The two specific modules are protected by two mechanisms:
- TeSS Polyethylene radiation protection tiles and bricks
- Water storage bags attached to the walls making a "water wall"
High densities of hydrogen are good at radiation protection, and water is a good hydrogen source that needs to be stored on the ISS. Another good source of dense hydrogen is polyethylene, which is nice and light.
The Zvezda module in particular was lined with Polyethylene in its construction to enable it to play the role of a radiation protection shelter. The radiation protection was modelled as part of the design:
Future deep space missions propose to utilise water storage walls as part of their design following from experiences on the ISS.
(1) Shavers et.al., 2004, "Radiation Measurements and Shielding Analysis for ISS", Workshop on Radiation Analysis for the International Space Station, Vienna.
(2) Barry & Phillips, 2000, "Water on the Space Station", Science@NASA, November 2000
(3) Azriel, 2012, "“Massively Redundant” Water Walls Spacecraft To Use Water for Everything", Space Safety Magazine, 10 Sep 2012