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Environmental radiation measurements at Barsebäck nuclear power plant during the decommissioning phase

Dahlström, Patrik (2022) MSFT01 20221
Medical Physics Programme
Abstract
Background and aim: The Barsebäck nuclear power plant (NPP) units ceased operations in 1999 and 2005. Now the NPP is in the phase of decommissioning, which is a complicated process that will take many years to complete. Radiological characterization of the surrounding area is a part of the decommissioning process. The aim of this thesis was to identify and quantify residual anthropogenic radioactivity at the site area, by selecting a number of locations around the NPP and carrying out different radiological measurements and then analysing the result. Radionuclides of interest were anthropogenic gamma emitting nuclides such as (137)Cs and (60)Co that are related to NPP activities.
Method: Measurements were carried out at 10 sites around... (More)
Background and aim: The Barsebäck nuclear power plant (NPP) units ceased operations in 1999 and 2005. Now the NPP is in the phase of decommissioning, which is a complicated process that will take many years to complete. Radiological characterization of the surrounding area is a part of the decommissioning process. The aim of this thesis was to identify and quantify residual anthropogenic radioactivity at the site area, by selecting a number of locations around the NPP and carrying out different radiological measurements and then analysing the result. Radionuclides of interest were anthropogenic gamma emitting nuclides such as (137)Cs and (60)Co that are related to NPP activities.
Method: Measurements were carried out at 10 sites around the NPP area. Each site was measured with in situ gamma spectrometry using a HPGe detector to assess the gamma emitting radionuclides. Dose rate was determined with a handheld dose rate meter. Soil samples were collected to determine the activity concentration of gamma emitting radionuclides at different depths of the soil. A spectrometer-dosimeter was used to assess the contribution of anthropogenic radionuclides to the dose rate. Mobile gamma spectrometry was carried out in the area to achieve a radiological coverage of larger areas than the in situ measurements. Additional measurements were made to cover other areas as well, i.e. the restricted area of the NPP. A 〖LaBr〗_3 scintillation detector positioned in a backpack was used to perform mobile gamma spectrometry on foot. Radioactivity along the roads were mapped by a car-borne system consisted of two large volume NaI(Tl) scintillation detectors.
Results: (137)Cs was detected at all measurement points with in situ gamma spectrometry, where the highest levels were found at site 9 and 10 (569 Bq/m^2 and 719 Bq/m^2). The majority of the (_^137)Cs contamination are residues from the Chernobyl accident and nuclear weapon tests. (60)Co was also detected at a few sites with in situ gamma spectrometry, where the highest values were found at site 8, 9 and 10 (65 Bq/m^2, 67 Bq/m^2 and 79 Bq/m^2). However, it should be emphasized that as a general trend the (60)Co activity concentrations were relatively low and that (60)Co was only detected in one of the soil samples. Activity concentration of (137)Cs in soil samples were at most 14.7 Bq/kg. Site 8 and 10 had elevated levels according to previous studies of these particular sites. Dose rate measurements at sites 1-10 showed no indication of significant increase in dose rate and resembled background radiation ~100 nSv/h), typical for the region. The backpack mobile gamma spectrometry did not distinguish any increases of dose rate above background at and around sites 1-10. However, inside the restricted area there were several sites with increased radiation levels, above the natural background. These elevated levels are, however, attributed to different building structures in the area. The car-borne measurements also discovered a few areas where the radiation levels were elevated. The spectrometer-dosimeter measurements showed the largest contribution from anthropogenic radionuclides at sites 8 and 10 (25% and 26%).

