ML20127P263

Proposed Tech Specs Converting Reactor,Gtrr,From High to low-enriched Uranium,To Improve Upon Present Reactor Performance & Margin of Safety & to Maintain TSs & Operating Procedures of Present HEU Core

ML20127P263
Person / Time
Site:	Neely Research Reactor
Issue date:	01/21/1993
From:	Neely Research Reactor, ATLANTA, GA
To:
Shared Package
ML20127P210	List: ML20127P207 ML20127P263 ML20128A148
References
NUDOCS 9302010226
Download: ML20127P263 (29)

Text

,,. f, ATTACHMENT 2 Changes to Technical Specifications Mandated by the conversion of-the GTRR to Low Enrichment Fuel 9302010226 930121 PDR ADOCK 03000160 l P PDR

p.- .

u Section 1. DEFINITIONS, Pages 1-5.

CHANGES REQUESTED - No changes 1are requested for this section.

Section 2. SAFETY LIMITS AND LIMITING. SAFETY SYSTEM SETTINGS A. Technical Specification .2.1.1.a, page 6, states:

"The reactor shall not exceed the limits.

specified in_ Figure II-l corresponding to values of reactor coolant flow."

REQUESTED CHANGE -

Figure II-1 (old) is replaced by Figure II-l (new)

' based on calculations - made at Argonne National Laboratory and included in Attachment 1.

B. SECOND AND THIRD PARAGRAPHS UNDER BASIS (PAGE

6) STATE:

"The basis - for establishing the safety limits ' on reactor power, coolant flow, and outlet temperature is a thermal hydraulic analysis- to calculate the -

values of-these parameters at which departure from nucleate boiling occurs."

"This analysism establishes that departure from nucleate: boiling =will.not occur.at power. levels up to 11.5 MW with the-coolant outlet temperature and-coolant flow at their respective limiting safety-system settings. The analysis l a -' n o t extended below 760 GPM~because the orifices are'not designed for extremely low flow. "

(1) Letter, R.S. Kirkland to USAEC, June 23, 1972, Enclosure 5.

REQUESTED CHANGE -

l. The - basis for establishing the safety limits : on l

reactor power, coolant flow, and . outlet temperature is thermal hydraulic analysis calculating the values of these parameters at which flow insta-

! bility and departure from nuclecte boiling occur.

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- This L analysisU+2*Lestablishes L that , flow - instability .

will not occur:- atl power Jlevels up' to .10.6;MWfand departure from _ n'icleate s boiling ' will not--- occurlat power levels - up: to -10,8' : MW. ' These results were obtained'.-with thel coolant outlet . temperature 1 - and  :,

-coolant flow at their respective, limiting:. safety ,

system settings.~ Theianalysis.is;not. extended below 760 GPM because- the orificesf are not designed .for -

extremely low flow.-

1. Letter, R. S. KirklandLto USAEC,_ June 23,'1972~,

Enclosuru 5.

la. " Analyses : for _ Conversion ^ ' of the' Georgia Tech .i Research Reactor from HEU to LEU. Fuel."z, TJ. .M.

Matos , . S . C . . Mo , : and W. L. - Woodruf f, f Argonne National Lab., Sept; 1992, Attachment-1. ,

C. SPECIFICATION 2.2.1;'UNDER' BASIS,;PAGE18,1IT'IS; _

STATED:.

"The' trip settings are chosen so that the reactor;isi ,

operated with.no incipient: boiling. (An-. analysis was. ~

made showing that ; at n1800 L gallons nper. minute ;t'otal -

coolantJflow, five Mir thermal power an ' inlet' . reactor' coolant ; temperature of f 114- F. and: the application; of - .

all the' engineering 3 uncertainty" factors, a E maximum' fuel _' surface temperature-8-.F less than theLlocal'.D 20' saturation ternperature might occur M"'

REFERENCE (1) ~ Letter, R.S. - Kirkland .to USAEC, October 22, 1971,:

Response?No. 10. .

