ML19310A200
| ML19310A200 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 05/28/1980 |
| From: | Swart F PUBLIC SERVICE CO. OF COLORADO |
| To: | Gammill W Office of Nuclear Reactor Regulation |
| References | |
| P-80120, NUDOCS 8006060266 | |
| Download: ML19310A200 (5) | |
Text
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puhuc service company "I cenende 12015 East 46th Avenue, Suite 440; Denver, CO 80239 l
May 28, 1980 Fort St. Vrain Unit No. 1 P-80120 Mr. William P. Gammill Assistant Director for Standardization and Advanced Reactors Division of Project Management U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Docket #50-267
Subject:
Supporting Documentation for Change to DF 6.1 j
References:
- 1) PSC Letter 0.R. Lee to W.P. Gammill, P-80003, dated January 11, 1980
- 2) PSC Letter D. Warembourg to W.P. Gammill, P-80020, dated February 8, 1980
Dear Mr. Gammill:
Enclosed is additional information supporting our requested change to Fort St. Vrain Technical Specification DF 6.1 concerning the fissile fuel Thorium / Uranium ratio.
The enclosure presents data demonstrating the effects of kernel burnup on TRISO dicarbide fuel performance under simulated core heatup conditions. This infonnation has been requested by NRC's Mr. Mike Tokar for use in completing his review c' PSC's Reference 1 submittal.
If you have any further questions, please contact Mr. J.R. Johns (303)571-6133.
f Very truly yours, a
i /sw Frederic E. Swart Nuclear Project Manager FES/JRJ:pa Enclosure 8006060 % 'f
Burnup Dependence of FSV Fissile Fuel Performance Under Simulated Accident Conditions i
Introduction / Conclusion The following is a presentation of data that demonstrste possible effects of kernal burnup on FSV fissile fuel (TRISO (Th/U)C ) perf rmance under simulated 2
accident (core heatup) conditions.
In summary, comparisons of TRISO UC2 and TRISO (Th/U)C2 cast data show that TRISO dicarbide fuel performance is not a function of kernal burnup for core heatup conditions.
i Discussion HIGR fuel performance under. hypothetical accident conditions is being studied in a continuing series of core heatup simulation tests (CEST) being conducted under the DOE sponsored HTGR Generic Technology Program.
The CHSTs are conducted by heating irradiated fuel particles from approx.1:>.00 to approx. 25000C using heat-ing rates that range from 20 to 2000C/h.
Fuel performance is evaluated from fission product release data (Kr85, Cs137, Cel44, Rul06) collected during each CEST.
Since significant release is generally not observed until test temperatures exceed 20000C, the Kr85 release fraction is assumed equal to the total coating failure fraction.
4 One FSV TRISO (Th/U)C., (18.2% FIMA) and several 1HIGR TRISO UC., (6 to 70% FIMA) fissile fuel samples Have been used for testing. While a direct demonstration of the relationship between TRISO (Th/U)C2 fuel performance and kernel burnup is not possible, comparisons of TRISO UC and TRISO (Th/U)C test results can be 2
2 used to evaluate the burnup dependence of TRISO dicarbide fuels.
TRISO UC fuels irradiated to kernal burnups ranging from 6 to 70% FIMA have 2
been used for CHSTs.
The nominal heating rates for these tests have been 20, 0
50 or 185 C/h.
Results have shown that Kr85 release fractions at any given temperature (1) tend to increase as the heating rate decreases and (2) are in-dependent of kernel burnup.
These observations are illustrated on Fig. 1, which shows Kr85 release. fractions determined as a function of temperature for several TRISO UC2 samples.
Krypton 85 release fractions for samples tested at heating rates of approx. 500C/h (solid points, Fig.1) are clearly independent of kernel burnup.
The data collected at heating rates of approx. 50 C/h are bounded by data collected on a 23% FIMA sample during testing using heating rates of 20.6 or 1850C/h.
The 20.6 C/h data, on Fig. 1, provide the upper bound to the observed release fraction at any temperature; the 1850C/h data provide the lower bound.
A direct comparison of Kr85 release fractiora determined during testing of TRISO (Th/U)C, irradiated to 18.2% FIMA (heating race 1520C/h) and TRISO UC, irrediated to 23 and 59% FIMA (heating race approx.185 C/h) is shown on Fig. 2. 'The IRISO (Th/U)C2 and UC2 results are virtually identical leading to the conclusion that TRISO dicarbide fuel perfortance for core heacup conditions is not a function of kernel burnup.
( The UC2 data showr. on Figs. 1 and 2 have been collected in an on-going program over the past two years and have been discussed in Ref. 1.
The (Th/U)C2 data shown on Fig. 2 were reported in Ref. 2.
References 1.
"HTGR Generic Technology Program Semiannual Report for the Period Ending September 30, 1979," GA-A15606, November, 1979.
2.
"HTGR Fuels and Core Development Program ' arterly Progress Report for the Period Ending November 30, 1977," GA-Al%744, December, 1977, p.9-9.
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