05000254/LER-1979-030-03, /03L-0:on 791012,GEB-type Fuel Exposures Exceeded Max Averge Planner Linear heat-generation Rate.Caused by Failure to Specify Limits for High Exposure GEB-type Fuel. Curves Extended to Exposure Limit

/03L-0:on 791012,GEB-type Fuel Exposures Exceeded Max Averge Planner Linear heat-generation Rate.Caused by Failure to Specify Limits for High Exposure GEB-type Fuel. Curves Extended to Exposure Limit

ML19210C670
Person / Time
Site:	Quad Cities
Issue date:	11/01/1979
From:	Lihou H COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19210C665	List: 05000254/LER-1979-030, Forwards LER 79-030/03L-0 05000254/LER-1979-030-03, /03L-0:on 791012,GEB-type Fuel Exposures Exceeded Max Averge Planner Linear heat-generation Rate.Caused by Failure to Specify Limits for High Exposure GEB-type Fuel. Curves Extended to Exposure Limit
References
LER-79-030-03L, LER-79-30-3L, NUDOCS 7911190411
Download: ML19210C670 (3)

LER-1979-030, /03L-0:on 791012,GEB-type Fuel Exposures Exceeded Max Averge Planner Linear heat-generation Rate.Caused by Failure to Specify Limits for High Exposure GEB-type Fuel. Curves Extended to Exposure Limit

Event date:
Report date:
2541979030R03 - NRC Website

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60 61 DOCKET NUM8ER 68 63 EVENT DATE 74 75 REPORT DATE do EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h 0

2 i On October 12, 5979, the station receiveid an extention of the Maximum Average l

Planner Linear Heat Generation Rate (MAPLHGR) limit curves for GEB UO and Pt.-UO,,

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o 3 ITTT1 i fuel.

Comparison of the actual limits and extrapolated values used by the computer l

[TTsl showed the extrapolated values to be slightly non-conservative for UO and Pu0 fuel l

0 6 l for exposures greater than 25,000 MWD /T and 26,500 MWD /T respectively.

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The cause of this occurrence was the fallure to have specific MAPLHGR 1imits for high l ITTTl U exposure GEB fuel. Corrective action was for G.E. to extend the MAPLHGR !!mit curves I g;77jl for GEB U0 and Pu-UO fuel to their licensed exposure limit of 40,000 MWD /T and g

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8 9 10 68 69 30 E 309-654-2241, Ext. 187 NAME OF PREPARER PHONE:

LER NUMBER: 79-30/03L-0 LICENSEE NAME: Commonwealth Edison Company Quad Cities Nuclear Power Station FACILITY NAME: Unit One DOCKET NUMBER:

050-254

EVENT DESCRIPTION

Shortly af ter Unit One Cycle 5 startup, Commonwealth Edison Nuclear Fuel Services (NFS) became concerned by the fact that some GEB (improved 7 x 7) type fuel exposures were starting to exceed the exposures for which Maximum Average Plainer Lirear Heat Generation Rate (MAPLHGR) limits had been analyzed. Thus, NFS requested further high exposure MAPLHGR analysis from General Electric. The Station process computer calculates actual operating MAPLHGR values and compares them with the analyzed MAPLHGR limits to determine the fraction of the MAPLHGR limit (MAPRAT = MAPLHGR > MAPLHGR Limit) at which the reactor is operating.

Since the computer had no GEB MAPLHGR limit curve data points greater than 25,000 MWD /T for UO fuel and 20,000 MWD /T for Pu-UO2 fuel, it 2

extrapolated the MAPLHGR limit curve through higher exposures. This extrapolated limit curve was then used to calculate MAPRAT for GEB fuel Fuel and 20,000 MWD /T with exposures greater than 25,000 MWD /T for UO2 for Pu-UO2 fuel. Operation with these extrapolated limits, until G.E.

provided additional analysis, was considered to be conservative since the extrapolated limits had a negative slope and the actual full power MAPLHGR had significant margin to the extrapolated MAPLHGR limits.

On October 12, 1979, the station received, from G.E.,

NEDO 24146A LOCA Analysis Report for Dresden 2, 3 and Quad Cities 1, 2 Nuclear Power Stations, Errata and Addenda Sheet #1, which provided an extention of MAPLHGR 1imit curves for GEB UO2 and GEB Pu-UO2 fuel up to 40,000 MWD /T.

Comparison of the actual limits and extrapolated values used by the computer showed the extrapolated values to be slightly non-conservative fuel f r exp sures greater than 25,000 MWD /T and 26,500 MWD /T, for U02 and Pu-UO2 respectively. The new G.E. MAPLHGR limit curve extentions were immediately entered into the computer.

PROBABLE CONSEQUENCES OF THE OCCURRENCE:

Due to the high exposure depletion of the GEB fuels, it was highly unlikely to obtain MAPLHGR limits using standard control rod sequencing techniques.

Review of the data revealed that the MAPLHGR limi t was never non-fuel arid 0.4% for Pu-UO fuel, all conservative by more than 1.2% for U02 2

other fuel types never exceeded exposures for which MAPLHGR was analyzed.

The smallest margin between any actual operating MAPLHGR and MAPLHGR limit was always greater than 4% for all types of fuel during Unit One Cycle 5, and typical full power margins were 10-20% of the limits.

GEB fuel type margins are significantly larger than these.

Thus, MAPLHGR limits were never exceeded.

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CAUSES

The c9use of this occurrence was the failure of General Electric to pro-vide the station specific MAPLHGR limits for high exposure GEB fuel.

CORRECTIVE ACTION

The MAPLHGR limit curves for GEB UO and Pt.-UO fuel have been extended 2

7 to their 1icensed exposure 1imit of 40,000 MWD 7T.

In addition the Unit Two MAPLHGR limit curve for 7 x 7 fuel, which extends to 30,000 MWD /T, was reduced by 10% of its 35,000 MWD /T extrapolated value of 11.6 KW/f t.

Thus, the 1Imit for 35,000 MWD /T Is presently about 10.44 KW/ft and wilI remain so until end of Unit Two Cycle 4, at which time G.E. will pro-vide high exposure MAPLHGR limits for Unit Two Cycle 5 These actions should preclude any further events of this type.

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