REQUESTED CHANGE "The trip settings are chosen-so that the reactor is operated- with. no incipient- ' boiling. .. Analyses incorporating all the1 engineering;uncertaintyLfactors were made at 1800 L gallons -~ per minute , totalE coolant flow, five MW therma 1 ' power and 'an inlet ' reactor-coolant temperature .of(114 F. The results showed' that '

a maximum fuel _ surface! temperature .11 F. less than the local D0 saturation temperature, would- beI obtained"h*) .

REFERENCE (1). Letter, R.S. Kirkland to USAEC, October 22,.1971',

Response No. 10.

la. " Analyses for Conversion of :the Georgia Tech Research' Reactor from HEU to LEU' Fuel..", J.-M.- y Matos , . S . C . .Mo, and W. L. . Woodruf f, _ Argonne ~

National- Lab. , Sept. :1992, Attachment .1.'-

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Section 3. LIMITING CONDITIONS FOR OPERATION,.PAGES_9-27a.

REQUESTED CHANGE -

No changes are requested .for this section.

Section 4. SURVEILLANCE REQUIREMENTS, PAGES_28-36.

REQUESTED CHANGE -

No changes are requested for-this section.

j Section 5. SITE DESCRIPTION -

.No changes are requested for-this section.

l Section 6. ADMINISTRATIVE CONTROLS, PAGES 38-49. i

4 REQUESTED CHANGE -

No changes are requested for this section.

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Attachment y Changes in the Safety: Analysis Report . mandated.

by the' conversion of the GTRR:to Low Enrichment Fuel b

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1. UNDER INTRODUCTION, PAGE 1, SECOND PARAGRAPH, FIRST SENTENCE, IT IS STATED:

"The GTRR is a heavy water cooled and moderated reactor using highly-enriched uranium fuel."

REQUESTED CHANGE -

The GTRR is a heavy water cooled and moderated' reactor ';

using low enrichment uranium fuel. l

2. UNDER

SUMMARY

,- PAGE 2, SECOND PARAGRAPH, FIRST-SENTENCE, IT IS STATED:

I "The GTRR is a heterogeneous, heavy water moderated and cooled reactor, fueled with highly enriched plates of aluminum-uranium alloy."

REQUESTED CHANGE -

The GTRR is a heterogeneous, heavy water moderated and I cooled reactor, fueled with low-enriched plates of l uranium silicide. j

3. UNDER

SUMMARY

, PAGE 2, THIRD PARAGRAPH, 4TH AND STH LINES, IT IS STATED:

"Each assembly contains 16 fuel plates. The total uranium-235 content of a full loading is about 3.2 Kg."

REQUESTED CHANGE -

Each assembly contains eighteen fuel plates. The total uranium 235 of a. full loading is about.4.275 Kg.

4. UNDER REACTOR DESIGN DATA, PAGES 7-10, TABLE 2.1'.

REQUESTED CHANGE -

Replace "old" Table 2.1 with a 'new" Table 2.1, Attachment 3.1.

5. UNDER 4.4.3 FUEL ELEMENTS, PAGE 48, IT IS. STATED:

"The standard fuel element for the GTRR contains- 16 individual curved aluminum-uranium alloy plates. The fuel matrix is 0.020 inches thick, 21/2 inches wide, and-23 1/2 inches long. Each plate-is clad with type 1100-aluminum alloy 0.015 inches thick, 2.848 inches wide, 25 inches long and has a~5 1/2 inch radius- of curvature.

The cladding is applied by the " picture frame" method used in -fabricating the MTR .-fuel. This process. develops a metallurgical bond between the fuel alloy and cladding at all interfaces. Each plate will contain approximately 11.7 grams of U-235."

i: .

REQUESTED CHANGE -

The standard fuel element for the GTRR contains 18'  !

plates.- The fuel matrix is 0.020 individual curved inches thick, U Si, 2 1/2 3

inches wide, and 23 1/2 inches long.

