Abstract: A spring pack for supporting a sprung mass relative to an unsprung mass includes a relatively low-rate spring unit and a relatively high-rate spring unit interconnected with each other and arranged between the sprung and unsprung masses, the relatively low-rate spring unit tending to respond to initial limited movement between the sprung and unsprung masses, a mechanical stop limiting the spring response of the relatively low-rate spring unit with relative movement beyond that limit tending to be absorbed by the relatively high-rate spring unit. A plurality of the spring packs are employed in a lateral restraint assembly for laterally supporting a reactor core relative to a vessel within a nuclear reactor, the relatively low-rate spring units absorbing initial multi-axial movement between the core and vessel with excessive movement of the core being absorbed by the relatively high-rate spring units.