No abstract

The rise in the number of occupationally exposed workers in the Philippines has made tracking, monitoring, and assessment of occupational exposures more difficult. Over the years, other than the DOST-PNRI, various private companies have started providing individual monitoring services (IMS). Although these providers are duly recognized by the regulatory agencies, it has resulted in a decentralized database of occupational exposure records in the country. To help address this and as required by the International Atomic Energy Agency (IAEA), a web-based National Dose Registry (NDR) was developed to maintain a centralized dose repository of occupational external exposures in the country. The NDR can automatically record and track an individual’s exposure history, provide an annual dose summary of the worker and facility, notify incidents of doses exceeding the regulatory limits, and allow regulatory agencies to have ready access to dose information, among others. The NDR also provides exposure profiles of workers according to the type of practices. The average annual doses due to external exposures received from various practices during 2013–2018 were evaluated in terms of personal dose equivalent Hp(10). Results show that in conventional radiology practices, more than 70% of workers did not receive doses above the recording level. In industrial radiography (IR) and nuclear medicine (NM) practices, on the other hand, workers received the highest average annual doses of 1.02 mSv and 0.44 mSv, respectively – with incidents of doses exceeding the limit of 20 mSv/yr. Practices in IR and NM, thus, pose higher risks of occupational exposures to workers. The NDR, therefore, can be used in recording, tracking, and assessing occupational exposure profiles and risks. The NDR can also also be tool to aid in the development of better regulations and thereby help in strengthening radiation protection in the country.

In medical applications, non-homogeneous radiation exposure conditions may be encountered and whole-body monitoring alone may not be an adequate assessment of doses received by workers. This paper investigated the exposure to extremities in medical applications in the Philippines in terms of personal dose equivalent Hp(0.07). Profile of monitored workers, dose level, implications on optimization of occupational exposures, and factors affecting the extremity monitoring implementation were studied. Results show that < 3% of workers are monitored for extremities, and there is no monitoring of eye lens dose. There is no extremity monitoring in diagnostic radiology, particularly interventional radiology. Dose levels to extremities were higher and more varied than whole-body doses. In nuclear medicine, median annual extremity dose is 1.2 mSv, interquartile range (IQR) is 7.6 mSv (Q1 = 0.5 mSv, Q3 = 8.1 mSv), and maximum dose is 35 mSv. These median and IQR dose values are 4 and 8 times higher, respectively, compared to the whole-body. In radiopharmaceutical distribution, extremity median annual dose is 5 times more than whole-body dose, and IQR value is 12 times higher where IQR is 12.1 mSv (Q1 = 0.1 mSv, Q3 = 12.2 mSv). Most notable is in cyclotron operations where < 40% of workers were monitored on their extremities, however, median dose is 100 times higher than the whole body, with maximum dose of 148 mSv. Results imply that there may be an underassessment of occupational exposures of workers in medical applications. As monitoring results are used for the establishment of a radiation protection program, lack of consideration of extremity doses can lead to inadequate measures in the optimization of worker protection. This study thus shows the need to enhance the implementation of extremity and eye lens dose monitoring in the Philippines to strengthen further the radiation protection of workers in medical applications.

No abstract

The 3 MW TRIGA (Training, Research, Isotopes, General Atomics) Philippine Research Reactor-1 (PRR-1) at the DOST-PNRI achieved its first criticality on 08 Mar 1988 after its successful upgrade from a plate-type reactor. However, due to unresolved technical problems discovered weeks after the upgrade, the PRR-1 was considered inoperable and has been in shutdown status since then. The slightly irradiated TRIGA fuel rods of the PRR-1 are currently in an interim storage tank and are planned to be utilized in a subcritical reactor assembly. As part of the project to reuse the fuels, simulation models for both present and proposed configurations are important. In this work, we present the complete model of the former configuration of PRR-1 with 115 TRIGA fuel rods developed with the Serpent Monte Carlo code version 2 for simulation of criticality and neutronic analysis. The model of the TRIGA fuel rods was validated in the fresh fuel configuration through the benchmark analysis described in the 1988 reactor criticality report. The effective multiplication factors from the Serpent-2 simulation (𝒌𝒆𝒇𝒇 = 1.0690 ± 0.0012) and measured value of 1.0661 have been found to agree with a deviation of 259 pcm. Neutron flux and fission power distribution simulations using the same reactor configuration were also presented to serve as reference for future burn up calculations and fuel characterization.