APPLICATION OF SAFETY ASSESSMENT METHODOLOGIES IN DISPOSAL OF DISUSED SEALED SOURCES USING BOREHOLE CONCEPT

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dc.contributor.authorALIYU, SA’ID
dc.date.accessioned2014-02-26T09:39:39Z
dc.date.available2014-02-26T09:39:39Z
dc.date.issued2011-07
dc.descriptionA DISSERTATION SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA. NIGERIA. IN PARTIAL FULFILLMENT FOR THE AWARD OF DOCTOR OF PHILOSOPHY IN PHYSICS DEPARTMENT OF PHYSICS AHMADU BELLO UNIVERSITY, ZARIA. NIGERIA July, 2011en_US
dc.description.abstractThis Dissertation develops safety assessment model appropriate for use in calculating doses to a resident farmer living in the far future in the vicinity of a borehole disposal facility around Zaria environs. Doses are assumed to arise from potential releases from the disused sources disposed in the borehole facility having inventories typical to those found in the African countries. A list of features, events and processes (FEPs) was developed, relevant to Zaria biosphere and an assumed requirement to calculate doses to the farmer via abstraction well water. An ‘interaction matrix’ was also developed to help define the FEPs and to identify the relationships between them. These relationships define how radionuclides escape from the container, migrate and accumulate in biospheric media, thereby giving rise to radiation exposure. FEPs were audited for inclusion in the matrix, and either include with an explanation of how, or excluded with an explanation of why. The doses to the farmer were calculated using GoldSim computer model. The model presented is probabilistic in nature that will reflects the current state of knowledge about the site by using probability distributions to capture what is expected (average or central tendency) and the uncertainty (standard deviation) associated with input parameters. The model was then run using Monte Carlo simulation over 100 realisations in each case. Each realization represents a possible combination of input parameter value. The output estimated values of contaminant release rate, concentration in environmental media and resulting doses to human receptors are obtained. Statistical summaries of the result were then compared with regulatory performance objectives (dose constraint). Initially the average value was found to be 0.76mSv/yr, which is greater than the dose constraint (0.3mSv/yr). This was found to be due to the daughters of 241Am radionuclide especially 239Np which has a Total Effective Dose Equivalent (TEDE) of 0.761mSv/yr. The 241Am inventory was then reduced to a value (2.95MBq) that gives a dose limit of 0.296mSv/yr.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/2738
dc.language.isoenen_US
dc.subjectAPPLICATIONen_US
dc.subjectSAFETYen_US
dc.subjectASSESSMENTen_US
dc.subjectMETHODOLOGIESen_US
dc.subjectDISPOSALen_US
dc.subjectDISUSED SEALEDen_US
dc.subjectSOURCESen_US
dc.subjectBOREHOLEen_US
dc.subjectCONCEPTen_US
dc.titleAPPLICATION OF SAFETY ASSESSMENT METHODOLOGIES IN DISPOSAL OF DISUSED SEALED SOURCES USING BOREHOLE CONCEPTen_US
dc.typeThesisen_US
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