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UNION CARBIDE CORPORATION
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U.S. ATOMIC ENERGY COMMISSION

   

ORNL- TM- 519

COPY NO. - 6‘,

DATE - March 14, 1963

 

MSRE MAINTENANCE PROPOSAL

E. C. Hise

ABSTRACT

It is psoposed that the MSRE primary circuit, cell, and shielding and
containment be so designed as to be adaptable to semi-direct maintenance
for certain suitable operations. »

The requirements for and features of semi-direct maintenance are
given. A tentative procedure for replacement of the special graphite bars
by semi-direct means is given.

NOTICE

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

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LEGAL NOTICE

This report was prepared as an account of Government sponsored work. Neither the United States,

nor the Commission, nor any person acting on behalf of the Commission:

A. Makes any warranty or representation, expressed or implied, with respect to the accuracy,
completeness, or usefulness of the information contained in this report, or that the use of
any informotion, apparctus, method, or process disclosed in this report may not infringe
privately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of
any information, apparatus, method, or process disclosed in this report.

As used in the above, "‘person acting on behalf of the Commission’ includes any employee or

contractor of the Commission, or employee of such contractor, to the extent that such employee

or contractor of the Commission, or employee of such contractor prepares, disseminates, or
provides access to, any information pursuant to his employment or contract with the Commission,

or his employment with such contractor.

 

 
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It is proposed that a semi-direct maintenance system.be.inporporated
in the MSRE design as a parallel to the remote system. The dual method
would provide the operator a-choice of system to be used depending upon
the magnltude and type of .work to be performed and would,provide the safety .
factor of a’ spare.

‘Many small cperatlons, such as visual inspections, retightening bolts,
replacing heaters, checking auxiliary system leaks, and changing over to
spare auxiliary connections of various kinds are well suited to the ssemi-
direct system. Several major operations, such-as the removal and replace-
ment of the pump motor; the pump rotary. element and the special core graphite
bars, appear to be amenable to semi-direct Work. -Other major operations,
such as the removal and replacement of the heat exchanger and core vessel,
would perhaps be best done by a combination of the methods whereby the dls—
connections will be done and the component prepared for lifting by sem1~
direct means and the operation completed by remote means.

The general design reguirements to enable semipdirect mbintenance are:

A modular seal membrane (Fig. 2) which could be removed either as a
unit or in modules,k :

 

A modular lower shield (Fig‘-o 2) which.Could,bewremovgdueithgr'as beams
or in modules. ' ‘ a

Arrangement of the modular shield with respect to reactor. components
to provide maximum accessibility.

 

Arrangement of auxiliary pipingkand\wiring in a few cases to permit lateral
movement of a component in a specifie direction within the cell.

The additional equipment required would be:

A portable work shield (Fig. U4) consisting of horizontal steel or lead
slides roller mounted on tracks and motor driven for remote opening and
closing. -The slides would have vertical holes for windows, .viewing devices,
lights, and tools. The holes would be filled with plugs when not in use.
It would cover the opening left by the- removal of one lower shield module.

 

Qnefor‘se?eral«sma11 shield windows~to*fit:€he holes.

A suitable periscope

 

Simple tools such as long handled wrenches and hooks. Many of these would
be fabricated as mneeded. - .

A generalized but entirely feasible procedure for the removal and replace-
ment of the special graphite bars is presented to illustrate the semi-direct
system. All operations described are with personnel in Zone II and on the
cell shield except where marked.with an *.

1. Remove the upper shield beams (probably two ) necessary to uncover the
-appropriate seal membrane module.
 

o
2. Cutpthe seal weld and remove the membrane module.

 

3. Place the portable shield assembly_over“the.modular shield plug
to be removed. Open the slides so as to clear the plug. Attach the crane
to the plug. . - : ' '

 

%l -Raise-the,shield:plug and close. the slides.

