ML20214P695

Safety Evaluation Supporting Amend 48 to License DPR-34

ML20214P695
Person / Time
Site:	Fort Saint Vrain
Issue date:	11/25/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20214H091	List: ML20214H088 ML20214P649 ML20214P673 ML20214P695
References
TAC-57625, NUDOCS 8612040312
Download: ML20214P695 (6)

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, (pa at%qk UNITED STATES

g NUCLEAR REGULATORY COMMISSION L ?j WASHINGTON, D. C. 20555

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 48 TO FACILITY OPERATING LICENSE N0. DPR-34 PUBLIC SERVICE COMPANY OF COLORADO FORT ST. VRAIN NUCLEAR GENERATING STATION DOCKET NO. 50-267

1.0 INTRODUCTION

By letter dated June 10, 1985, the Public Service Company of Colorado (the licensee) requested certain changes to the Technical Specifications (TS) for the Fort St. Vrain (FSV) Nuclear Generating Station. One of these changes concerned the addition of a formalized Fuel Surveillance Program. 10 CFR 50, Appendix A, stipulates that the reactor core be designed with appropriate margin to assure that specified acceptable fuel design limits are not exceeded during any condition of normal operation, including the effects of anticipated operational occurrences. The licentee's Fuel Surveillance Program includes the capability to meascre such fuel design limits as fluence, temperatun, and fucl barnup through the use of destructive post irradiation examinations of the fuel  ;

elements. This testing will &llow the' licensee to determire what operating conditions the fuel was expgsad to in the core. The-program is also designed to detect ar# evaluate any significant abnormalities which could have an effect on the structural integrity of the fuel elements. The licensee's proposal is discussed and evaluated below. ,

i 2.0 BACKGROUfiD s The nuclear fuel in the FSV rewtor is in the form of small kernels.

Each fuel kernel is coated with four protective spherical shells designed to prevent-fission product release. The first shell around the fuel kernel is porous carbon. The porosity provides the space for the gaseous fission products. This porous carbon is held in place by a surrounding shell of pyrocarbon. Next is a silicon carbide shell which stops both the gaseous and metallic fission products and prevents them from escaping. Finally, the fourth shell, which is pea

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pyrocarbon, holds the silicon carbide shell in compression and protects the silicon carbide shell from damage during fuel rod fabrication.

These two outer shells form the pressure boundary for the gaseous fission products.

These small, coated fuel kernels are mixed with a graphite pitch in 3- short, rod-shaped molds and sintered to form fuel rods. These fuel rods are then stacked in longitudinal holes in hexagonal, graphite cylinders, which are about 14 inches across the flats and 31 inches 4 -

long. Each fuel rod channel in the cylinder has three equilaterally-spaced coolant channels around it. In some cylinders there are also longitudinal channels filled with boron carbide, which is the

" burnable poison" that compensates for the change in reactivity caused-by the transmutation of nuclear fuel. This fueled, hexagonal, graphite cylinder comprises the Fort St. Vrain fuel element.

This fuel element was designed in the early 1970's and it was extensively tested. However, in order to comply with the NRC requirements contained in 10 CFR 50, Appendix A, the Public Service Company of Colorado (PSC) had to make commitments to the NRC regarding fuel surveillance. At that time, the portion of the U.S.

Atomic Energy Commission which is now the Department of Energy (DOE) had a program that included the surveillance of some of the FSV fuel elements. This was part of DOE's research and development program for High Temperature Gas Cooled Reactors (HTGRs). A consequence of

this DOE program was that PSC's public health and safety commitments to the NRC became mixed with the research and development comitments '

to DOE, As a result, some of PSC's commitments to the NRC involved the use of some DOE funds and equipment. Also, there were only individual ccnnitments; there was no overall fuel surveillance program.

In 1985, PSC incorporated all of its commitments for the l survaillance of FSV fuel into one program and submitted f t to the NRC for approval. The NRC replied with comments and a request for additional information. After incorporating the NRC comments, PSC sut'mitted a revised fuel Surveillance Program (Reference 1). The NRC had the Idaho National Engineering Laboratory (INEL) review this revised Fuel Surveillance Program and report its findings (Reference i 2). INEL's finoings are included as Attachment 1. After reviewing l INEL's findings, the staff requested that PSC further revise their r Fuel Surveillar.ce Progrem ba

ed on these findings. .The following evaluation is based on tnis revised Fuel Surveillance Program (Reference 3).

3.0 EVALUATION l

l PSC's second revision of its Fuel Surveillance Program is included as Attachment 2. The degree to which this revised Fuel Surveillance

. Program incorporate INEL's six findings is described below.

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- INEL recommended that PSC commit to a time duration within which the NRC would be informed of any significant abnormalities. In the revised program, PSC committed to inform the hRC within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of any significant abnormalities identified which could have an effect on the structural integrity of a fuel element.

