ABSTRAKLinac yang dioperasikan di atas 10 MV akan menghasilkan radiasi sekunder berupa emisi neutron yang berasal dari reaksi energi foton tinggi menumbuk material penyusun linac seperti target, kolimator dan filter. Radiasi sekunder ini akan menaikkan resiko kanker sekunder pada pasien akibat bertambahnya dosis radiasi yang diterima. Studi ini mengevaluasi fluks neutron termal spasial pada ruangan Linac yang dioperasikan 15 MV menggunakan metode aktivasi foil. Sebanyak 14 foil 115 In ditempatkan tersebar di dalam ruangan treatment yang terpapar pesawat linac 15 MV selama 1 menit. Hasil menunjukkan fluks tertinggi terdapat di sekitar isocenter sebesar , × • • Dengan nilai fluks tersebut dosis tambahan akibat neutron sebesar 0,04 Sv/menit.Nilai fluks menurun seiring bertambahnya jarak dari sumber berkas.Terkait dengan upaya proteksi radiasi untuk pekerja radiasi, adanya kontribusi dosis yang berasal dari neutron perlu ditindak lanjuti dengan menambah shielding pada pintu.Kata kunci: Fluks neutron thermal, LINAC, indium, aktivasi foil. ABSTRACTLinac is operated at above 10 MV will generate secondary radiation in the form of neutron emission from the reaction of the high photon energy linac striking the material components of linac such us targets, collimators and filters. Secondary radiation will increase the probability of the secondary cancer risk in patients due to increasing the dose of radiation received. This study evaluated the thermal neutron flux at the indoor spatial operated 15 MV linac using foil activation method. A total of 14 Indium-115 foil placed in the treatment room were exposed to 15 MV linac plane for 1 minute. Results showed the highest flux are around isocenter ( , × • • ). With the flux value of additional dose due to the neutron flux at , Sv/menit. FLux decreases as distance function. Related to radiation protection efforts for radiation workers, the contribution coming from the neutron dose necessary acted upon by adding shielding on the door.

MONITORING OF EYE LENS DOSE HP(3) CATHLAB STAFF USING SOCA DOSIMETER. The International Commission on Radiological Protection (ICRP) reduced the cataract threshold dose from 2‒5 Gy to 0.5 Gy, followed by a decrease in the dose limit value (NBD) of the radiation worker's eye lens to 20 mSv/year. Cathlab staff is one of the workers vulnerable to receiving high doses of eye lenses because they work near radiation sources, so staff's eye lens doses need to be monitored. Monitoring is carried out to analyze the dose of eye lenses received by workers and ensure workers are well protected. Eye lens measurement is carried out at Hp(3) or a depth of 3 mm because the lens is sensitive to radiation. Monitoring was carried out for one week on 14 staff (doctors, nurses, and radiographers) and four procedures with an eyepiece dosimeter (SOCA Dosimeter). The eye lens dose obtained for a week ranged from 0.108 – 1.642 mSv, and monitoring per procedure was 0.033 – 0.393 mSv. The annual dose received by workers is based on estimates mostly exceeding the NBD, so tracking with an eye lens dosimeter needs to be done, and eye protection equipment needs to be used to reduce the eye lens dose received. Keywords: Cathlab staff, eye lens dose Hp(3), SOCA dosimeter

