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| {{Adams
| | #REDIRECT [[05000315/LER-1998-037, :on 980812,ice Condenser Bypass Leakage Exceeds Design Basis Limit of 5 Square Feet Occurred.Caused by Lack of Understanding of Design Basis of Containment as Sys. Procedure Will Be Developed to Guide Insp.With]] |
| | number = ML17265A823
| |
| | issue date = 05/24/1999
| |
| | title = :on 990422,determined That Ice Condenser Bypass Leakage Exceeds Design Basis Limit.Caused by Pressure Seal Required by Revised W Design Not Incorporated Into Aep Design.Numerous Matl Condition Walkdowns & Assessments Made
| |
| | author name = Berry L
| |
| | author affiliation = INDIANA MICHIGAN POWER CO.
| |
| | addressee name =
| |
| | addressee affiliation =
| |
| | docket = 05000315
| |
| | license number =
| |
| | contact person =
| |
| | document report number = LER-98-037, LER-98-37, NUDOCS 9906030254
| |
| | package number = ML17265A821
| |
| | document type = LICENSEE EVENT REPORT (SEE ALSO AO RO), TEXT-SAFETY REPORT
| |
| | page count = 6
| |
| }}
| |
| {{LER
| |
| | Title = :on 990422,determined That Ice Condenser Bypass Leakage Exceeds Design Basis Limit.Caused by Pressure Seal Required by Revised W Design Not Incorporated Into Aep Design.Numerous Matl Condition Walkdowns & Assessments Made
| |
| | Plant =
| |
| | Reporting criterion = 10 CFR 50.73(a)(2)(ii)
| |
| | Power level =
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| | Mode =
| |
| | Docket = 05000315
| |
| | LER year = 1998
| |
| | LER number = 37
| |
| | LER revision = 0
| |
| | Event date =
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| | Report date =
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| | ENS =
| |
| | abstract =
| |
| }}
| |
| | |
| =text=
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| ~U.S. NUCLEAR REGULATORY COMMISSION 16.19981 L(CENSEE EVENT REPORT (LER)
| |
| TEXT CONTINUATION FACILITYNAMEI1)
| |
| DOCKET I2)
| |
| LER NUMBER Iel PAGE I3)
| |
| Cook Nuclear Plant Unit 1 O5000-315 SEQUENTIAL REVISION 3
| |
| OF 5
| |
| NUMBER NUMBER 1998 037 01 TEXT (Ifmore spece js reqvfred, vse addi donel copies ofNRC Form 866A) I17)
| |
| With the current ice condenser design, the bottom of the ice baskets is 10 ft above the bottom of the lower plenum fioor.
| |
| When an event occurs, the air and steam enter the Ice condenser lower plenum and can pressurize the area up to 12 psi, exposing the DBS seal at the end walls to that same pressure.
| |
| Due to the design of the seal, it is conservatively assumed that the seal willfail and allow the steam to bypass the ice baskets and enter into upper containment directly.
| |
| | |
| ==Cause Of The Event==
| |
| The individual bypass conditions reported in the original LER were attributed to unauthorized modifications.
| |
| A tack of documented configuration and inadequate implementation of the design change control process resulted in the creation of
| |
| . bypass paths via material substitutions, original construction discrepancies, Inadequate service life, and unseating of spare penetrations during the performance of work activities. The root cause of the cumulative bypass was attributed to lack of understanding of the design basis of containment as a system, and of the divider barrier in particular.
| |
| This was coupled with a lack ofa comprehensive inspection program for detection of defects and damage to the divider barrier.
| |
| The apparent cause of the newly discovered ice condenser bypass is that the pressure seal required by a revised Westinghouse design was not incorporated into the AEP design.
| |
| The reason for this discrepancy is unknown. According to the original Westinghouse ice condenser design, the ice baskets on the containment wall'side started at the level of the ice condenser bottom slab and extended upward 58 feet. This design was to ensure that ail steam entering the ice condenser would travel through the ice baskets before entering upper containment.
| |
| With this design, only a ventilation barrier was needed to seal the end walls. Later, Westinghouse implemented a new design which located the bottoms of all ice baskets 10 ft above the ice condenser bottom slab.
| |
| This is the basket design that was installed at Cook Nuclear Plant.
| |
| : However, when the later design was introduced, the ventilation barrier was not upgraded to a include a pressure seal capable of withstanding 24 psi.
| |
| Anal sls Of The Event The originally identified condition was determined to be reportable on August 12,
| |
| : 1998, in accordance with 10CFR50.72(b)(2)(i), as a degraded condition discovered white the unit is shutdown that, if found while the reactor was operating, would have resulted in the plant being in an unanalyzed condition, and an ENS notification was made at 1530 hours EDT. The original LER was submitted in accordance with 10CFR50.73(a)(2)(ii) as an event or condition outside the design basis of the plant. An additional ice condenser bypass condition involving the DBS identified on April22, 1999 was also determined to be reportable pursuant to the requirements of 10CFR50.73(a)(2)(ii).
