January 10, 2016

Project Pacer And the Unbuilt Pacer Economy Part 1: The 1975 Report

A guest post by Joseph Friedlander  

This is the first of two articles. This gives some history of the possible need for near term D-D fusion to maximize fission fuel supplies. It ends with coverage of the 1975 report. The second part covers more modern redesigns of the concept, notably by Ralph Moir in the 1990s.

When writing my extremely speculative article on what would happen if we could make unlimited isotopes of our choice (http://nextbigfuture.com/2016/01/what-if-we-get-unlimited-cheap-isotopes.html

I mentioned that we would need  to master fusion to guarantee fission in the long term:  "We have enough fissionables on this planet ... to last for about 60,000 years in an all nuclear world at American rates of energy consumption. But to do that will require mastering D-D fusion to produce Uranium 233 and Plutonium 239."

Reader comments on that included:

There are a number of break-even burner reactors, as well as net breeders, already at the design stage, which should run indefinitely on thorium or Pu238, once started. No fusion needed.

Indeed. With aggressive fission breeding, the Earth has energy for several billion years.

Both comments are of course correct-- it simply depends on your assumptions.

  • What reactors (not just what specific reactors but also what underlying reactor tech) will actually be funded?
  • What reactors (not just what specific reactors but also what underlying reactor tech) will actually be built and capable of routine and successful operation?
  • What reactors will actually be politically allowed to operate?
  • What percentage of the known Uranium/Thorium content of the Earth will politically be allowed to be mined?  (Note: The Earth is one of the richest bodies of the Solar System in U/T content and most of it should be concentrated in the crust so this boils down to, over geological time can we mine the entire crust? Or only pinprick surface mines as now is legal?)
  • What percentage of that mined resource will be used to power reactors?  .4 of the .7 if you use a cheap stripping once through uranium only cycle because your planet's nuclear authorities refuse to fund/allow etc development of molten salt throium reactors and  restrict mining and nuclear industry at every turn?

You get one answer  if you allow  with total and cheap massive nuclear breeding, total crustal mining full reactor family development, thorium power cycle enabling etc.

And if you prohibit everything, license grudgingly and yank licenses willfully while hampering mining and prohibiting imports of course you get an entirely different answer.

To be ridiculous about it:  The Earth's mass is 1% of volume and .5% of the mass of the whole ball of wax.
That should be on the rough order of 2.5 x 10e22 kg or 2.5 x 10e19 tons  Much depends on what you count as the lower boundary,  assumptions as to density, etc. Estimates vary from 2.35 to 2.8 x the above powers of ten so I called it 2.5 because to be blunt we are talking about enough rock that it makes very little difference.

Why did I stop at the crust?  Because most fissionables are concentrated there.  Because we will certainly mine there first. And because the resources there will illustrate the arguments just fine. (Note that if you ever develop the tech to mine deeper than the crust there may be certain risks involved beyond the scope of this article) 

2.5 x 10e19 tons is 250 million trillion tons. 1 part per million of that is 2.5 x 10e14 tons.

To give a rough idea of a trillion tons, the lesser moon of Mars is 1.47 trillion tons https://en.wikipedia.org/wiki/Deimos_(moon) So the Earth's crust is the equivalent of  170 million times Deimos.

In reality I think it will be far easier to move most humans offworld than dig up and process the entire Earth's crust, even over a hundred thousand years. But the scale of these future operations is so different from our own time when you would never get permission to open a Bingham Canyon scale mine today, that comment is best withheld here.

A part per million means a million tons for each trillion tons.
 120 million million tons of thorium @ 12 ppm in crust of the earth according to some estimates.  https://en.wikipedia.org/wiki/Occurrence_of_thorium 120  trillion tons is a part per million of 120 million trillion tons. Based on 250 million trillion tons Earth crust this would imply 2 ppm but the true figure is closer to 12 according to other estimates. 
   40 million million tons of uranium @ 3 ppm in crust of the earth according to some estimates.  https://en.wikipedia.org/wiki/Peak_uranium#Uranium_supply 40 trillion tons is a part per million of 40 million trillion tons.  Based on 250 million trillion tons Earth crust this would imply 6 ppm but the true figure is closer to 2.7 according to other estimates.

