Eval u a tion of the Tech ni cal Ba sis for 

Ex tended Dry Storage and 

Trans por ta tion of Used Nu clear Fuel 

— Ex ec u tive Sum mary 

U.S. Nuclear Waste Technical Review Board 

De cem ber 2010 
U.S. Nu clear Waste Tech ni cal Re view Board 

Au thors 

This report was pre pared for the U.S. Nu clear Waste Tech ni cal 

Re view Board by Dr. Douglas B. Rigby, staff mem ber, in sup port of 

the Board’s anal y sis of is sues as so ci ated with ex tended dry stor age 

and transportation. The ef fort is led by Dr. An drew C. Kadak, 

Board mem ber. 

A full copy of this report and other reports by the NWTRB are 

available on the Board's web site at: WWW.NWTRB.GOV 

ii 
Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

U.S. Nu clear Waste Tech ni cal Re view Board 

B. John Garrick, Ph.D., P.E., Chair man 

Consultant
 

Newport Beach, California
 

Mark D. Abkowitz, Ph.D. 

Vanderbilt University
 

Nashville, Tennessee
 

Wm. Howard Ar nold, Ph.D., P.E.

Consultant
 

Macatawa, Michigan
 

Thure E. Cerling, Ph.D.

University of Utah


Salt Lake City, Utah
 

Da vid J. Duquette, Ph.D.

Rensselaer Polytechnic Institute


Troy, New York
 

George M. Hornberger, Ph.D.

Vanderbilt University


Nashville, Tennessee
 

An drew C. Kadak, Ph.D.

Exponent Corporation


Natick, Massachusetts
 

Ron ald M. Latanision, Ph.D.

Exponent Corporation


Natick, Massachusetts
 

Ali Mosleh, Ph.D.

University of Maryland


College Park, Maryland
 

Wil liam M. Murphy, Ph.D.

California State University


Chico, California
 

Henry R. Petroski, Ph.D., P.E.

Duke University


Durham, North Carolina
 

iii 
U.S. Nu clear Waste Tech ni cal Re view Board 

Nu clear Waste Tech ni cal Re view Board Staff 

Ex ec u tive Staff 

Nigel Mote, Executive Director
 

Joyce M. Dory, Director of Administration
 

Tech ni cal Staff 

Carlos A. W. Di Bella, Senior Professional Staff 

David M. Diodato, Senior Professional Staff 

Bruce E. Kirstein, Senior Professional Staff 

Daniel S. Metlay, Senior Professional Staff 

Douglas B. Rigby, Senior Professional Staff 

Gene E. Rowe, Se nior Pro fes sional Staff 

Ex ter nal Af fairs Staff 

Karyn D. Severson, Director 

In for ma tion Tech nol ogy Staff 

William D. Harrison, Systems Administrator 

Ad min is tra tive & Sup port Staff 

Davonya S. Barnes, Information Systems Specialist 

Linda J. Coultry, Program Support Specialist 

Linda L. Hiatt, Management Analyst 

iv 
Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

Eval u a tion of the Tech ni cal Ba sis for 

Ex tended Dry Stor age and Trans por ta tion of 

Used Nu clear Fuel — Executive Summary 

Introduction 

The U.S. Nuclear Waste Tech nical Review Board (Board) is tasked 

by the amend ments to the Nuclear Waste Policy Act of 1982 to 

inde pend ently eval uate U. S. Depart ment of Energy (DOE) 

tech nical activ i ties for managing and disposing of used nuclear 

fuel and high-level radio ac tive waste. This report was prepared to 

inform DOE and Congress about the current state of the tech nical 

basis for extended dry storage1 of used fuel and its trans por ta tion 

following storage. The Board expects that the report also will be 

valu able in informing the Blue Ribbon Commis sion on Amer ica’s 

Nuclear Future, and other inter ested parties, on these issues. 

When the used nuclear fuel that is currently stored at commer cial 

nuclear power plant sites will be trans ported to other loca tions is 

not known. Under standing the length of time that used fuel can be 

stored, without the fuel or the storage system compo nents 

degrading to the extent that the ability to meet the regu la tory 

require ments for continued storage is affected, is a primary concern. 

