Verification of shielding effect by the water-filled materials for space radiation in the International Space Station using passive dosimeters

The dose reduction effects for space radiation by installation of water shielding material (“protective curtain”) of a stack board consisting of the hygienic wipes and towels have been experimentally evaluated in the International Space Station by using passive dosimeters. The averaged water thickness of the protective curtain was 6.3 g/cm2. The passive dosimeters consisted of a combination of thermoluminescent detectors (TLDs) and plastic nuclear track detectors (PNTDs). Totally 12 passive dosimeter packages were installed in the Russian Service Module during late 2010. Half of the packages were located at the protective curtain surface and the other half were at the crew cabin wall behind or aside the protective curtain. The mean absorbed dose and dose equivalent rates are measured to be 327 uGy/day and 821 uSv/day for the unprotected packages and 224 uGy/day and 575 uSv/day for the protected packages, respectively. The observed dose reduction rate with protective curtain was found to be 37 ± 7% in dose equivalent, which was consistent with the calculation in the spherical water phantom by PHITS. The contributions due to low and high LET particles were found to be comparable in observed dose reduction rate. The protective curtain would be effective shielding material for not only trapped particles (several 10 MeV) but also for low energy galactic cosmic rays (several 100 MeV/n). The properly utilized protective curtain will effectively reduce the radiation dose for crew living in space station and prolong long-term mission in the future

Evaluation of Dose Rate Reduction in a Spacecraft Compartment due to Additional Water Shield

The dose reduction rates brought about by the installation of additional water shielding in a space craft are calculated in the paper using the particles and heavy ion transport code system PHITS, which can deal with transport of all kinds of hadrons and heavy ions with energies up to 100 GeV/n in three dimensionalphase spaces. In the PHITS simulation, an imaginary spacecraft was irradiated isotropically by cosmic rays with charges up to 28 and energies up to 100 GeV/n, and the dose reduction rates due to water shielding were evaluated for 5 types of doses: the dose equivalents obtained from the LET and linear energy spectra, the dose equivalents to skin and red bone marrow, and the effective dose equivalent. The results of the simulation indi cate that the dose reduction rates differ according to the type of dose evaluated. For example, 5 g/cm2 water shielding reduces the effective dose equivalent and the LET dose equivalent by approximately 14% and 32%, respectively. Such degrees of dose reduction can be regarded to make water shielding worth the efforts required to install it

Overview of the Liulin type instruments for space radiation measurement and their scientific results

Ionizing radiation is recognized to be one of the main health concerns for humans in the space radiation environment. Estimation of space radiation effects on health requires theaccurate knowledge of the accumulated absorbed dose, which depends on the global space radiation distribution, solar cycle and local shielding generated by the 3D mass distribution of the space vehicle. This paper presents an overview of the spectrometer–dosimeters of the Liulin type, which were developed in the late 1980s and have been in use since then. Two major measurement systems have been developed by our team. The first one is based on one silicon detector and is known as a Liulin-type deposited energy spectrometer(DES) (Dachev et al., 2002, 2003), while the second one is a dosimetric telescope (DT) with two or three silicon detectors. The Liulin-type instruments were calibrated using a number of radioactive sources and particle accelerators. The main results of the calibrations are presented in the paper. In the last section of the paper some of the most significant scientific results obtained in space and on aircraft, balloon and rocket flights since 1989 are presented