Each plate is clad with type 6061 aluminum alloy 0.015 inches' thick, 2.848 inches: wide, 25' inches long and has )

a 5 1/2 inch radius of curvature.. The cladding is j applied by the " picture frame" method used in fabricating i the MTR fuel. This process develops a metallurgical bond i between the fuel and cladding at all interfaces. Each l plate will contain approximately 12.5 grams of U-235.

I

6. UNDER 4. 4. 3 FUEL ELEMENTS, PAGE 4 8, SECOND PARAGRAPH, ' IT ' l IS STATED: I "The maximum size core is comprised of 304 plates i contained in 19 assemblies (elements) of 16 plates each.

The fuel bearing section of the assemblies- is' a-completely enclosed box 2.959. inches by 2.772 inches by 27 1/2 inches long. Coolant flow passages, nominally 0.106 inches thick by 2.583 inches wide, are'obtained by inserting the edges of the fuel plates into longitudinal slots machined in the side plates. The fuel plates are permanently fastened to the side plates.'"

REQUESTED CHANGE - ,

The maximum size core is comprised of 342 -plates contained in 19 assemblies (elements) of 18 plates each.

The fuel bearing section of the assemblies -is a completely enclosed box 2.959 inches by 2.772 inches-by 27 1/2 inches long. Coolantcflow passages, nominally 0.089 inches thick by 2.583 inches wide, are obtained by inserting the edges of the fuel plates into longitudinal slots machined in the side plates. The fuel plates are permanently fastened to the side plates.

1

7. SECTION 4.4.10, REACTOR PHYSICS, PAGES 89 THROUGH 105.

REQUESTED CHANGE -

Delete' the whole section. The results given in this section no longer apply to the GTRR. The analyses for the conversion reported by ANL ( Attachment 1), supersede these data.

8. UNDER 8.5.1, CLADDING FAILURE, PAGE 154, IT IS STATED:

"The fuel element used in the GTRR is an aluminum-uranium alloy plate, ....

7 REQUESTED CHANGE.~

The-fuel-element used in the.GTRR is~ uranium silicide' plate,- .... <

The:above eight items comprise all the changes' requested for the'SAR. . ,

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Attachment 3.1 (Table 2.'1 Reactor Design-Data) h e- *o

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TABLE 2.1- ,

REACTOR DESIGN DATA - -i Reactor Heterogeneous,.D,0  ;

Type [ moderated and< cooled,2

- low -- enriched ;

Thermal power (Mw) 5' q

Operatino pressure (osia) '15 Feactor Outlet temperature, moderator (*F) 131'.

Active core volume Ift 3) 7.3

-Length (ft --in)L 2-0 Equivalent' diameter 'ft - in) _ 2-4 PowerLdensity,-avct.3je core (kw/1) 24.2 Power density,-average moderator--(kw/1) c32.8 Power density,'averagelcoolant:(kw/1)L

' ~

=173.7

Specific power, average (kw/kg U-235) s 1389-Fuel

'U 2351 content (kg)' U'.Si'-

36 ' .i Cladding Aluminum.

-Volumo_ composition of active core U Si2 2.97-Aluminum-(%) 9.20

- D,0 coolant- 14.00 m D,0 moderator' 74.03-Weicht composition of' active ~ core

-U;.235 fuel (kg) 1 3.6'

'D0 1bs) 422 Alum (!.num 1(1bs ) 107 Fuel' assemblies

Number inEreference design core 16 __

{

coolant ' flow -area per Lassrembly - ( f t*) '0.0302-Total U-235 per-assembly-(grams)- 225-2 Fuel: Dlates Numbersper assembly- .18 . _

. Plate _ width, overall1(in) 2.854'

, Plate-thickness, overall-(in) 0.050 Plate ~ ler.gth, t overall/ (in) -25 Plate -length, fuel :(in) 23.5-

-Facefclad thickness (in) 0.015:

-Edge: clad thicknees (in) -0.204J

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. y

. 1 Shim-safety bladgp.

