ML19341A654

Forwards Supplementary Info for Proposed Change to Tech Specs Table 6.1 Re 801003 Request for Extension of Fuel Element Core Residence Time Compatibility W/Reactor Core Refueling Intervals

ML19341A654
Person / Time
Site:	Fort Saint Vrain
Issue date:	01/21/1981
From:	Swart F PUBLIC SERVICE CO. OF COLORADO
To:	John Miller, Tokar M Office of Nuclear Reactor Regulation
References
P-81021, NUDOCS 8101270629
Download: ML19341A654 (5)

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'6) 90 sjt11th public servlee company af osado 12015 East 46th Avenue, Suite 440; Denver, CO 80239 January 21, 1981 Fort St. Vrain Unit :lo. 1 P-31021 fir. James R. tiiller, Chief Special Projects Branch Division of Project lianageaant Office of :luclear Reactor Regulation U.S. Iluclear Regulatory Conaission liashington, D.C. 20555 ATTErlTI0ft: Dr. iiichael Tokar Docket 150-257

Subject:

Supplementary Information for Proposed Change to Technical Specification Table 6.1-1

Reference:

(1) PSC Letter 0.R. Lee to J.R. f4111er, P-80203, Dated October 3,1980

Dear Mr.11111er:

As requested in discussions between Dr. iiichael Tokar of the flRC and fir. i4ichael Holmes of PSC, enclosed is supplementary information for our requested change to Table 6.1-1 of the FSV Technical Specifications.

The information relates to PSC's request in Reference (1) for extension -

of the fuel test elements core residence time to be compatible with the present Fort St. Vrain reactor core refueling intervals.

The following attachments are included with this submittal:

Attachment 1 -- tiew Table 6.1-1. This new Table 6.1-1, which is the proposed Technical Specification modification, differs from the previous Table 6.1-1 of Reference (1) only in the units of residenc1 time; these have been changed from equiva-1 lent full power years to equivalent full power days. These new A f units directly correspond to the units used in the safety evaluations which have been performed.

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, c, l l Hr. James R. fiiller January 21, 1981 P-81021 Page 2 Attachment 2 -- Revised Reason for Technical Specification Revision. These revised reasons for the proposed change to Table 6.1-1 more clearly describe the reasons for the FTC core residence times as they are currently specified in Table 6.1-1, and the reasons for changing the existing residence times.

Attachment 3 -- P-78165, dated October 9,1978 P-79025, dated January 25, 1979 These letters, previously submitted to the ilRC, are being enclosed for reference-purposes.

In addition, your attention is directed toward Section 3.5 of the Fort St. Vrain FSAR for a discussion of the reactor core refueling schedule. In Amendment No. 24 to the FSAR, PSC and General Atomic reduced the length of tne first two refueling cycles from annual intervals to semi-annual intervals. The original basis for this reduction has been found to be without merit considering actual plant operating experience (see P-78165 and P-79025). Therefore, PSC has evaluated and authorized the extention of the first two refueling cycles from 150 equivalent full power days to 200 equivalent full power days. However, NRC approval of the proposed change to Technical Specification Table 6.1-1 is also required.

Please let us know if any further supplementary information may be required to support the proposed Fort St. Vrain Technical Specification change.

Very truly yours, 3.: 451), \

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Frederic E. Swart '

Nuclear Project Manager FES/MHH:ler Attachments

TAllLE 6.1-1 11ESCR1rTION OF FORT tlT. VRAlli FUEI. EI.EHElfrS FIE-1 Tilluiticil FrE-H FIE-1 FIE-2 FIE-3 F10-4 FlE-5 FIE-6 01E-7 FIE-fl -

Segment 2 3 4 5 6 7 7 7

Graplitle Type H-451 11-451 H-451 H-451 11-451 11-451 H-451 11-451 Fissi1e Fuel Type UC UC UC,, UC., UC., (lli,U)C (lli,U)C 1R$50 UC}SO 2 2 1R 1R$50 TR150 1RISO 1R150 1RISO IRISO plus test plus test plus test fuel (a) fuel (a) fuel (a)

Fertile Fuel Type Th0 1hD Th0 . lho lho lhC liiC TRI$0 1RI$0 TRI$0 1ho$0 1RI 1RI$0 1RI$0 1RI$0 1RI$0 i

plus BISO plus 0150 plus H150 Hethod of Fuel Rod Curing (h) CIP CIP CIP CIP CIP CIP Cin CIB Residence Tline, Equivalent Full Power Days 200 500 800 1100 1400 1700 1700 1700 (a) Test fuel includes: (Th,U)C 1RISO, 2