Conclusion: Anthropogenic radionuclides were detected in the surroundings of the Barsebäck NPP, both inside and outside of the industrial area. The observed results for (137)Cs are comparable to other areas in Skåne. Sites closer to the contaminated ponds contained more (60)Co than sites further away from the ponds, with the highest levels found at sites 8, 9 and 10. The radioactivity in the ponds originate from previous dredging activities where contaminated sediments were placed in the two ponds. The activity concentrations of (60)Co were below minimum detectable activity (MDA) in the soil samples. The results of the thesis can be used as a reference for the future site clearance and constitute a basis for future investigations. (Less)
Popular Abstract (Swedish)
Barsebäcks kärnkraftverk driftsattes 1975 och den första reaktorn togs ur drift 1999 och den andra 2005. Nedmontering och rivning av kärnkraftverket har inletts och processen beräknas vara klar på 2030-talet. Syftet med detta examensarbete är att kartlägga eventuell radioaktiv kontamination i området runt Barsebäcksverket. Mitt mål är att ta fram en metod för att särskilja bakgrundsstrålning från antropogena radioaktiva ämnen, dvs. radioaktiva ämnen producerade genom mänsklig interaktion med naturen såsom vid kärnvapensprängningar och drift av kärnkraftverk. Av särskilt intresse är antropogena radionuklider som härrör från Barsebäcksverkets aktiva tid likväl dess nedmontering och rivning. I omgivningen kring Barsebäcksverket finns... (More)
Barsebäcks kärnkraftverk driftsattes 1975 och den första reaktorn togs ur drift 1999 och den andra 2005. Nedmontering och rivning av kärnkraftverket har inletts och processen beräknas vara klar på 2030-talet. Syftet med detta examensarbete är att kartlägga eventuell radioaktiv kontamination i området runt Barsebäcksverket. Mitt mål är att ta fram en metod för att särskilja bakgrundsstrålning från antropogena radioaktiva ämnen, dvs. radioaktiva ämnen producerade genom mänsklig interaktion med naturen såsom vid kärnvapensprängningar och drift av kärnkraftverk. Av särskilt intresse är antropogena radionuklider som härrör från Barsebäcksverkets aktiva tid likväl dess nedmontering och rivning. I omgivningen kring Barsebäcksverket finns framförallt två sådana intressanta gammaemitterande radionuklider, cesium-137 och kobolt-60 som är av betydelse när området så småningom ska friklassas. För denna kartläggning användes ett antal olika mätinstrument och mätmetoder som kan detektera och kvantifiera radioaktiva ämnen och strålning. Aktivitetskoncentrationen kvantifieras med jordprover och fältmätning, så kallat in situ gammaspektrometri. Båda metoderna använder en germaniumkristall (HPGe) halvledardetektor som mäter energifördelningen hos gammafotoner vilka emitteras från jordprovet respektive marken vid in situ gammaspektrometri. Aktivitetskoncentrationen hos samtliga radionuklider mäts i Bq/kg för jordprover medan ute i fält enbart naturligt förekommande radionuklider mäts i Bq/kg, medan antropogena radionuklider mäts i termer av Bq/m^2. Utöver dessa metoder utfördes in situ mätningar med en spektrometer-dosimeter vilken ger aktivitetskoncentrationen för naturligt förekommande radionuklider samt miljödosekvivalent doshastighet. Med dessa värden är det möjligt att beräkna antropogena radionukliders bidrag till doshastigheten. Doshastighetsmätning utfördes även med ett doshastighetsinstrument för att beräkna ett medelvärde av doshastigheten i ett visst område. För radiologisk kartläggning av ett större område användes mobil gammaspektrometri, som kan utföras på många olika sätt. Till exempel kan man vandra med ryggsäck som innehåller en spektrometer kopplad till GPS och en bärbar dator. Det möjliggör att man kan studera doshastigheten i olika koordinater, vilket är användbart för att lokalisera områden med förhöjd radioaktivitet. Mobil gammaspektrometri genomfördes också med en specialutrustad bil som innehåller detektorer och på samma sätt som nämns ovan läser av doshastigheten och koordinater. Ett urval av 10 platser valdes för att utföra noggranna mätningar, där ingick 4 platser utanför kärnkraftverkets område samt 6 platser innanför området. Mätningarna visade svagt förhöjda nivåer av antropogena radionuklider på ett fåtal platser. Dessa var belägna innanför stängslet, i två dammar samt på ett område bredvid dammarna. I övrigt visade mätningarna att inga signifikanta spår från driften syns och aktivitet från antropogena radionuklider ej översteg de normala bakgrundsnivåer från Tjernobylolyckan (1986) och de atmosfäriska kärnvapentester (1950- och 1960-talet). (Less)
Please use this url to cite or link to this publication:
author
Dahlström, Patrik
supervisor
organization
course
MSFT01 20221
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9099115
date added to LUP
2022-09-03 14:52:29
date last changed
2022-09-03 14:52:29
@misc{9099115,
  abstract     = {{Background and aim: The Barsebäck nuclear power plant (NPP) units ceased operations in 1999 and 2005. Now the NPP is in the phase of decommissioning, which is a complicated process that will take many years to complete. Radiological characterization of the surrounding area is a part of the decommissioning process. The aim of this thesis was to identify and quantify residual anthropogenic radioactivity at the site area, by selecting a number of locations around the NPP and carrying out different radiological measurements and then analysing the result. Radionuclides of interest were anthropogenic gamma emitting nuclides such as (137)Cs and (60)Co that are related to NPP activities.
