CINCH NucWik

Developed by
Department of Chemistry
Radiochemistry
University of Helsinki

The aim of this exercise is to learn basic practises and safe working methods while working with radionuclides in a radiochemistry laboratory. Furthermore, the students will be introduced to sample preparation for unsealed source measurement and they will learn how to perform a surface contamination measurement.

Protection from external radiation
The storage and application of radionuclides requires the setting up of appropriate shielding from their damaging external radiation. The most noteworthy external radiation types are gamma, high-energy beta and neutron radiations. Alpha and low-energy beta radiations are not capable, for example, of penetrating through the walls of a glass container. The most important methods for protection from external radiation are:

• radiation sources are located as far away as possible from people
• exposure to radiation is not longer than necessary to complete the task
• radiation shielding is used when it is practical to reduce radiation exposure
• radiation sources are kept as harmless as possible
• the doses of radiation workers are monitored
• radiation sources are always labelled clearly and visibly

Protection from internal radiation – radionuclide radiation poisoning aka radiotoxicity

Precautions should be taken when working with radionuclides to prevent them from getting into the body. Internal contamination, especially by alpha and low-energy beta nuclides, can be more dangerous than their damaging external radiation. The most toxic internal radiation sources are alpha emitters. The next listing classifies some common radionuclides according to their level of radiotoxicity:

Radiotoxicity classification of some commonly used radionuclides

a) Group 1 (highly radiotoxic): ²¹⁰Pb, ²¹⁰Po, ²²⁶Ra, ²²⁷Ac, ²³⁸Pu, ²⁴⁰Pu, ²⁴¹Am, ²⁵²Cf

b) Group 2 (radiotoxic): ⁶⁰Co, ⁹⁰Sr, ¹⁰⁶Ru, ^110mAg, ¹²⁴I, ¹²⁵I, ¹³¹I, ¹³⁴Cs, ¹³⁷Cs, ¹⁵²Eu, ¹⁵⁴Eu

c) Group 3 (moderately radiotoxic): ¹⁴C, ²²Na, ²⁴Na, ³²P, ³³P, ⁴⁵Ca, ⁵⁴Mn, ⁵⁵Fe, ⁵⁹Fe, ⁵⁷Co, ⁵⁸Co, ⁶³Ni, ⁶⁵Zn, ⁷⁶As, ⁸⁵Sr, ⁹⁵Zr, ⁹⁹Mo, ²⁰³Hg

d) Group 4 (slightly radiotoxic): ³H, ¹¹C, ¹⁸F, ^99mTc, ¹²⁹I, ²⁰¹Tl

Laboratory working practises with radionuclides

Before you start working with radionuclides, PLAN your work well. It is important to know with what kind of substance you are working: what is the nuclide’s half-life, radiation type, energy and radiotoxicity. Of the following certain “laboratory rules”, some are to be followed without exception, and others are to be followed when the need arises:

• always beware of contamination
• protect the work surface with an absorbent covering
• when necessary, e.g., if you are using high radioactivities, use a protective container. Keep bottles containing radionuclides in wide-bottomed beakers so that they do not fall over when moved. Protect an experiment by containing the whole apparatus within a protective basin that has sufficiently high rims to prevent spillage of radionuclides onto the table or floor
• always keep absorbent tissue paper available to wipe up splashes of solution. The used tissue paper must be disposed of immediately to the radioactive waste
• if a solution containing radionuclides spills onto the table, floor or yourself, report it to the Lab Supervisor and request guidance on cleaning up
• pipetting by mouth in the radionuclide laboratory is prohibited
• eating, drinking and smoking are prohibited in the radionuclide laboratory
• always wear protective gloves when handling radioactive solutions
• wash your hands after completion of work with radionuclides
• if there is a detector in the laboratory for monitoring hand contamination, always monitor your hands when you suspect contamination
• laboratory coats used in a radionuclide laboratory are not allowed to be used in clean areas
• always wear your dosimeter
• prepare samples in different room to where you perform activity measurements to avoid contamination of measuring equipment. Ensure that the container to be measured is closed securely. Sometimes after sample preparation there is also cause to wash or wipe the outside of the container before measurements
• always label the radionuclide container with the nuclide name, activity, date and your name
• do not store radionuclides unnecessarily on your work surface, thus minimizing radiation dose and contamination risk
• use different labware for radioactive and inactive solutions
• perform exercises that demand high radioactivities in a fume cupboard. For instance, a radionuclide solution ordered from a supplier should always be diluted in a fume cupboard. All heating and vaporisation must be done in a fume cupboard. Handling of dusty radioactive material should be performed in a fume cupboard or low-pressure cupboard
• always adhere to cleanliness and order in your work. Change the work surface protective covering when it gets torn or dirty. Do not leave dirty labware on your work surface, wash them as soon as possible after completing the work
• loitering in the radionuclide laboratory is prohibited

