Waste Isolation Pilot Plant

Compliance Certification Application

Reference 625

Thome, B.J., and D.K. Rudeen, 1980. Regional Effects of TRU Repository Heat, SANDS0-7161, Albuquerque, NM, Sandia National Laboratories.

Submitted in accordance with 40 CPR §194.13, Submission of Reference Materials.

I I r r r r I I I I I I I I I I I I I

THORNE,M BILLY JOE RUDEEN, D.K.

1980 REGIONAL EFFECfS OF TRU REPOSITORY

HEAT SANDS0-7161

scteNce APPIIcanoNS

INCORPORateD

I

J

--~

SAND 80-7161 csi 2053-05

Unlimited Release Printed Jan 1981

REGIONAL EFFECTS OF

TRU REPOSITORY HEAT

LONG-TERM REGULATORY COMPLIANCE

Billy Joe Thorne D. K. Rudeen

Prepared for

Sandia Laboratories P. 0. Box 5800

Albuquerque, N. M. 87185

Prepared by

Civil systems, Incorporated (CSI) 505 Marquette, N. W.

Albuquerque, N. M. 87102 (505) 247-8787

Contract No. 13-4435

INTRODUCTION

A modification of a calculation reported in Reference 1

was used to estimate the impact of heat from a 730,000 m2

(180 acre) 0.69 W/m 2 (2.8 kW/acre) RH TRU repository at the

WIPP site. The original calculation, reported in SAI-FR-145,

was designed to estimate the effect of a 81,000 m2 (20 acre)

7.4 W/m 2 (30 kW/acre) spent fuel repository. This calculation

is on much too coarse a scale to accurately predict details

of the response. However, estimates obtained by this method

are ac~urate enough to determine whether or not heat effects

are large enough to justify more finely zoned calculations.

COMPUTATIONAL SETUP

All materials models, boundary conditions, initial condi-

tions and computing techniques were identical to those described

in Reference 1. The initial temperature distribution (Figure la)

is a piece-wise linear solution to the equilibrium equations

completely determined by the surface and bottom boundary tern-

perature. Only five significant figures of the equilibrium

solution were used for initial temperatures. For the calculation

in Reference 1, this was adequate. However, the heat source

in this calculation is so weak that initial temperatures should

have been set accurate to at least 12 significant figures. The

damping was changed to w0

= 5 x 10 11 and the initial time step

1D.E. Maxwell, K.K. Wahi, B. Dial, The Thermomechanical Response of WIPP Repositories, Science Applications, Inc., SAI-FR-145, Sandia National Laboratories, SAND 79-7111, May 1980.

,~was reduced to 1 x 10 6 s (11.6 days) in order to restrict any

numerical oscillations to early time.

The major change required was a modification of the size

of the first three zones in from the center line to give a disk

area of 730,000 m2 (180 acres) to approximate the repository

size. This resulted in using zones with a 160-m radial dimension

(Figure lb). With the 151-m vertical dimension of the zone at

the 637 m (2100 feet) depth of the repository this gives a volume

of 12 million m3 (430 million cubic feet) for the center repository

zone. Thus heat in the center repository zone is spread out over

26 x 10 9 kg (290 million tons) of salt. This averaging effect

causes the peak calculated temperature to be much lower than

would be expected in a drift of the repository.

The heat source used was taken from a Sandia-Labs-provided

list of the thermal power produced by various actinides and fission

products expected to be in RH TRU wastes. The first 200 years of

the normalized decay curve is given in Figure 2. In order to

show more detail, Figure 3 gives a log-log plot of this curve

to 10,000 years assuming a start date of 10 years (since 0 can-

not be used as a reference on log paper). Emplacement density

is assumed to yield a 0.69 W/m 2 (2.8 kW/acre) initial power

density.