Method: Measurements were carried out at 10 sites around the NPP area. Each site was measured with in situ gamma spectrometry using a HPGe detector to assess the gamma emitting radionuclides. Dose rate was determined with a handheld dose rate meter. Soil samples were collected to determine the activity concentration of gamma emitting radionuclides at different depths of the soil. A spectrometer-dosimeter was used to assess the contribution of anthropogenic radionuclides to the dose rate. Mobile gamma spectrometry was carried out in the area to achieve a radiological coverage of larger areas than the in situ measurements. Additional measurements were made to cover other areas as well, i.e. the restricted area of the NPP. A 〖LaBr〗_3 scintillation detector positioned in a backpack was used to perform mobile gamma spectrometry on foot. Radioactivity along the roads were mapped by a car-borne system consisted of two large volume NaI(Tl) scintillation detectors.
Results: (137)Cs was detected at all measurement points with in situ gamma spectrometry, where the highest levels were found at site 9 and 10 (569 Bq/m^2 and 719 Bq/m^2). The majority of the (_^137)Cs contamination are residues from the Chernobyl accident and nuclear weapon tests. (60)Co was also detected at a few sites with in situ gamma spectrometry, where the highest values were found at site 8, 9 and 10 (65 Bq/m^2, 67 Bq/m^2 and 79 Bq/m^2). However, it should be emphasized that as a general trend the (60)Co activity concentrations were relatively low and that (60)Co was only detected in one of the soil samples. Activity concentration of (137)Cs in soil samples were at most 14.7 Bq/kg. Site 8 and 10 had elevated levels according to previous studies of these particular sites. Dose rate measurements at sites 1-10 showed no indication of significant increase in dose rate and resembled background radiation ~100 nSv/h), typical for the region. The backpack mobile gamma spectrometry did not distinguish any increases of dose rate above background at and around sites 1-10. However, inside the restricted area there were several sites with increased radiation levels, above the natural background. These elevated levels are, however, attributed to different building structures in the area. The car-borne measurements also discovered a few areas where the radiation levels were elevated. The spectrometer-dosimeter measurements showed the largest contribution from anthropogenic radionuclides at sites 8 and 10 (25% and 26%).

Conclusion: Anthropogenic radionuclides were detected in the surroundings of the Barsebäck NPP, both inside and outside of the industrial area. The observed results for (137)Cs are comparable to other areas in Skåne. Sites closer to the contaminated ponds contained more (60)Co than sites further away from the ponds, with the highest levels found at sites 8, 9 and 10. The radioactivity in the ponds originate from previous dredging activities where contaminated sediments were placed in the two ponds. The activity concentrations of (60)Co were below minimum detectable activity (MDA) in the soil samples. The results of the thesis can be used as a reference for the future site clearance and constitute a basis for future investigations.}},
  author       = {{Dahlström, Patrik}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Environmental radiation measurements at Barsebäck nuclear power plant during the decommissioning phase}},
  year         = {{2022}},
}