As NASA prepares for a mission to Mars, concerns regarding the health risks associated with deep space radiation exposure have emerged. Until now, the impacts of such exposures have only been studied in animals after acute exposures, using dose rates ∼1.5×10 5 higher than those actually encountered in space. Using a new, low dose-rate neutron irradiation facility, we have uncovered that realistic, low dose-rate exposures produce serious neurocognitive complications associated with impaired neurotransmission. Chronic (6 month) low-dose (18 cGy) and dose rate (1 mGy/d) exposures of mice to a mixed field of neutrons and photons result in diminished hippocampal neuronal excitability and disrupted hippocampal and cortical long-term potentiation. Furthermore, mice displayed severe impairments in learning and memory, and the emergence of distress behaviors. Behavioral analyses showed an alarming increase in risk associated with these realistic simulations, revealing for the first time, some unexpected potential problems associated with deep space travel on all levels of neurological function.

TitleHeavy fragment production cross sections from 1.05 GeV/nucleon 56Fe in C, Al, Cu, Pb and CH2 targets GeV/nucleon Fe projectiles incident on H, C, Al, Cu, and Pb nuclei.The energy region covered by this experiment is critical for an understanding of galactic cosmic ray propagation and space radiation biophysics. Surviving primary beam particles and fragments with charges from 12 to 25 produced within a forward cone of half-angle 61 milliradians were detected using a silicon detector telescope to identify their charge, and the cross sections were calculated after correction of the measured yields for finite target thickness effects. The cross sections are compared to model calculations and to previous measurements. Cross sections for the production of fragments with even-numbered nuclear charges are seen to be enhanced in almost all cases.

Most accelerator-based space radiation experiments have been performed with single ion beams at fixed energies. However, the space radiation environment consists of a wide variety of ion species with a continuous range of energies. Due to recent developments in beam switching technology implemented at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL), it is now possible to rapidly switch ion species and energies, allowing for the possibility to more realistically simulate the actual radiation environment found in space. The present paper discusses a variety of issues related to implementation of galactic cosmic ray (GCR) simulation at NSRL, especially for experiments in radiobiology. Advantages and disadvantages of different approaches to developing a GCR simulator are presented. In addition, issues common to both GCR simulation and single beam experiments are compared to issues unique to GCR simulation studies. A set of conclusions is presented as well as a discussion of the technical implementation of GCR simulation.

The work reported here was originally motivated by a discussion of Monte Carlo computer codes for electron transport in water given in Report No. 130 by the National Council on Radiation Protection and Measurements (NCRP). It was pointed out (correctly) that a published depth-dose distribution calculated by the Oak Ridge electron transport code, OREC, for 800 keV electrons normally incident on a water slab was apparently in error, possibly due to inadequate treatment of elastic scattering. In this paper we describe the replacement of the original OREC elastic cross sections by current ones from the National Institute of Standards and Technology (NIST). This investigation led also to the critical examination and revision of some other parts of the program, as described here. The revised code, which we have renamed NOREC, represents the first substantial review and modification of the Oak Ridge code in a number of years. We also present some comparisons of results calculated with the old and new versions and discuss their implications with respect to earlier studies. We have also written a version of NOREC in C++ language, which is available to other investigators. This paper provides a record of a response to the NCRP published statement and documentation for the revised code, NOREC.

Ionizing radiation causes many types of DNA damage, including base damage and single- and double-strand breaks. Photons, including X-rays and γ-rays, are the most widely used type of ionizing radiation in radiobiology experiments, and in radiation cancer therapy. Charged particles, including protons and carbon ions, are seeing increased use as an alternative therapeutic modality. Although the facilities needed to produce high energy charged particle beams are more costly than photon facilities, particle therapy has shown improved cancer survival rates, reflecting more highly focused dose distributions and more severe DNA damage to tumor cells. Despite early successes of charged particle radiotherapy, there is room for further improvement, and much remains to be learned about normal and cancer cell responses to charged particle radiation.