ML20027E409
| ML20027E409 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 07/19/1982 |
| From: | Tokar M Office of Nuclear Reactor Regulation |
| To: | Mattson R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20027E400 | List: |
| References | |
| FOIA-82-428 NUDOCS 8211150185 | |
| Download: ML20027E409 (1) | |
Text
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JdL191982 NOTE FOR:
R. J. Mattson, Director Division of Systems Integration FROM:
Michael Tokar
~
s Reactor Fuels Section, CPB:DS
SUBJECT:
C0t1 MENT ON FSV LRACKED FUEL ELD 1ENTS On the positive side, there has been no evidence of significant fuel particle coating failure (coolant astivity remains low), all replacement elements are of a different (stronger) gra were still integral (no pieces broken off)phite, and the cracked blocks On the negative side, 2 of 54 blocks examined were cracked (out of~1400 in the core) so there is a high prsbability of more cracked blocks (yet undetected), the 2 observed cracked blocks were of relatively low exposure (so the problem may get worse with time), and the crack in the 2nd block appears to be an extension of the crack in the other (vertically adjacent) block (thereby indicating a possible common cause). Since further cracking cannot be ruled out, it is conceivable that a localized cooling problem could develop if.a piece of cracked block were to shift laterally and block coolant passages.
The significance of the cracks is under study by GA.
In my view, the investigation should center on what the cracks mean_ relative to the core mechanical and structural design adequacy.
According to FSAR-type
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calculations, these cracks cannot exist. Since -they do exist, something must be wrong with (a) the codes, (b) the way the codes were used, (c) the graphite, or (d) other (u'nknown) factors.
DL seems to be taking a low-key approach. They have known abc'ut this i
for weeks, but I am unaware of any DL action, request for DSI help, or documentation (other than the July 8,1982 " highlight").
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Michael Tokar Reactor Fuels Section, CPB:DSI l
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I-September 15, 1982 s
Fort St. Vrain
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Unit No. 1
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_. C P-32394 Mr. George Kuzmycz rroject Manager Special Projects Branch Division of Project Management Office of Nuclear Reactor Regulation U.S. (Nuclear Regulatory Cmra$ston Washington. D.C.
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SUBJECT:
Status' of Cracked Fuel Element Webs v
REFERENCES:
P5C Letter P-82130 dated 5/4/82 PSC Letter P-78146 dated 9/6/78
Dear Mr. Xuzmycz:
The purpose of this letter is to update the status of the cracked fuel element webs discovered as a
result of the Segment 2
nuncestructive examination, progra:n.
The letter also presents PSC's reasons for believing that these cracked webs ao not cons ti tute a
significant hazard to public.' health and safety and briefly describes current plans for further evaluation of the cracks.
In letter P-82130, aated May 4,1982, PSC reported that a hairline l
crack was seen on th'e center of one face of fuel element 1-2415.
I Observations of the elem nt in. the FSV Hot Service Facility (IISF) indicated that the crack extends across the minimwn cross-section batween the element face and a coolant hole and vertically down the
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full length of.the element.
Based upon observations in the HSF, it appeared tnat tne crack did not extena frora the coolant hole to the nearby Gowel socket.
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P-82394 Page 2
Based upon later review by General Atonic Cmpany (GAC) of the video tapes made during the examinations, it was detemined that a similar, but thinner crack might also exist on the corresponding face of fuel element 1-0172.
(Fuel element 1-0172 was located in tne initial core directly unoer fuel element 2415.)
In order to determine conclusively whetner a crack also occurred in fuel element 1-0172 it, along witn-1-2415 and. three other fuel elements were sent to San Otego for closer examination in the GAC liot Cells.
The core location l
of these elements is shown in Figure 1.
Elements 1-2415 ana 1-0172 were viewed for the fIrst time in the GAC l
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Hot Cells on July 7,1982. The initial examination revealed tha t,
- 1) element 1-0172 does.
In
- fact, have a crack similar to that in element 1-2415. and 2) the crack in element 1-2415, contra ry to l
observations in the H5F, does exteno to the dowel socket.
This new l
Information was reported to you by telephone on July 8,1982 and was discussed further in Cathesde on July 14,198Z.
Later examinations indicate that the crack also extends to the dowel socket.
The three adat tional elements sent to GAC were 1-0108, 2-Z693, and 5-0801.
Element 1-0108 was selected for further examination because it was next to element 1-2415 in the core ana had similar irradiation condi tions.
