ORNL-TM-0268.txt

 

 

   

| ORNT,
Pl R T e .
OAK RIDGE |q‘\7[§i"“tJefiijfiggfifiavnfi3152}5?3‘E’

operated by
UNION CARBIDE CORPORATION
for the '
U.S. ATOMIC ENERGY COMMISSION

ORNL- TM- 268

COPY NO. - 4

DATE - July 5, 1962

EXPERIMENTAL 5 Mw THERMAL CONVECTION MOLTEN SALT REACTOR
J. Zasler

Abstract

A preliminary study has been made of an experimental 5 Mw
thermal convection molten salt reactor. This reactor can
be converted, after a veriod of low power operation, to a
50 Mw pilot power plant by adding a fuel pump, a larger
sodium pump, and a turbo generator with associated equip-
ment.

NOTICE

This document contains information of a preliminary nature and was prepored
primarily for internal use ot the Oak Ridge National Laboratory., It is subject
to revision or correction and therefore does not represent g final report. The
information is not to be abstracted, reprinted or otherwise given public dis-
semination without the approval of the ORNL patent branch, Legal and Infor-
mation Cantrol Department,

 
Introduction

Based on the history of other reactor types, the development and demon-
stration of the molten salt power reactor concept will reguire the operation
of a small axperimfintal reactor and a medium sized pilot plant. The simplest
and most reliable experimental reactor system appears to be a thermal convec-
tion reactor. The chief dlsadvantages of the natural convection system - in-
creased fuel volume and larger heat exchangerb are not major factors in a five
Mw reactcr.

By adding a fuel pump to the 5 Mw reactor, it is possible to increase the
capacity of the fuel system from 5 to 50 Mw. This, of course, must be accom-
panied by a corresponding increase in the capacity of the heat dump. It is
thus possible to build one reactor that will serve. successively as a small ex-
perimental reactor and a pilot plent.

fieséription of Reactor

 

Fig. l shows an elevation of the reactor plant; Fig. 2 is a plan view The
dimensions and operating conditions for 5 and 50 Mw operation are given in Table
I. The reactor is five feet in diameter with a 6 inch thick blanket surrounding
the core {see Appendix A). Prcvisions are made to connect the blanket and fuel
regions so that the reactor can be operated as a one reglon reactor.

The 5 Mw reactor is inherently simple anéxrellable aflfi requlres no develop-
ment of componerts. No fuel or blenket pumps are required. The sodium pump is -~
a standard PK pump- : ’

In order to provide for future 50 Mw operation of the system, it is necessary
that the fuel expansion tank be so designed that'a sump type fuel pump can be
installed in it and the sodium lines leading to the heat exchanger be sized to
" handle the flow required for 50 Mw operation.

The 5 Mw reactor, would serve the following purposes:

1. Demonstrate the continuing operation of a molten salt reactor.

2. Provide in-pile corrosicn data. (Thls could be done by inserting removable

- samples in both the het and cold legs.)

5. Develop and demonstrate remote,malntengnce(grocedureso

L. By replacing the air heat dump with a steam heat dump it could be used to
demonstrate sodium to steam heat transfer. ‘

Conversicon to 50 Mw operation

 

Waen the above has been accomplished, the system can be converted to 50
Mw coperation and operated as a pilot power plant. Although this plant would
not be identical to the reference design plant, there would be enough points
of similarity, especially in contrcl, cerrosion, and maintenance problems so
that successful operation would lead directly to the design and comnstruction
of a large power plant.
Conversion to 50 Mw Operation {continued)

The only modification required to the fuel circuit is the installation
of & sump type fuel pump in the fuel expansion tank. The fuel to sodium heat
exchanger designed for the 5 Mw operation would be satisfactory for 50 Mw
operation, because of the reduction in the fuel film resistance in going from
laminar flow at the lower power to turbulent flow at the higher power.

A complete analysis of the blanket circuit has not been made, however,
rough caléulations show the pessibility of &851gning a thermal convection
blanket circuit that could be used at both power levels. If this turns out
to be impracticsel, a blanket pump can be installed for. 50 Mw operation.

The sodium systém is cut at the points shown in Figs. 1 an& 2 and a new
system consisting of a 10,000 gpm pump and sodium to steam heat exchanger is
installed.

A turbo-~generator and asscaaafied equipment is also installed to ccmplete
the pilet plant.

Cost Estimate

Table II shows & rough cost estimate, of approxrmafiely $10 000, 1000 for
the constrtuction of the 5 Mw plant. ‘For approximately $10 000, 000 addltzonal,
this plant could be converted to the 50 Mw - 51ze, as shown in Table 1I1.

No attempt was made in thls llmited study to optimize ezther the 5 or 50
Mw plants.

