Radi-N2 Neutron Field Study (Radi-N2) - 11.22.16
Radi-N2 Neutron Field Study (Radi-N2) is a follow on investigation designed to characterize the neutron radiation environment aboard the International Space Station (ISS). Eight neutron “bubble detectors” produced by the Canadian company Bubble Technology Industries are attached to fixed locations inside the ISS, including one carried by a crew member. The objective of this investigation is to better characterize the ISS neutron environment and define the risk posed to the crew members’ health and provide the data necessary to develop advanced protective measures for future spaceflight. Science Results for Everyone
Data from detectors placed in four modules of the space station showed good agreement with the neutron exposure measured in previous studies; changes in location and altitude of the space station and increased solar activity caused no notable change in the measurements. Additional experiments showed that the neutron exposure measured by the Radi-N2 detectors was lower inside a spherical phantom (made of tissue-equivalent material) than outside the phantom. This agreed with Monte Carlo software simulations performed on the ground. The Radi-N2 experiment is ongoing and measurements are planned up to 2020. Experiment Details
Leena Tomi, Canadian Space Agency, Saint Hubert, Quebec, Canada
Martin B. Smith, Bubble Technology Industries Inc, Chalk River, Ontario, Canada
Vyacheslav A. Shurshakov, Institute of Biomedical Problems, Moscow, Russia
Bubble Technology Industries, Incorporated, Chalk River, Ontario, Canada
Sponsoring Space Agency
Canadian Space Agency (CSA)
ISS Expedition Duration
September 2012 - March 2016; March 2016 - February 2017; March 2017 - September 2017
Radi-N1 (Increment 20/21)
- Study is a continuation of Radi-N1 done in Increment 20/21, and will repeat the measurements in the same/equivalent locations aboard the ISS: USLab, JEM (Nominal), COLUMBUS, Node2 (Reserve) The additional data increases the statistical accuracy of the neutron measurements and also allow comparison of neutron fields at different periods of the solar cycle.
- Results of Radi-N 1 and 2 study allows better understanding of radiation environment aboard the ISS. The utilization of newly developed Bubble Detector Spectrometer will help characterize the neutron spectrum on board, and measurements in different ISS locations will provide a means of assessing the neutron field symmetry in different modules of the Station. Measuring the average dose within different segments of ISS will help with development of radiation protection plan for future missions.
Neutrons are nuclear "splinters" produced when cosmic rays strike the atoms of a spacecraft or even the human body. Earlier experiments with Matroshka-R, a "phantom" body, revealed that astronauts absorb larger doses of neutron radiation than expected, possibly from cosmic rays striking atoms in their bodies. Mapping across the ISS will help reveal neutron sources and exposure dangers.
Because they carry no electrical charge, neutrons have greater potential to penetrate the body and damage tissue. Radi-N2 will help doctors understand better the connections between neutron radiation and DNA damage and mutation rates, cataracts that affect some astronauts, and other radiation health issues.
Operational Requirements and Protocols
Decadal Survey Recommendations
Information Pending^ back to top
At the time of writing, the neutron exposure measured by the ongoing Radi-N2 experiment is similar to the previous Radi-N measurements conducted in the same locations within the ISS. The data show that changes in ISS location, altitude, and solar activity do not appear to create a notable increase or decrease in neutron passes through the bubble detectors. This agrees with earlier bubble-dosimeter readings in the Russian segment, suggesting that these potential influences have little effect on the neutron field in the ISS. Additional experiments concluded that the neutron exposure measured by the Radi-N2 detectors was lower inside a tissue-equivalent, spherical phantom than outside the phantom. This is in agreement with ground-predicted Monte Carlo software simulations. The Radi-N2 experiment is planned to continue until 2020; conclusions from the experiment will be made following an analysis of the complete set of data. (Smith MB 2016)^ back to top
Smith MB, Khulapko S, Andrews HR, Arkhangelsky VV, Ing H, Koslowsky MR, Lewis BJ, Machrafi R, Nikolaev IV, Shurshakov VA. Bubble-detection measurements of neutron radiation in the International Space Station: ISS-34 to ISS-37. Radiation Protection Dosimetry. 2016 March; 168(2): 154-166. DOI: 10.1093/rpd/ncv181. PMID: 25899609.
Ground Based Results Publications
El-Jaby S, Tomi L, Sihver L, Sato T, Richardson RB, Lewis BJ. Method for the prediction of the effective dose equivalent to the crew of the International Space Station. Advances in Space Research. 2014 March; 53(5): 810-817. DOI: 10.1016/j.asr.2013.12.022.
El-Jaby S, Lewis BJ, Tomi L. A model for predicting the radiation exposure for mission planning aboard the international space station. Advances in Space Research. 2014 April; 53(7): 1125-1134. DOI: 10.1016/j.asr.2013.10.006.
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NASA Image: ISS035E031921 - Radi-N2 detector floating on board the International Space Station.
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NASA Image: ISS039E011243 - View of eight Radi-N2 Neutron Field Study (Radi-N2) bubble detectors still packed in their case.
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