Bernard Cohen, inventor of the neutron bomb, supplied Professor John McCarthy with this figure http://www-formal.stanford.edu/jmc/progress/cohen.html  The crust contains 6.5x10^13 tonne of uranium.That is 65 trillion tons of Uranium.

Wikipedia says Nuclear power stations of 1000 megawatt electrical generation capacity require around 200 tonnes (440×10e3 lb) of uranium per year. https://en.wikipedia.org/wiki/Peak_uranium

So for a 30 terawatt all nuclear world (electrical) that is 200 tons x 30,000 (gigawatts, or 30 terawatts) or 6 million tons of uranium a year.  Depending which estimate you believe and how much you believe you can mine you get wildly different results but let's imagine mining out the whole crust: 6 megatons for 6 million years is 36 trillion tons of uranium.  You will see a once through cycle does not go that far in terms of geological time.  But with a number of adaptations the same mass of U and Th can go far further.  You can use all the uranium, not just the 235. The same for the thorium. 

If you do that you will find that the actual fissioned up heavy metal is only about a ton a gigawatt year or 30,000 tons burned for a 30 terawatt world, not 6 million tons. so things last 200 times longer or about 1.2 billion years and 4 times longer if you add the thorium. 

This is a lot, frankly more than I expected but the estimates could be off, and it makes many assumptions key of which is that people won't increase their energy consumption. 

 I was assuming a different kind of reactor, but you get the idea.  Your assumptions dictate your results.  Given the inconvenient sizes of likely working fusion plants it makes sense to reserve fissionables for things like space, sea and underground use.  Given the radioactivity problems it makes sense to plan ahead so disasters become mere inconveniences. 

 Imagine a world of huge nuclear powered large cargo ships-- every one of which has a detachment of marines on board to guard the reactor. Imagine a world of coastal nuclear powered cities -- powered by barge which can be towed from the coast and scuttled in case of a Fukushima https://en.wikipedia.org/wiki/Fukushima_Daiichi_Nuclear_Power_Plant 
within a single hour. Imagine many fewer and much better guarded underground or soon to be undersea power sources --in that context conservation of fissionables makes a great deal of sense because it reserves a dirty and dangerous power source for where it is most useful and conserves that resource where it is not needed and AC mains power will do. 

As the source of 1% rather than 100% of our power it would then last many billion years and it is hard to believe that wouldn't buy enough time to come up with a lot of new tech fixes.

But to get to those halcyon years of future energy paradise we have to slog through the near present.  Some people have speculated that a new dark age is not only coming but that all our present problems are symptoms that we actually have begun to enter it and just don't realize it.

Fossil fuels are going to end at some point... It is a little late to plan only when shortages actually begin:
 "most chillingly, there is little recognition for the fact that a high density post industrial society like the United Kingdom is utterly dependent on cheap energy to maintain any existence at all.
 Imagine a large city like London or Manchester without water, sewage disposal facilities, heat, light or fuel. Within days food would be spoilt due to lack of refrigeration, with no power to pump water or sewage, public health would collapse into an epidemic of disease – for which the equally powerless hospitals and emergency services would be utterly unable to provide any solution. The half life of an urban inhabitant without the infrastructure that the cities depend on, is not years,

months, or even weeks, it is days."

Brendan McNamara’s thoughts on the role of fusion-fission hybrids in a nuclear energy future that he believes will be even shorter of Uranium than I do... "The existing and proposed fleets of thermal nuclear reactors, with an overall efficiency of about 33%, use a Once-Through-Then-Out, or OTTO, fuel cycle. The natural Uranium is enriched by centrifuge to produce fuel with 4.5% of 235U, leaving a large stock of ‘depleted’ Uranium containing 0.3% of 235U. The fuel is burned in a PWR or other reactor and extracted as spent fuel after 18 months to two years in the reactor. The spent fuel contains 1.1% 235U, 1.3% of newly bred 239Pu, and 0.12% of Actinides, which is to say 2.52% of fissile fuels, and 5.15% of fission products – the ash which still produces heat after fission has ceased. All this is stored in cooling ponds and could eventually be buried in nuclear waste disposal facilities. Exclusive use of this system would lead to the ‘Easter Island Collapse’ scenario by 2100, with the oil, gas, and Uranium depleted or buried, and irreversible global warming. Power would come from tens of millions of windmills, coal, and billions of acres of biofuel agriculture." 