08 rods per element CIll 350 rods per element CIP /

UC,01* 1RISO/Th02 B150, 110 0 .o >

g h g**.., % '

UC TRISO/Th0,,TRISO, 176 rods per element CIP fN $ ,

(1h,U)D TRIS 0/1h0 1RISO 2 2 118 rods per element CIT} HEU '(f,b*k

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(b) .ly 'd ~

CIP = cure-in-place fuel rod carbonization; CIR = cure in aluniina bed - reference fSV process;

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CIT = cure-in-tuhe, graphite crucibles, simulating conditions as expertenced in cure-in-place. (6 m '

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r, " i:s r :3 8 d  ;

x and y represent the mean quantilites of carbon and oxygen and do not signify a specific compound. " '

linese values will he explicit in'the final fuel specification. All kernels of tills type are derived from WAR heads.

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.pe Attachment tio. 2 to P-81021 REAS0fi FOR TECHilICAL SPECIFICATI0fl REVISI0tl Technical Specification Table 6.1-1 describes the design features of the eight Fuel Test Elements (FTE's) that were inserted into the Fort St. Vrain reactor core during the first refueling. Tatle 5.1-1 also includes a list of residence times for the FIE's that indicates the amount of time the FTE's are expected to reside in the core. The phasea removal of the FTE's provided for in Table 3.1-1 would allow for the early examination of the FTE irradiated H-451 graphite, prior to H-451 graphite being frradiated in production fuel to comparable levels.

The FTE resident' times in Table 6.1-1 correspond to the original expected Fort St. Vrain reactor core operating ard refueling schedule as described in Section 3.5 of the Fort St. Vrain FSAR. Under the graded fuel cycle used for the Fort St. Vrain co e, about one-sixth of the core will be replaced at each refueling. With the plant operating at rated full power conditions, the first segment was to be replaced after 6 months (150 equivalent full power days) and the second segment was to be replaced after the second six months (an additional 150 equivalent full power days) Subsequent refuelings were to be perfarned annually (after 300 equivalent full power day operating intervals).

Under this refueling schedule the maximum residence time of fuel in the core would be six years (1800 equivalent full power days-EFPD).

This maximum fuel residence time in the rector core is cor.crolled by Technical Specification LOO 4.1.1.

With the FTE's being inserted after the end of the first cycle, the first FTE was expected to be removed after 0.5 years (150 EFPD), the second FTE would be removed after 1.5 years (450 EFPD), and so forth, with the last FTE's being removed after 5.5 years (1650 EFPD).

Actual Fort St. Vrain operations have not taken place at rated full power conditions. Consequently, measuring FTE residence times in terms of calendar years is not appropriate, and changing the measure of residence times to " equivalent full power days" is proposed.

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Further, based on the actual performance of the Fort St. Vrain fuel to date, PSC has evaluated and found that extended operation of the first two reactor core operating cycles from 150 EFPD to 200 EFPD, to obtain additional life from these two cycles, is justified, and this extended operation has no adverse safety impacts on the plant or the public. The phased FTE removal has been retained in the revised residence times to allow for the continued early examination of the H-451 graphite (with 50 EFPD of additional exposure to each FTE).

The length of the first two reactor core operating cycles was reduced via Amendment No. 24 to the Fort St. Vrain FSAR from 300 EFPD for each cycle, to 150 EFPD for each cycle by PSC and the reactor supplier based on a potential concern regarding fuel particle coating integrity.

Certain initial core fuel particles did not fully meet the specification requirements. Based on actual fuel performance during Cycle 1, and on Page 1 i

'r,..

actual fuel performance to date-during Cycle 2, .the: initial concern RT' about this out-of-specification fuel was not warranted. (The last of l4 the out-of-specification fuel will be removed from the reactor core

~during the next refueling). The Fort St. Vrain primary coolant fission-

- product inventory continues to be well below both the Technical Specification limit and'the original expected level (using fuel within specification

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l imi ts) .

Extending the length of Cycle:2 fran 150 EFPD to 200 EFP0 requires an extansion of each FTE residence time shown in Technical Specification Table 5.1-1 by 50 EFPD. The safety significance of these extanded FTE

, residence times has been evaluated in ~ Amendment 3 to General Atomic Document GLP-5494. Per the evaluation in GLP-5494, as amended, the extended core residence times of the eight.FTE's do not significantly affect any accident analysis presented -in the FSAR, and do not involve any increased hazard to the health and safety of either plant personnel or the public. .