Number in core 4 Shape. _

-_ Rectangular

-Dimensions ~(in) 5.5 x11 x 45.5 Composition  : Aluminum-clad cadmium -

Reaulatina rod

-Number in core 1-Shape Tubular Dimensions (in) 1.38 I.D. x 1.42

-0.D._x-24 long.

Composition Aluminum-clad cadmium Coolant flow Total flow area in core (f t') 0.'483 Total weight flow entering core (1bs/hr) 998,395 Total volume flow entering-core (gpm) .

1,800~

Inlet velocity, average coolant within assembly (ft/sec) 9.45-Temperatures ( F) ~

Coolant entering core 114 Coolant leaving core 131 Plate surface, average 163-Plate surface, maximum 178 Fuel centerline, average 165; Heat transfer Area in core (fta) 229' Heat flux, average (Btu /f t 2-hr) .

'71,600-Thermal conductivity, U Si2 (Btu /hr-f t- F) 51.99-Thermal conductivity, A11 (Btu /hr-f t-9P) 104 ReactorVessek, Design pressure-(psig)- 9 Design temperature ("F) 150 Diameter 1(nominal outside diameter, ft-in) 6-0 Diameter (maximum at opening, ft-in) 6-6 Height of vessel (ft-in). 10-4.

Wall thickness-(base metal, nominal,rin) 0.375 Composition _

Type 1100 JL1 Design strength at 150 F (psig) 2350 V Tl

., > o: 1 Lower head-Shape- Dished-Thicknese (in) 0.50 Nozzles r Coolant outlet nozzle lo- 10 in Coolant' inlet nozzle 1 - 10-in Liquid level 1 - 3 in

. Experimental facilities 3 - 6-in 8 - 4 in 1 - 2 1/2.in x 5 in (obround) 1 in x 6-in (rectangular)

Over -pressure relief vent 1 - 6 in:

Shim-safety drives 4 - 3 in.

Approximate vessel weight (lbs) 2000-Shieldina Thermal shielding (in) 0.25 boral~plus 3.5 lead Annular concrete shield (ft - in) 4-9 Reactor Containment Buildina Shape . Cylindrical' with .-

torispherical top-- and flat bottom-Shell diameter, inside (ft - in) 82 - 2 Shell composition . ASTM-A201 Grade B:

Shell' thickness (in) . Bottom-and sides 7/16- . .

Top side 1-3/4-Top center 5/8

-Maximum expected pressure (psig) 2.1 Design pressure (psig) 2.0 Safety factor 3 Test pressure (psig) 2.0 Maximum expected temperature at 2.1 psig ( F) 109 Air locks 2 Truck door 1 l'

4 Physics Coolant void coefficient of reactivity, core center -3. 3 x 10-2

% (ak/k)/%_ void Temperature coefficient of reactivity- -0.023

% (ak/k)/*C-Reactivity, cold to hot (%) 0.3 Reactivity, Xe plus Sm (%) -3.8 '

Reactivity, experiments (%) 2.0 Reactivity,.burnup allowance (%) 3,6-Reactivity, control allowance (%) 2.4 Maximum reactivity to be controlled (t) 11.9 Reactivity controllable by 4 shim-safety blades (%) 21-

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1. INTRODUCTION This report has boon prepared for prosontation to the Division of Roactor Licensing of the Atomic Energy Commission in support of an application to amend Fac111 tion Licenso No. R-97 to authorizo operation of the Georgia Toch Rosearch Reactor (GTRR) at a maximum power of 5 mogawatts thermal. Since the issuance on December 29, 1964 of tho licenso authorizing 1 megavatt operation, the GTRR has ,

boon operated in a routino manner, and at present operatos at 1 megawatt on a two-shift, fivo day por wook basis. The. nature of prosent and planned experimental programs at Georgia Tech indicates that throu-shift operation at 5 megawatts is essential tn maximum utilization of the facility.