Some writers have looked around them, noted that the nuclear age is literally a lifetime old and no such practical recycling/breeding tech has succeeded in getting going and many of those writers have started getting worried about the sustainability of human civilization--- that simply this refusal to allow the Plutonium 239/U-233 economy is itself an existential risk to human civilization.

Reality check: Is this speculation of a civilization collapse for lack of future energy alarmist?

Arguing against is the nearly always sensible Richard Garwin, the man who actually designed the working sketches of the first hydrogen bomb:  https://fas.org/rlg/010409-nci.htm
 He thinks there are 1-2 centuries of uranium even in an all nuclear world at increasingly high prices ahead, and has many specific recommendations.  He thinks it is not worth reprocessing to buy more time against proliferation (If I am not misreading him at the link above)

My concern is not that Garwin is in error on any given statement, but that he is mortal and those who would follow him may adopt his restrictive views on nuclear technologies but not his simultaneously given views on developing the supporting technologies he mentions to assure future energy supplies.

My own view? Interesting as I find nuclear science I would rather have Criswell's lunar solar power plan
 be the baseline of human power needs than fusion, I'd rather have fusion than fission, and I'd rather have fission than natural gas and I'd rather have natural gas powering civilization than coal. 

But in the end I do want civilization powered at a reasonable price, not power-starved and money drained because of foolish government decisions or political lobbying. So it's not like my job depends on fusion research. But unless one of those  alternatives is allowed to proceed, your job might depend on fusion research, however indirectly.

If government fusion projects as currently funded continue the no real deliverables promised/endless rescheduling endless orbit of the government funding sun they have described for literally the last 60 years it is folly to stake human civilization's future on the idea that they will suceed in producing a generation of practical, rapidly field deployable hardware for moving mankind's baseline power leads to fusion power.

Here is a PDF discussing the fact that renewable energy is a gimmick if you don't have reliable baseline power
Also many fission reactors do not operate well with wild load variations http://www.templar.co.uk/downloads/0203_Pouret_Nuttall.pdf

Wallace Manheimer on the incredibly self-indulgent lack of timeline described by government fusion projects--  no hard plans; just fund us for literally generations and we'll see what we decide is deliverable-- or not.  http://www.ralphmoir.com/media/manAltMagFus.pdf

Wallace Manheimer on the wisdom of developing fusion power of some kind now to make it easier to breed nuclear fuel by substituting fusion neutrons for (more dangerous breeder configurations designed to conserve neutrons in fission only breeders)  ---
Key takeaway is that fusion and fission are made for each other fusion  is neutron rich + energy poor while  fission is neutron poor + energy rich -- http://www.ralphmoir.com/media/manHyKeyJourn.pdf 
This would save time for human civilization to continue in case the 'try fusion each generation and fail' game continues.  The idea is that fusion reactors bad enough to be a failure as a standalone reactor can still generate fissionables in natural or depleted uranium just by neutron output.

It is entirely possible that one of the new innovative private fusion companies that Brian covers http://nextbigfuture.com/2015/10/how-close-are-we-to-nuclear-fusion.html  will come up with a winner. I hope so.

If we take a cautious approach and  assume that controlled nonexplosive fusion will NEVER be developed because either 1) powerful political forces 2) powerful economic forces or 3) laws of nature resist it what then?

Well, if you had to contract to deliver practical fusion neutrons 10 years from now-- no weasel words, no escape clause, you had to guarantee it would be done-- and the government would provide whatever funding it took and any law change you needed but at the end of 10 years you had to have a working fusion plant-- there is only one approach that would be near certain to work.

 It is the approach that worked just over 10 years after the very first fission reactor built by man in 1942.  I refer of course to intertial confinement of fusion, aka the hydrogen bomb. That was Project Pacer--the idea to develop a fusion economy in underground shot caverns. The heat from the bombs would be tapped to generate power directly.  The extra neutrons would breed reactor fuel for fission reactors. Many, many more fission reactors than the number of Pacer reactors.