- INEL recommended oat PSC submit to the NRC a preliminary report on the fuel examinations before returning to power and then issue the final detailed report within 12 months. PSC stated that the Hot Service Facility (where the fuel examinations are performed) has a very limited availability during refueling outages due to its use to perform control rod drive and orifice assembly surveillance activities. Therefore, the detailed fuel examinations may be delayed until after rise to power, in which case a preliminary report could not be prepared. PSC would still notify the NRC of any observed fuel abnormalities within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and prepare the final detailed report within 12 months after withdrawal of the elements from the reactor. The staff has found this acceptable.

- INEL stated that no part of PSC's revised Fuel Surveillance Program should be based on the availability of DOE funding.

PSC's revised Fuel Surveillance Program is not contingent on any DOE funds or equipment that may not be available when needed. Therefore, the commitments made therein are expected to be accomplished regardless of what happens to DOE's HTGR program.

- INEL recommended that PSC provide additional information on fission product releases from stored irradiated fuel to confirm that there is no need.to include this task in the current Fuel Surveillance Program. Due to the low inventory of fission products in the primary coolant dizing cperations, the staff determined that measurement of fission product releases from sto ed irradiated fuel was not necessary.

- INEL recommended that PSC perform the full-13 tasks defined by the original Fuel Perfonnance Progran et the next shutdcwn following detection of circulating activity the.t exceeded twice that expected in FSAR Table L 7-1 (SE60 curies). IriEL recommended that FSV be shut down imediately if the circulating activity exceeds the design basis activity limit of 30900 curies as established by LC0 4.2.8 and that PSC perform the original 13 tasks or propose another program acceptable to the NRC that would determine what caused the high activity.

PSC has stated that a coolant activity level of twice that listed in the FSAR (5260 curies) is still well within the TS limit and that performance of the entire 13 task Fuel Surveillance Program would add nothing to PSC's understanding of the fuel performance. PSC did commit, however, to performing

i asufficientnumberofpost-irradiationinspections(PIES) .

(commencing with the next refueling) to determine the cause of the excess activity levels in the event tnat the circulating activity exceeds the TS limt of 30900 curies. This is acceptable to the staff.

While the Fuel Surveillance Program is designed to provide the first '

detection of an intolerable geometric distortion in the fuel' '

elements, it will not provide the first detection of increased failures of the fuel kernel coatings, i.e., fuel failures.

Increased fuel failures will first be detected by an increase in the radioactivity in the helium coolant,.i.e., the primary coolant activity. There is a TS limit on the FSV primary coolant activity (LCO 4.2.8) which is based on a nonmechanistic assumption that 5% of the fuel kernel coatings fail. This is called the " design" activity level in the Final Safety Analysis Report (FSAR), and it was used for the initial source terms for all of the accident analyses. As described above, this " design" activity level is 30900 curies. If this " design" activity level is ever exceeded, PSC has committed to performing a sufficient number of PIES on fuel elements to determine the cause of the excess activity levels.

There have been three refuelings at FSV. The geometries of all of the fuel elements removed from the core have been found to be within tolerance. However, since the fuel elements are designed to remain in the core for six refuelings (i.e., one sixth of the core is replaced at each refueling), the maximum distortions have probably not been obtained. As described above, PSC has committed to report to the NRC (within 12 months after withdrawal of the elements from tha reactor) any fuel element dimensional changes that may have occurred. Since t the results of the surveillance of the fuel elements removed so far indicate that intolerable gecmetric distortions will be incurred very gradually, we find the 12 month reporting period PSC committed to 1n item 4 of the fuel Surveillance Program to be acceptable.

In Reference 1, PSC committed to putting ite apprcved FSV Fuel Surveillance Program in an appendix to the FSAR and to implementing the program via the PSC Core Management Guides.

The staff finds that the second revision of the FSV Fuel Surveillance Program (Atta hment 2 to this report) is adequate to shev centinued i compliance with NRC regulations and that it thereby protects the health and safety cf the public. We therefore tind this program acceptable, and we recommend that it be promptly implemented at FSV.

4.0 ENVIRONMENTAL CONSIDERATION

The amendneent relates to changes in recordkeeping, reporting or administrative procedures or requirements. The staff has determined that the amendment involves no.significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite and ths:t there is no.significant increase in individual or

cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, this amendment meets the eli for categorical exclusion set forth in 10 CFR 551.22(c)(gibility criteria 10). Pursuant to 10 CFR $51.22(b), no environmental impact statement or. environmental assessment need be prepared in connection with the issuance of this amendment.

5.0 CONCLUSION

We have concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.

Dated: November 25, 1986 Principal Contributors: E. Lantz C. Hinson Attachments: INEL TER Fuel Surveillance Program i

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REFERENCES

1. Letter from 0. R. Lee, PSC, to H. N. Berkow, USNRC, " Fort St. Vrain Fuel Surveillance Program," November 27, 1985.

2. Technical Evaluation Report, EGG-NTA-7247, " Assessment of the Proposed Fuel Surveillance Program for Fort St. Vrain," May 1986.

3. Letter from H. L. Brey, PSC, to H. N. Berkow, USNRC, " Fort St. Vrain Fuel Surveillance Program " May 22, 1986.

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