ML18113A302

LER 1976-35-00 for St. Lucie Unit 1, During Power Ascension Testing It Was Determined That the Power Distribution in the St. Lucie Unit 1 Core Was Not as Predicted for 80% Power

ML18113A302
Person / Time
Site:	Saint Lucie
Issue date:	12/20/1976
From:	Schmidt A Florida Power & Light Co
To:	Moseley N NRC/IE, NRC/RGN-II
References
PRN-LI-76-303 LER 1976-035-00
Download: ML18113A302 (4)

Text

P. O. BOX 013100, MIAMI, FL 33101 FLORIDA POWER & LIGHT COMPANY December 20, 1976 PRN-LI-76-303 Mr. Norman C. Moseley, Director, Region Office of Inspection and Enforcement II U. S. Nuclear Regulatory Commission 230 Peachtree Street, N. W., Suite 818 Atlanta, Georgia 30303

Dear Mr. Moseley:

REPORTABLE OCCURRENCE 335-76-35 ST. LUCIE UNIT 1 DATE OF OCCURRENCE: JULY 10, 1976 POWER DISTRIBUTION ANOMALIES UPDATE REPORT NO. 1 The attached Licensee Event Report is being submitted to update our initial report of July 23, 1976.

Very truly yours, D. Schmidt Vice President Power Resources MAS/cpc Attachment cc: Robert Lowenstein, Esquire Director, Office of Inspection and Enforcement (40)

Director, Office of Management Information and Program Control (3)

PEOPLE... SERVING PEOPLE $ +

July 3, 1976 CONTROL BLOCK: UPDATE Il (PLM PRltIIT ALL RBQUlAED IHFGRti1ATlOil)

LICENSEE <CENSE EVEt4T NAMi LCENSE t4UMBER TYPE TYPE O1~ F L S L S 1 0 0 0 0 0 0 0 0 0 4 I 1 ~os 89 14 15 25 26 30 31 32 DOCKET NUMBER EVEN% GATE Supplementary I:EPORT 1

8 COili S7 SB SB 60 61 0 5 0 0 3 3(5 68 69 0 7Ij 0 7 6 74 1

75 2 2 GATE 0 7 6 80 EVENT OESCRIPTION 8 9 Dur'n gower ascension testin it was determined that the ower distribu-3 tion in the St. Lucie Unit 1 core was not as redicted for 80% ower.

8 9 80 Power was reduced to Hot Zero Power conditions and physics testing was 89 80 oerformed to determine the cause. The lant was then shut down until 89 60 lBI evaluation of the test data could be corn leted. Further investi ation as 8 9

~i CCCF-CAUSE CCGF- CQMPCi4ENT CQOE PRII4 e CCMPCNdlT SUeiFUeER MAtsl'FACTUFEII 60 p

6 9 10

~Pe ~B 12 F U 3 L X X 17 C49)0 N 11 47 CAUSE OESCRIPTION 89 The cause of the ower distribution anomalies has been determined to ~be 80 ls erforated burnable oison rods within t: he fuel assemblies. Boron loss 8 9 lp'rom and redistribut.ion within the erforated ooison rods were the 69 FACs~ 80 MEiHOO OF SiATUS POWER OTHER STATUS OISCOVERY GiSCQVERY OESCRIPTIQt4 8 9

~o ~os 10 o N/A N/A FORM QF 12 13 44 45 46 60 ACTMTY CQat e.'4T PE'EASeO Or RELEASE AMOUNT QF ACTIVIIY LCCATIQN GF RELEASE l2 ~Z ~Z N/A N/A S 9 1i0 11 44 45 60 PcRSCNNEL EXPOSURcS t4UMBER TYPe CESCRIPTICN s Lo I oo lI ooJ ~z N/A 8 9 11 12 i3 eo FEPSONNEL liNJURIES tIUMSER CeSCRTICN

- LoaooJ N/A 8 9 11 12 qp>~Z.c CO¹EGUENCES N/A 8 9 60 LOSS OR OAMAGE TO FACILlTY

~ YPE CESCP,'PTFGN 6 ~L Loss of generating capability since July, 1976.

89 10 SO FUBUClTY Press releases made b both FP&L and NRC 69 AOOI IICNAL FACTORS See Pa es two and three for continuation of Event Description and Cause 1 Description.

60 M. A. Scho man 305/552-3779

Reportable Occurrence 335-76-35 Licensee Event Report Update Cl Pa e Two EVENT DESCRIPTION (Continued) described below in the Cause Description was later performed.

(335-76-35)

CAUSE DESCRIPTION (Continued) sources of the observed anomalies and occurred throughout the core.

This conclusion is based on poolside (spent fuel pool) inspection hot cell observations, and laboratory testing, as well as the pre-shutdown core flux measurements. Brie ly, the following was done:

(l) A statistically significant number of fuel assemblies containing poison rods were visually inspected at poolside. From these observations it was evident that perforated poison rods were distr-buted throughout the core. It should were observed.

be noted that no fuel rod anomalies (2) Poison rods were then removed from selected fuel assemblies for visual and eddy current testing in the spent fuel pool.

(3) Based on (l) and (2) above, poiso.. rods were sent to outside consultants for hot cell examination and reactivity measure-ments.

The. results from (1), (2), and (3) confirmed the cause to be boron loss from, and redistribution within, the poison rods.

After review and approval in accordance with 10 CFR .50.59, the original poison rods were removed, and replaced by new poison rods. A retention assembly was added to p ovide supplementary rod retention capability at that portion of each flow plate which was removed to allow access to the poison roc locations. The replacement burnable poison rods are of ssentially the same design as the rods described in he FSAR except for mino" changes which minimize the probability for recur"ence of the mechanism which caused the failures among the original rods, and minor changes to update the rods to the vendor's latest design. The boron content 's equivalent to +he as-bu'lt loading in the original rods.

Reportable Occurrence 335-76-35 Licensee Event Report Update 51 Pa e Three CAUSE DESCRIPTION (Continued)

This reworking process results in fuel assesbli s which are not significantly changed from the original design. A design review has demonstrated that the reworked fuel assert~lies have no significant effect on the nuclear and thermal hydraulic aspects of core performance. All input parameters to the accident and transient analysis have been reviewed to determine the effect of the poison rod replacement. It has been deter'ne" that all key input parameters are bounded by the values us d in the FSAR.

Based on the evaluations made, it is concluded tha- the reworked fuel assemblies can be operated at full power th cughout the original design life. Changes to the FSAR and Technical Specifications are not required and operation does not result in an unreviewed safety question.

For further details see our "St. Lucie Uni" 51 Repair Report" CEN-38 (F), Revision l.

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