Prairie Island nuclear plant shuts down Dec 2015

1 of 2 reactors at Prairie Island nuclear plant shuts down
Written by Associated Press on December 18, 2015

The Nuclear Regulatory Commission says one of the two reactors at Xcel Energy’s Prairie Island nuclear plant shut down automatically after a problem developed in the unit’s turbine.

NRC spokeswoman Viktoria Mitlyng says officials are looking into why the turbine went offline Thursday. After that happened, she says, fire alarms went off.

Because it took more than 15 minutes for operators to confirm there was no fire, she says, they had to report it to the NRC as an “unusual event,” and did around 1:15 p.m.

Mitlyng says they’re investigating why the alarms went off.

Xcel Energy spokesman Randy Fordice says there’s no indication yet that the turbine problem and the false fire alarms in the Unit 2 containment building were connected, but there was no danger to the public.

This isn’t good for the resort, but those who like to play at Frontenac will likely find better [safer?] ice right now with this shut-down. Trailer Point may be holding a few fish too with this event. Hok-Si-La beach could be a producer too.

“The cooling tower pumps intake water from
the discharge basin and discharge into
individual distribution pipes to
the top of the cool
ing towers. The pumps are vertical, dry
pit pumps mounted so that t
he casing will be flooded with the water in the discharge
basin at normal level. The pump motors
are mounted on, and suppor
ted by, the pump.
The intakes to the pumps are
submerged to prevent the intake
of air from any cause.
Spray nozzles at the top of the cooling towers break-up the wate
r stream into small
streams which drop by gravity through a maze of “fill” to a basin
at the base of the
towers. Fans draw air up through the stream
s of water and the heat of the water is
carried into the atmosphere by the airstream. Fr
om the cold water basin at the bottom of
the towers, the water flows through the coo
ling tower return canal to the distribution
basin (NMC 2007). The towers are designed to accommodate the full circulating water
flow of the plant and are capable of remo
ving up to 96 percent of the waste heat
generated by plant operation (AEC 1973).
Operation of PINGP’s circulating water syst
em is governed by spring and fall “trigger
points.” The spring trigger point is defined as
the point in time that the daily average
ambient river temperature increases to
43 degrees Fahrenheit (F) or above for five
consecutive days, or April 1, wh
ichever occurs first. The fall
trigger point is the point at
which the daily average upstream ambient ri
ver temperature falls below 43 degrees F
for five consecutive days. From the spri
ng trigger point through the fall trigger point,
PINGP is required to operate the cooling to
wers as necessary to meet the following
requirements: (1) the temper
ature of the receiving wate
r immediately below Lock and
Dam No. 3 can not be raised by more than
5 degrees F above ambient, (2) the cooling
water discharge can not exceed a daily aver
age temperature of 86
degrees F, and (3) if
the daily average ambient rive
r temperature reaches 78 degr
ees F for two consecutive
days, all cooling towers shall be operated to the maximum extent practicable (NPDES
Permit No. MN0004006).
From the fall trigger point
through March 31, the temperat
ure of the receiving water
immediately below Lock and Dam No. 3 can not be raised above 43 degrees F for an
extended period of time. If
the receiving water temperat
ure exceeds this 43-degree F
limit for two consecutive days, NMC must
notify the Commissioner
and the MN DNR.
The Commission may require NMC to operate t
he cooling towers or take alternative
action to meet the 43-degree F crit
erion (NPDES Permit No. MN0004006).
PINGP is equipped with a deicing
system to prevent the formation of ice on trash racks,
traveling screens, and bypass gates (Stone and Webster 1983). Warm water is
pumped from the discharge canal to the inta
ke screenhouse via a 30-inch-diameter pipe
buried below the frostline. The warm water is
discharged at the bottom of the approach
canal, directly in front
of the intake screenhouse.”

More then you would like to know about re licensing of Prairie Island Nuclear Plant.

” Water temperature below Lock and Dam 3 (O
utfall SW 001) is not raised more than 5
degrees above ambient (ups
tream) temperature, and
•
Water temperature below Lock and Dam 3
(Outfall SW 001) does
not exceed a daily
average of 86°F”

Licensing Renewal Application Link

Wow!! Maybe the river at E’s won’t thaw for awhile?

Tom Sawvell wrote:

This isn’t good for the resort, but those who like to play at Frontenac will likely find better [safer?] ice right now with this shut-down. Trailer Point may be holding a few fish too with this event. Hok-Si-La beach could be a producer too.

So true Tom. There are always trade offs.

One piece that concerned me two years ago was that Excel wouldn’t give us a notice when the reactor was back on line.

This of course will make unsafe ice in many locations down stream and put life at risk.

The reason I was given was the price Excel would have to pay to buy power from other companies would be higher if those companies knew when the reactor was going back on line ahead of time.

That infusion of warmer water can really mess with things, especially the ice.

What I’m really looking for is the difference in temp of the discharge when one reactor is shut down compared to both up and running.

Curious as to anyone’s guess on what it will do to the fishing?

Last year? the Monticello plant shutdown and the dieoffs were pretty evident, as a whole no biggie, but they were there. As well the rest of the season was OK with many fish IMO dropping back to greener pastures. Apples and oranges I know, curious on others thoughts, or in years past when this happened what was effect, if any.

N, I didn’t hear or see of any die offs two years ago when we had a longer stretch of colder weather and one reactor was down. But being at the top end of P 4 I might not have seen anything.