Howard Morland has said that fusion loves fission and fission loves fusion.  When considering the reactor economy and synergies that Project Pacer would make possible that comment seems doubly appropriate.

Pacer links if you'd like to read up on it:

Pacer in Bulletin of the Atomic Scientists October 1976 https://books.google.co.il/books?id=4QsAAAAAMBAJ&pg=PA24&lpg=PA24&dq=project+pacer+nuclear&source=bl&ots=K23zbQnYEb&sig=ixSOZkxRxtRkZQZ_ty2EOOtoLQ0&hl=en&sa=X&ved=0ahUKEwjJucXulsLJAhWHPBoKHbGnBPMQ6AEIMzAE#v=onepage&q=project%20pacer%20nuclear&f=false
the version under discussion is 2 x 50 Kiloton fusion devices each day. 750 bombs year, (can only cost $42000 to keep cost same as uranium then) 2000 megawatts output
Salt dome cavern 5000 feet down, 1000 feet diameter leached out,  temperature 525 C

(Interestingly a discussion of peaceful nuclear explosions ends with "at the very minimum a 10 year moratorium on peaceful nuclear explosions would seem to be a modest price to pay for the significant progress toward arms control and detente that a (comprehensive test ban treaty) would represent"-- this is interesting because it appeared to be imposed on the US side unilaterally and the Soviets went on testing until they disappeared--but by then the US Project Pacer  in particular as well as the Project Plowshare in general was long dead as was the tech infrastructure to ressurrect it.)

More on Project Pacer

 The following excerpts will end part I of this article. Part II will cover more modern developments:

The 1975 study Issued: January 1975

PACER Program. FY 1974 LASL Activity.
of the University of California
Compiled by
R. G. Shreffler
 LA-5764-MS (warning: 22 MB file)


This document is a progress report of the unfortunately interrupted 1970s Pacer Project. 
Some editing on the quotes has been done for clarity.-- The page number in front is usually the page of the PDF.  JF

p. 94 The operation of PACER in a primarily production mode has been
suggested, s i n c e a 2 GW(e) PACER (800 x 50 KT yr 40 megatons of D-D fusion a year) or can breed fission fuel for eight 1 GW(e) fission
r e a c t o r s . Thorium would be t h e f e r t i l e material, and t h e
U-233 produced would be d i l u t e d  with natural uranium before shipment
t o r e a c t o r s , eliminating it as a t a r g e t f o r thieves.enter image description here

p 98 of the pdf-- choices of working fluid

The use of steam as a working fluid is the first choice for the following
1. It is condensible, making possible shutdown without venting
all the fluid, a quenching system for safety release in event
of leak, and low-pumping power and hence reasonable thermal
2. It is available, economical, and no new engineering practice
is needed.
3. As far as is known, it is chemically compatible with the
salt walls and properly-chosen steel pipes.
(Experiments have been designed to test this point p161.)
A second choice, as a backup, is CO2 Although not condensible, it is nearly so
 and therefore provides good thermal efficiency. Chemically less reactive than steam.

Both steam and C02 require the addition of a few percent NO2 to provide
sufficient opacity in the visible and infrared to shield the walls from
fireball radiation.Other fluids which were considered and discarded were:
nitrogen and argon -- too expensive
 hydrogen -- many engineering problems, too
expensive, and the assumed advantage
of shock reduction was
found not to be true
air -- economical, but reactive and poor
thermal efficiency.
All the gases, excluding CO2
great deal of extra piping as compared to H20 and would probably be
ruled out on that account alone.

p. 113 a 50-kT charge would produce about 11 Kg of
U-233 or 239Pu if half the neutrons could be captured in fertile material.
This seems a reasonable expectation, since capture can occur
at fireball temperatures where the capture cross section is large. The
great advantage of PACER over conventional fission reactor breeders is
shown in Figure 5.
p. 115 The geology of t h e Gulf Coast basin salt dome f i e l d s was reviewed, and
many p e r t i n e n t references t o t h i s well-studied area have been assembled.
A perusal of t h e domes having a top s u r f a c e a t s u f f i c i e n t l y shallow
depth t o accommodate PACER c a v i t i e s i n d i c a t e s t h e r e are about 166 domes
of which 26 a r e i n use.
remaining 140 are l a r g e enough f o r t h e 300-meter diameter cavity.
course, some can accommodate more than one c a v i t y , o r a l a r g e r one, and
f u t u r e f u e l charge developments may open t h e p o s s i b i l i t y of using
smaller domes.
Other p o s s i b l e salt dome sites are portions of t h e Paradox basin i n
Utah and Colorado, and possibly a newly discovered deposit i n Arizona.
The probable sites a v a i l a b l e i n the Gulf Coast region alone, l a r g e enough
t o accommodate the "baseline" 2000-MW(e) p l a n t , can account f o r an
a d d i t i o n a l 200-GW(e) of capacity--more than enough t o m e e t t h e n a t i o n a l
goals f o r increased nuclear-generating capacity.


