Speaker
Description
Background: The increasing presence of radioactive materials in non-nuclear facilities such as
scrap metal stores and waste dumpsites poses significant radiological safety and security threats to
workers, the public, and the environment. In urban settings like Dar es Salaam, Tanzania, scrap
metal yards and dumpsites are often located in close proximity to residential and commercial areas,
raising concerns about uncontrolled radiation exposure and potential illicit trafficking of
radioactive materials.
Objective: This study aimed to assess radiological safety and radiological security risks in selected
scrap metal stores and dumpsites in Dar es Salaam.
Methods: The study was performed by evaluating the radiation exposure levels and radon
exhalation rates in five scrap metal stores and three dumpsites in Dar es Salaam respectively. The
radiation exposure rates were measured using an Ionization Chamber Survey Meter (ICSM) and a
Gamma Scout Detector (GSD) while the radon (²²²Rn) exhalation rates were measured using an
AlphaGUARD radon monitor. Annual effective dose equivalent (AEDE) and excess lifetime
cancer risk (ELCR) were calculated.
Results: The average radiation exposure rates ranged from 0.15 ± 0.03 μSv/h to 1.02 ± 0.18 μSv/h.
Store S₁ recorded the highest exposure (1.41 μSv/h at chest level), exceeding the ICRP public
exposure limit of 0.57 μSv/h. Calculated AEDE values ranged from 1.76 ± 0.57 mSv/y to 9.55 ±
1.22 mSv/y, all above the ICRP public limit of 1.0 mSv/y but below the occupational limit of 20
mSv/y. ELCR values ranged from (5.79 ± 1.56) × 10⁻³ to (31.42 ± 4.01) × 10⁻³, significantly higher
than the global average of 0.29 × 10⁻³. Meanwhile, the mean radon exhalation rates at dumpsites
ranged from 123.0 ± 10.0 mBq m⁻² h⁻¹ (Pugu-Kinyamwezi) to 216.0 ± 40.0 mBq m⁻² h⁻¹ (Tabata).
Yet, all radon concentrations remained below ICRP (300 Bq m⁻³) and WHO (100 Bq m⁻³) safety
limits.
Conclusion: The findings reveal significant radiological safety and security concerns at scrap
metal stores, where workers are exposed to radiation doses exceeding public limits, with elevated
lifetime cancer risks. While radon levels at dumpsites remain within international safety
thresholds, continuous monitoring is necessary to maintain these levels. Urgent regulatory
interventions are recommended, including mandatory radiation screening protocols for scrap metal
shipments, provision of personal dosimeters for workers, radiological safety training, and
establishment of a centralized national database to track radioactive sources. These measures are
essential to mitigate health risks, prevent illicit trafficking of nuclear materials, and enhance
overall radiological security in Tanzania.
Keywords: Radiological safety, radiological security, radiation exposure, scrap metal, dumpsites,
radon exhalation, annual effective dose equivalent, excess lifetime cancer risk, Dar es Salaam.
