A simple model of evaporation from warm pools of water with turbulent, natural convection flow in the vapor phase is presented. The model is applicable from the dilute, low mass-transfer rate regime (room temperature) through the high mass-transfer rate regime (up to 99 degrees C). The model is applied to spent-fuel pool (SFP) heat and mass transfer during emergency conditions (e.g., plant blackout), and, in particular, to Fukushima. Comparisons with previous models are made. A simple analytic formula is presented that is nearly explicit in solving for pool temperature. The formula separates the more temperature-dependent properties from less temperature-dependent ones via a non-dimensional ratio Q(u) = q(u)/q(u,b). where q(u )is the arbitrary (but specified) evaporative (latent) heat flux (similar to decay heat for SFP) and q(u,b) is the latent heat flux characteristic of incipient boiling. The latter has a simple, relatively temperature-independent expression, q(u,b) = (h(fg )Le(2/3) h*)/C-p, where h(*)is the dilute-limit heat transfer coefficient This formula predicts that for natural convection at 99 degrees C (h* similar to 10 W/m(2) K) q(u,b) is approximately 18 kW/m(2), slightly greater than, but of the same order of magnitude as, pool boiling heat flux at the onset of nucleate boiling. A new blowing factor correlation is presented for high-rate mass-transfer (B-m > 1) of air-water vapor (Pr similar to 0.7, Sc similar to 0.6) turbulent natural convection flow over a heated horizontal surface for pool temperatures up to 99 degrees C (incipient boiling). (C) 2017 Elsevier Ltd. All rights reserved.