Tho GTRR is a heavy-water coolod and moderated reactor using low enrichmont uranium fuel. The initial design, very similar to o the MIT and CP-5 reactors, was based on eventual operation at 5 megawatts. Both tho MIT and CP-5 reactors have demonstrated the ,

safety of this basic design in the 5 megawatt power level range.

L Tho operating experiences, and conversion and licensing procedures for 5 megawatt operation of the MIT and CP-5 reactors have boon l studied carefully in planning the conversion of the GTRR.

An analysis of the increased requirements for 5 megawatt operation, and of the performanco of the GTRR systems at 1 megawatt ,

has been the basis for planning the 5 megawatt modifications. The cooling system was redesigned by Southern Nuclear Engineering Corporation personnel involved in the original design. A gravity feed emergency cooling system has been developed to handle increased decay heat. Emergency lighting and communications systems _are being installed. The reactor instrumentation is'being expanded to include full redundancy and a backup system on reactor safety channels. Improved instrument calibration and performance l verification systems and procedures have boon devised. The argon-l 41 release rate already has been significantly reduced,- and will be within presently allowed limits at 5 megawatts. The' basis for conversion decisions, a description of_the modified systems, and __

references to the detailed calculations, experiments, and information sources are given in this report.

I - . _ _ , - , -

2.

SUMMARY

2.1 Gonor.Al The Georgia Toch Rosearch Reactor (GTRR) is located on the campus of the Georgia Institute of Technology, approximately two miles from the contor of downtown Atlanta. The two-acre sito is near one corner of the present campus which extends for soveral thousand foot to the southeast and providos facilitios for a student body in excess of 7000. The campus is surrounded by a residential and commercial area. Approximately 30,000 peoplo live within one mile of the sito.

The GTRR is a hotorogeneous, heavy-water moderated and cooled reactor fuelod with low-onriched plates of uranium silicido. It is' designed to produce a thermal noutron flux of more than 10" n/cm /sec at a power of S Mw and an exit moderator temperaturo of 8

132T. A cutaway perspectivo view of the reactor is shown it.

Figuro 2.1.

The reactor core is approximately 2 foot in diamotor, 2. foot high and, when fully loadef, contains provisions for up to 19 fuel assemblies spaced 6 inchos apart in a triangular array. Each l

assembly contains eightoon fuel plates. The total uranium 235 of a full loading is about 4.275 Kg. The fuel is centrally located in a 6 foot diameter aluminum reactor vessel which provides_a 2 foot thick D,0 reflector completely surrounding the core.

The reactor vessel is mounted on a stool support structure and is suspended within a thick-walled graphite cup. The graphite provides an additional 2 feet of reflector both radially and bonaath the vessel. The coro and reflector system is completely enclosed by the lead and concrete biological shield.

The reactor is controlled by means of four cadmium shim-safety blades and one cadmium regulating rod. The four shim-safety blados are mounted at the top of the reactor vossol and swing downward through the core between adjacent rows _ of fuel assemblies. The regulating rod is supported on the reactor top shield and extends downward into the radial D,0 reflector region. This rod moves -

vortically betwoon the horizontal midplano and the top of the core.

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TABLE __2 1 REACTOR DESIGN DATA Reactor Hotorogeneous, D,0 Type moderated and coolod, low onriched Thermal power (Mwi- 5 Qagrating pressure fosial 15 Hgaetor Outlet tom.pprature, modgrator l'F) 131 Active coro volumo (ft') 7.3 Length (ft - in) 2-0 Equivalent diamator (ft u in) 2-4 Power density, average core (kw/1) 24.2 ,

Power density, average moderator (kw/1) 32.8 Power density, average coolant (kw/1) 173.7 Specific power, averago (kw/kg U-235) 1389 Fuel U3 Si, U-235 content (kg) 3.6 Cladding Aluminum Volume composition of activo core U Si2 -2.97 Aluminum (%) 9.20 D,0 coolant 14.00 D,0 moderator 74.03 Weicht composition of activo core  ;