SOMPUTATIONAL RESULTS

The peak temperature rise of 1.6°C occurs in the central re­

pository zone at 80 years (Figure 4). With such a small tempera­

ture increase in the hottest source zone it is clear that the

total impact of heat will be small. This is confirmed by the

0.25°C peak temperature rise at the top of both the Salado and

the Rustler Formations (Figures 5 & 6).

In the surface zone the temperature rise is so small

(0.03°C) that a 0.006°C temperature drop is significant in Figure 7.

This smarl change in temperature is the result of the grid moving

into temperature equilibrium from initial conditions that were

in equilibrium to 5 significant digits. This initial tempera­

ture drop resulted in a small downward motion of the grid which

must be taken into account when estimating uplift.

The top of the central repository zone reaches its peak

uplift of 10.4 mm at 200 years (Figure 8). At 1000 years Figure

8 indicates an uplift of 4.3 rnm. However, Figure 9 indicates that

far outside zones of the grid have moved down 2.1 mm because of the

temperature drop resulting from inaccuracies in the equilibrium

temperature. Thus the effective uplift at 1000 years is 6.4 mm.

By 1500 years (~igure 10) the effective uplift has dropped to

5.4 mm of which more than half is masked by the downward motion

resulting from the grid coming into equilibrium more accurately.

-----~~·----·--···-·····-····-··--·-· ~----------

Figures 11 thru 16 give uplift profiles at 1000 and 1500

years for the top of the Salado (Figures 11 & 12), the top of

the Rustler (Figures 13 & 14) and the surface (Figures 15 & 16).

In all cases uplift is much smaller than for the 730,000 m2

( 2 0 acre) 7. 4 ~J/m 2 ( 3 0 kl-7/acre) spent fuel re;,osi tory modeled

in Reference 1 (Figure 17). Even though the initial energy-de­

position rate in the TRU repository is 84 percent of the energy­

deposition rate in the spent fuel repository, the TRU-waste heat

output falls off much more rapidly, dropping to less than half

the spent fuel energy-deposition rate in 100 years. Thus, the

total energy deposited by the TRU waste is very small, resulting

in negligible temperature change and uplift.

CONCLUSION

The calculated temperature increase and uplift are so small

that further study of the regional effects of RH TRU-repository

heat is not justified.

FOREWORD

The calculations presented here were performed for Sandia

National Laboratories in 1979 and are consistent with the evalu­

ation of options for the Waste Isolation Pilot Plant (WIPP) at

that time.

The information here was presented in draft form in CSI

2053-05, by Civil Systems, Incorporated.

0

"" "-.

1000 -

2000

3000

20

" \ \ I

\ \

"" "' "' "" ~ "" ~

~ ~

I I I I I I I .

30 40 50 60 TEMP. (°C)

70

'SANDSTONE

MIX A

SALT

MIX B

SALT

ANHYDRITE

SANDSTONE

~ ~ ~ ~ ~

I I I

80 90

Figure la: Initial Equilibrium Temperature Versus Depth

~

--

-O. DOE+O u

TRU Repositor y_

-1. OOE+D a_

---2. OOE+D i3_

-

-3. DDE+O ~~

O. OOE+OO

180 acres

I I 2.50E+03

Radius (m)

Jewey Lake Redbeds Rustler Salado

Anhydrite

Sandstone

Figure lb: Computational Grid Showing Repository Location and Layering.

1.0

\

.8

4-1 :::! Cl.o 4-1 :::!

0 ,.. (II

:3 0

p...

"1:! (II N .4 'ri

....-! ro 13 ,.. 0 z

0

0 so 100 150 200

Time (years)

Figure 2. RH TRU Normalized Reference Waste Power Output

1

\

.1 ~ ::l 0. ~ ::l

0

'"' (])

~ 0

p...

"tl (]) N

..-I

.--1 I'd 13

'"' 0 .01 z

.001

10. 100, 1000. 10,000 Time (years)

Figure 3. RH TRU Normalized Reference Wnste Power Output

,..._ u

0 '-'

~ ~ ....

