ML19354E578
| ML19354E578 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 01/26/1990 |
| From: | Cockfield D PORTLAND GENERAL ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-89-003, IEB-89-3, NUDOCS 9001310405 | |
| Download: ML19354E578 (4) | |
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David W. Cockfield Vice President, Nuclear Trojan Nuclear Plant Docket 50-344 License NPF-1 U.S. Nuclear Regulatory Comission Attn:
Document Control Desk Washington DC 20555 Dear Sirst Portland General Electric Company (PCE)
Response to Nuclear Regulatory Comission (NRC)Bulletin 89-03, " Potential Loss of Required Shutdown Martin Durina Refuelina Operations" The NRC issued Bulletin 89-03, " Potential Loss of Required Shutdown Margin During Refueling Operations", on November 21, 1989. The bulletin specified threo (3) action items to assure that adequate shutdown margin is main-tained during all refueling operations.
This letter provides PCE's posi-tion for each of the three specific action items.
Sincerely, Attachment c:
Mr. John B. Martin Regional Administrator, Region V U.S. Nuclear Regulatory Comission Mr. David Stewart-Smith State of Oregon Department of Energy Mr. R. C. Barr NRC Resident Inspector Trojan Nuclear Plant escribedandswo he%L) &
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License NPF-1 Attachment Page 1 of 3 l
PORTLAND GENERAL ELECTRIC COMPANY (PGE)
RESPONSE TO NUCLEAR REGULATORY COMMISSION (NRC)
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BULLETIN 89-03, " POTENTIAL LOSS OF REQUIRED SHUTDOWN MARCIN j
DURING REFUELING OPERATIONS". DATED NOVEMBER 21. 1989
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Background
This bulletin addressed the potential loss of required shuldown margin l
during the movement and placement of fresh fuel during refueling operations.
1 Fresh fuel assemblies may be placed in a more reactive configuration than anticipated during the reload process.
Previously performed design I
analyses may not be sufficient to assure that the shutdown margin will be 1
maintained for all intermediate fuel assembly positions. The grouping of fresh reactive fuel assemblies could cause an inadvertent loss of shutdown margin below the 5 percent AK/K required.
All pressurized water reactor (PWR) licensees were requested to assure that adequate shutdown margin be maintained during all refueling operations. PGE's position on each of the raquested action items is provided below.
WDC Bulletin 89-03 Action Item 11 Assure that any intermediate fuel assembly configuration (including H
control rods) intended to be used during refueling is identified and evaluated to maintain sufficient refueling boron concentration to result in a minimum shutdown margin of approximately 5 percent AK/K.
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PGE Response:
The Trojan Nuclear Plant fuel assemblies may be stored in temporary locations during refueling because.of the difficulty encountered in seating a fuel assembly in the desired core location. When this-
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situation occurs, the fuel assembly is " parked" in a core perimeter J
baffle location, usually at a corner for lateral support of the assembly on two sides. This perimeter location always allows neutron leakage in at least one radial dimension which lowers the reactivity of the configuration. Only the core perimeter locations are used to " park" fuel assemblies, and the inboard core space will normally be vacant until near the completion-of the reload when the reactivity for the analyzed design configuration is approached. The reload fuel assemblies contain rod control clusters, if called for in the core design, which reduces positive reactivity of those assemblies.
Trojan Nuclear Plant Document Control Desk Docket 50-344 January 26, 1990 License NPF-1 Attachment Page 2 of 3 The Trojan Plant Operating Manual Fuel Handling Procedure (FMP) 5-13
" Fuel Shuffle and Position Verification", provides the administrative controls for the fuel shuffle procedure to regulate the location of fuel assemblies during the refueling process.
Trojan Technical Specification (TTS) 3.9.1 requires that the refueling boron concentration be 1,000 ppm.
This amount of boron results in a 2
shutdown margin of typically 9 percent AK/K in the fully loaded core.
Reactivity scoping studies have previously been performed for the types of intermediate fuel assembly configurations that arise during the Trojan core reloading evolution.
The results of these studies conclude that the shutdown margin will be g5 percent AK/K.
The Trojan Nuclear Plant has only used nuclear fuel enriched to 13.5 percent to date.
The 1990 Refueling Outage will have some fuel assemblies enriched to 3.6 percent. TTS 5.6.1.1 allows the fuel enrichment to be 4.5 percent. Studies have been performed to analyze the reactivity inglications of using 4.5 percent enriched fuel and the practice of using core perimeter temporary storage locations with 2,000 ppm boron. The studies concluded that the shutdown margin will always be 15 percent AK/K provided the boron concentration is g2.000 ppm and the temporary locations are decoupled from the remaining core by a vacant position.
When the core is near its fully loaded configuration, the core decoupling cannot exist, but at this condition the core reactivity is near the analyzed core design configuration which will have the necessary shutdown margin.
NRC Bulletin 89-03 Action Item 2:
Assure that fuel loading procedures only allow those intermediate fuel assembly configurations that do not violate the allowable shutdown margin, and that these procedures are strictly adhered to.
PGE Response:
FHP 5-13. " Fuel Shuffle and Position Verification", will be revised to include the results of the reactivity scoping studies summarized in Item 1 above, and to stress and highlight the concerns of this bulletin.
This will be done by including a precaution step in FHP 5-13 that -
specifies the temporary placement of fuel assemblies be located on a perimeter location on the baffle plates with the inbcard position vacant (unless near fully loaded) and not be grouped together in.a local area.
Any intended deviation from this procedure will require that the Reactor Engineering Group be contacted to evaluate alternate locations. This l
procedure revision will be completed before the 1990 refueling core unload / reload begins.
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Trojan Nuclear Plant Document Control Desk Docket 50-344 January 26, 1990 License NPF-1 Attachment page 3 of 3 NRC Bulletin 89-03 Action Item 3:
Assure that the staff responsible for refueling operations is trained in the procedures recommended in Item 2 above and understands the potentini consequences of violating these procedures. This training should include the fundamental aspects of criticality control with higher enriched fuel assemblies.
PCE Response:
The Trojan Nuclear Plant personnel involved with specifying the core reload sequences are knowledgeable of the reactivity concerns of this bulletin. The Trojan reactor engineering and nuclear fuels design staffs had previously reviewed intermediate fuel. configuration reactivity effects of 3.5 percent enriched fuel prior to NRC Information Notice 89-51, " Potential Loss of Required Shutdown Margin During Refueling Operations", dated May 31, 1989. To support 1) a TTS amendment in March of 1989 to allow higher fuel enrichments, 2) WRC Information Notice 89-51, and 3) NRC Bulletin 89-03, intermediate fuel configuration reactivity effects were reevaluated at enrichments of up to 4.5 percent.
The staff responsible for performing refueling operations will be trained on the procedure revisions recommended in Item 2 above and the potential consequences of violating these procedures. This training will be completed before the 1990 refueling core unload / reload begins.
CFM/bsh 4204W.0190
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