Early in the project, a review of Kennedy’s experimental results led
to lowering the cavity steam pressure from 440 bars to 300 bars to ensure
dry steam with no liquid phase...
dependence of the cost of piping became apparent, the pressure was further
reduced to 200 bars. The cavity size was decreased to 300 meters in diameter
and the device yield to 50 kT to keep the depth below the surface not
less than 4 cavity diameters, somewhat arbitrarily. The nominal choices
for the critical PACER parameters are now as follows:

Later, as the very sensitive pressure
Cavity diameter 300 meters
Cavity depth 1200 meters
Device yield 50 KT
Steam pressure 200 plus minus 20 bars
Steam temperature 525 plus minus 5O degrees  C
Nominal power level @ 2 GW(e)
Explosion per year 804 (@ 80% of peak)

(Note the text says the fuel charge was optimized at $100k per bomb and the large cavity at shallow depth is because the piping rapidly becomes expensive the deeper you go. Another place in this document says they should be able to get the cost below $40K a bomb.)

p 119-20 abundant neutrons a v a i l a b l e from t h e D-D
r e a c t i o n make possible t h e operation of a PACER f a c i l i t y primary as a
producer of r e a c t o r f u e l with power as a by-product.
In this mode of operation the approximately 100 available salt
dome sites could provide for 1000 GW(e) of additional nuclear power,
200 GW(e) in the south provided by PACER plants, and the remaining
800 GW(e) from 233U burner reactors.
(Each PACER could supply f u e l for 8 separate 1 gw electrical fission reactors (100 pacers in the Gulf Coast area would produce 200 gw directly and export)
... clean U 233 which would  be downblended on site with DU or natural uranium and sent to 800 1 gw e fission reactors offsite...
 located c l o s e t o t h e u s e r s of power, thus eliminating transmission
 The design and construction of t h e s e reactors--burners, not breeders--would be relatively simple because neutron economy is not an

 p 125 Judging by their electronic states, hydrogen, helium,
nitrogen, sulfur vapor, argon, steam, and carbon dioxide will all be
quite transparent to visible radiation at temperatures up to several
thousand degrees, and methane also up to almost as hot. Accordingly, the
thermal pulse will probably penetrate these gases and melt some of the
cavity wall.
temperature and pressure, which makes it quite unsuitable for this application.)
(NO2) , which is opaque in the visible.
equilibrium NO2 concentrations, LASL has calculated a very small thermal
pulse at the wall. We have verified qualitatively that this result is
reasonable, and that the NO reaction rates in this situation are fast
enough to keep the air opaque, even though photodissociation can reduce
the NO2 concentration to 20% of its equilibrium value.
one wishes to minimize the thermal pulse on the wall one should use a
mixture like nitrogen/oxygen, nitrogen/steam, nitrogen/carbon dioxide, or
possibly nitrogen/graphite dust or argon/graphite dust
p 126-130 Nice discussion of opacity problems -- will the environment inside the cavity shield it from the thermonuclear bursts?