U-235 fuel (kg) 3.6 D0 lbs) 422=

Alum (inum (1bs) 107 ,

Fuel assemblies Number in referenco design core 16 ,

Coolant flow area per assembly -( f t') 0.0302 Total U-235 por assembly (grams) 225_  ;

Fuel plates Number por assembly _

18' Plate width, overall-(in) 2.854-Plate thickness, overall-(in) 0.050-Plato length, overall (in) 25 Plato length,_ fuel-(in) 23.5'

-Face clad thickness (in) 0.015; Edge clad thickness-(in) 0.204 7-6 p- y -

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,, a Shim-safety blados Number in core 4 Shapo Rectangular Dimonsions (in) 5.5 x 1 x 45.5 Composition Aluminum-clad cadmium Rooulatina rod Number in coro 1 Shapo Tubular i DJmonsions (in) 1.38 I.D. x 1.42 0.D. x 24 long 1 Composition Aluminum-clad cadmium Coolpnt flow Total flow area in core (f t') 0.483 Total weight flow ontoring core (1bs/hr) 998,395 Total volume flow ontoring coro (gpm) 1,800 Inlot velocity, average coolant within assembly (ft/ soc) 9.45 Temperatures f*F) I Coolant ontoring core 114 l ,

Coolant loaving coro 131 Plato surface, average 163 -

Plato surface, maximum 178 Fuel contorlino, averago 165 Heat transfer >

Area in core ( f t') 229 ,

Heat' flux, averago (atu/f t'-hr) 71,600 Thermal conductivity, U S12 (atu/hr-f t *F) 51.99 Thermal conductivity, Al (Btu tr-f t- F) 104 Enoctor vossol Design pressure (psig) 9 Design temperature ( F) 150 Diameter (nominal outsido diameter, ft-in) 6-0 Diamator'(maximum at opening, ft-in) 6-6 Height of vessel (ft-in) . 10-4 Wall thicknosa (base metal, nominal, in) 0.375 Composition Type 1100 Al Design strength at 150"F (psig) 2350

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Lower head Shapo Dished Thickness (in) 0.50 H2zzlos Coolant outlet nozzlo 1 - 10 in Coolant inlot nozzlo 1 - 10 in Liquid lovel 1 - 3 in Experimental facilities 3 - 6 in 8 --4 in 1 - 2 1/2 in x 5 in (obround);

1 - 2 in x 6 in (rectangular)

Over -prosauro relief vont 1 --6 in Shim-safety drives 4 - 3 in Approximate vossol weight (lbs) 2000 Shieldina ,

Thormal shielding (in) 0.25 boral plus 3.5 load-Annular concroto shield (ft - in) 4-9 Enoctor containment Building Shapo Cylindrical with

- torispherical-top and- flat bottom Shell diamotor, inside (ft - in) 82 - 2 Shell composition ASTM-A201 Grado D Shell thickness (jn) Bottom and sides 7/16 Top side 1-3/4 Top conter 5/8-Maximum expected pressuro (psig) 2.1 Designpressuro (psig) 2.0 Safoty factor. 3 Test prosauro (psig) 2.0 Maximum expected temperature at 2.1 psig ("F) 109 Air locks 2' Truck door l' m - w

Physics i

! Coolant void coefficient of roactivity, core contor -3.3 x 108

% (6k/k)/% void -0.023 Temperaturo coefficient of reactivity

% (ak/k)/ C Roactivity, cold to hot (%) 0.3 Reactivity, Xe plus Sm (%) -3.8 Hoactivity, experiments (%) 2.0 Roactivity, burnup allowanco (%) 3.6 Reactivity, control allowanco (t) 2.4 Maximum reactivity to be controlled (%) 11.9 Reactivity controllable by 4 shim-safety blados (%) 21

5 The lower hand of the vossol is dished and is penetrated by the coolant inlet and outlet pipes, moderator overflow and drain lines, and the overpressuto rollof duct. The lower head also contains the core support plate and guido tube assembly upon-which the core is mounted. Those gonoral features are shown in the previously montioned figuros.