In addi tion, under standing how the condi tion of the used fuel 

changes with time is impor tant to deter mining when this may affect 

the ability to transport the fuel without signif i cant risk of damage or 

release of radio ac tive mate rials. Finally, being able to predict 

1 U.S. nu clear util i ties are op er at ing dry-stor age fa cil i ties for used fuel that are li ­

censed for op er at ing pe ri ods of up to 60 years. The fuel in these fa cil i ties and the used 

fuel that will be dis charged in the fore see able fu ture may need to re main in stor age for 

much lon ger pe ri ods. Some have sug gested that this pe riod could ex tend to as long as 

300 years. This re port eval u ates the tech ni cal ba sis for dry stor age of used fuel dur ing 

such ex tended pe ri ods but does not encom pass ex tended wet stor age of fuel. In this 

re port, the term “fuel” re fers to both the ura nium pel lets and the metal clad ding. 

1 
U.S. Nu clear Waste Tech ni cal Re view Board 

confidently how used fuel will behave when it is handled after 

trans por ta tion to a repos i tory or a processing facility also is 

neces sary. 

This report pres ents the results of a review of publicly avail able 

liter a ture and published infor ma tion on research completed to date 

related to extended storage and trans por ta tion of used fuel. The 

Board reports these results without chal lenging the technical 

find ings of researchers but believes that they form a suit able basis 

for the eval u a tion presented here. In addi tion, regu la tory authority, 

National Labo ra tory, and industry experts have been consulted to 

confirm the current state of knowl edge and the research and 

devel op ment recom men da tions to enhance confi dence in the 

evaluation of extended storage included in this report. 

Back ground 

Figure 1 shows graphics of typical pres sur ized- and boiling-water 

reactor fuel assem blies consisting of fuel rods arranged in 

assem blies. After irra di a tion, these consti tute the “used fuel” that 

is stored at reactor sites in pools and in dry-storage systems. 

Following discharge from the reactor, used fuel is initially stored 

in racks under water in pools up to 40 feet deep (see Figure 2 ). 

During this period of wet storage, some degra da tion may be 

detect able, although it is typi cally minimal. 

Before the pools at a nuclear power plant are filled to their 

licensed capacity, the oper ator needs to provide addi tional storage 

capacity so that the power plant can continue oper ating. Thus, 

many util i ties have built dry-storage facil i ties (referred to as 

Inde pendent Spent Fuel Storage Instal la tions, or ISFSIs) on their 

sites. These instal la tions are large parking-lot-type concrete pads 

with protec tive fencing and contin uous security surveil lance. The 

2 
 

Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

Fig ure 1.

Typ i cal

Pres sur ized-Wa ter 

Re ac tor (left) and 

Boil ing-Wa ter Re ac tor

Fuel As sem blies (right) 

Cour tesy West ing house (left) 

and 

http://gepower.com/prod_ser 

v/prod ucts/nu clear_en ergy/e 

n/down loads/gnf2_adv_poste 

r.pdf (right) 

Fig ure 2.

Typ i cal Used-Fuel

Stor age Pool 

(from 

http://www.nrc.gov/waste/spe 

nt-fuel-stor age/pools.html) 

fuel may be stored verti cally 

in metal or concrete casks or 

hori zon tally in modular 

concrete storage facil i ties. 

The fuel inside concrete 

dry-storage casks is in bolted 

or welded canisters that are 

loaded in the spent-fuel pool 

and trans ferred to the ISFSI in 

an on-site transfer cask. 

Similar canis ters are used for 

fuel that is stored in 

horizontal storage modules 

and may be used to contain 

fuel in metal storage casks, 

although some metal casks 

contain the fuel in open 

baskets without an inner 

canister. 

3 
U.S. Nu clear Waste Tech ni cal Re view Board 

Fig ure 3.

In de pend ent Spent-Fuel 

Stor age In stal la tion 

Photo from NAC 

In ter na tional, Inc. with 

per mis sion 

Fig ure 3 shows con crete casks stor ing used fuel at the Con nect i cut 

Yan kee Nu clear Power Plant site. Fig ure 4 shows typ i cal 

com po nents that con sti tute a con crete stor age-cask sys tem, 

in clud ing the mul ti pur pose can is ter (MPC) and the vents that 

pro vide the air flow to cool the can is ter. Metal casks that con tain 

the fuel in open bas kets do not have the same ven ti la tion 

ar range ment but typ i cally have ex ter nal heat-trans fer fins to as sist 

with the cool ing. 