To heat s a l t from 800 degrees K t o its melting temperature of 1073 degrees K r e q u i r e s 4.1 kcal/mole, while t h e l a t e n t heat of melting i s 6.7 kcal/mole.
Since t h e molecular weight of s a l t i s 58.4 and its density is 2.17 g/cm ,
one can e a s i l y c a l c u l a t e  t h a t  t o  heat  a  l a y e r around  t h e outside of a
200 m  r a d i u s  c a v i t y  t o  melting  r e q u i r e s  0.8 kilotons/cm, and t o melt it
completely r e q u i r e s an a d d i t i o n a l 1.2 kilotons/cm.
Hence if a few percent or more of t h e energy of a 100 k i l o t o n b u r s t were emitted as thermal r a d i a t i o n ,
penetrated t h e colder gas t o reach t h e w a l l , and were absorbed i n t h e f i r s t
few centimeters of salt, s e r i o u s changes i n t h e c a v i t y s i z e and shape
due t o melting would occur a f t e r a few hundred b u r s t s ....

a s seems more l i k e l y , t h e absorption mean f r e e path f o r thermal r a d i a t i o n
(mostly v i s i b l e r a d i a t i o n ) i n t h e salt is of t h e order of a meter, t h e
f i r s t few b u r s t s would not be enough t o cause melting, but t h e heat would
b u i l d up over many b u r s t s , s i n c e t h e thermal d i f f u s i v i t y of s a l t i s only
about 1 m /10 days, so t h a t t h e long-term melting r a t e would be almost
as g r e a t as i f t h e salt were more absorptive.

....if carbon dioxide were used a s
the energy absorbing and heat transport material f o r the PACER p r o j e c t ,
an overall thermal efficiency of perhaps 30% could be expected.
The carbon dioxide would be removed from t h e cavity a t a high temperature
which was limited by the creep r a t e of t h e hot salt cavity w a l l .
would be returned t o t h e cavity a t a low temperature determined by t h e
wish t o have a high density of returning f l u i d t o save on t h e c o s t of t h e
pipes from t h e surface t o t h e cavity...
I n t h e proposed system t h e cavity contains carbon dioxide a t a temperature
of over 5OO degrees C and a pressure somewhat above 200 bars....

 p 374 In Project Sterling a 380-ton nuclear device
was detonated in a 34-meter diameter spherical cavity in a salt dome
near Hattiesburg, Mississippi. The depth was 828 meters and the cavity
contained only air at ambient conditions.

.... caused by the explosion was attenuated very rapidly in the salt and
did not lead to an observable seismic signal. The decoupling factor for
the teleseismic signal was approximately 100. Since the strength of the
shock at the wall scales as yield/volume for the same ambient pressure,
the yield in the 100-meter cavity that would lead to the same shock OR
the wall is 0.38 x (100/34)e3 or ~10 KT. 

The 100-meter s i z e can therefore  374be expected t o produce a teleseismic s l g n a l appropriate t o a 100-ton
explosion from an actual 10 KT test.

It is worth noting t h a t , on re-entry, the cavity used f o r the Sterling
experiment was i n t a c t , and could presumably have been used f o r another
 Similarly we have no reason to believe that a larger cavity would not be s u i t a b l e for  many explosions.

 p 396 the nuclear fusion of heavy hydrogen (deuterium).
... burning deuterium is
accompanied by the release of neutrons whlch can be used to provide a
plentiful source of reactor fuel--about 20 gm of enriched fuel for each
gram of deuterium consumed. Unlike the other programs which propose to
obtain energy from fusion ..., the
technology for accomplishing the nuclear fusion by explosive means is
proven and successful as a result of the AEC weapon development program.
The PACER concept is a valuable civilian spinoff from the large sums of
money spent for defense. Almost all the basic technology of the power
production scheme is available, requiring only engineering development
supplemented by a very modest scientific research program.

Typically, the underground cavity required for a PACER steam tank would
be from 100 meters to 400 meters in diameter, depending on the energy of
the fuel charge. This will be no more than 100 kT of fusion with very
little associated induced activities or fission products.The rate of firing the fuel charges determines the power station capacity;
for example, a 2000 megawatt electric power plant requires a 50 kT charge
800 times per year, o r about twice a day. (A 30% n e t efficiency and an
80% load f a c t o r have been used t o obtain these'numbers.)

p 397 the small amount of generated radioactivity--a few percent of that from an equivalent reactor--is diluted by the very large (%l million ton) steam inventory, to the order of a few parts in a hundred million after one year. A

p 399 The only unusual radioactive nuclide present in a PACER reactor in quantity
is tritium (3H) produced by the explosions.. will be bound
in the water as HTO so that it cannot be released as a gas...
produced annually will be ~40kg or four parts in 10e8 of steam.

