ML20140H250

Discusses Re Proposed Change 1 to TS, License DR-15 for SEFOR Reactor.Change Would Permit Use of New Thermocouples Installed in Nickel Reflector Segments or Existing Thermocouples in Aluminum Guide Structure

ML20140H250
Person / Time
Site:	05000231
Issue date:	06/05/1970
From:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
To:	Cohen K GENERAL ELECTRIC CO.
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References
FOIA-97-34 NUDOCS 9705130027
Download: ML20140H250 (6)

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\

DISTRIBUTION

" W;:Dooly, DR i , R. Engelken, CO (2)

H K. Shapar, OGC N. Dube, DRL (5)

,JUN 5 1970 J. Buchanan, ORNL H. McAlduff, OR00 W. B. Kenna, NMS Docke't' No. 50-231 .

T. Laughlin, DTIE PDR

/ Dock't e File DRL Reading l

General Electric Conapany DR Reading 310 DeGuigne Drive Branch Reading Sunnyvale, California 94086 D. J. Skovholt R. Boyd Attention: R. DeYoung Dr. Karl Cohen, General Manager ACRS (3)

Breeder Reactor Development Operation F. Schroeder, R. Woodru E. Fleury, S. Teets Centleenen:

R. Vollmer R. Schemel

~ By letter dated April 17, 1970, you proposed Change No. I to the Techni-cal Specifications appended to License No. DR-15 for the SEFOR reactor.

The proposed change would permit use of new thermocouples installed in the nickel reflector segments or use of existir.g thermocouples in the surrounding aluminum guide structure for monitoring the temperature in i

the guide structure and providing input signals to the safety system.

Mr. Meyer and Mr. Russel of your staff have agreed to clarify the pro-posed change by stating in'the Technical Specifications the requirement for connecting a thermocouple in each reflector segment bay to the safety system.

Pursuant to Section 50.59 of 10 CPR Part 50, we have considered the effect of the proposed change on the margin of safety associated with possible guide structure damage and have concluded that the proposed change does not present significant hasards considerations not described or implicit in the Final Safeguards Report as amended, and that there is reasonable assurance that the health and safety of the public will not be endangered.

Accordingly, the Technical Specifications appended to License No. DR-15 are hereby changed as indicated in Attachment A to this letter which con-tains replacement pages 2.2 2 through 2.2-5.

Sincerely, Original Signed by ME6N0f!N <

Peter A. Morris, Director Division of Reactor Licensing) l

Enclosure:

v'g Attachment A . Changes to Technical Specifications O m.3h 4 / /// 7e

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.- J ATTACit(ENT A 1

REVISED PAGES FOR THE i

i SEFOR TEQiNICAL SPECIFICATI0 TIS l I

CHANGE NO. 1 i

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TABLE 2.2-1

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! SCRAM FUNCTION i

i q FUNCTIOR SAFETY SYSTEM SETTINGS i<

i High Flux, =

105% of Rated Flux l Wide gange Monit.or #

1 4

Loir Level, =

4 inches below lip of operating Reactor godium 4 level overfloor pipe High Temperature, =

900*F Core Outlet. Upper gegion <

l Low Flow, =

20% beloir the operating floor set j Main Primary 4 point *

! High Tegerature =

350*F for themmocouples on the

! Reflector Regiea** 4 reflector guide structure inner j

diameter and radial web.

i 4

= 275'F for themmocouples en the

" < reflector guide structure, outer

! dimoster.

1 = 450*F for therusseouples in the ' l l 4,

]

Imr end of the reflector ses- l enents.

1 -

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! *The operating fleer set points shall be specified in written procedsres.

• • At least ten therunocouples shall be connected in the safety system, locluding at least see in each reR ectar boy.

2.2-2 Chemes me. 1 JUN 5 1970

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gases l- The limiting safety system setting (LSSS) of 105% of rated flux provides i a 5% margin below the* safety limit of 110%. This will assure protection

! of the safety limit for normal reactor operation. The actual safety

{ system setting will generally be less than 105% of rated flux since a

large percentage of the plant operating time will be spent at power levels below 20Beit where the trip setting would normally be reduced a corre-

! spending amoimt (Only a limited number of esperiments will be conducted j at rated flux.)

l The Lags for reactor vessel sodium level provides assurance of reactor l scram in the event that reactor cooling capability should be jeopardised d

because of a leak in the coolant system and consequent loss of sodium from the reactor vessel. Normal operation of the pusp-around loop and overflow nossle in the vessel will maintain the soditma at a constant level in the i vessel. A loss of about 15 gallons of sodies from the reactor vessel will

! cause the level to fall below the level trip probe and scram the reactor.

l The level trip probes are tuo inches below the overflow nossle, providing j margin with respect to the LSS8 of four inches. j 4

i l The core outlet sodium high temperature trip at 900*F provides a 150 F

! margin to prevent the sodiesa t prature from reaching the safety limit.