35.875

34.5

O.OOE+OO

sd Years

S.OOE+lO

TIM (S)

u 0

-=· ,......;

Figure 4: Temperature in Central Zone of the Repository

--

.--... u

0

29.7

0. OOE+OO 5. OOE+l 0

I 320 Years TIM (S)

Figure 5: Temperature in Central Zone at Top of Salado

-·~

u 0

a. :1: 1-

27.7

27.7

c.; 0

27.6

27.6

27.S

27.51

27.50

O. OOE+OO I

480 Years

S.OOE+lO

TIM (S)

Figure 6: Temperature in Central Zone at Top of Rustler

ll"\ N

c

------------------------------~~~~·--·-··~~---·-····--------

_ ....

,........ u 0 -a. E ....

22.50

22.4639

O.OOE+OO S.OOE+lO

640 YeaiJM (S)

Figure 7: Temperature in Central Zone at Surface

u 0 C")

0 . 0

0 ..0 0 0

,......._ ;;o

'-"

c 0 ...... .u ...... tl)

0 :::;..

- ,.....; tO u ...... .u ,.... Q)

>

-560.99

-560.99

-560.99

-560.99

-561.00

O.OOE+OO S.OOE+lO I

200 Years 1000 Years TIM (S)

Figure 8: Uplift of Top of Repository Zone

E E

~

..~

,.....;

,...... E

"--'

c: 0

"M .j..J

"M cr. 0

0..

....-! Cll u

"M .j..J ,._. (l!

::>

-560.997

-561.000

-561.002

0. OOE+OO

Position

2.SOE+03 Radius (m)

~

..;:

'-'.:·

Figure 9: Uplift Profile at Repository Level at 1000 Years

~ 0

•-" .u •-" rJJ

Original Position E E

re -561.ooo ........ --1---+---- . L"'\

.-I - co

u •-" .u .... Q)

:> -561.001

-561.002

-561.003

O.OOE+OO 2.50E+03 Radius (m)

Figure 10: Uplift Profile at Repository Level at 1500 Years

-258.995

0 . cc

Original Position

-259.002

O.OOE+OO 2.SOE+03

Radius (m)

Figure 11: Uplift Profile.at Top of Salado at 1000 Years

-258.997

-259.002

O. OOE+OO

Original Position

2.SOE+03 Radius (m)

5 E

N

Figure 12: Uplift Profile at Top of Salado at 1500 Years

-E -c: 0

·r-4

-~ -164.997 ~~ 0

P-<

;=.1

Cll C)

•r-4 ... 1-1 C1J

. co

Original Position

:> -165. 000

-165.002

O.OOE+OO 2.50E+03 Radius (m}

Figure 13: Uplift Profile at Top of Rustler at 1000 Years

-·-4'

c 0 ..... ...,

..... Cll 0

p..

.--i C\l u ..... ..., H

- ClJ ::>

-164.997

-165.002

O.OOE+OO

Original Position

2.50E+03 Radius (m)

E E

Figure 14: Uplift at Top of Rustler at 1500 Years

,..... !: '-'

!: 0 .,., .u .,., Cl)

0 ~

,...; C1l

-CJ .,., .u !-< Q)

:>

:5. ODE-D

2.5DE-O

a.ooE•o

-2. 50E-O

O.OOE+OO

Position

2.50E+03

Radius (m)

Figure 15: Surface Profile at 1000 Years

E !:

..0

r-....

-s '-'

c 0 ...... ..... ...... rD 0

j:l...

,...., co u

...... ..... l-; (!)

>

-2.SDE-0

O. OOE +·oo

Figure 16:

2.SOE+03 Radius (m)

Surface Profile at 1500 Years

s s ,....,

lf"\

1 2 3

Radius (km)

Figure 17. Surface Profiles at Selected Times for 20-Acre 30kW/acre Spent Fuel Repository (Ref. 1)

4