Radiation Protection Today - Winter 2022 Issue 4 | Page 12

measurements were made , there were no retrievable records for the use of radioactive materials in laboratories prior to 1985 . There were also no staff who could remember what work was conducted prior to that time . After 1985 , records of usage had been maintained on a database .

I therefore had to resort to looking for references and publications prior to 1985 . The site had produced Annual Research Reports from 1949 onwards , but the first entry describing the use of radioactivity was in 1967 , with a report of field studies using phosphorous-32 ( P-32 ) for research . Further reports of field investigations with P-32 were found in annual reports for 1967 and 1968 . There were no references to the use of longer-lived radionuclides , so on this assumption it was concluded that only P-32 had been used for research , and only in trace quantities .
After 1985 , the majority of open radioactive sources used were short half-life radionuclides which , in the time interval between being used to the present day , had undergone decay to the point where they would no longer be detectable as contamination or present a radiological hazard . Any potential for residual contamination therefore only related to the long half-life radionuclides carbon-14 ( halflife 5,730 years ) and tritium ( half-life 12.32 years ). No historical evidence was found to indicate that carbon-14 ( C-14 ) or tritium open sources had been used in locations other than laboratories , or that C-14 or tritium wastes were present in any locations other than those designated .
Recent monitoring records were compiled to demonstrate that laboratories had been thoroughly monitored prior to closure or decommissioning . Where unsealed sources had been used , staff used benchkote or plastic trays to protect the benches , so there was no widespread low-level contamination . The monitoring for C-14 and tritium was carried out using smears analysed by liquid scintillation counting . Only a few areas were found to have contamination levels in excess of the set clearance level of 3 Bq / cm ², and these were cleaned immediately .
Contamination was mainly on trunking , inside fume cupboards and around sinks . Drains were also monitored and cleaned as appropriate .
Generally , contamination levels were below background .
The statement was submitted to the Environment Agency after some discussion as to what it should contain . They requested the following :
• Clear description of what and where nuclides were used and wastes accumulated
• Explanation of how areas to be monitored were determined
• Criteria used during sampling and clearance surveys
• Identification of where contamination was found and remediated
• Evidence that drainage was not contaminated
• Who was responsible for overseeing the work .
In 2017 , after answering various minor queries and having removed all radioactive sources and waste , the Environment Agency finally agreed to accept surrender of the facility ' s permit for the use of unsealed radionuclides .
The challenges described are typical of older facilities which require decommissioning . There was no formal requirement for the keeping of records of radioactive substances activities in the non-nuclear sector until the introduction of the Radioactive Substances Act 1960 ( which came into force in 1963 ). Even then , records only had to be kept if the authorisation holder was instructed to do so , and the details of what records needed to be kept , and for how long , were not specified in the Act .
The moral of the story is that you should keep as many records relating to historical activities as you can . You can never have too much evidence , and without these data it is difficult to confirm that effective decommissioning has taken place .
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