Re: Scientists turn attention to world's poles to gauge global warming

Earl wrote:
Islander <nospam@xxxxxxxxxxx> wrote in
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Earl wrote:


Islander <nospam@xxxxxxxxxxx> wrote in
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Earl wrote:


Islander <nospam@xxxxxxxxxxx> wrote in
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Earl wrote:



So the boat was motionless, without power at xxx feet in
an act that took only a about 8 seconds from start to
finish.

Naturally there was fallout. NR ruled with an iron fist
and woe betide anyone who strayed form the approved
course. And an instrumented SCRAM was definitely off
course.

Officers relieved>
Captain -- always
XO -- in charge of training
Engineer -- magic words, and general responsibility

Officers required to requalify
EOOW
MPA -- in charge of throttleman

Enlisted required to requalify
Chief of Watch aft -- bystander
MDiv chief -- signed off on throttleman quals
EPCP -- wrong moves
RO -- was not observant enough of throttlemans
actions throttleman -- (since this was beginning
watchstation there was not far to fall)


The boat spent some time in the yards checking the
reactor because THOU SHALT NOT EXCEED 100% POWER


I had not heard that story before. Was this a personal
experience? What boat?


Definitely not a personal story. My luck was better. I
even managed to dodge 3 cases of negligent homicide by the
shipyard (with me as the corpse). So my luck was working
overtime during my Navy days.

This was one of the "there for the grace of God" stories
that were required reading in the mid '60s.

So I would guess that it was one of the early nucs, back
in the days when Rickover would can anyone for the
slightest infranction of his Commandments.

Off hand I would guess it was one of the S boats or even
as late as a Thresher class.

There are a lot of stories that circulate in the military
and are embellished in the retelling, so I wonder if this
is a true story or just one told to impress the new members
of the crew.

The Navy prides itself in the safety record of the Nukes,
having lost only two subs in the '60s due to problems other
than the reactors. I've also heard people make the argument
that the Navy's safety record is testament to how nuclear
reactors can be built and run safely. Your story discounts
that record and I wonder if repeating it without verifying
if it is accurate is a good idea.



Given that it was in an official publication of the nuclear
navy detailing accidents and incidents involving the
submarine service I definitely believed it to be true.

Just as the aviation services publish (in house) detailed summaries of crash investigations, so too did the sub
service pass detailed info within the community of things
that were done wrong. Things that you should avoid at all
costs. (and as with all accident reports, the serial
numbers are filed off to confuse the identities of the
guilty, the point is the mistake not the persons involved)

Even my boat managed to get a mention. We had a discharge
pipe on the ASW system that was 75% eaten away in only 3
years of operation. Problem was the CO2 scrubber discharged
into that line and the weak acid was slowly eating the pipe
away. (new piping arangement to fix problems identified
from Thresher -- which introduced new problems)

This story just shows how the Navy got the reputation of
safety. The plants were built robust and redundant so that
even exceeding limits was not severly damaging. And the
operators were required to produce perfection, with failure
being punished severly.

But you have to realize one very important point. The sub community (nucs and diesels) was very small. There were
only 2000 officers in the whole sub service -- not even as
much as a high school in a good city. It was a community
with a great deal of manditory trust between individuals.
But it was also a community under a great deal of stress.


As for loss of subs -- yes the official loss is two. The
real loss is higher, the boats were lost but not the crews.
1968 was a bad year for subs everywhere. The Soviets lost
one, the Israelis lost one the French lost one, and the US
lost two -- only one making the papers. Scorpion we all
know about (some more than others), but we also had a (ww2
Guppy) diesel that went into an uncontroled dive. Roughly
60 degrees down angle on decent due to stern plane jam,
with the depth gage (in the middle of the boat hitting over
1000 ft) (the torpedo room was deeper). The correct
response by one man (without orders) saved the boat. It did
however go into a 70 degree rise on the way to the surface.
The crew was allowed on deck to steady the shaking, and the boat made a one way trip to the razor blade factory.
Massive shell buckling on the hull -- one step short of
hull failure.


There were several incidents where greater than 100% power
was inadvertantly yielded. In each case the cores were
undamaged or only slightly buckled. The reactors were built
tough, with lots of safety margins. (But each violations
required detailed inspections to check for damage.) But the
operating environment was to not rely on safeguards. Do so
and you were through!!!

Richover was playing a very delicate political game with Congress. They allowed him to get away with murder, but he
had to deliver on his promises. He promised Nautilus would
stay in commission for 20 year. It did -- we always refered
to it as Building 571 because it was tied up and was never
going to go to sea in the last years of her commissioning.
To hold the perfect record he ran NR and the engineering
sub program with a ruthlessness that the KGB would be proud
of. It worked and delivered what was promised, but there
were high costs.


