Note that this paper describes a 3-day heat after death event, on p. 16:
The plain curve of fig. 9 emphasizes both the remarkable temperature
increase paralleling electrolysis (I = 0.150 A) and a quite unexpected
phenomenon: after 240 min of electrolysis, in o.c. conditions, the
electrolyte temperature did not decrease to its original value. In other
words, the system showed a persistent thermal “after effect”: 0.300 W were
still emitted by the electrode 4000 min after the cell had been taken to
The terminology is a little obscure:
"After effect" means heat after death.
o.c. means open circuit; i.e. turned off.
4000 min = 66 hours or ~3 days. That is the longest Ni-H heat after death
event I have ever heard of. The few other heat after death events with Ni-H
are reported in other papers, but I do not recall any as long as this.
I assume heat after death is sustained by hydrogen or deuterium outgassing
from a hydride, and reacting near the surface. The heat only lasts as long
as it takes outgas. That's Ed Storms' hypothesis. It is surprising that it
took 3 days to outgas from nickel, because it does not hold much gas. It is
indeed "quite unexpected" as the authors say.
Look carefully at Fig. 9, p. 17 to see what the authors mean.