IEEE Spectrum February, 2007 - 10

as it stood then in IEEE Spectrum [see
"Earthquake Alarm," December 2005].
That summary drew criticism from
seismologists, who have tended to see
quakes as inherently unpredictable.
Electronic precursor studies, according
to the mainstream view, chase a will-o'the-wisp of inconsistent, retrospectively
identified phenomena.

Cold Fission
Liquid semiconductors could yield a better
nuclear battery
what	if	you	could	make	a	miniature,	superefficient	nuclear	
power	plant	that's	simple	to	
build	and	doesn't	get	much	hotter	than	a	kitchen	oven?	That	
could	be	the	result	of	an	innovation	being	developed	by	scientists	at	global	Technologies,	
in	Idaho	Falls,	Idaho.
gTI's	president,	Francis	
Tsang,	and	colleagues	are	
working	on	a	nuclear	voltaic	
cell	consisting,	basically,	of	a	
semiconductor	and	an	amount	
of	radioactive	material	[see	
photo,	"Innovator"].	The	semiconductor	sits	between	two	
conductors	to	form	a	Schottky	
diode,	and	it	is	bombarded	by	
particles	from	uranium,	plutonium,	or	some	less	dangerous	
radioactive	material.
Radiation	has	essentially	the	
same	effect	on	a	semiconductor	
that	light	has	on	a	typical	solar	
cell.	In	a	solar	cell,	the	impact	of	
a	photon	with	the	semiconductor	crystal	creates	an	electron	
and	a	positively	charged	particle	
called	a	hole.	Because	the	cell's	
semiconductor	has	been	doped	
with	chemical	impurities,	it	has	
a	natural	polarization	that	draws	
the	electron	to	one	electrode	
and	the	hole	toward	the	other,	
thereby	producing	current.
If	a	nuclear	version	of	a	solar	
cell	sounds	like	one	of	the	old	
atomic	battery	concepts	from	
the	1950s,	it	is,	but	with	a	potentially	all-new	twist.
Some	of	those	early	concepts	sought	to	harvest	semiconductor	energy	from	alpha	
radiation	(positively	charged	
helium	nuclei)	or	beta	radia16	

tion	(electrons).	Although	they	
offered	the	hope	of	efficient	
batteries	that	would	last	for	
decades,	they	were	limited	by	
what	seemed	to	be	insurmountable	problems	associated	with	
their	radiation	sources.
	"Beta	cells	are	restricted	
to	low-energy	beta,	and	they	
can't	use	alpha,"	says	Jake	
Blanchard,	a	professor	of	
engineering	physics	at	the	
University	of	wisconsin,	
madison,	who	develops	mEmSbased	radioisotope	batteries	
[see	"The	Daintiest	Dynamos,"	
IEEE Spectrum,	September	
2004].	Alpha	particles	and	
other	high-energy	radiation	
"will	trash	the	semiconductor	by	displacing	the	atoms,"	
Blanchard	says.	That	has	kept	
this	class	of	nuclear	battery	
from	housing	enough	radioactive	material	to	produce	more	
than	mere	milliwatts	of	power.
Tsang,	a	former	U.S.	Energy	
Department	researcher,	was	
well	aware	of	the	beta	cell's	
problems.	"Shoot	a	bullet	into	
a	block	of	ice,	and	the	ice	will	
shatter	and	can't	go	back	into	
its	original	form,"	Tsang	says.	
"But	if	you	shoot	a	bullet	into	
water,	the	water	repairs	itself."	
So	he	began	experiments	
replacing	solid	semiconductors	with	molten	selenium	and	
molten	sulfur,	both	of	which	
become	semiconductors	in	
their	liquid	state	and	melt	at	
less	than	300	°c.	Because	liquids	don't	suffer	any	structural	
damage,	Tsang's	nuclear	battery	could	run	on	much	more	
powerful	radiation	than	a	beta	

IEEE	Spectrum	|	February	2007	|	NA		

It's too soon to say whether Freund's
theories will be upheld or refuted, but
the balance of expert opinion and evidence clearly is beginning to shift in his
favor. Bryant and others, in work not
yet published, have compiled hundreds
of anomalous infrared events that
are sharply aligned with faults and
preceded quakes. -ALBERTO ENRIqUEz

cell,	and	therefore	generate	
more	electricity.
A	liquid	nuclear	diode	could	
catch	energetic	alpha	and	beta	
particles,	gamma	rays,	and	even	
the	new	atoms	left	over	from	the	
fission	of	larger	atoms,	Tsang	
says.	Fissile	fragments	could	
be	a	particularly	good	source	of	
energy.	In	the	fission	of	U-235,	
for	example,	the	fragments	
carry	85	percent	of	the	energy	
released.	Because	the	fragments	are	heavy,	as	they	plow	
through	the	semiconductor	they	
"make	a	shower	of	electron-hole	
pairs	along	the	path,"	he	says.

INNOVATOR:
GTI's Francis
Tsang at his
Idaho office.

Tsang's	idea	is	not	widely	
known,	and	for	now,	that's	the	
way	he	likes	it.	The	U.S.	Patent	
and	Trademark	office	posted	
gTI's	key	patent	application	
only	in	November.	Tsang	has	
not	published	data	in	a	peerreviewed	journal	(though	some	
of	the	experiments	were	replicated	at	lawrence	Berkeley	
National	laboratory,	in	

california),	and	he	would	reveal	
no	hard	numbers	for	this	article.
The	University	of	
wisconsin's	Blanchard,	
reserving	final	judgment	until	
he	sees	published	data,	thinks	
the	concept	of	a	liquid	nuclear	
battery	is	a	good	one.	"It's	a	
clever	idea,"	he	says.	"It's	not	
totally	crazy."
At	the	moment,	gTI's	battery	is	far	from	useful,	not	
having	quite	reached	1	percent	
efficiency.	Its	development	has	
gone	far	enough,	however,	to	
make	an	impression	at	the	U.S.	
Defense	Advanced	Research	
Projects	Agency.	The	
agency	gave	Tsang's	
company	funds	to	support	its	liquid	Electronics	
Advanced	Power	System	
(lEAPS)	program:	first,	
US	$1.4	million	to	prove	
the	concept	by	producing	current	in	a	test	cell,	
with	a	provision	that	
would	have	allowed	for	
additional	funding	of	up	
to	$26.6	million	for	over	
four	and	a	half	years.	
with	submarine	power	
plants	in	mind,	DARPA	
wanted	gTI	to	run	full	
speed	toward	proving	
that	a	reactor	of	the	
100-	to	1000-kilowatt	
scale	could	be	built.
But	in	october,	
Tsang's	group	rejected	
the	additional	work,	figuring	
that	the	effort	envisioned	
by	DARPA	would	overwhelm	
gTI's	resources.	Tsang	says	
gTI	ultimately	will	make	more	
progress	by	going	after	smallscale	power	sources	first.	So	
for	now,	nuclear	reactors	will	
have	to	take	a	backseat	to	
nuclear	batteries.	
	
	
-SAMUEL k. MOORE
www.spectrum.ieee.org

lANcE	w.	clAyToN

quately for weather and ocean effects.
Park reports that he has had no success
finding changes in the resistance of rock
at the San Andreas Fault.
A little over a year ago, Freund and
Thomas Bleier, CEO of QuakeFinder, a
Palo Alto-based quake-sensing network,
summarized the theory and observation
of electronic earthquake precursors
http://www.spectrum.ieee.org
Table of Contents for the Digital Edition of IEEE Spectrum February, 2007