Analyses presented in the FDBAR / show that the coolant temperature will l not approach the safety limit for accident conditions except for extreme a

assumptions involving failure to scram or failure of both main primary pommy flywheels.

The law flow trip for the main primary coolant system provides assurance

that the coolant temperature will not approach the safety 11anit due to

{

1ess of coolant flow. If the main primary coolant flaw rate decreased to 80% of the ser point value, the temperature rise across the vessel usuld increase iv,s than 25% (to a vessel outlet temperature of 830*F) before the safety system would receive the scram signal and shut down the reactor. i Thus, the low flew trip provides the earliest trip in the event of sudden reduction in coolant flow.

Adequate cooling of the reflector guide structure, segments, and neutron flux saanitors, is required to assure operability of the reflectors and the neutron monitors. Thermocouples installed in the reflector guide struc- ~

ture and segments are maattered by the safety system to provide this assurance. The guids structure temperatures at the posittees monitored are predicted to renam in value from 200*F to 250*F with all reflector segments raised med a reactor power lovel of 20 left. The variations espond en whether the thermocospies are loested is the immer or outer 2.2 3 Change No. 1 JUN 5 1974

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! . web of the giaide structure. If one segument is lowered, the guide struc- -

! .,ture temperature levels in that region will increase by about 25'F. The j ' actual trip level used for t.5e safety systems will be set a mariness of ~

] 135'F above~the temperature readings observed at power for therunocouples on the inner diameter and radial web, and 80*F above the readings for I

thermocouples on the outer diameter of the guide structure. If the j eperating temperatures in the reflector region were to increase by these

! sanoonts (135'F or 80*F), a cooling flow reduction of less than 50% would j be implied.

l-l Calculations have been made to show that stresses and deflections due i to therust distortion and mechanical tolerances are acceptable for the I

'! design condition. (3) Extrapolation of these calculations shows 'that I i these stresses and deflections are also seceptable for conditions corre-l spending to a cooling flow reduction of 50%. At 50% coolant flow, the i relative expansion between the reflector segument and guide structure i would cause less than 60 mils compression of the T-pad spring in the

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1 segument, which is well within the demonstrated capability of the system. g -

4 The limiting safety system settinas of 350*F for thennoceuples en the inner I i diameter and 275'F for thennocopples on the outer diameter may be more j restrictive for operation at rated power than the values described above.

1 _ The values are also safely below the temperature (400*F)ist which the prop- l l erties of the aluminum used in the guide structure begin to change j significantly.

1

~

l Thermocouples installed in the ref1,ector segments can also be anonitored by

the safety systesa to provide assurance of proper cooling. The temperature

of each segment thermocotyle is espected to be 340*F at 20 m, based on j the marimmt predicted heat generation in the reflector and guide structure.

i If the tempesuture at 20 m is louer .than 340*F due to lauer best generatica 1 rates, the safety system trip level 0111 he w.. ; M agly reduced to keep i the trip level no more than 110*F above the actust 20 W eperating temper.

store so that a safety system trip will occur if cooling flew is reduced l

e to about 60% of the aorusal value.

l l If the segment temperature at the themmecouple leesttom inessesed to the j Lggs of 450*F, the ==wi- aluminia guide structure temperature would be i aheet 300 to 315'F ukich is well below the temperature (about 400*F) at i which the properties of alumines used in the guide structure begin to

! ahange significantly. _

i 2.2-4 Change No. 1 JUN 5 1970 j

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i The ten reflector region thermocouples used by the safety system can be j

i chosen from any of the applicable thermocogles listed in Table 2.2 1, j

' 'since a different trip level can be set for each thermocongle. The choice of the ten thermocouples to be used for the safety system will be

'made so as to monitor tangeratures in sach of the ten reflector bays.

A safety system trip at 50% to 60% of the normal coolant flow rate also provides assurance that the temperature of the neutron monitors will j

remain below the manufacturer's certified operating temperature of 300*F.