4.4.3 Fuel Elements The standard fuel element for the GTRR contains 18 individual curved U3 Si, plates. The fuel matrix is 0.020 inches thick, 2 1/2 inches wide, and 23 1/2 inchos long. -Each plato is clad with type 6061 aluminum alloy 0.015 inches thick, 2.848 inches wide, 25 inches long and has a 5 1/2 inch radius of curvaturo. The cladding is applied by the apicture framo" method used in fabricating - tho MTR fuel. This process develops a metallurgica, sond between the fuel and cladding at all interfaces. Each plato will contain approximately ,

12.5 grams of U-235.

The maximum size core is comprised of 342 plates contained in 19 assemblies (olements) of 18 platos each. Tha fuol bearing section of the assemblies is a completely onclosed box 2.959 inchesL by 2.772 inches by 27 1/2 inches long. Coolant flow passages, nominally.0.089 inches thick by 2.583 inches wide, are obtained by inserting the edges of the fuel plates into longitudinal slots machined in the side plates. The fuel platos are permanently fastened to the side plates.

The fuel section is-equipped with a lower locating end-fitting and an upper box extension piece and mounting flange. Theso" items are attached to the fuel section by inert gas - shielded, electric arc fusion wolds. The mounting flange of the upper box extension piece

~

is bolted to tho underside of the lower top shie1d port' plug which supports the assembly and provides top alignment. The lower locating end-fitting-is inserted in a guide tubo of the core support plate accomplishing bottom alignment. This method insures proper location-of each assembly in the desired lattico position and,-because-of the weight of the supporting - shield plug, provides positive hold down action.against upward coolant flow forces. The standard-GTRR fuel assembly is shown in Figure 4.16.

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Normally, all the f acilities are filled with graphite plugs when not in use. During this time a rupture of both nozzle and thimble would be little worse than rupture of the nozzle alone. However, it is expected that experimental requirements will necessitate the removal of these plugs from time to time. A rupture of both the nozzle and thimble in this situation could produce a substantial reactivity offect. The replacement of void by D,0 has been measured and is 0. 8% for a 6 inch diameter tangent-tube and about 0.34% for a 6 inch diameter beam port. Positive reactivity insertions of.this magnitude are quite capable of being compensated for in an orderly way through temperature and void feedback mechanisms should period and overpower trips fail. They are well below the values for which fuel molting becomes a consideration.

8.5 Relefse of Radjoactivity to Surroundina Area Since relatively large amounts of fission products are associated with an operating reactor, the possibility of escape of these fission products must be considered. The succeeding sections discuss circumstances which could possibly result in release of fission products, and the precautions which have been taken to eliminate or alleviate this hazard, 8.5.1 Claddino Failure The fuel element used in the GTRR is uranium silicide plate, clad with aluminum. Aluminum is highly resistant to corrosion'by low-temperature, high-purity water. Consequently, the clad will, under I

normal circumstances, prevent any corrosion of the fuel bearing part of the plate. However, mechanical damage or corrosion of the cladding can result in exposure of the Al-U allow with subsequent fuel corrosion and some- fission product release to the D,0. Experience has shown that with fuel of this type, the extent'of the corrosion and release will be largely a function of the amount of fuel bearing plate surface which is exposed. The system contamination resulting from a cladding failure will be small and will present little impediment to l reactor operations or hazard to the reactor and environs.

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2.0 SAFETY LIMITS AND LIMITING SAFETY SYSTEN SETTINGS 2.1 SAF_ETY LIMITS 2.1.1 SAFETY _ LIMITS IN THE FORCED CONVECTION MODE APPLICABILITY This specification applies to the interrelated variables associated with core thermal and hydraulic performance in the steady state with forced convection flow. The variables are reactor thermal power, reactor coolant flow, reactor coolant inlet temperature, and the moderator level in the reactor vessel.

