Safe Transportation of Spent Nuclear Fuel

Center for Reactor Information

Safe Transportation of Spent Nuclear Fuel (part 2)

Spent Fuel Shipping to Yucca Mountain

Because of the incredible efficiency of the atom as a power source, very little spent fuel is produced each year.

A typical modern nuclear reactor that operates at a 1,000 megawatt electrical power level will use 20 to 30 metric tons of uranium per year¹⁴ and, therefore produce, at the most, 30 tons of spent fuel. This 30 tons of fuel will make about 8,000,000,000 kilowatt-hours (kwh) of electricity. (To get some idea of how much electricity this is, look at the number of kilowatt-hours (kwh) that appears on your monthly electric bill! Possibly 1,500 kwh in the summertime.)

(At an electricity cost of 5 cents/kwh, the electrical output of the 1,000 megawatt reactor represents an income of $400,000,000 per year to the owner of the reactor.)

An annual production of spent fuel would require less than three rail shipments to Yucca Mountain per year, each shipment consisting of a special train of three rail cars, each car containing one cask.

For perspective, to generate this same amount of electricity from coal requires burning about 3,000,000 tons.¹⁵ Transporting this much coal, each year, takes over 300 train loads, each train consisting of over 100 rail cars, each car containing 100 tons of coal -- in all 30,000 car loads.

In 1999 there were about 40,000 tons of spent fuel stored at reactors⁸ and in away-from-reactor storage around the country and another 20,000 tons would be produced before Yucca Mountain is ready to receive any spent fuel.

How quickly the spent fuel needs to be removed from the reactors and transported to Yucca Mountain will determine the rate at which the spent fuel will need to be shipped and will require answering a number of questions. The logistics of the spent fuel shipping system, including availability of casks, turn-around time, etc., will determine the most efficient method of operation.

Answering these questions is simply a typical business problem -- one that requires good interfacing between the Yucca Mountain disposal site, the shippers, the railroad, and regulators. Though the transportation process is not simple, it is a routine commercial activity, and many experts will pay close attention in the planning and execution.

Effects of Sabotage Explosive Assault

The risks associated with a sabotage assault on a spent fuel shipment depend on how much radioactive material will be released from the cask as a respirable aerosol. In the earliest regulations there was no empirical information available, so risks were based on speculative scientifically based estimates. A Sandia study, SAND 77-1927 to estimate the radiological consequence of a sabotage event, assumed that 0.07 percent of the spent fuel in the cask could be converted to a respirable form. This value was acknowledged to be very conservative and fraught with uncertainty.

Based on the potential risk that this study suggested, the NRC imposed a number of temporary rules to reduce the chance that such a sabotage event could occur.

Both the NRC and the Department of Energy, realizing that realistic data were needed as a basis for realistic regulations, sponsored experimental programs to pin down the question of how much spent fuel subject to a violent explosive attack would be converted to a respirable aerosol.

Battelle Memorial Institute conducted experiments using actual spent fuel. Sandia National Laboratory conducted a full-scale program using an obsolete shipping cask and unirradiated fuel. The results of these programs complemented each other and it was learned that the actual formation of respirable fraction was very much less than had been estimated in the previous study.

In Sandia's full-scale test⁶ the amount of material in the respirable range was found to be only about 1/10 of an ounce of uranium dioxide from 220 pounds damaged in the spent fuel.. This is about 0.0006 percent of the fuel or less than 1/100 of that assumed in the earlier study.

This full-scale test confirmed that the effect of the explosive charge was to shatter the material affected rather than to pulverize it. This knowledge is also useful in planning for clean-up after such an event should it occur.

In applying this new experimental data to a radiological consequences analysis, it was learned that if such a sabotage event were to take place in Manhattan, New York City, it would result in no early fatality nor morbidity -- apart from the effects of the explosion -- and no more than one later cancer fatality.

Actual Cask Accident Experience

In the CRS Report for Congress "Transportation of Spent Nuclear Fuel"¹⁶ Mark Holt quotes the NRC:

"The safety record for spent fuel shipments in the U.S. and other industrialized countries is enviable. Of the thousands of shipments completed over the last 30 years, none has resulted in an identifiable injury through release of radioactive material."

He goes on to say that in the period from 1979 through 1995, 356 metric tons of spent fuel were shipped in 1,168 highway shipments and 979 metric tons in 138 rail shipments.

During 1971 to 1995 eight accidents involving casks took place, with no release of radioactive material in any of them. In four of these accidents, the casks were loaded with HLW.