Further study would undoubtedly be profitable. The 5 ané 5Q. Mw pover
levels wer= chosen arbitrarily and it is quite possible that a differént choice
is preferable. A number of problems remain which were not investigated but
which appear to be cgpable of solution. Among these are: 1) the design of the
blanket c1rcu1t, 2) the method of removing fission gas, 3) the design of the
5 Mw heat dump, and 4) the design of the steam system. 7

Acknowledgements

 

Acknowledgement ‘iz made to L. G. Alexander for sélecting the Uranium con~-
centration and core size and to G. D. Whitman and M. E, Lackey for consultation
on the cost estimate and heat transfer, respectively.
Table I

Power Output Mw {thermal}. 5,19 50 Mw
Reactor
Core Size ft
Blanket Thickness £t | 1/2
Power Density watts/cc 1.5 15
Fuel Pump none Sump type
Riser and Downcomer Dia. in 10"
Height of Fuel Heat Exchanger
{above reactor centerline) £t 20
Fuel Velocity in Riser  ft/sec .64 6.17
Fuel Head ft . 39 12.66
Fuel Volume £t5 " 120
Fuel Flow gal/min- 158 1515
Sodium Flow gal/min 578 9250
Sodium Pump PK
Heat Exchanger
Tube I.D. in .6
Tube Wall Thickness in 050
Tube Length ' ft 20
No. of Tubes 250
Shell C. Dia. in 18
Shell Wall Thickness in . 375
Fuel Temp. in OF 1210 1210
Fuel Temp. out Op 1010 1010
Na Temp. in : op 850 850
Na Temp. out OF 1100 10C0
D.

Table 1T

Cost Estimate ~ 5 Mw Experimentsal Reactor

Engineering, Design and Inspection
Construction Costs -
1. Land and Land Rights
2. Improvement and Land
3. Buildings ~
Reactor Plant and Auxiliary
Reactor Structure
(containment and shielding)
Instruments and Control
Reactor System
Fuel
Blanket
Bodium
Maintenance
Auxiliaries
Inventories
Building
Sub~Total
Heat Removal
Contingency st 10%

Total

$ 800,000
500,000
480,000
480,000

60,000
162,000
500,000
200,000
416,000

2,000,000

g 3,000,000

750,000

5,118,000
500,000
1,000,000

 

g10, 368,000
2

& & ° <o

OO O~ OV £

ot

¢

Teble 111

Additional Cost to Convert to 50 MH‘

Fuel Pump

Blanket Pump

Na Pump

Blanket Na Pump

Additional Instrumentation
Steam and Electrical System
Spare Parts.

Installation

Engineering

Contingency

TOTAL

g 500,000

100,000
200,000

50,000
500,000

4,000,000

500,000

2,000,000
1,000,000

99,950,000
Appendix A
Selection of Uranium Concentration and Core Size

The design variables'in the Referenée Design Reactor, described in refer-
ence 1, which it is desirable to match in a test reactor are, in order of their
importance:

power density in fuel,

. heat flux and delta T in exchanger,
uranium concentration,

raedigtion level at pump,

. power density in core vessel, and

~ thorium concentration.

O i o

The design of the test reactor will require a compromise among these variables.
It seems desirable to sacrifice thorium concentration first. Using RDR-1 data
for a basis, an eight foot core with 1% ThFj will go critical at a U-235 con-
centration of 12.5 X 1019 atoms/cco This concentration will render a .five foot
core critical when no thorlum is present, and the critical mass will be about

85 kg. A concentration of 36 x 1019 atoms/cc would make a four foot core criti-
cal, with a critical mass of about 150 kg.

A blanket three to six inches thick should suffice to test the reliability
of the core vessel. In the case of a six inch blank@t on a five foot core, if
the core vessel failed and the system were operated as a one region reactor, the
critical concentration would fall to sbout 4 x 1019, and the critical mass
would be sbout 50 kg. Adding about 5/8 mole per cent thorium would raise the
critical- concentratlon back to 12 x 1019, and the critical mess to 140 kg.
References
1. "Molten Salt Reactor Program"; Status Report, ORNL 58-5-3

2. F. E. Romie and B. W. Kinyon, "A Molten Salt Natural Convection Reactor
System", ORNL 58-2-46

- -
 

 

 

 

UNCLASSIFIED
PHOTO 31645

 

 

 

 

 

 

 

 

 

 

 

X

 

 

 

 

 

 

 

 

 

  

 

 

Ty

Y

e ——"

gy

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TURBO-GENERATOR ROOM
{for fulure axpansion)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   
 

 

 

 

  

 

¥

 

Tt G tue e oL
2ttt ® T

T R

AN < N

FIG.I ELEVATION OF 5MW EXPERIMENTAL MOLTEN SALT REACTOR PLANT

 

. & LI . - " * - - ® _"' - - - - . - “‘. . 4 - - " - oa R
a> e 2 ey . A e “ v m a e a w .,y
W A R NP NI I e 7 NN
UNCILASSIFIED
PHOTO 31646

 

 

 

FUEL TO SODIUM
HEAT EXCHANGER

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TURBO-GENERATOR ROOM
{for future expansion)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 5 0
{1y ;Et]gf;ia [ihde]
SCALE-FEET

84

 

 

 

 

 

 

143 FT.

FIG.O PLAN VIEW OF 5MW EXPERIMENTAL MOLTEN SALT REACTOR PLANT

FT.

_0‘[_.
-&"

1-3.
b,

wld-

Distribution

DTIE, AEC
M. J. Skinner