Be fore used fuel is loaded from a pool into a can is ter, the can is ter 

is low ered into the stor age pool in side a shielded trans fer cask. If 

the fuel is to be loaded into a metal cask with an open bas ket, the 

cask is low ered into the pool with the basked in stalled. Fol low ing 

load ing of the fuel, a lid is in stalled and the cask is re moved from 

the pool. The water is drained from the cask and, if a can is ter is 

4 
Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

Figure 4.

Typical Vertical Dry-Cask

Storage System 

Graphic Courtesy of Holtec 

International, Inc. 

be ing used, the wa ter also is drained from the can is ter. The lid 

then is bolted or welded in place, and op er a tions to dry the fuel 

are started. 

This pro cess typ i cally in volves sev eral cy cles of al ter nately 

ap ply ing a vac uum and backfill ing the can is ter, or the cask, with 

he lium. Dur ing the pe ri ods when the vac uum is ap plied, the fuel 

rods lose much of their cooling and the tem per a ture of the fuel 

rises. The tem per a ture rise enhances dry ing, but the tem per a ture 

has to be controlled be low pre de ter mined lim its to pre vent 

5 
 

U.S. Nu clear Waste Tech ni cal Re view Board 

ther mal stresses that could result in clad ding dam age. Once the 

dry ing process is com pleted, the canis ter or cask is pressur ized 

with he lium, both to pro vide im proved heat trans fer and to 

min i mize the po ten tial for fuel deg ra da tion dur ing sub se quent 

storage. 

Find ings 

This re view finds that fuel rods dis charged from nu clear power 

plants are typ i cally in good con di tion with only a very small 

per centage of rods hav ing clad ding de fects. Early ref er ences 

re ported that less than 0.04 per cent of fuel rods failed, while later 

plant re cords in di cate that the fail ure rate has de creased to less 

than 0.0005 per cent for more re cently dis charged fuel. Dur ing 

prep a ra tion for trans fer to dry-stor age fa cil i ties, failed fuel 

as sem blies are loaded into spe cif i cally de signed com part ments in 

the canis ters or metal casks, sepa rate from intact fuel as sem blies. 

The fuel-dry ing pro cess is not perfect. Af ter dry ing, re sid ual The most sig nif i cant wa ter re mains in un known amounts that can af fect sub se quent po ten tial deg ra da tion in ter nal deg ra da tion pro cesses. The vac uum-dry ing heat cy cles 

mech a nisms af fect ing can change the nature of the hy dro gen in the clad ding and stress 

the fuel clad ding the fuel. 

dur ing ex tended 

Ac cord ing to the lit er a ture re view, the fuel, the dry-stor age sys tem stor age are ex pected to 

com po nents (can is ter, cask, etc.), and the con crete foun da tion pad be those re lated to may all de grade dur ing dry stor age. Some deg ra da tion hydriding, creep, and mech a nisms may be ac tive dur ing the early years of dry stor age, stress cor ro sion while dif fer ent mech a nisms may be ac tive at the lower 

crack ing. tem per a tures that would be ex pected dur ing ex tended stor age. 

The most sig nif i cant po ten tial deg ra da tion mech a nisms af fect ing 

the fuel clad ding dur ing ex tended stor age are ex pected to be those 

re lated to hydriding, creep, and stress cor ro sion crack ing. These 

6 
Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

In suf fi cient
 

in for ma tion is avail able 


yet on high-burnup
 

fu els to al low re li able
 

pre dic tions...
 

mech a nisms and their inter ac tions are not yet well under stood. 

New re search sug gests that the ef fects of hy dro gen ab sorp tion and 

mi gra tion, hy dride pre cip i ta tion and re ori en ta tion, and de layed 

hy dride crack ing may de grade the fuel clad ding over long pe ri ods 

at low tem per a tures, af fect ing its duc til ity, strength, and frac ture 

tough ness. High-burnup fu els tend to swell and close the 

pel let-clad ding gap, which in creases the clad ding stresses and can 

lead to creep and stress cor ro sion crack ing of clad ding in ex tended 

stor age. Fuel tem per a tures will de crease in ex tended stor age, and 

clad ding can be come brit tle at low tem per a tures. 