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! Refarences i

(1) GEAP 5576, " Final Specification for the SEFOR Esperimental Program",

Jaumary, 1968.

(2) SEFOR FDSAR, Volume II, Section 16.3,; pp 16-10, ff.

] (3) SEFOR FDSAR, Supplement 11 Appendix A and B. I l

f (4) SEFOR FDSAR, Suppleasant 11, p 7-20.

l 1 (5) SEFOR FDSAR, Supplement 17, y G-5. ~

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1 i 2. M Chan'ge No. 1  !

JW 5 1970

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. UNITED STATES i 1

. ATOMIC ENERGY COMMISSION

'* 4, . 9- '* u. WAS.WNGTON, D.C. 20545

, . June 5,.1970 j

Docket-No. 50-231 .

1

,e General Electric Company i 310 DeGuigne Drive '

Sunnyvale, California 94086 '

Astention: Dr. Karl Cohen, General Manager. Change No. 1 Breeder Reactor Development Operation License No. DR-15 Gentlemen:

By letter dated April 17, 1970, you proposed Change No. I to the Techni- -

cal Specifications appended to License No. DR-15 for the SEFOR' reactor, i The proposed change would permit use of new theruocouples installed in j the nickel reflector segments or use of existing thermoccuples in the

! surrounding aluminum guide structure for monitoring,the temperature in the guide structure and providing input signals to the safety system.

Mr. Meyer and Mr. Russel of your staff have agreed to clarify. the pro- '

posed change by stating in the Technical Specifications-the requirement l for connecting a thermocouple in each reflector segment bay to the

safety system.

Pursuant to Section 50.59 of 10 CFR Part 50, we have considered the effect i

of the proposed change on the margin of safety associated with possible guide structure damage and have concluded that the proposed change does

! not present significant hazards considerations not described or implicit l in the Final Safeguards Report, as amended, and that there is reasonable assurance that the health and safety of the public will not be endangered.

l Accordingly, the Technical Specifications appended to License No. DR-15 are hereby changed as indicated in Attachment A to this letter which con-  ;

tains replacement pages 2.2-2 throush 2.2-5. '

i Sincerely, l

l l Peter A. Morris, Director Division of Reactor Licensing

Enclosure:

! Attachment A - Changes to Technical Specifications i

i

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ATTAC9 TENT A 1

REVISED PAGES FOR THE i i

SEFOR TECHNICAL SPECIFICATIONS i

CHANGE NO. 1 l

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. ThBLE 2.2-1 >

SCRAM FUNCTION 1

FUNCTION SAFETY SYSTEM SETTINGS ,

High Flux, = 105% of Rated Flux Wide Range Monitor '

Low Level,- = 4 inches below lip of operating Reactor Sodium d' level overflow pipe High Temperature, = 900 F Core Outlet-Upper Region #'

Lsw Flow, = 20% below the operating flow set Main Primary #'

point *

, High Temperature = 350 F for thermocouples on the Reflector Region ** A- reflector guide structure inner l

i diameter and radial web.

7, 275 F for thermocouples on the reflector guide structure, outer diameter.

~

450 F for thermocouples in the 7 lower end of the reflector seg-1 l

ments.

• The operating flow set points shall be specified in written procedures, l **At least ten thermocouples shall be connected in l the safety system, including at least one in each

reflectof bay.

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l 2.2-2

' Change No. 1 June 5, 1970 l

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l Bases .

l The limit 1ng safety system setting (LSSS) of 105% of rated flux provides a 5% margin bplow the safety limit of 110%. This will assure protection of the safety limit for normal reactor operation. The actual safety l system setting will generally be less than 105% of rated flux since a '

large percentage of the plant operating time will be spent at power levels below 20MWt where the trip setting would normally be reduced a corre-sponding amount )(Daly a limited number of experiments will be conducted at rated flux.)

The LSSS for reactor vessel sodium level provides assurance of reactor scram in the event that reactor cooling capability should be jeopardized because of a leak in the coolant system and consequent loss of sodium from the reactor vessel. Normal operation of the pump-around loop and overflow nozzle in the vessel will maintain the sodium at a constant level in the vessel. A loss of about 15 gallons of sodium from the reactor vessel will cause the level to fall below the level trip probe and scram the reactor.

The level trip probes are two inches below the overflow nozzle, providing j margin with respect to the LSSS of four inches. i The core outlet sodium high temperature trip at 900 F provides a 150 F margin to prevent the sodium te g rature from reaching the safety limit.

