ML20028G169
| ML20028G169 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 01/24/1983 |
| From: | Madsen G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Lee O PUBLIC SERVICE CO. OF COLORADO |
| References | |
| TAC-57625, NUDOCS 8302070479 | |
| Download: ML20028G169 (8) | |
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January 24, 1983 Docket:
50-267 Mr. O. R. Lee, Vice President Electric Production Public Service Company of Colorado P. O. Box 840 Denver, Colorado 80201
Dear Mr. Lee:
We have reviewed your December 11, 1981 letter (P-81322) concerning the modification of the Fort St. Vrain post-irradiated fuel element surveillance program.
Your request to eliminate the examination of a Segment 2 fuel assembly has been determined to be acceptable; however, we feel that supple-mental, destructive examinations should be performed as a substitution.
The supplemental examinations we find acceptable are the destructive examination of:
(1) one or more fuel rods in the cracked Segment 2 fuel element currently in the General Atomics hot cell, and (2) one or more fuel rods in fuel test assembly, FTE-2.
Our evaluation of your request is provided as an attachment to this letter.
In order for us to complete our review of this issue, we request that you provide, within 30 days of your receipt of this letter, your commitment to perform the above-mentioned substitution examinations er an alternate proposal including your basis for the alteration.
Since this reporting requirement relates solely to the Fort St. Vrain Nuclear Station, fewer than ten respondents are affected; therefore, OMB clearance is not required under P.L.96-511.
If you have any questions on this inatter, please contact your NRC Project Manager.
Sincerely,
" Original signed trn o.' p. MADSEN"-
Glen L. Madsen, Chief Reactor Project Branch 1
Enclosure:
Evaluation RCP #1 RCP:BC D/DRRP PCWagner: emh GLMadsen JEGaglia o 1/;.) /83 1/J)/83 1/21/f}3 8302070479 830124 I
PDR ADOCK 05000267 P
Fort St. Vrain cc list C. K. Millen Chairman, Board of County Commissioners Senior Vice President of Weld County, Colorado Public Service Company Greeley, Colorado 80631 of Colorado P.O. Box 840 Regional Representative, Radiation Programs Denver, Colorado 80201 Envi-'nmental Protection Agency 1866 cincoln Street James B. Graham, Manager Denver, Colorado 80203 Licensing and Regulation East Coast Office Don Warembourg General Atomic Company Nuclear Pruduction Manager 2021 K Street, NW, Suite 709 Public Service Company of Colorado Washington, DC 20006 P.O. Box 368 Platteville, Colorado 80651 J. K. Fuller, Vice President Harold R. Denton, Director Public Service Company Office of Nuclear Reactor Regulation of Colorado U.S. Nuclear Regulatory Commission P.O. Box 840 Washington, D.C.
20555 Denver, Colorado 80201 M. W. Dickerson NRC Senior Resident Inspector P.O. Box 640 Platteville, Colorado 80651 Director, Division of Planning Department of Local Affairs 615 Columbine Building 1845 Sherman Street Denver, Colorado 80203 l
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a ATTACHMENT FORT ST. VRAIN SEGMENT 2 FUEL ELEMENT DESTRUCTIVE EXAMINATION
Background
Fuel surveillance, including both destructive and non-destructive post-irradiation examination (PIE), has been a subject of concern for the Fort St. Vrain (FSV) high temperature gas cooled reactor (HTGR) for several years (Refs. 1-9).
FSV is a first-of-a-kind reactor with a unique fuel design
- developed largely under a government-funded program.
While as part of that government-backed HTGR development program, a fuel PIE program was established, DOE-funding for the PIE work is not assured over the several-year duration of the 1st-core irradiation life.
Understandably, the licensee, Public Service Company of Colorado (PSC),
has been reluctant to accept full responsibility for a PIE program.
PSC has, however, committed to submit a minimal reference-fuel PIE program to the NRC for review and concurrence in the event of a major change in the DOE-funded reference-fuel PIE program (Ref. 9). As noted in refer-ence 10, funding for the FSV Fuel Surveillance Program was reduced for FY82.
While the program had called for destructive PIE of one fuel element each from Segments 1, 2, 4, and 6 (there were 6 segments in the initial core loading; i.e., Segment 7 comprised the first reload), PSC now requests NRC approval to eliminate the destructive PIE of the Segment-2 surveillance element.
- The fuel rods are 2-inch long,1/2-inch diameter cylindrical compacts of random close-packed, coated particles bonded with a carbonaceous matrix material which is cured at high temperature. The fuel rods are loaded into holes drilled vertically in graphite blocks (elements) about 32 inches long with an hexagonal cross section approximately 14 inches across the flats.
The fuel elements each weigh about 300 lbs. when fully loaded.
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- Regulatory Evaluation The destructive PIE program for reference-design FSV fuel was to consist (Ref.11) of the following:
1.
Selective gamma-scanning for relative power, flux and burnup distribution.
2.
Analysis of temperature, burnup, and flux monitors.
3.
Fuel rod metrology.
5.
Metallographic and TRIGA activation measurements of kernel mi-gration (amoeba effect).
These examinations would be perfonned on so-called surveillance elements, one of which would be removed at the time of the first, second, fourth, and sixth refuelings and returned to the General Atomic hot cells in San Diego. As described in Section 3.4.1.1 of the FSV FSAR, there were 32 fuel elements in the 1st core loading of FSV that were designated as surveillance elements and which were extensively characterized for graphite structure, fuel rods, burnable poison rods, etc. and which contained small temperature and fluence monitors. These elements were placed in pre-selected core locations which have specific temperature and fluence conditions of interest. The first surveillance element was remo'ced in 1979 after 174 EFPDs exposure, and the results of the PIE of that element are described in reference 12.