Element 2-Z693 was chosen because it is a control element and also had irradiation conditions similar to element 1-2415.
Element 5-0801 was chosen because it may have experienced higher than average stresses.
A thorough visual examination of these five elements at GAC has revealed,no cracks other than those described above.
Because of the locations of the cracks in elements 1-Z415 and 1-0172, 1
the cracks were hypothesized to have been caused by s tresses resulting from an improper fit between the dowel in element 1-0172 and the corresponding dowel socket in element 1-2415.
- However, a
i stacking test was perfomed, ano element 1-2415 was placed on top of element 1-0172 without difficulty.
While the elements were in this stacked configuration, the clearance be tween the dowel and dowel socket was determined by moving element 1-2415 as far as it would go to the lef t and the right and observing the change in position of the crack in this element relative to the s ta tionary crack in element 1-0172.
A double exposure photograph recorded the relative movement.
This test inoicated that the clearance is approximately 1 mm, which is as it should be.
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P-82394 Page 3 in addition to these examinations at GAC, P5C has inen conducting a visual examination of all Segment 2 fuel elements as they are loaoed into shipping casks for delivery to the Arco. Ioano storage site.
These examinations are perfanned in the fuel handling machine with a remotely operated camera.
To date, the examinati9ns have revealea no adat tianal fuel, element cracks.
The ceci sion to perfonn these adoi tional examinations was made prior to confirmation of the crack
.in element 1-0172.
Wita regard to the safety-related aspects of the crocked webs, PSC believes that these cracks do not constitute a significant hazard to publfc health and safety.
As dif, cussed in letter P-82130, the cracks do not' involve the area around tne fuel rods; there fore, fuel integri ty is not affected by tne cracks.
The presence of the cracks did not affect the cooling geometry of the fuel or the ability of the fuel hanaling machine to safely renove the fuel elements.
Maintenance of proper cooling geometry is the most important safety issue which one might associate with cracking of fuel element webs.
In this
- regard, it should be noted that the consequences of fuel alament damage resulting in coolant flow obstruction era reviewed with the NRC in response to questions raised in 1978 concerning fluctuations at F5V.
Those evaluations were documented in letter P-78146, cated September 6.1978.
In P-78146, a conservative bounding assessment was made of a scenario in which coolant flow through an entire column is blocked due to misalignment resulting fr7n dowel failure, A conservative evaluation of fuel particle failure, fission product release, and reactivity control was conducted.
The consequences of coolant flow restoration were also assessed.
This assessment is applicable in that it envelopes the conseq.:ences that might occur in the unlikely event that limiteo cracks of the type discovered were to propagate through a
fuel element to the extent that cooling geometry were somehow altered.
It was concluded that the consequences of this conservative scenario are well within those previously accepted by HRC for other Fort St. Vrain accident sequences.
Based upon the above considerations, PSC believes that the cracked webs do not constitute a significant hazard to public heal th and safe ty.
PSC continually moni tors the circulating activity of the l
primary coolant helium.
Any fuel abnormali ties that significantly alter the cooling geometry would be readily detected 4nd action quickly initiated to mitigate the consequences of any adverse fuel geometries.
Further evaluations of the cracked fuel element webs are planned for FY-83.
It is currently planned that GAC will, under 00E
- funding, perfons scoping analyses of the opersang history of the elements with cracked webs.
These analyses may provide insight regarding why the cracks -occurred.
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In
- aaottion, it is currently planned that pos t-f eradia tion examination of the fuel einents with cracked webs will continue at GAC under FY-83 DOE funaing.
Destructive examination will begin, and
' measurements of ecnanical properties will be parfomed.
The results of these physical examinations can be used in conjunction with the
, analyses discussed above.
- Finally, as analyses ana examinations proceea.
PSC and GAC will continue to assess the safety-related aspects of the cracked webs in light of any new infomation which may be gained.
P$C will continue to keep you informed of any new aevelopments regarding these ef forts.
Very truly yours.
