How frequent should surveys be ? The frequency of a routine survey depends on many factors such as :
• Operations carried out in the area and the potential for release of contamination .
• Designation of the area and access requirements .
• Other indicators available to identify a breakdown in controls ( e . g . activity in air alarms , operator monitoring ).
• Is the survey perhaps for reassurance in an area adjacent to a designated area ?
How is the survey carried out ? Surveys should be carried out using appropriate monitoring equipment and techniques , which depend on a number of factors :
• What are the radionuclides you are looking for ? Choose the right instrument to detect the radiation , e . g . C-14 requires an instrument capable of detecting low energy beta .
• How much contamination or radiation are you looking for ? Identify the instrument sensitivity , range , efficiency , response time and energy dependence .
• Where will you use the instrument ? Is it adequately portable , rugged , reliable , and easy to read in the survey environment ?
• Is direct surface monitoring with a portable instrument appropriate ? Be aware of background radiation or other physical or chemical conditions that might affect the instrument response .
• Do you need smear monitoring to identify loose or fixed contamination , or for specific radionuclides such as tritium ?
• Are large area smears monitored using a portable instrument suitable ?
• Should Whatman smears over a small
2 area ( usually 100 cm ) be used for very low levels of contamination ?
Whatman smears James Whatman invented wove paper in the 1750s ; all paper made before this was laid . In the 1930s the Whatman company began making scientific filter papers which are used to this day .
When would you use each monitoring technique ? For example , only use very large area smears to check an area is clean ( possibly an adjacent non-designated area ). The survey itself must not be a vehicle for spreading contamination ! Don ' t use Whatman smears on potentially high levels of contamination and put them directly into counting equipment . Initial direct monitoring will give an indication of what is present before smearing .
Setting up a survey schedule This requires agreed procedures . Visit the area and talk to monitoring staff , operators and facility management to determine requirements and how the schedule can be implemented successfully and efficiently , e . g . access requirements , fitting in with operations , time and staffing constraints . Consider the principle of ALARP ( As Low As Reasonably Practicable ) and the safety of those carrying out the survey . Ensure there are contingencies for unexpected finds . As a minimum , the instrument used , radiation detected , background , efficiency , and readings must be recorded . Establish and stick to a standard recording format e . g . counts per second ( cps ), disintegrations per second ( dps ), becquerels per square
2 centimetre ( Bq / cm ), microSievert per hour (µ Sv / h ), millisievert per hour ( mSv / h ). Preferably avoid recording “ less than ” results , as these could mask trends .
What to do with survey results ? Anything unexpected needs investigation and action to prevent a deterioration in radiological conditions . Prompt decontamination , waste disposal , and marking of fixed contamination for future reference are required . Look regularly for trends in results . These can identify gradual deterioration in conditions or working practices and the requirement for prompt appropriate action . Be careful to always compare like-for-like results , especially if different equipment is being used .
Finally , review personnel monitoring results and revise the survey schedule as necessary .
20 Radiation Protection Today www . srp-rpt . uk