Only lim ited ref er ences were found on the in spec tion and 

char ac ter iza tion of fuel in dry stor age, and they all were 

per formed on low-burnup fuel af ter 15 years or less of dry stor age. 

In suf fi cient in for ma tion is avail able yet on high-burnup fu els to 

al low re li able pre dic tions of deg ra da tion pro cesses dur ing 

ex tended dry storage, and no in for ma tion was found on 

in spec tions con ducted on high-burnup fu els to con firm the 

pre dic tions that have been made. The in tro duc tion of new 

clad ding ma te ri als for use with high-burnup fu els has been 

stud ied pri mar ily with re spect to their re ac tor per for mance, and 

lit tle in for ma tion is avail able on the deg ra da tion of these ma te ri als 

that may occur dur ing extended dry stor age. Con se quently, 

with out any data for predict ing how aging af fects the fuel 

con di tion over lon ger stor age pe ri ods, ven dors model the 

con di tion of high-burnup used fuel currently in stor age on the 

ba sis of the lim ited se ries of exam i na tions of fuel that have been 

performed to date. These also form the ba sis for pre dict ing the 

be hav ior of used fuel dur ing extended dry stor age and nor mal 

han dling and trans port of used fuel and in the event of 

trans por ta tion ac ci dents. 

7 
U.S. Nu clear Waste Tech ni cal Re view Board 

...ac cu rately pre dict ing
 

how the used fuel and
 

can is ter tem per a tures
 

will change over
 

ex tended dry stor age is
 

im por tant.
 

As noted above, one of the main de ter rents to cor ro sion of the fuel 

clad ding and the can is ter or metal cask in ter nals dur ing ex tended 

dry stor age is the pres ence of he lium. If the he lium leaks and air 

is al lowed to en ter the canis ter or cask, this, to gether with the 

mois ture in the air, can re sult in corro sion of the fuel cladding, the 

can is ter, and the cask. How ever, al though pro vi sion is made to 

mon i tor the pres sure of the he lium dur ing ex tended stor age in 

bolted can is ters, there is cur rently no means of con firm ing the 

pres ence of he lium in welded con tain ers or casks, nor is there a 

re quire ment for pe ri od i cally in spect ing the in teg rity of the clo sure 

welds for de fects. If these stor age sys tems were in spected for 

weld de fects and/or tested for he lium pe ri od i cally, this would 

al low welded con tain ers and casks with leaks to be re paired and 

re filled with he lium. 

Dur ing ex tended dry stor age, deg ra da tion mech a nisms also act on 

the outside of can is ters, on stor age casks (con crete or steel), and on 

mod u lar con crete fa cil i ties as well as on the stor age pads. The 

ef fect of these degra da tion mech a nisms will de pend on the 

en vi ron men tal con di tions at the spe cific lo ca tion, on di ur nal and 

sea sonal tem per a ture vari a tions, and on the pres ence of cor ro sive 

agents and mois ture in the air. The re view iden ti fied ref er ences to 

gen eral metal and con crete de te ri o ra tion mech a nisms and 

mod el ing, but none in cluded the in for ma tion nec es sary to pre dict 

the deg ra da tion of dry-stor age can is ters, casks, or con crete 

struc tures dur ing ex tended stor age. 

Given the tem per a ture de pend ence of many of the deg ra da tion 

mech a nisms de scribed above, ac cu rately pre dict ing how the used 

fuel and can is ter tem per a tures will change over ex tended dry 

stor age is im por tant. Dur ing this re view, how ever, lit tle 

in for ma tion was found on de tailed ther mal mod el ing dur ing the 

pe riod of ex tended dry stor age. 

8 
 

 

Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

Re gard less of the length of stor age, used fuel even tu ally will have 

to be moved from the re ac tor sites, ei ther to off-site interim stor age 

fa cil i ties or to used-fuel pro cess ing fa cil i ties for re cy cling or for 

management of waste. Trans por ta tion reg u la tions are largely 

fo cused on the in teg rity of the trans por ta tion casks, which con tain 

the used fuel, and main tain ing subcriticality of the fuel. The 

pri mary goal is to en sure that the cask does not fail in the event of 

a trans por ta tion ac ci dent, with the po ten tial for re lease of 

ra dio ac tive ma te ri als. The reg u la tions re quire that un der both 

nor mal and ac ci dent con di tions, the trans por ta tion cask and its 

con tents are ca pa ble of meet ing strin gent per for mance 

spec i fi ca tions that in clude main tain ing geo met ric con fig u ra tion of 

the fuel to cer tain lim its, largely for crit i cal ity control, and to 

ad dress con cerns about ex ter nal ra di a tion levels. 

