Correct. Regardless of its type, radiation can be measured over a conceptual two-dimensional space of energy and intensity. For particle radiation, such as the trapped radiation belts, energy equates to particle velocity. Energy deposited during absorption equates to particle velocity combined with particle mass—essentially kinetic energy. Intensity is how dense the particle presence is. That's measured in the number of particles passing through a conceptual small square window in one second—the "flux density." Radition is isotropic if it doesn't matter which direction that window is facing. But in the end you have a measurement like, "such-and-such flux density at such-and-such energy—for all energies present."
Total effect for some encounter, then, is energy times flux density times time of exposure. The thing you have to realize is that because you're moving through a zone where energy and flux vary greatly from place to place, a proper time-integral of exposure equates to a gnarly space-integral. You follow a path through the trapped radiation where time spent at each instance of a flux/energy profile is dictated by your orbital mechanics. The shape and location of that path matters. The speed matters, but is rigidly determined by your orbital mechanics—which depends on the shape of the path.
The AE-8 and AP-8 models developed from data collected by Apollo spacecraft were the gold standard of predicting exposure in the trapped radiation belt for decades. They have only recently been superseded by AE-9 and AP-9. If those models had been wrong, hundreds of space engineering projects would have failed dramatically (e.g., GPS, GLONASS).
Absorption in non-living materials is cumulative. Solar panels are especially susceptible to this. It doesn't largely matter whether damage accumulates via long-term, low-level exposure or acute high-level exposure. In contrast, absorption in living tissue is a more complex phenomenon. Tissue heals, so even fairly acute doses can be healed from (e.g., a chest x-ray). Injury is semi-cumulative, barring very high-order acute exposure (e.g., people at Chernobyl). Long-term exposure to low-level radiation is often more dangerous. I usually illustrate this by saying one is like having someone throw a glass of water at you. You're momentarily quite wet, but you dry off. Other exposure is like standing under a light drizzle for hours. You aren't especially wet right away, but you never dry off. Thus the real concern has been the astronauts in the ISS who pass through a relatively mild low-hanging region of the inner belt six times a day.
The aeroshell of the Apollo CM was made of stainless steel honeycomb. The inner pressure vessel was made from aluminum. In between was a fibrous insulation material specifically of low molecular density. In addition, much of the operation equipment surrounded the lower portion of the CM cabin, where the crew was most likely to be. The shielding factor was nominally 7-8 g/cm2 and up to 10 g/cm2 in places. This is perfectly adequate for a fast transit of the trapped radiation belts.
