I have read conflicting reports on the cool down time for nuclear plants. I realize that not all of the plants are exactly the same in various means, but does that also include the cool down time? Thank you for any help you can provide me. Nancy

-- Anonymous, January 26, 1999

Answers

Spent Fuel Rods: 5 Months to Cool

Info is from the Uranium Institute's site. I got it from Dr. Gary North's Site. You can verify this at the Uranium Institute's site is http://www.uilondon.org/nfc.htm

This was from Dr. North's Site (garynorth.com) - His comment:

It takes spent fuel rods 5 months to cool. This is why a nuclear power plant must not be allowed to lose power from the outside. It does not supply its own electricity. It buys electricity from an outside source. This electricity is required to run the system that cools the spent rods.

This is why the Nuclear Regulatory Commission will be faced with a major decision on July 1, 1999: whether to enforce its own rule and order a shutdown of any plant that cannot show that it will be compliant, tested, and re-tested -- ready for compliant operation on Jan. 1, 2000.

This is from the Uranium Institute's site. * * * * * * * * * * * * Spent fuel storage

When removed from a reactor, a fuel bundle will be emitting both radiation, primarily from the fission fragments, and heat. Spent fuel is unloaded into a storage facility immediately adjacent to the reactor to allow the radiation levels and the quantity of heat being released to decrease.

These facilities are large pools of water; the water acts as both a shield against the radiation and an absorber of the heat released. Spent fuel is generally held in such pools for a minimum of about five months. . . .

Link:

http://www.uilondon.org/nfc.htm

-- Anonymous, January 26, 1999

There's a couple of good threads on this topic elsewhere in the forum. You might want to take a look under the category NUCLEAR and see what you find.

Here's one to start you out:

http://www.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=000Cf9

-- Anonymous, January 26, 1999

Gary north has obviously not gotten his doctorate in nuclear engineering.It takes aproximately 2days to cool down a reactor with an 18 month operating history to ambient temperature. Spent fuel is as you said contained in a pool that is continually supplied with cooling water. Some fuel cells can later be stored out of water in a dry cask system (for details see www.nrc.gov). And lastly, nuclear power plants most certainly do supply thier own power. this is a licensing requirement for all plants to have an onsite source of power independent of the main generator and the grid.

-- Anonymous, January 27, 1999

While it is true that each nuclear power plant has its own backup diesel electric generator, its unfortunately also true that they have only 2 or 3 days of diesel fuel onsite. Y2k seems to be exposing the weak points, albeit few in number, that the rush for automation has created.

-- Anonymous, January 27, 1999

Dear Worried,

While my experience may not accurately reflect the situation at every nuclear power facility, at the nukes where I've worked (3 all told, one of those for 13 years) 30 days onsite fuel for the diesel gen's was required at all times. I'm not sure where you found a reference to "two or three days".

-- Anonymous, January 27, 1999

The "2 or 3 days" figure was a direct quote from Michael Mariotte, from the The Nuclear Information & Resource Service (NIRS), which is admittedly an anti-nuclear group. This group is proposing to the NRC that all nuclear power plants be required to have sufficent diesel fuel stored onsite to assure emergency generation of electricity. I am glad that your plant has already made similar storage provisons, but what about the other 103 nuclear plants? or if the crisis lasts longer then 30 days and resupply isn't possible?

-- Anonymous, January 27, 1999

This could be kind of an endless circle, but...

I believe that licensing criteria for all nuclear plants (not just the ones I worked at) require 30 days of emergency diesel generator fuel storage onsite. The fuel has to be sampled on a periodic basis, and topped off after routine periodic testing of the engines.

IIRC, part of the NRC Y2k contingency planning document (available at www.nrc.gov)covers this issue as well. In short, a locally available, continuous supply of diesel fuel must be verified as available and under contract for delivery, in the event that the onsite diesel fuel supply is exhausted.

Once again, my concern with nuclear plants, having worked in them for so long, is not operational in nature, ie. the ability to shutdown and maintain a given plant in a cold shutdown condition. There are enough administrative checks and balances, and system redundancies to assure this level of "nuclear safety". My concern is that operators have the appropriate instrumentation and telemetry available to make informed, safe, and adequate operating decisions w/respect to how (and where in the "operating envelope") the plant is running. The absence of correct operator decisions based on available plant monitoring devices directly contributed to both TMI and Chernobyl.

-- Anonymous, January 27, 1999

For those who are able to withstand actual facts, the following information is from the Technical Specifications bases of the plant where I work:

"Each diesel generator (DG) is provided with a storage tank which, in combinatgion with the associated day tank, has a fuel oil capacity sufficient to operate that DG for a period of 7 days while the DG is supplying maximum post loss of coolant accident load demand (Ref. 1). ... Additional onsite storage is also provided by the axuiliary boiler fuel storage tank. The quality of the fuel in this tank is maintained in accordance with the requirements for the fuel stored in the DG storage and day tanks. However, no credit for accident mitigation is allowed for the quantity of the fuel stored in the auxiliary boiler fuel storage tank."

We have 3 DGs on site, one of which is dedicated to a single high pressure coolant supply system. Also note that the power required for shutdown cooling is less than that required to supply maximum post loss of coolant accident load demand.

Every nuclear plant has a set of Technical Specifications, which are public information (though not necessarily available on the internet).

-- Anonymous, February 01, 1999