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% H.L. Brey. Hanecer Fluclear Enginaaring uifision HLB /SEF:pa
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...... l FIGURE 1~ CORE PosITtor OF ELEHEtiTS (Shipped To GAC)
COLtPiN NtNBER
_36 37 2
REG 21 35 7
3 ntma g
I 0
18 5
34 22 9
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2 7
I 3
23 10 1
6
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24 16
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32 11 5
4 2
15 7
25 3
31 3
12 6
4 6
14 30 26 f
27 29 ELEMENT REGION COLtFIN ACTIVE CORE LAYER 1-2415 8
5 3
1-0172 8
5 4
1-0108 8
6 3
2-2693 8
1 3
5-0801 25 3
4
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NUCLEAR REGULATORY COMMISSION j*
.j WASHf fJG10N, D. C. 20555
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. July-30, 1982 Ms. Andrea L. Kronzek t oi Services, Inc.
12315 Wilkins. Avenue IN RESPONSE REFER Rockville, MD 20852 TO FOIA-82-301-
Dear Ms. Kronzek:
This is in response to your letter dated July 7,1982, in which you requested,' pursuant to the Freedom of Information Act, a ' copy of all.
documents consisting of or containing information on (a) licensing violations involving any of the NFS-4 shipping casks; (b) licensing restrictions imposed upon any of the NFS-4 casks including any reports, studies or evaluations which in any way discuss or set forth reasons for said restrictions; (c) any other report, investigation or evaluation ~of or involving the NFS-4 shipping casks in. connection with licensing or relicensing efforts; (d) any material discussing or describing. the surface characteristics of any of the NFS-4 shipping casks; and (e) including but not limited to_ all documents referenced in Revision No. 9 of the Certificate of Compliance 6698, Docket No. 71 6698.
In response to your request we have determined that the documents listed on Appendix A are already on file in the NRC Public Document Room (PDR) located at 1717 H Street, N.W., Washington, DC..The documents identified with an asterisk (*) on Appendix A are being placed. in the PDR where they will be available for public inspection and copying.
The charge for reproducing records located in the PDR is five cents ($0.05) per page, as specified in 10 CFR 9.14(a).
If you do not wish to visit the PDR to inspect or copy these records, you may obtain copies by calling (202)634-3273 or by writing directly to the PDR.
Upon your agreement to pay the reproduction charges, the PDR will arrange for the records to be reproduced by Literature Research Company, a private reproduction i
contractor servicing the PDR.
You will be billed by the Literature Research Company for the reproduction charges, plus tax and postage.
Sincerely,
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. J/ M. Felton, Director f; l Division of Rules and Records l
Office of Administration
Enclosure:
Appendix A l
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Reb T01A-82-301_
APPENDIX _ A 1.
4/2/79 flRC Letter Informing NRC _ Staff Deviations in Fabrication -
- 2.
4/2/79 Memo for L. B. Higgenbottom re: Noncompliance of NFS-4, Serial No. A Cask Owned by _ Duke Power Company (2 pages) 3.
4/6/79 Order to Show Cause -Suspended Use of (7) Casks Model No. NFS-4 4.
4/12/79 NAC Letter Giving Historical Data on Cask Usage
- 5.
4/12/79 Memo for J. H. Sniezek from R. E. Cunni'gham re: Nonconforming Model NFS-4 Cask (2 pages) 6.
4/18/79 NFS NAC-1 Cavity Measurements Report 7.
5/79 Cavity Measurements of NAC-1 Spent Fuel Shipping _ Casks' Report-
- 8.
5/9/79 Memo for G. H. Bidinger, FFMSI, IE, re: Measurement of Inner Cavity of NAC Fuel Shipping Cask NAC-1B (3 pages)
- 9.
5/10/79 Memo for Files re: Trip Report - Observation of NAC-1 A Fuel Shipment Cask Measurements (3 pages) 10.
5/18/79 Inspection Report No. 71-6698/79-01 IE, Region IV
- ll.
6/4/79 Memo for Docket File 71-6698 re: Meeting with Applicants Concerning 4/6/79 Order to Show Cause.
Meeting date 4/17/79 (2 pages).
- 12, 6/4/79 Memo for Docket File 71-6698 re: Meeting with Applicants Concerning 4/6/79 Order to Show Cause.
Meeting date 4/30/79 (6 pages)
- 13.
6/4/79 Memo for Docket File 71-6698 re: Meeting with Applicants Concerning 4/6/79 Order to Show Cause.
Meeting dated 5/11/79 w/ copy of preliminary measurements attached (22 pages) 14.
6/8/79 f>RC Letter Submitted Review of QA Records 15, 6/8;7/26; Letters from f1AC Requesting an Amendment to Certificate of 10/31/79 Compliance 16.
7/16/79 NRC Region IV - Inspection Report - Inspection Conducted on 4/19/79 and 4/20/79 17.