If the fuel de grades dur ing ex tended stor age, it could be 

sus cep ti ble to dam age from the vi bra tion and shocks encountered 

dur ing trans port op er a tions. The con se quences may in clude 

re lease of fis sion-prod uct gases into the can is ter or the cask 

in te rior, which must be con tained dur ing a trans por ta tion 

ac ci dent. 

Used-fuel trans por ta tion casks are de signed to with stand a se ries 

of trans por ta tion ac ci dents with out re lease of ra dio ac tive 

ma te ri als. Fig ure 5 shows a full-scale crash test per formed by 

Sandia Na tional Labo ra tory in 1977 in which a lo como tive 

trav el ing at ap proxi mately 80 miles per hour was crashed 

broad side into a used-fuel trans por ta tion cask. In this test, the 

cask and the dummy fuel in side it per formed in accordance with 

the reg u la tory re quire ments. 

Upon reach ing the in terim stor age lo ca tion, the re posi tory site, or 

other pro cess ing fa cil ity, the used fuel may have to be han dled, 

and the in teg rity of the fuel fol low ing the trans por ta tion and 

han dling op er a tions may not be known with con fi dence. If the 

9 
U.S. Nu clear Waste Tech ni cal Re view Board 

Figure 5.

Spent-Fuel Crash Test 

http://www.sandia.gov/records 

mgmt/ctb1.html 

fuel is to be processed in stead of be ing placed in a re pos i tory af ter 

trans por ta tion, the casks and used-fuel can is ters will need to be 

opened and the fuel re moved. Be fore this is done, con sid er ation 

will need to be given to the condi tion of the fuel, and a means will 

need to be avail able for de ter min ing whether the fuel has failed. 

This may re quire open ing the cask in a hot cell as op posed to the 

more tra di tional spent-fuel pool. Following ex tended stor age, the 

in teg rity of the used fuel af ter trans por ta tion can not be en sured 

be cause some long-term deg ra da tion pro cesses are un cer tain and 

trans por ta tion-ac ci dent load ing pre dic tions for aged fu els have 

not been fully val i dated. 

Re view of the rel e vant tech ni cal sources used as the ba sis for this 

re port has shown the fol low ing: 

Lit tle data are pub licly avail able on the be hav ior of 

high-burnup fuel dur ing dry stor age or on its behavior during 

sub se quent han dling and trans por ta tion. No in for ma tion is 

10 
Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

avail able on the be hav ior dur ing dry stor age of the more
 

ad vanced ma te ri als now be ing used for fuel clad ding and
 

fab ri ca tion of fuel-as sem bly struc tural com po nents. 


The phys i cal state of the cladding when fuel is placed into dry 

stor age is not cur rently well char ac ter ized. There may be 

zones of physi cal weak ness and, in some cases, the clad ding 

may be close to fail ure. Nor mal han dling of fuel as sem blies, 

off-nor mal oc cur rences, and ac ci dent events would then be 

more likely to re sult in addi tional dam age to fuel rods. 

Clad ding-deg ra da tion mech a nisms, their in ter ac tions with 

each other, and the ex pected be hav ior of clad ding af ter 

ex tended dry stor age are not well un der stood. Also not well 

un der stood are some of the con di tions that af fect these 

deg ra da tion mech a nisms, such as the changes in fuel 

tem per a tures that will occur over time and the amount of 

re sid ual wa ter pres ent af ter dry ing. 

At the low tem per a tures ex pected to be reached dur ing 

ex tended dry stor age, and even in the pres ence of air, 

used-fuel-pel let ma te rial ox i dizes at a very slow rate. Even if 

a gross breach oc curs and fuel-pel let ma te rial is re leased from 

the fuel cladding, it will not ox i dize to pow der eas ily or 

quickly. Con se quently, if fuel ma te rial is released in side the 

can is ter or cask, con tain ing and re pack ag ing it safely once the 

can is ter or cask is opened should not pres ent any un due 

prob lem. Fis sion-prod uct gases also would be re leased in side 

the canis ter or the cask. If the canister or cask were to be 

opened, they would need to be dealt with by the ven ti la tion 

sys tem in the fuel-han dling facil ity. 