In addition to the reference-fuel surveillance elements, FSV currently contains 7 " fuel test elements" (FTEs), which were inserted at the first refueling (Segment 7).
These elements, described in reference 13, contain various types of fuel particles and are fabricated from a more-Isotopic type of graphite (H-451) than the reference elements.
FTEs 2, 4, and 6 each also contain 88 FSV reference fuel rods. While the FTEs were not part of the original surveillance plan, they are currently scheduled for destructive PIE under DOE funding. The table below shows the estimated exposure (in EFPD) that will be accumulated by the surveillance elements and the three FTEs (from Ref.10).
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, Element Removed Estimated After Cycle ___
Element EFPD Exposure 1
SURV-1 174 3
FTE-2 489 4
SURV-4 963 5
FTE-4 1089 6
SURV-6 1563 7
FTE-6 1689 As indicated in the table, FTE-2 is projected to have 489 EFPDs at discharge (E0C-3), which is $125 more EFPDs than the exposure for the SURV-2 element at E0C-2.
Inasmuch as (1) no kernel migration was observed during the destructive PIE of SURV-1 (Ref.12), (2) the incre-mental exposure of the Segment 2 (SURV-2) element over the Segment 1 (SURV-1) element is not great, (3) the smallest kernel migration distance that can be detected by metallographic techniques is 3 or 4 microns (Ref.14), (4) analyses indicate that kernel migration at the end of Cycle 2 is expected to be below the 3 to 4 micron limit of detectability, and (5) the reference fuel rods in FTE-2 will be available for destructive PIE when that element is removed after Cycle 3, we believe that the destructive PIE of a SURV-2 reference fuel element can be eliminated and that a partial substitution can be made in the reference fuel destructive PIE program; viz., one or more FTE-2 reference fuel rods can be destructively examined in place of the reference SURV-2 fuel rods.
The planned surveillance of SURV-4 can then be carried out after Cycle 4 as originally scheduled to provide performance information at higher exposure.
In addition, General Atomic currently has a cracked fuel element in the hot cells in San Diego. That element, one of two graphite blocks with cracks discovered by visual examinations performed at the time of the Cycle 3 reloading (Ref.15), contains reference-type fuel rods.
Since the cracked block is already in a GA hot cell and is to be subjected
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to various destructive tests (to determine the cause of the crack), it would not be a significant burden to perform a destructive PIE of one or more fuel rods in that element.
Accordingly, we conclude that one or more fuel rods from the cracked block should be sectioned metallographically to confirm that the fuel has performed as predicted.
Sumary PSC's request for approval to eliminate the destructive PIE of a Segment-2 (SURV-2) reference fuel element is approved on the condition that (1) one or more fuel rods from the cracked element currently in the GA hot cell are sectioned metallographically and examined to confirm-predicted fuel performance (with respect to the fuel particles) and (2) one or more reference fuel rods in a Segment-7 (FTE-2) fuel element will be examined in a similar fashion upon removal after Cycle 3 (after approximately 489 EFPDs exposure).
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. References 1.
M. Tokar (NRC) memorandum to D. F. Ross, " Fuel Surveillance Require-ments for Fort St. Vrair. and the First Large HTGR's," December 16,19/4.
2.
M. Tokar (NRC) memorandum to D. F. Ross, " Summary of Generic Meeting With General Atomic Company on HTGR Fuel Surveillance and Proof Testing," March 26, 1975.
3.
D. F. Ross, Jr. (NRC) memorandum to R. P. Denise, " Fort St. Vrain Fuel Surveillance," March 4, 1977.
4.
M. Tokar (NRC) note to D. F. Ross, " Current Lack of Fort St. Vrain Fuel Surveillance Requirements" August 25, 1977.
5.
D. F. Ross, Jr. (NRC) memorandum to R. P. Denise, " Fort St. Vrain Reload 1 Test Elements (TACS 4693)," October 28, 1977.
6.
R. P. Denise (NRC) letter to J. K. Fuller (PSC),
Subject:
Fort St. Vrain Fuel Surveillance, April 6, 1978.
7.
D. F. Ross, Jr. (NRC) memorandum to R. P. Denise, " Fort St. Vrain Test Fuel Elements," April 19, 1978.
8.
M. Tokar (NRC) note to R. Ireland, " Comments on Proposed Post-Irradiation Examination Program for Fort St. Vrain Test Fuel Elements," September 26, 1978.
9.
J. K. Fuller (PSC), (letter No. P-79012) to W. P. Gammill (NRC),
Subject:
Standard Fuel -- Post-Irradiation Examination, January 24, 1979.
10.
O. R. Lee (PSC) letter (No. P-81254) to T. M. Novak (NRC),
Subject:
FSV Segment 2 Fuel Surveillance, December 11, 1981.
11.
J. K. Fuller (PSC), letter (No. P-78103) to W. Gammill (NRC),
June 20, 1978.
12.
J. A. Saurwein, C. M. Miller, and C. A. Young, " Post-Irradiation Examination and Evaluation of Fort St. Vrain Fuel Element 1-0743,"
General Atomic Report GA-A16258, May 1981.
13.
" Safety Analysis Report for Fort St. Vrain Reload 1 Test Elements FTE-1 Through FTE-8," General Atomic Report, GLP-5494, June 30,1977.
14.
H. L. Brey (PSC) letter (No. P-81322) to R. Clark (NRC),
Subject:
May 4, 1982 Telecon GAC/PSC/NRC Fuel Surveillance Program, June 2, 1982, 15.
G. Kuzmycz (NRC) memorandum for H. Denton, et al, " Daily Highlight,"
July 8, 1982.