In one accident the truck left the road and the cask was thrown from the trailer. The cask was slightly damaged but was repaired. The driver was killed.
In two incidents the truck/trailers failed. The casks were undamaged.
In the fourth accident a train carrying two casks of Three-Mile Island core debris collided with a car. The casks were undamaged.

Environmental Impact Statement

"The purpose of the environmental impact statement (EIS) is to provide information on potential environmental impacts that could result from a Proposed Action to construct, operate and monitor, and eventually close, a geologic repository for the disposal of spent nuclear fuel..."¹⁷

The EIS analysis considered the impact of 10,700 rail shipments over a 24-year period using 21 rail-accident cases that ranged from very common accidents to those so very unlikely as to be almost impossible -- "the maximum reasonably foreseeable accident." Latent cancer fatalities from the latter improbable event were estimated to be five for the rail scenario. For this same kind of accident three traffic fatalities were calculated.

Consequences from various collisions, fires, and combinations of collision and fire were examined.

The consequences of an accidental crash of a large jet aircraft into a cask were also calculated. The cask would not be penetrated, but failure of the cask seals would result in a fraction of one latent cancer fatality.

International Spent Fuel Shipping Experience

"Internationally, more fuel has already been shipped and successfully transported than is scheduled to be shipped to Yucca Mountain."¹⁸

Existing Spent Fuel Shipment Procedure

Following is an abbreviated description of the various activities that are currently undertaken in the shipment of spent nuclear fuel. This listing may not include every item, but should provide a reasonable understanding of the process.

For simplicity's sake this description deals only with rail shipment, since this is the most likely shipment mode to Yucca Mountain. Currently, rail shipments are made by special train and it is assumed that that policy will continue.

Preliminary

Advance arrangements are made to assure a compatible schedule between the shipper of the spent fuel (the utility), the receiver of the spent fuel, the provider of the shipping casks, and the railroad.

A schedule is made for notification of regulatory and other organizations as may be required.

The route is established and whether it will require armed guards and state notification.

Shipping site activities

Standard Operating Procedures are prepared and approved.

Site personnel are trained in loading the cask.

Equipment is identified and checked out.

The empty cask is received.

Measurements are made on the empty cask to assure shipping regulations have been complied with.

The cask's personnel barrier is removed, the impact limiter is removed, and the cask moved to the preparation area. It may require cleaning.

The nuts or bolts that hold the cask head on are removed.

The cask is moved to the transfer area of the spent fuel storage pool and the head removed to its temporary storage spot.

Spacers, if needed to adjust for various fuel assembly lengths, are installed.

The spent fuel assemblies are transferred from their storage positions to the grid in the shipping cask.

(All movements of the spent fuel under water must maintain at least nine feet of water over the fuel.)

Fuel identification numbers are recorded for accountability purposes.

The cask head is replaced and the cask removed from the storage pool.

The cask is drained of residual water.

The cask head is fastened down and the cask leak-tested.

Records that all operations were done according to the appropriate Standard Operating Procedures are verified.

The cask is scrupulously cleaned to assure that surface contamination is well below regulatory limits.

The loaded cask is returned to its rail car, the personnel barrier is re-installed and final measurements made to determine radiation levels outside the cask.

Shipping papers are provided the carrier.

Final confirmation is made that all transportation safety requirements have been met.

The cask is tendered to the railroad, which transmits it to its destination.¹⁹

Acknowledgments

The author gratefully acknowledges critical reviews by Martin J. Steindler and Richard A. Beatty who have retired from life-long careers in the nuclear field.

Footnotes to part two

14. Nuclear Waste. The About Network downloaded from the Internet. (An abridged version of a Congressional Research Service Report by Mark Holt, Resources, Science, and Industries Division, April 23, 2001.) (Return to article.)

15. Based on 0.47 tons of coal per 1000 kilowatt-hours. (Return to article.)

16. Holt, Mark. Transportation of Spent Nuclear Fuel. Updated May 29, 1998. This document is a Congressional Research Service Report for the U.S. Congress. (Return to article.)

17. Final Environmental Impact Statement for a Geologic Repository for the Disposal of Spent Fuel... DOE/EIS-0250. U.S. Department of Energy. February 2002. Summary, p. S-1. (Return to article.)

18. Nuclear News 45, 8 p. 13. (Return to article.)

19. Shipments of all hazardous materials are made under authority of the U.S. Department of Transportation. This authority is codified in the Code of Federal Regulations, Title 49, Transportation, Parts 170-179. Routing of high levels of radioactive materials are addressed in a rule commonly referred to as HM-164. (Return to article.)