Subs were not alone in having terror from on high. Read up
on the stories of Curtis LeMay and SAC. Richover was small
and quiet, and would stab you in the back (this not as
derogitory as you might think, remember that the
personality type for fast attack submariners is a knife
fighter engaging the enemy in a dark room) while LeMay was
big and broad and would stomp you into the ground for
messing up in the slightest.

I ran your story past a friend who was in the service. He
did not recall hearing this particular story, but verified
that the details made sense for the early nuclear sub
technology. There is only part that did not make sense to
him initially:

"Here is the part which raises real confusion for me. A sub
nuclear reactor has a double coolant system. That is, there
is a primary coolant which runs through the reactor and is
heated. This cools the reactor as well as providing heat to
the heat exchanger. However, the steam to the turbines is
provided through secondary steam system, connecting through
a heat exchanger to the primary reactor system, such that
the steam going to the turbine is from a non-radioactive
secondary source. Consequently, if the secondary coolant
system went low level or dry, it would play havoc with the
secondary system, but not necessarily the primary reactor
coolant system. I do not know where this slug of very cold
water was coming from, but I would assume that it would be
in the secondary system and not the primary one which is
chugging along providing heated water by circulating around
the reactor core."

He sent me a subsequent message explaining that the first
generation nuclear subs had only a single stage system and
that would explain the problem, not something that would be
an issue in nuclear subs presently in service.

So, I'm satisfied that the story is not relevant to current
technology.





There were some experimental systems that used a boiling primary, but they never appeared in the Navy.

All naval reactors (from the original S1W in Idaho, onwards to the current natural convection systems) used a two loop design. The contamination nightmares of a single loop are beyond my imagination!!! (And I cringed when I visited S1W)

S1W did have a poor design, it used steam drive (from secondary loop) reactor coolant pumps and other wierd arrangement (with lots of places to inadvertantly trap radioactive rust) (It was an interesting time in the 10 years from the initial S1W to the S5G which is the predecessor to all the nat circ plants now in the navy. We learned a lot, the hard way!)

To explain the accident, please follow this train.

The steam generator is a saturated steam system, the temperature of the steam depends on the loop temperature and the rate that you are pulling steam out of the generator. High steam rates mean a low temperature in the SG. This low temperature is reflected in the primary loop outlet temperature from the SG. No steam demand and the inlet temp (== reactor exit) is high and equal to SG outlet temp, thus reactor is at constat power, approximately zero but still critical.

The low water alarm is a symptom of the problem, not the accident itself. The real accident was the abnormal steam demand (which lowered water levels). This created the ultra large cold water slug in the primary loop exiting the SG.

As steam load increases, the temperature of the primary coolant exiting the SG drops. This reduced temperature will result in an increase in power at the reactor because of the negative thermal coefficient of the reactor power. The increased power will provide more energy and thus heat the water back up to the operating temperature.

The cold water slug I refered to is just the lowering of the water temp going back to the reactor. Part of the problem is that there are three things that affect the reactor reactivity level. The rod positions, the temperature of the water, and how fast the reactivity (from rod or water temp) is changing.(If you pull rods too fast you get disasters like SL1, if you change Tav too fast you get major power transients)

At 100% power you have a fairly large drop in temperature across the SG. To prevent getting too much power from injecting really cold water there are thermometers that calculate average temperature in the system, and also the difference between the hot and cold legs. Too much of a delta T and the instrumentation sends a scram signal.

The problem you have to worry about is the time delay between starting to get cold water in the cold leg and its arrival back at the reactor. In the early pump driven systems it could be vevy short which effected the response time. Temperatures were more even but a transient could still put enough reactivity into the system to allow you to exceed 100% (and I remember cases where the transient was over 1000%)

On modern natural circ plants there is a dangerous time delay built into the flow system so you can build up a big slug of cold water. But this is planned for and the trip point for the instruments are set finer.


The only way you could get a Naval plant to have an accident like you hear about in civilian plants is if the Captain ordered the Battle Short Switch used. (this removes all protective interlocks and shutdowns on the plant). This is the "I need power, come hell or high water" option. If he uses it, he will come into port with the gratitude of the crew, a small commendation from the Navy, and receive his discharge papers as he ties up.

More detail than I wanted. The only point that I wanted to make is that the Navy seems to have proved that nuclear energy can be used safely. If I am wrong on that point, then public trust in nuclear energy is diminished.

.

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