7/26/79 NRC Letter Submitted Revised Drawing to be Incorporated into Certificate of Compliaxe
I Reb F01A-82-301 l
O APPENDIX A 18.
9/19/79 NAC Letter to NRC - Region IV, 18E, Response to NRC Inspection Report 19.
10/4/79 NAC Letter Transmitting Information to NRC - Region IV, I&E 20.
10/5/79 NFS L tter Requesting Renewal of Certificate of Compliance with tipulation that NFS Casks will not be used until cond.. ions of 4/6/79 Order have been met 21.
10/31/79 NAC Letter Requesting Revision to Certificate of Compliance Incorporating Revised Drawing and Changes in Dimensions, Tolerances, and Materials Resulting from QA Inspections and Reviews 22.
11/9/79 NAC Letter on Hondestructive Examination of Weld 23.
12/12/79 Order Amending Certificate and Terminating in Part Order to Show Cause 24.
12/12/79 Certificate of Compliance No. 6698, Rev. 9 25.
5/21/80 NAC Letter Requesting Amendment to Certificate of Compliance and termination of Order to Show Cause. dated 4/6/79.
26.
7/3/80 NAC Letter Requesting Revis.an to Certificate of Compliance to Provide Flexibility of Inner Shell Measurement Schedule 27.
7/15/80 NAC Letter Provided Corrections to NAC Report No. NAC-E-801 dated 5/16/80 28.
9/80 NAC Report NAC-E-803 Cavity Measurements of NAC-ID Spent Fuel Shipping Cask
- 29.
9/11/80 Memo for Docket Files re: Shipment Made in Apparent Violation of Certificate of Compliance No. 6698 - Model No. NFS-4, Serial No. NAC-lD (1 page) 30.
10/17/80 NAC Letter Requesting Arendment to Certificate of Compliance Requiring Periodic Cask Cavity Measurements - Letter also Uithdrew Letters of 9/12/80, 9/30/80, 10/2/80 and 10/6/80
- 31.
10/30/80 NRC Region 11 Letter to C. E. MacDonald (22 pages) i 32.
11/5/80 NAC Letter Requesting Authorization to Move Contaminated Cask l
k
' t, Re. 101A-82-301 r.*
-APPErlDIX A-93.
11/18/80' Memo for C. E. MacDonald NAC-1 Cask Cavity Measurements (26 pages) 34 12/1/80 NAC Letter Requesting Amendment to Certificate of Compliance Revising Requirement on Cavity Measurements 35.
2/4/81 NAC Letter Requesting use.of a Protective-Coating on Cask Surfaces 36.
2/5/81 NRC Letter Authorizing use of Strip Coating 37.
2/17/81 NAC Letter - Notification that Measurements will be Taken 38.
2/24/81 NAC Letter Reporting Experience using a Protective Paint on Surface of NAC-10 Package 39, 3/4/81 NAC Letter Requesting Amendment to Certificate of Compliance Authorizing Shipment of NAC-IE Package Specially Prepared for Shipment (Contamination Problem) 40.
3/20/81 NRC Letter Authorizing Preparation of Model No. NFS-4, Serial No. NAC-IE Packaging Per NAC Letter dated 3/4/81.
Authorization Expired 5/10/81 (Contamination Problem) 41.
6/3/81 Letter from NAC, Requesting Amendment to Certificate of Compliance Authorizing use of Plastic Cover Applied to Outside Surfaces of Package.
42.
6/4/81 NRC Letter Autnorizing Plastic Cover Over Cask 43.
7/22/81 Order to Show Cause (Decontamination Problem) 44.
7/24/81 Letter from NAC, Requesting Information Pertaining to Order to Show Cause dated 7/22/81 (Decontamination Problem) 45.
9/17/81 Letter from NAC, Response to Order to Show Cause dated 7/22/81 - Report Attached (Decontamination Problem) 46.
10/9/81 Partial Recision of Order (Decontamination Problem) 47.
11/6/81 Letter from NAC re: " Partial Recision of Order" dated 10/9/81 (Decontamination Problem) 48.
12/23/81 Letter to W. G. Counsil f rom R. T. Carlson re: Combined Investigation No. 50-213/80-20 and 50-219/80-38 (100 pages) 49.
Revision No. 9 of Certificate of Compliance No. 6698 and all Documents Referenced therein are available from the PDR 4
under Docket No. 71-6698
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