notebook. P/E 2910 123456 1/1/11 Dr. Who 12/27/10 14 Check to see when the last SNC or IPA was run. This is a self check of the LSC. It is done by counting the unquenched standards that came with the LSC. The printout should be in the back of the notebook. It must have been done within the past 7 days. You are now ready to start counting your swipes. Be sure the information at the top of the page is filled in. Fill in the date and your name. Enter the number of the program you are using to count your swipes. Check the calibration status of the LSC. This information is in the back of the notebook. The LSC must have been calibrated within the past 12 months. This is the data page inside the notebook.
Cerenkov Counting • You must use scintillation fluid (preferably Ecoscint, only the original, order # LS-271, from National Diagnostics or Optifluor from Perkin Elmer) when counting your swipes. Use of water for counting high energy beta emitters is not considered a acceptable method for counting swipes for contamination surveys required by the WSU radiation safety office.
COUNTING. • Place swipes into vials, one swipe per vial. Add the scintillation fluid to each vial. Without the scintillation fluid you will get incorrect counts. You can set up your machine to read the first vial as a background vial if you wish. These background counts will then be subtracted from the other vials counts. Remember there is always background radiation.
COUNTING. • Select the appropriate protocol designator (usually a flag or id plate) If using a Packard, place the protocol designator on the first cassette of the batch. Reset the cycle flag by pushing the slide toward the front end of the cassette. Load the cassette into the sample changer. Close the cover on the sample changer and start the machine counting.
MAINTAINANCE • The LSC must also be maintained in accordance with manufactures recommendations. You must also run the normalization (SNC) standards in accordance with the manufactures recommendations. These things must be done to keep the LSC in compliance for Radiation Safety use.
Test Time! • Follow this link to the test. https://myresearch.wsu.edu • Use your WSU user name and password to sign in. • Click on the training tab. • Then click on the available training tab • Find the radiation safety training LSC course, in the “OR” section, click on it and take the test.