11 
 

 

U.S. Nu clear Waste Tech ni cal Re view Board 

Cor ro sion mech a nisms will cause deg ra da tion of the metal 

com po nents of dry-stor age sys tems dur ing ex tended 

dry-stor age pe ri ods: for ex am ple, the outer sur faces of fuel 

can is ters. Con se quently, es tab lish ing an ef fec tive reg u lar 

in spec tion and main te nance pro gram is im por tant. 

In order to develop a better understanding of how the 

conditions of fuel and storage systems change during 

extended dry-storage, it will be im por tant to es tab lish a 

pro gram for in spect ing and char ac ter iz ing the phys i cal 

condi tion of used fuel and dry-stor age sys tems over time. 

This will re duce the uncer tainty in pre dict ing the fu ture state 

and behav ior of the used fuel and the stor age-sys tem 

com po nents dur ing sub se quent op er a tions. 

Sev eral con crete de te ri o ra tion and rebar-cor ro sion 

mech a nisms are known to cause deg ra da tion of re in forced 

concrete in dry-stor age sys tems, includ ing the stor age pad. 

Con se quently, es tab lish ing a reg u lar in spec tion and 

main te nance pro gram for these sys tems is im por tant. 

Some plau si ble off-nor mal and ac ci dent sce nar ios for the 

han dling and trans port of used-fuel casks have not been fully 

eval u ated. Per form ing full-size test ing of trans port pack ages 

to dem on strate the be hav ior of both the pack age and the fuel 

may be ben e fi cial. At a min i mum, val i da tion of com puter 

mod els us ing scaled tests should be car ried out. How ever, the 

per for mance of some com po nents, such as bolts and welds, 

are partic u larly dif fi cult to scale. Con se quently, if scaled tests 

are per formed, ad di tional test ing of full-scale com po nents 

may be needed to ver ify that the per for mance of these 

com po nents is be ing mod eled cor rectly. 

There are secu rity risks as so ci ated with the dry stor age of 

used fuel, and the risks will likely change with time. These 

risks and how they change need to be ad dressed us ing a 

12 
 

Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

risk-in formed pro cess that con sid ers the prob a bil ity of the 

risks and the po ten tial con se quences. This pro cess then should 

be used as the ba sis for deter min ing what ac tion, if any, is 

needed to pro vide the nec es sary level of se cu rity dur ing 

ex tended dry-stor age pe ri ods. 

Re search and De vel op ment Rec om men da tions 

On the ba sis of this re view, we rec om mend that a num ber of 

re search and de vel op ment pro grams be im ple mented. They are 

fo cused pri mar ily on im prov ing the un der stand ing of key 

fuel-deg ra da tion mech a nisms and in creas ing con fi dence in the 

pro jec tion of the behav ior of the used fuel and stor age sys tems 

dur ing ex tended dry-stor age pe ri ods and sub se quent 

trans por ta tion of the fuel. The inten tion is to pre vent prob lems 

that may oth er wise be en coun tered dur ing later fuel-han dling 

op er a tions fol low ing trans por ta tion of used fuel to dis posal or 

pro cess ing fa cil i ties. The rec om mended re search pro grams 

in ves ti gate the fol low ing is sues: 

Un der stand ing the me chan i cal clad ding be hav ior and 

fuel-clad ding deg ra da tion mech a nisms po ten tially ac tive 

dur ing ex tended dry stor age, in clud ing those that will act on 

the ma te ri als in tro duced in the last few years for fab ri ca tion of 

high-burnup fu els 

Un der stand ing and mod el ing the time-de pend ent con di tions 

that af fect aging and degra da tion pro cesses, such as 

tem per a ture pro files, in situ ma te rial stresses, quan tity of 

re sid ual wa ter, and quan tity of helium gas 

Mod el ing of age-re lated deg ra da tion of metal can is ters, casks, 

and in ter nal com po nents dur ing ex tended dry stor age 

13 
 

 