Specific guidelines on the radiation safety requirements of a radionuclide laboratory are in regulatory guides of national radiation and nuclear safety authorities.

Decontamination – washing labware and hands, and monitoring of workers and work areas

Each contamination requires is own appropriate decontamination method. The following are some examples:

a) If you get radioactive solution in contact with your skin, wipe the solution away with absorbent tissue paper and wash the skin thoroughly. Monitor the contaminated area if necessary. Do not use acids, bases, solvents or strong detergents. Brush, but not so vigorously, that the skin would break. Remember also your palms and lower arms.

b) If radioactive solution spills onto the table or floor, wipe it first with dry tissue paper, then with tissue paper dampened with dilute acid or EDTA solution, and finally with tissue paper moistened with water. Monitor the contaminated area if necessary. Wear protective gloves during the clean-up procedure.

c) If solid radioactive material spreads onto the table or floor, collect it with moistened tissue paper. Proceed afterwards with the decontamination steps described in b).

The method for washing labware depends on the radionuclide activity and the quantity of solid material. The following are general washing guidelines:

• pour the solution or solid material into a waste container
• rinse with a small volume of water and pour it into the waste container
• if the radioactive substance is an ionic solution, it is often sufficient to immerse the container in dilute acid then rinse thoroughly with tap water and finally with distilled/deionised water
• if there was solid material, and especially if the solid material is stuck on the walls of the container, then the container should be immersed in a detergent solution (2% Deconex, Decontamin, Extran, etc.), in dichromate-sulphuric acid or in an ultrasonic bath. Afterwards proceed with acid washing and rinsing with water.

Handling radioactive waste

The handling and storage of radioactive waste follow several criteria:

• radionuclide’s radiotoxicity
• radionuclide’s half-life
• radionuclide’s activity
• state of substance containing the radionuclide (solid, liquid)

The principal rule is that radioactive waste is handled immediately after completion of the work and that waste is stored only when clearly justified (e.g., aging of substances containing short-lived radionuclides). Waste for storage should be labelled well (radionuclide, activity, date activity determined, chemical form, responsible person, when and how the waste is to be disposed). Specific guidelines regarding radioactive waste and its discharge are in regulatory guides of national radiation and nuclear safety authorities.

Solution waste is stored in sufficiently large (> 10 L) plastic containers with wide mouths, and is disposed of sensibly in accordance with optimization principles. Solution waste is divided most commonly according to radionuclide half-life:

1. short-lived (t1/2 < 100 d): aged so that radioactivity is practically negligible and then poured down the drain
2. moderately long-lived (t1/2 = 100 d – 1 a): aged if possible (e.g., 10 half-lives) and poured down the drain in accordance with national authority’s regulations
3. long-lived (t1/2 > 1 a): either poured immediately down the drain in accordance with national authority’s regulations, or if exceeding discharge limits then concentrated, solidified and sent to final disposal

Solutions containing organic solvents should be stored separately. Liquid scintillation solutions can be sent for incineration at a waste treatment facility in their measurement bottles packed into a metal barrel. Liquid scintillation waste has its own activity limits, which are worthwhile considering already when planning your work. Liquid scintillation bottles tend to swell and leak, and so they should be sealed in plastic bags before dumping in a metal barrel.