N Page 2

Attachment 3 k to P-810?1 s

PC'BLIC SERVICE COMPANY OF COLOFLADO P. C. 40x e40 +

0CNVE2 C 3 f. O M A Q Q 90201 J. K. Ft;Lt.ra Octocer 9, 1978

,,cc ..cu ce Fort St. Vrain Unit No. 1 P-73165 Mr. William Gamill Assistant Director for Advanced Reactors Division of Project Management -

U. S. Nuclear Regulatory Ccemissicn Washingt:n, D.C. 20555 Occket No. 50-257

Subject:

Extension of Cycle 1 Operation Cear Mr. Gamill:

Tne Fort St. Vrain reactor core is designed to operate on a graded fuel cycle and to have about one-sixth of the core removed and replaced at planned annual refueling outages. The fuel is designed to reside in the core for six years at full power.

During the manufacture of the fuel particles for the initial core, some particles were produced which were clearly not capable of residence in the 4

core for a full six years. Accordingly, the initial reactor core was loaded in such a manner so as to assure that those particics would be removed after less than six years exposure. In addition, the first refueling was arbitrarily and conservatively scheduled to take place after six months of equivalent full power operation, (150 EFPD), so that refueling outages could be kept on an annual or semi-annual basis.

Experience to date has indicated that fuel particle performance has been -

much better than originally expected, as indicated by the fission product release to the primary coolant. At the present time, the primary coolant circulating fission product inventory is at least a factor of thirty less than I

the design inventory given in the FSAR and the limit given in Technical Speci-fication LCO 4.2.8. l On the basis of the observed fuel particle performance, operation of Cycle 1 beyond 150 EFPD was considered and found to be acceptable. It was also determined that extension of Cycle 1 operation would not require a Technical Specification change nor did it involve an unreviewed safety question per the guidelines of 10 CFR 50.59.

A recomendation to extend Cycle 1 operation from 150 to 200 EFPD was l submitted to the Nuclear Facility Safety Committee (NFSC) for consideration 7rse 47$ D7

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2 Pusuc S cavicc compamv or CCLORADO bre 10/9/78 P-73165 and was accordingly approved on August 3,1978.

In accordance with the requirements of Technical Specificaticn LCO 4.1.3,.

we have attached an approved revised Base Reactivity Curve for your information.

It snould be noted that the,only. change to the curve has been to extend it from 3.0X100 MWHr to 4.2X100 MWHr to account for the extended operation of Cycle 1 (4.05X106 MWHr is the' equivalent of 200 EFPD).

If there are any questions, please let us knew.

Very truly yours, A

M . K. ruller, Vice President F.gineering and Planning .

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, Attachment 3 to P-81021  !

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M].MZ Y55 p.a.ecx 340 CENvER.COLCFAcc 3 CEC 1 January 25, 1979 Fort St. Vrain Unit No. 1 P-79025 Mr. William P. Gammill Assistant Director for Standardi:aticn and Acvanced Reactors Division of Project Management

• U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Cocket No. #50-257

Subject:

Extensicn of Cycle 2 (Reload 1)

Operation Gen-lemen:

In the ..cnth of March,1979, six of the thirty-seven fuel regions in the Fort St. Vrain (FSV) core will be replaced with fresh fuel elements.

With the exception of eight fuel test elements, the replacament fuel ele-ments are identical to the fuel elements existing in the core, having changes m.ade only in the fuel and burnable poison loadings to satisfy the

. reactivity and pcwer distribution requirements of Cycle 2.

An analysis of the Cycle 2 core was performed to determine if opera-tion of the core could be extended from 150 effective full-power days (EFPD) to 200 EFFD. Results of the analysis indicate that operation of the FSV core for up to 200 EFPD is acceptable, would not involve an un-reviewed safety question per the guicelines of 10CFR 50.59, and would not require a cnange to the FSV Technical Specifications.

A recommendation to extend the Cycle 2 operation from 150 to 200 EFPD _

was subsequently submitted to the FSV Nuclear Facility Safety Committee for consideration and received approval on October 24, 1978.

As required by FSV Technical Specification LC04.1.8, an approved, ,

revised Base Reactivity Curve for the extended Cycle 2 will be forwarded to tne Office of Nuclear Reactor Regulation shortly after the upcoming refueling.

Very truly yours, 9

.K. Fuller, Vice President Engineering and Planning p J F . LP:ler 7 r) *i Ies* ]h o n])'.l]u N M Y[h

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