Measurements of Thermal and Resonance Neutron Fluence and Induced Radioactivity Inside Bunkers of Medical Linear Accelerators in the Center of Oncology in Opole, Poland

Abstract

The ISOLDE radioactive beam facility is the dedicated CERN installation for the production and acceleration of radioactive nuclei. Exotic nuclei of most chemical elements are available for the study of nuclear structure, nuclear astrophysics, fundamental symmetries and atomic physics, as well as for applications in condensed matter and life sciences. In order to broaden the scientific opportunities beyond the reach of the present facility, the ongoing HIE-ISOLDE (High Intensity and Energy) project provides major improvements in energy range, beam intensity and beam quality. A major element of the project is the increase of the final energy of the post-accelerated beams to 10 MeV/u throughout the periodic table. Physics with post-accelerated beams at 4 MeV/u has started this autumn. The increase in energy up to 10 MeV/u is fully funded and it will be implemented at the rate of one cryo-module per year reaching 10 MeV/u for A/q = 4.5 at the start of 2018. In this contribution, a description of the ISOLDE facility including some highlights will be discussed. The present status of the HIE-ISOLDE project will be described as well as the first experiment realised this year.

Breakthrough whole body energy-specific and tissue-specific photoneutron dosimetry by novel miniature neutron dosimeter/spectrometer

“…As stated in the introduction, in spite of important scientific and technical advances made on PN dosimetry 1 – 4 , 13 – 15 , 18 – 22 , 24 , 25 , 33 , having a neutron dosimeter/spectrometer with high spatial resolution to provide also energy-specific and tissue-specific dose equivalents of PNs generated from the beam and from the phantom or body has been of vital need. In this context, the neutron dosimeter/spectrometer and methods introduced in this study while well meeting such requirements have been extremely instrumental in providing matrix of energy-specific and tissue specific depth PN dose equivalent data, as follow: Detailed matrix of whole body energy-specific and tissue-specific PN dose equivalent/Gy X-ray dose data responses on and in phantom organ depths as well as in/out-of-field remote organs away from the central axis were determined which can be applied for energy-specific and tissue-specific PN-SPC risk estimation.…”

“…Neutron dosimetry in mixed radiation fields is rather complex in general and in exotic mixed-field situations when neutron fluence is very low in high-dose low-LET radiation fields such as PNs in high-energy high-dose rate X-ray beams 1 – 6 , 8 , 16 or deuterium-deuterium fusion neutrons in the presence of low-LET X-rays and electrons as well as high-LET high-fluence ions in plasma focus devices in particular 43 . Regardless of complexities, different interesting methods have been advanced for in and out of the field and/or depth dose studies such as super-heated drop/bubble detectors 4 , 13 – 15 ; polycarbonate neutron dosimeters (PND) 1 – 3 , 16 , 17 ; CR-39/ 10 B (with no cadmium cover) 4 ; activation of material 2 , 7 , 18 ; paired ionization chambers 19 ; online digital detector in 5 accelerators (15, 18 and 23 MV) 20 ; paired 6 LiF:Mg,Ti and 7 LiF:Mg,Ti TLDs 21 , 22 ; silicon diodes 23 ; BF 3 and 3 He proportional counters 24 ; and thermal neutron pulse detectors and solid state thermal neutron rate detectors 25 . One extensive study used a digital thermal neutron detector inside a radiotherapy bunker with simultaneous use of passive CR-39 and 6 Li / 7 Li TLD pairs on an anthropomorphic phantom for head and abdomen treatments 20 .…”

Technical Note: Induced radioactivity in stereotactic body radiation therapy with a flattening‐filter‐free 10 MV beam model

“…Using γ spectroscopy and dose decay curve measurements on various linacs, many induced radioisotopes have been identified, including 24 Na, 28 Al, 38 Cl, 56 Mn, 57 Co, 57 Ni, 62 Cu, 122,124 Sb, 187 W, and 196 Au. 14,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Based on the properties of the radioisotopes, several models were established to describe the induced activity and discuss the occupational dose [20][21][22] that ranged from 0.1 mSv/y to 5.9 mSv/y [21][22][23][24][25][26][27][36][37][38][39] and 17 mSv/y under extreme conditions. 21 However, establishing a universal model to predict the dose is difficult because it depends sensitively on many factors, such as the different treatment installations (linac, bunker, console room, etc.…”

“…Many studies have been dedicated to the investigation of induced activity in various aspects 14–40 . In general, as beam energy increases, the induced activity tends to increase greatly 17–20 .…”

“…γ spectroscopy and dosimetry measurements are necessary to analyze the induced activity. Using γ spectroscopy and dose decay curve measurements on various linacs, many induced radioisotopes have been identified, including 24 Na, 28 Al, 38 Cl, 56 Mn, 57 Co, 57 Ni, 62 Cu, 122,124 Sb, 187 W, and 196 Au 14,17–36 . Based on the properties of the radioisotopes, several models were established to describe the induced activity and discuss the occupational dose 20–22 that ranged from 0.1 mSv/y to 5.9 mSv/y 21–27,36–39 and 17 mSv/y under extreme conditions 21 .…”