| |
| The DBS ice condenser bypass condition is applicable to both units. For Unit 2, refer to LER supplement 316l98-004-01.
| |
| The known bypass flow paths summarized below represent the condition as reported on August 12, 1998:
| |
| Refueling Cavity Drains Backdraft damper of air return fans Ice Condenser AirHandling Unit line 1-CPS-209, 1-CPS-210 1-VMO-101 Divider Barrier Hatches Glycol Lines through Ice Condenser End Wall Open Area in Ft2 2.20 0.36 0.005 0.017 1.069 1.4 0.66 TOTAL5.71
| |
| | |
| NRC FORM 36BA U.S. NUCLEAR REGULATORY COMMISSION IB-1998)
| |
| LlCENSEE EVENT REPORT (LER)
| |
| TEXT CONTINUATION DOCKET Iz)
| |
| LER NUMBER (Bl PAGE I31 Cook Nuclear Plant Unit 1 05000-315 YEAR 1998 SEQUENTIAL NUMBER 037 REvisioN 4 OF 5
| |
| NUMBER 01 The known bypass flow paths summarized below represent the current condition:
| |
| Refueling Cavity Drains Backdraft damper of air return fans Ice Condenser AirHandling Unit line 1-CPS-209, 1-CPS-210 1-VMO-101 Divider Barrier Hatches Glycol Lines through Ice Condenser End Wall CEQ Staiiwell and Vent Well Drain Lines CEQ Fan Room Divider Barrier Seal Open Area in Ft2 2.20 0.36 0.005 0.0 (repaired) 0.0 (repaired) 1,4 0.66 0.1 0.007 30.78 TOTAL 35.51 The cumulative bypass has been evaluated, and it has been concluded that the safety significance of this condition is negligible.
| |
| Therefore, there were no implications to the health and safety of the public.
| |
| Updated Final Safety Analysis Report (UFSAR) Chapter 5, Section 5.2.2.4 states that the design basis bypass'area is 5 ft2.
| |
| UFSAR Chapter 14.0 describes the accident analyses for different size pipe breaks and the allowable ice condenser bypass flowfor each case.
| |
| Analysis results indicate a value of 35 ft2 as the allowable deck leakage area for the, entire spectrum of break sizes.
| |
| The limiting case is an 8 inch break with one spray pump operating (2000 gpm at 80,degrees F).
| |
| A second UFSAR analysis, using a more realistic method, states that with one spray pump the deck leakage could be 56 ft2 for an 8 inch break.
| |
| This analysis takes credit for passive heat sinks and additional containment spray.
| |
| Thus the identified value of historical value of bypass (approximately 30.78 + 5.71 = 36.49 ft2) for Unit 1 is bounded by UFSAR
| |
| : analysis, but is outside of the ice condenser design basis value of 5 It2.
| |
| Therefore, since the plant was not in an
| |
| 'nanalyzed condition, the ENS report made August 12, 1998, in accordance with 10CFR50.72(b)(2)(i), was determined to have been unnecessary.
| |
| | |
| ==CORRECTIVE ACTIONS==
| |
| Numerous material condition waikdowns and assessments have been performed, which have increased the potential to identify bypass paths in the divider barrier.
| |
| Significant degraded conditions resulting in divider barrier bypass are being corrected via corrective maintenance or design changes as they are identified.
| |
| The Refueling Cavity Drains are permanent bypasses, which of course will remain open.
| |
| The backdraft damper of the air return fans, ice condenser AHU fine and the CEQ stairwell and vent weil drain line bypasses are currently not scheduled for repair and represent an insignificant contribution to the cumulative ice condenser bypass.
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| The DBS ice condenser bypass will be corrected via a design change prior to Mode 4.
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| To prevent unauthorized or inadvertent design changes, 12 PMI 5040.DCP.001 "Design Change Determination", has been developed and implemented.
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| To enhance recognition of a design change, 12 PMI 2291.PLAN.001 'Work Control Planning Process," is being implemented, Additionally, the UFSAR validation project willenhance the quality of the design basis and configuration documentation.
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| Containment is one of the selected systems. | |
| Procedure 12 EHP 6040 PER.154, "Containment Divider Barrier Walkdown," has been developed to guide inspection of the divider barrier on a refueling outage frequency for possible bypass paths. | |
| This procedure includes provisions to ensure that the design basis allowable cumulative bypass is not exceeded, through correction andlor tracking of any identified bypass paths.U.S. NUCLEAR REGULATORY COMMISSION (6-1998I LICENSEE EVENT nEPORT (LER)
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| TEXT CONTINUATION DOCKET (2I LER NUMBER (6I PAGE (3)
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| Cook Nuclear Plant Unit 1 05000-315 YEAR 1998 SEQUENTIAL NUMBER 037 REVISION 5
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| QP 5
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| NUMBER 01 SIMILAREVENTS 316/98-00440
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