Monitoring of dose rate beta and gama radiation exposure in nuclear medicine installation so that the received beta and gama doses can be estimated workers during work. Measurements were carried out in 2 stages: a detector without a filter and a 1.5 mm thick Aluminum beta-blocking filter. Distance is measured by the position of the worker at work. The results of measurements without a filter obtained a dose rate (H'(0.07) and H*(10)), and measurements with a filter obtained a dose rate of H*(10). The dose rate of beta radiation exposure (0.07) was obtained from the difference between the results of the first and second measurements, and the results were multiplied by a correction factor. The real dose rate in the room can be determined through the dose rate adjusted to the background dose rate and multiplied by the calibration factor of the measuring instrument. The results of the measurement of the dose H'(0.07) were 0.03 – 5608.77 Sv/hour and dose H*(10) was 0.02 – 68.65 Sv/hour. With the exposure dose rate that exceeds, workers, are at risk of receiving directed equivalent doses of H'(0.07) and ambient H*(10) that exceed the dose limit set by BAPETEN of 500 mSv/year for H'(0.07) and 20 mSv/year for H*(10). Therefore, routine monitoring of beta and gama radiation exposure in nuclear medicine installations needs to be carried out to prevent and minimize the occurrence of excessive beta and gama radiation exposure doses received by workers. Keywords: H’(0,07), H*(10), Nuclear Medicine

As one of the externa laboratories engaged in radiation safety, NuklindoLab has an individual dose evaluation service hp (10) and hp (0.07) using a TLD CaSO4:Dy thermoluminiscence dosimeter. Currently NuklindoLab has served as many as 1350 customers in the health sector consisting of clinics and hospitals classes A, B, and C, so that dose evaluation services must be guaranteed well. This study covers the internal and external quality assurance of Hp(10) and Hp(0.07) dose evaluation services at NuklindoLab – Kop JKRL. Internal quality assurance is carried out, namely background analysis of TLD CaSO4:Dy, QC Chart TLD Reader, calibration curve, all of which are in a good range. To verify this, calibration was carried out with a mixed radiation field Cs-137 and Sr-90 with dose variations of 10x, 15x, and 20x of the detection limit. The resulting uncertainty is still below 42% so it is still within the range of the IAEA tolerance limit. In addition, blind tests were also carried out to see the performance of equipment and personnel with mixed irradiation between Cs-137 and Sr-90 and with the ash of gas mantles. The deviation obtained by the ash of gas mantles is better, which is 11.2% for Hp (10) and 10.8% for Hp (0.07) so this indicates that the blind test can also be done with the source ash of gas mantles. Meanwhile, the external quality assurance carried out, namely comparing the external intercomparation that have been carried out in 2019 and 2021, has good performance, where the results obtained are 95% in the trumpet curve. Keywords: quality assurance, individual dosimeter, TLD CaSO4:Dy, beta radiation, gama radiation

Keberadaan radiasi neutron yang mempunyai rentang energi luas memiliki implikasi yang cukup signifikan untuk diperhatikan terkait dengan proteksi radiasi.Oleh karena itu, telah dilakukan pengukuran laju dosis neutron termal dan epitermal di tunnel reaktor serba guna G. A. Siwabessy yang merupakan saluran yang mengalirkan hasil reaksi fisi pada reaktor berupa radiasi neutron dan energi panas. Pengukuran dilakukan dengan metode aktivasi keping Indium dan Indium dilapisi Cadmium di atas tunnel tersebut. Setelah itu, keping Indium meluruh menghasilkan radiasi gamma yang dicacah menggunakan spektrometer gamma HPGe (High Purity Germanium). Hasil cacahan tersebut digunakan untuk menghitung besarnya fluks dan laju dosis neutron termal dan epitermal. Sehingga didapatkan bahwa fluks dan laju dosis thermal maupun ephitermal yang paling besar diperoleh di titik sambungan antara parafin. Selain itu, didapatkan bahwa pada titik tersebut laju dosis neutron epitermal sebesar 9,2 μSv/jam dan neutron termal sebesar 2,2 μSv/jam atau 80,7% didominasi oleh neutron epitermal. Hasil tersebut hampir sama jika dibandingkan dengan hasil pengukuran spektrum radiasi neutron dengan menggunakan Bonner Sphere yang menunjukkan bahwa di titik tersebut laju dosis neutron didominasi oleh neutron epitermal sebesar 74,6%. Hasil ini menunjukkan bahwa metode aktivasi keping indium bisa menjadi metode alternatif yang praktis dan murah sebagai acuan atau referensi dalam pertimbangan tindakan proteksi radiasi neutron untuk pihak yang terkait.