 

5. Install windovs and lights in the portable shield.

6. Insert the appropriate tools and, with dlrect vision through the
windows or perlscope if necessary, dlsconnect the pump power and instrument
leads and the service piping. Remove the rotary element hold down bolts.
‘Withdraw the tools. These can be pulled into plastic bags if necessary.

T .Center the:cranetwith special hook:fiXture over the motor 1lift bail

 

: %8, gpen the portable shleld slides, lower the hook fixture through the
shield; and close the slides.

9. By dlrect observatlon attach the crane to.the‘llft bail. Raise
the rotary element approx1mately 2 1/2 £t to clear. the fixed pump hous1ng
The rotary element will still be well below the. bottom of the portable
shield. ,

 

10. Using the movable . slide, crane,‘and'dlreCt vision, transport the
‘rotary element to a preplaced hook within the. cell ‘hang up the rotary
-element, and dlsengage the crane hook o

-*ll. gpen the slldes remove the hook and close the slides

12. Place a shlelded carrler w1th open tqp and bottom through the portable
shield over the pump bowl. Insert the graphite removal tool through the carrier
and latch it onto a graphite bar. Withdraw the bar into the carrier and '
close the bottom door. = Unlatch the tool, withdraw it from the carrier, and
park it in the.cell. Close the top door of the carrier, withdraw the carrier
into a plastlc bag, and withdraw the shielded and contained bar from the cell.
Repeat for each bar to ‘be removed. Alternatlvelyplt may be more desirable
to have one carrler accommodate all five graphite bars.

 

13, At th1s tlme,'lf it is des1rable, viewing devices can be placed in
the core vessel and the upper and lower plenums, etc -examined.

1L4. . Attach each replacement bar in turn to the insertion tool and place
in. reactor :

15.. Reassemble the.reactor“andnshield with the reverse of steps'léll
above. - . o

A recapitulation of the features-of.the:semirdirect System follows:
1. Access to the primary system for a specific operation requires the

removal of “two upper shield beams, one membrane module, and one lower
shleld.module, and the placement of the portable- shleld
 

 

 

 

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2. .The required air flow is that to maintain a down draft through the
small openings in and around the portable shield and thereby prevent airborn
contamination.

3. Direct vision or optical aids may be used at all times.

4. Multiple "hands" may be used simultaneously.

5. "Feel" is retained by the operater.

6. Access to Zone IT is<assured duringealmost all of the;operationd

7. Maintenance equlpment failure is ea81ly ramedled with the p0581ble'
exception of the coincidental failure of the crane while tranaportzng an
unshielded, radioactive item in Zone 11 which is a- dlfflcult prdblem regardless
of method. : :

8. Special or replacement tooling can usually be fabricated Quiekly

since much of it will be standard wrenches o7 hand tools with -long handles
attached. ‘ -

9. Proper control of air flow and of all items removed from the cell
will prevent: contamlnatlon of Zone II. :

10. Clean up after.an operation requires the replacement;ofvthe lower.‘

‘shield module, removal of the portable shield, rewelding the membrane

module, and replaclng the upper beams

Figure 1 shows the upper shield in 3 l/Z ft wide beams. -The division
of the upper shleldlnto beams of approximately this width is dictated by
the capacity of the building crane. ‘The reinforcement and fastening of these

‘beams would be the same as in the presently contemplated design.

Figure 2 shows the modules for both the seal membrane and the lower
shield. In the case -of the seal membrane,the circumferential weld can be
cut permitting the membrane to be removed as a unit or the peripheral weld
of any 3 1/2 ft x 5 ft module can be cut and the module remowved.

.In the case of ‘the lower shield each 3 1/2 ft wide- beam may be removed
as a unit or any of the 3 1/2 ft x 5 £t modules may be removed 1nd1v1dually

Figure 3 shows how.the seal membrane'modules are welded together and
how clearance for the seal weld lip is provided in the upper shield besms.

‘The steel structure that supports and ties together the lower shield
modules into a beam is shown. '

»Figure.h,is borrowed but illustrates the principle of:d portable
shield having movable slides and access holes.
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