Above ground, an emergency containment and suppression system will be
provided. These will include a pressure vessel and a small lake with
enough water to combine with and condense any escaping steam which would
then be trapped in a covered catch basin or in the cavity itself,

Seismic effects, which are peculiar to PACER are kept small: the baseline
2000 Mwe station produces "thumps" so small as to go unnoticed a
few miles from the site

p 400 The l o c a t i o n of PACER power  p l a n t s  i n  s a l t domes is  a  n a t u r a l choice because t h e domes a r e  q u i t e pure, are l a r g e enough t o accommodate the PACER caverns which can be constructed cheaply by s o l u t i o n mining, and
most important, because s a l t  i s  a p l a s t i c , s e l f - s e a l i n g material a t t h e
PACER operating conditions. 

(The report goes on to say that lined rock caverns are also under consideration because there is a finite supply of salt dome sites)

  • 401-- using co2 as a working fluid would facilitate tritium recovery
  • Pacer is the only likely D-D burning fusion reaction concept deployable soon and thus is a net producer of neutrons (implication here is D-T fusion eats neutrons because you have to produce the tritium itself from lithium)

  • If techniques for recovery of materials from the power cavity are successful,then a 2000 Mwe power plant could produce approximately 25 Kgof 239Pu or 233U per day, if half the excess neutrons are captured in fertile material. Such an abundance of fuel would make the construction of expensive conventional breeder reactors unnecessary. available 233U  or 239Pu could be used, if desired, to fuel inexpensive, efficient burner reactors, leaving all the "breeding" to PACER facilities. 

p 403--  U233 produced by PACER would not be highly irradiating since it is formed by D-D neutrons which would not act on daughter products but only on the mother isotope, Th232 as well as the neutrons being braked in the steam.  (One presumes any Pu239 would be of equal supergrade quality)

p 404-- early AEC published data [would give cost of a 50KT charge] as $420,000. will be able to produce PACER fuel charges at least an order of magnitude cheaper than this.

109-- Funding levels 1970s dollars The AEC has funded PACER during the first year at a level of $447,000 with $347,000 from the Division of Military Applications and $100,000 from the Division of Applied Technology. $200 K to LASL and $247 K to RDA. at a level of $300 K; $50 K at LASL and $250 K at RDA.

How many billions have been spent on endless studies of approaches not guaranteed to work since then? Naturally this work was cut and the others funded...

p 404-- about the reprocessing plant to recover isotopes---

We estimate the capital investment in a recovery plant at
about $50 M for one cavity; however, the actual plant would probably
be larger serving several cavities in a power complex. 

p 411 Appendix 1

Detailed study of the explosion phenomenology in the steam filled cavity
has shown that:
1) The wall shock is smaller than expected. This will
probably reduce seismic effects or allow a somewhat
smaller cavity,
2)The hot fireball probably mixes with steam and cools
before it can rise to the top, and
3)A mixture of a small amount of air with the steam is
sufficient to keep thermal radiation from the cavity
Engineering conceptual design studies have shown that there are no severe
costs of materials problems, but have dictated a move to lower working
pressure (from 320 to 200 bars). The expected thermal efficiency is 30%.
Calculations of salt cavity deformation and rise over a period of years,

although not yet completed, indicate it is not a serious problem. 

p 413 Appendix 2 CONSTRAINTS ON
Constraints on t h e design of t h e PACER thermonuclear device are as follows:
1. Security: Procedures for device manufacture, assembly, and handling
must ensure t h a t n e i t h e r design information nor c l a s s i f i e d device components
can be acquired by unauthorized personnel.
2. Safety: The device must be designed so t h a t it i s incapable, under
any condition, of producing any nuclear y i e l d p r i o r to the intended time and
place of explosion. The probability of destruction o r of plutonium
contamination through detonation of t h e device explosive must be remote.
The device must also be designed t o minimize t h e consequences of any
accidental leakage of working f l u i d .
. Deuterium should be emphasized as the thermonuclear f u e l r a t h e r than tritium or lithium...

p 511 the cavity must be isolated from the surface with proper seals, heat exchangers, and other devices.

P 529 of pdf-- description of an explosion in the cavity

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