U.S. Nu clear Waste Tech ni cal Re view Board 

In spec tion and mon i tor ing of fuel and dry-stor age sys tems to 

ver ify the ac tual con di tions and deg ra da tion be hav ior over 

time, in clud ing tech niques for en sur ing the pres ence of 

he lium cover gas 

Ver i fi ca tion of the pre dicted me chan i cal per for mance of fuel 

af ter ex tended dry stor age dur ing cask and container 

han dling, nor mal trans por ta tion op er a tions, fuel re moval 

from casks and con tain ers, off-nor mal oc cur rences, and 

ac ci dent events 

De sign and dem on stration of dry-trans fer fuel sys tems for 

re mov ing fuel from casks and can is ters fol low ing ex tended 

dry stor age 

Con clu sions 

...ad di tional
 

in for ma tion is re quired
 

to dem on strate with
 

sim i larly high
 

con fi dence that used
 

fuel can be stored in
 

dry-stor age fa cil i ties
 

for ex tended pe ri ods
 

with out the fuel
 

de grad ing...
 

The tech ni cal in for ma tion cur rently avail able, to gether with the 

ex pe ri ence gained to date in the dry stor age of spent fuel, 

dem on strates that used fuel can be safely stored in the short term 

and then trans ported for ad di tional stor age, process ing, or 

re pos i tory dis posal with out con cern. How ever, ad di tional 

in for ma tion is re quired to dem on strate with sim i larly high 

con fi dence that used fuel can be stored in dry-stor age facil i ties for 

ex tended pe ri ods with out the fuel de grad ing to the ex tent that it 

may not per form sat is fac to rily dur ing con tin ued stor age and 

sub se quent trans por ta tion. 

Consequently, the Board recom mends that a num ber of re search 

and de vel op ment pro grams be im ple mented to dem on strate that 

used fuel can be stored safely in dry-stor age fa cil i ties for ex tended 

pe ri ods. Re search alone will not be suf fi cient. Be cause the 

ex pe ri ence base for ex tended dry stor age of used fuel is short and 

the cred i ble deg ra da tion phe nom ena are sev eral and not ro bustly 

14 
Ex tended Dry Stor age and Trans por ta tion of Used Nu clear Fuel 

...an in-service
 

in spec tion and
 

main te nance pro gram
 

ap pears to be necessary
 

as part of a used fuel
 

management program
 

that includes long-term 


dry stor age.
 

pre dict able in a quan ti ta tive sense, an in-ser vice in spec tion and 

main te nance program ap pears to be necessary as part of a used 

fuel management program that includes long-term dry stor age. 

The tech ni cal details of such an in-ser vice in spec tion pro gram 

ob vi ously will de pend on the de sired safety ob jec tives of ex tended 

dry stor age. Con se quently, a prac ti cal en gi neer ing ap proach that 

is based on the ob ser va tional method and pe ri odic as sess ments 

will likely be re quired to pro vide an ade quate safety ba sis in 

ad di tion to what can be learned from tar geted sci en tific 

in ves ti ga tions. 

The regu la tions con cern ing dry storage of used fuel do not 

cur rently ad dress stor age for ex tended pe ri ods. There also is some 

in con sis tency be tween the reg u la tions that ap ply to dry stor age 

and those that ap ply to trans por ta tion, and how to meet both sets 

of reg u la tions is un clear. It would be help ful in man ag ing 

ex tended dry stor age of used fuel if the reg u la tions were re vised 

as an in te grated set and based on a risk as sess ment for safety 

sig nif i cance and con se quence. In addi tion, the Board thinks that 

the reg u la tory re quire ments re lated to phys i cal se cu rity and 

ter ror ist threats also should be re viewed on a risk-in formed ba sis 

us ing po ten tial con se quence anal y sis and in te grated with the 

stor age and trans por ta tion reg u la tions. 

At this point, the nuclear waste man agement pol icy of the United 

States is unclear, and the re sult is that used fuel will be stored at 

re ac tor sites for lon ger than orig i nally fore seen. It is thus es sen tial 

that the ap pro pri ate re search and de vel op ment pro grams and 

mon i tor ing and in spec tion pro grams are im ple mented as a mat ter 

of pri or ity to dem on strate that used fuel can be stored safely for 

ex tended pe ri ods and then trans ported and han dled as part of a 

fu ture waste man age ment pro gram. 

15 
16 

U.S. Nu clear Waste Tech ni cal Re view Board
 

2300 Clar en don Blvd, Suite 1300
 

Arlington, Vir ginia 22201
 

703-235-4473 

www.nwtrb.gov