OBJECTIVR To maintain the integrity of the fuel element cladding and prevent the release of significant amounts of fission products.

SPECIFICATION

a. The reactor power shall not exceed the limit specified in-Figure II-1 corresponding to values of reactor coolant flow.

b. The reactor coolant-inlet temperature shall not exceed 123'F.

c. The moderator level shall be within 12 inches of overflow.

BASIS Gross fuel element failure and concomitant fission product release will not occur unless there is departure from nucleate boiling. The integrity of the fuel element cladding can be assured by control of the reactor power, the reactor coolant flow rate, and reactor coolant outlet (or inlet) temperature.

The basis for establishing the safety limits on reactor power, coolant flow, and outlet temperature is thermal hydraulic analysis I

calculating the values of these parameters at which flow instability i

and departure:from nucleate. boiling occor.

This analysisO'2*) establishes that flew instability will not occur at power levels up to 10.6 MW and departure from nucleate boiling These results were will not occur obtained with at thepower coolantlevels up totemperature outlet 10.8 MW. . and coolant flow at l their respective limiting safety system settings. -The analysis is not extended below 760 GPM because the orifices are not designed for extremely low flow.

(1) Letter, R. S. Kirkland to USAEC, June 23, 1972, Enclosure 5.

I (la) Analyses for conversion of the Georgia Tech Research Reactor l from HEU to LEU Fuel, J. M.- Matos,-S. C. Mo, and W. L.

Woodruff, Argonne National Laboratory, Sept. 1992.

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Fig.II-l GTRR Safely Limit for Forced Convection 16 . , . . . , , . . . ,

BASES: Moderator Within 12 inches of Overflow Tin - 123*F Max When the Fbw is Minimired '

14 A Power is Maximized: Applicable for Mode 2 Or.ly

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-SAFE OPERATING REGION 6 #

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o G - Nominaloperating j Conditions, Tin - 114'F -

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ModeI m_ Nominal Operating -

Conditions. Tin .114'F 0 ' ' ' ,

500 1000- '1500- ,

_2000' _ 2500; Reactor . Coolant . Flow :(GPM):

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BASIS "The trip settings are chosen so that the reactor is operated with no incipient boiling. Analyses incorporating all the engineering uncertainty factors were made at 1800 gallons per minute total coolant flow, five MW thermal power and an inlet reactor coolant temperature of 114'F. The results showed that a maximum fuel surface .

temperature 11 F less than the local D,O' saturation temperature would be obtained.mg" Operation during the period 1964 to 1973 has demonstrated that a 1000 GPM flow trip setting provides for safe operation of the reactor at power levels less than or equal to one Md. The 1.25 MW power trip setting has been chosen to ensure that no incipient boiling occurs with the reduced coolant flow.

REFERENCE (1) Letter, R. S. Kirkland to USAEC, October 22, 1971, Response No. . -

10.

(la) Analyses for Conversion of the Georgia Tech Research Reactor from IIUE to LEU Fuel, J. M. Matos, S. C. Mo, and W. L. Woodruf f, Argonne Nat'l Lab., Sept., 1992. -

2.2.2 LIMITING SAFETY SYSTEM SETTINGS IN NATURAL CONVECTION MODE APPLICABILITY Applies to the values of safety system settings when operating in the.

natural convection mode.

OBJECTIVE To assure the reactor is not operated at a power level suf ficient to cause fuel damage.

SPECIFICATION The reactor thermal power safety system setting sh'all not exceed'1.1 kW when operating in the natural convection mode.

BASIS In the- natural convection mode of reactor operation the main coolant pumps are not operating. The reactor isolation valves may be closed so that only int;ernal, natural convection-is : available for= cooling.

Experience with the GTRR has shown that- the reactor can be operated at one kW indefinitely without exceeding a bulk reactor temperature of 123 F.

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