Solid waste should be separated depending on activity for disposal to normal waste, transportation to a dumping site or final disposal. Sharp and other dangerous objects must be protected before being disposed of, and objects of practical value should be broken.

Disposal of contaminated glass and plastic waste depends on the level of contamination and cost. Strongly contaminated glassware is to be disposed of as per radioactive waste if its activity is high and it is difficult to clean. Glassware though tends generally to be cleaned. Plastic ware, such as measurement vials, are considered disposable and immediately after the work is completed are handled as per solid waste. Slightly contaminated plastic ware can be washed and reused in order to minimize waste and costs.

Performed the exercise on a tray, and always keep absorbent cellulose available. Wear gloves when pipetting. Use an adjustable automatic pipette and change tips between different solutions. Never contaminate the pipette by turning it so that the tip is uppermost.

Preparation of ³²P samples

1. The activity concentration of the ³²P stock solution used in this exercise is XXX kBq/mL. It also contains carrier phosphate of concentration ~10^-4 M.
2. Take a tray for your group and cut some protective paper (shiny side up) to cover its upper, inner surface. Draw a grid on the paper, and mark the columns A–D and the rows 1–5.

1. Take five 20 mL plastic vials and mark them 1, 2,.., 5. To each vial, pipette 4 mL of gelatine solution (0.2% gelatine, 10-4 M phosphate, 0.03% sodium dodecyl sulphate and 2∙10-2 M sodium hydroxide). Pipette 1, 2,.., 5 mL of ³²P stock solution into vials 1, 2,.., 5, respectively. Fill each vial with water so that the total volume (gelatine + ³²P solution + water) in each vial is 10 mL. Close vial caps and shake the vials gently ten times (vigorous shaking will cause undesirable foaming).
2. Make four parallel counting samples for each ³²P dilution: Take twenty aluminium discs and mark their reverse sides 1A, 1B,.., 5D. Place the discs in their designated positions on the tray. Pipette 0.15 mL solution from vial 1 to each disc in row 1, and proceed similarly for rows 2–5.
3. Use a surface contamination meter to make a few control measurements. The instructor will direct you in correct procedure.
4. Leave the samples in a fume cupboard to dry overnight.
5. Dispose of your ³²P dilutions accordingly. The dilutions and first washings of the vials go into the waste container. Rinse the vials many times with tap water and then dispose of them in the normal waste.

Detecting surface decontamination

1. Switch on surface contamination meter (for example, PCM 5/1, Electra, or other suitable model) to position "β". Check the condition of the batteries and note the high voltage used. Switch the sound on. Test the meter with an appropriate calibrated source.
2. Measure the surface count rate of each cell in the test grid and write down the readings to the provided form ).
3. The Lab Supervisor will contaminate the test grid with one or more drops of ¹³⁴Cs solution (β and γ emitter). Locate the drops using the meter and record the coordinates of the contaminated grid cells.

• All work with ³²P and ¹³⁴Cs must be carried out in the spill tray.
• Lab coat, gloves and safety spectacles must be worn
• MSDS (Material Safety Data Sheet) for each of the used reagent gives necessary information about working safely with that particular chemical, and its disposal after the work. The MSDSs are easily available from the websites of the chemical manufacturers and authorities.
• Dispose all liquid and solid waste in the provided waste buckets, not down sinks or in waste bins.

• PCM 5/1, Electra, or other suitable model of surface contamination meter

• absorbent cellulose
• protective paper
• tray
• gelatine solution (0.2% gelatine, 10^-4 M phosphate, 0.03% sodium dodecyl sulphate and 2∙10^-2 M sodium hydroxide)
• 20 mL plastic vials
• aluminium discs
• distilled or milli-Q H₂O
• 1-5 ml autopipette
• 1-5 ml pipette tips
• permanent marker

• 15 ml or more of ³²P solution XXX kBq/mL, with carrier phosphate of concentration ~10^-4 M
• few drops of ¹³⁴Cs solution

Fill in the exercise form provided, and submit it within two week after completion of the exercise.

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