Analyses presented in the FDSAR show that the coolant temperature will not approach the safety limit for accident conditions except for extreme assumptions involving failure to scram or failure of both main primary pump flywheels.

The low flow trip for the main primary coolant system provides assurance that the coolant temperature will not approach the safety limit due to loss of coolant flow. If the main primary coolant flow rate decreased to 80% of the set point value, the temperature rise across the vessel would increase less than 25% (to a vessel outlet temperature of 830 F) before the safety system would receive the scram signal and shut down the reactor.

Thus, the low flow trip provides the earliest trip in the event of sudden reduction in coolant flow.

Adequate cooling of the reflector guide structure, segments, and neutron flux monitors, is required to assure operability of the reflectors and the neutron monitors. Thermocouples installed in the reflector guide struc ~

ture and segmeats are monitored by the safety system to provide this assurance. The guide structure temperatures at the positions, monitored are predicted co range in value from 200 F to 2500F with all reflector _

segments raised and a reactor power level of 20 MWt. The variations l

depend on wheti;er che thermocouples are located in the inner or cuter 2.2-3 Change No. 1 June 5,1970

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. web -of the guide structure. If one segment is lowered, the guide struc-~

. ture temperature levels in that region will inc.rer se by about 25 F. The_

actual trip level use-d for the safety system will be set a maximum of

'1350F above the temperature readings observed at power for thermacouples on the inner diameter and radial web, and 80 F above the readings for

! thermocouples on the outer diameter of the guide structure. If the operating temperatures in the reflector region were to increase by these o

amounts (1350F or 80 F), a cooling flow reduction of less than 50% would be implied.

~

! Calculations have been made to show that stresses and deflections due i to thermal distortion and mechanical tolerances are acceptable for the i

design condition. (3) Extrapolation of these calculations shows that  !

these stresses and deflections are also acceptable for conditions corre- I l sponding to a cooling flow reduction of 50%. At 50% coolant flow, the 1 l relative expansion between the reflector segment and guide structure would cause less than 60 mils compression of the T-pad spring in the segment, which is well within the demonstrated capability of the system. 4)_

i The limiting safety system settings of 350 F for.thermocouples on the inner l diameter and 275 F for thermocouples on the outer diameter may be more i

restrictive for operation at rated power than the values described above.

The values are also sa' ly below the temperature (400 F) at which the prop-

! erties of the aluminum aand in the guide structure begin to change significantly.

Thermocouples installed in the reflector segments can also be monitored by )

the safety system to provide assurance of proper cooling. The temperature 1 of each segment thermocouple is expected to be 3400F at 20 MW, based on the maximum predicted heat generation in the reflector and guide structure. ]

If the temperature at 20 MW is lower than 340 F due to lower heat generation j rates, the safety system trip level will be correspondingly reduced to keep the trip level no more than 110 F0 above the actual 20 MW operating temper-ature so that a safety system trip will occur if cooling flow is reduced to about 60% of the normal value.

If the segment temperature at the thenmocouple location increased to the LSSS of 450 F, the maximum aluminim guide structure temperature would be about 300 to 3150F, which is well below the temperature (about 4000F) at which the properties of aluminum used in the guide structure begin to change significantly. _

2.2-4

Change No. 1 l

June 5, 1970 l

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The'. ten reflector region thermocouples used by the safety. system can be -

. phosen from' any of the applicable thermocouples listed in Table 2.2-1, )

'ince a different trip level can be set for each thermocouple. The s

• hoice c of the ten thermocouples to be used for the safety system will be i

made.so as to monitor temperatures in each of the ten reflector bays.

1 A safety system trip.at 50% to 60% of the normal coolant flow rate also I l provides assurance that the. temperature of the neutron monitors will l

remain below the manufacturer's certified operating temperature of 300 F. .

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References

( (1) GEAP 5576, " Final Specification for the SEFOR Experimental Program",

l January, 1968.

(2) SEFOR FDSAR, Volume II, Section 16.3, pp 16-10, ff.  !

l (3) SEFOR FDSAR, Supplement 11, Appendix A and B. -

(4) SEFOR FDSAR, Supplement 11, p 7-20.

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]- (5) SEFOR FDSAR, Supplement 17, p G-5. -

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i 2.2-5 Change No. 1 June 5, 1970 L __ ._. _ - _ . _ . _ . . _ .-. -

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