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Werner. Lute, editor

COMPUTATIONS

OF TEMPERATURE PROFILES IN THE MEDIUM/LOWaLEVEL

WASTE CEMENT AND IN THE ROCK SALT SURROUNDING THE DISPOSAL CAVERN W. HAUSER, E. SMAILOS, R. KOSTER Kernforschungszentrum Karlsruhe GmbH., Institut fQr Nukleare Entsorgungstechnik, Postfach 3640, D-7500 Karlsruhe, Federal Republic of Germany

INTRODUCTION Prior to disposal of cemented medium level waste and low level waste in large caverns 1000 m below ground it is important to 1.

know what temperatures will be caused by heat generation in waste product.

the

During the disposal period the heat produced by hy-

dration of the cement used as the binder as well as by decaying radionuclides in ratures in

the waste may give rise to inadmissibly high tempea deterioration of the

the waste product resulting in

produc:t qualities.

To avoid such undesirable processes,

permissible product temperature vestigations,

i.e.

of 90°C was specified

significantly below the

a temperature that is

boiling point of the water contained in

a maximum

for the in-

the cemented product.

Earlier investigations have shown that temperatures occur in the salt cavern during disposal and fixation of a cemented waste suspension which are well above this maximum acceptable temperature.

The fixation of the liquid wastes in

release their heat of hydration already

posal of a granule/grout product results in setting in

cement granules which

above ground,

and the dis-

temperatures during

the cavern which are significantly below 900 C /i/.

This has been terature data,

shown by one-dimensional

calculations,

based on li-

for the hydration heat of the cements used.

In the investigations discussed in this paper, a three-dimensional computer program was employed using experimentally determined data on the heat generation of the granule/grout product. tion,

this made it

the waste product as well as in 2.

In

addi-

possible to calculate temperature profiles in the surrounding rock salt.

DESCRIPTION OF THE MODEL OF CALCULATION

2.1 HEAT SOURCES IN THE IN-SITU WASTE PRODUCT For calculating the temperatures in

the cavern and in

the sur-

860 rounding

source sides heat

rock which undergo

salt

dependent

heat power

to be

taken

into

the decay heat of hydration

was determined

account in

time,

the computation

of radionuclides

resulting

by

with

variations

the time

of the waste product must be known.

contained in

from cement setting.

calorimetric

measurements

model is,

be-

the waste,

This

made

The heat

the

variable

on an in-situ

re-

ference product. The investigations

have

the development with bed mathematically teristic the

time

in

that

in

decay

Q0.

heat power

the process heat 0(t)

of the hydration

good approximation

of radioactive initial

revealed

such as

Accordingly

of setting

can be

by the parameters

the decay

constant

descricharac-

A and

the following equation

app-

lies:

(t) Fig. in-situ

1 shows

=

Qo

exp

(-A't)

the development with time

waste product /2/

made

of the heat power. of t