ML17325B516

LER 99-007-00:on 981020,calculations Showed That Divider Barrier Between Upper & Lower Containment Vols Were Overstressed.Engineers Are Currently Working on Analyses of Loads & Stress on Enclosures

ML17325B516
Person / Time
Site:	Cook
Issue date:	04/01/1999
From:	Kosloff D INDIANA MICHIGAN POWER CO.
To:
Shared Package
ML17325B513	List: ML17325B512 ML17325B516
References
LER-99-007, LER-99-7, NUDOCS 9904070426
Download: ML17325B516 (1)

Text

NRC Form 366 U.S.NUCLEAR REGULATORY COMMISSION (6-1998)LICENSEE EVENT REPORT (LER)(See reverse for required number of digits/characters for each block)APPROVED BY OMB NO.3160%104 EXPIRES 06/30)2001 ESTIMATED BORDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COILECAON REOVEST'.50 0 HRS.REPORTED lESSONS lEARNED ARE INCORPORATED NTO THE LICENSING PROCESS AND FED SACK TO INDVSTRY, FORWARD COMMENTS REGARIXNG SVRDEN ESTNATE TO THE INFORMATION ANO RECORDS MANAGEMENT BRANCH (T4 F55).V.S.NVCLEAR REGVLATORY COMMISSlON.

WASHINGTON, DC 20555400), ANO TO THE PAPERWORK REDVCTION PROJECT (51504)05), OFFICE OF MANAGEMENT ANO SICGET.WASHINGTON.

OC 20505 FACIUTY NAME (1)Cook Nuclear Plant Unit 1 DOCKETNUMBER(2) 05000-315 PAGE (2)1 of 1 TITLE (4)Calculations Show that the Divider Barrier Between Upper and Lower Containment Volumes May Be Overstressed EVENT DATE (5)LER NUMBER (6)REPORT DATE (7)OTHER FACILITIES INVOLVED (8)MONTH 10 DAY YEAR 20 1998 YEAR 1999 SEQUENTIAL NUMBER 007 REVISION NUMBER 00 MONTH DAY 04 01 YEAR 1999 A I I NAM Cook Unit 2 ILI NAM D NUMB R 05000-316 D NUM OPERATING MODE (9)re)(11)20.2201 (b)50.73(a)(2)(viii) 20.2203(a)(2)(v) 50.73(a)(2)(i)

THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR li: (Check one or mo POWER LEVEL (10)00 20.2203(a)(1) 20.2203(a)(2)(i) 20.2203(a)(2)(ii) 20.2203(a)(2)(iii) 20.2203(a)(2)(iv) 20.2203(a)(3)(i) 20.2203(a)(3)(ii) 20.2203(a)(4) 50.36(c)(1) 50.36(c)(2)

LICENSEE CONTACT FOR THIS LER (12)50.73(a)(2)(ii) 50.73(a)(2)(iii) 50.73(a)(2)(iv) 50.73(a)(2)(v) 50.73(a)(2)(vii) 50.73(a)(2)(x) 73.71 OTHER Speofy SI Abetraor be)rwr or n NRC Form 366A Mr: Donald C.Kosloff, Compliance Engineer TELEPHONE NUMBER (Indude Area Code)616/465-5901, X2129 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE To EPIX CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO EPIX SUPPLEMENTAL REPORT EXPECTED (14)X YES (If Yes, complete EXPECTED SUBMISSION DATE)NO EXPECTED SUBMISSION DATE (15)MONTH 08 DAY 20 1999 Abstract (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)(16)While working on a preliminary calculation for the Unit 1 steam generator replacement project, it was concluded that some of the structural load cases indicated overstressed conditions in the steam generator enclosures.

Based on these preliminaiy analyses, on October 20, 1998, with both units in Mode 5, engineering personnel determined that a postulated steam line break could result in calculated stresses exceeding the code allowable stresses for the Unit 1 steam generator enclosures.

These reinforced concrete enclosures are part of the divider barrier between the upper and lower containment volumes.Overstressed conditions in these enclosures could allow increased steam bypass flow around the ice condensers which could result in higher than expected containment pressure.When the potential overstress conditions were identified, it was concluded that the conditions could be due to significant conservatisms in the preliminary calculation and in its interpretation.

Engineering continued their evaluation of this issue.However, as evaluations continued, a lack of information confirming an acceptable condition led to the conclusion that there was no longer a reasonable expectation that the structures would not be overstressed.

On March 2, 1999, with both units still in Mode 5, the apparent overstress conditions were determined to be reportable under 10CFR50.72(b)(2)(i) and 50.73(a)(2)(ii).

Based on this determination, an ENS notification was made on March 2, 1999, at 1314 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />4.99977e-4 months <br /> in accordance with 10CFR50.72(b)(2)(i).

Structural engineers are currently developing appropriate analyses of the loads and stresses on the enclosures.

The results of these analyses will determine if an overstressed condition could have occurred and, if so, the safety significance of the overstressed condition.

Appropriate corrective action will be developed based on an evaluation of the analytical results.9904070426 990401 PDR ADQCK 05000315 S , PDR