United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 90-77: Inadvertent Removal of Fuel Assemblies from the Reactor Core

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C.  20555
 
                              December 12, 1990
 
 
Information Notice No. 90-77:  INADVERTENT REMOVAL OF FUEL ASSEMBLIES 
                                   FROM THE REACTOR CORE
 
 
Addressees:
 
All holders of operating licenses or construction y�tC��K�C�pressurized-water
reactors (PWRs).
 
Purpose:
 
This information notice is intended to alert addressees to potential 
problems pertaining to the removal of nuclear fuel from the reactor core.  
It is expected that recipients will review the information for 
applicability to their facilities and consider actions, as appropriate, 
to avoid similar problems.  However, suggestions contained in this 
information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required.
 
Description of Circumstances:
 
On October 4, 1990, Indian Point Nuclear Generating Unit 3 was in a 
refueling outage.  The licensee was removing the upper core support 
structure (upper internals) from the reactor vessel in preparation for 
refueling the core.  Upon initiating a lateral move of the upper core 
support structure, crane movement was stopped upon the discovery that two 
peripheral fuel assemblies were attached to the bottom of the upper core 
plate, which is part of the upper internals package.  An underwater 
camera inspection had been conducted after vertically lifting the upper 
core support structure from the reactor vessel.  This inspection was 
prompted by earlier analysis of noise diagnostics data, confirming the 
existence of a loose part which resembled a fuel assembly locating pin in 
the steam generator channel head.  Due to poor camera location and 
lighting, the attached fuel assemblies were not recognized during the 
initial camera inspection.  
 
The licensee's fuel assembly retrieval procedure developed to facilitate 
their recovery included: (1) performing a static lift (no lateral 
movement) of the upper internals package until the fuel assemblies were 
approximately 1 foot above the vessel flange, (2) rotating the upper 
internals package so that the fuel assemblies would pass over the cavity 
seal one at a time, and (3) positioning the assemblies such that they 
could be lowered into specially fabricated steel baskets, which were 
located in the deep end of the refueling cavity.  During retrieval 
activities, one of the assemblies inadvertently dropped into its basket 
when the brakes on the overhead crane were applied with the assemblies 
positioned over their baskets.  The licensee lowered and 
 
 
9012060205 
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                                                       IN 90-77 
                                                       December 12, 1990 
                                                       Page 2 of 3
 
 
freed the remaining assembly without incident.  No radiological release 
or breach of fuel integrity resulted from dropping the fuel assembly.
 
Discussion: 
 
The licensee was using a 350,000 lb-capacity polar crane with a Dillon 
load cell to lift the upper core internals package (weighing 
approximately 119,800 lbs).  The suspended fuel assemblies together 
weighed approximately 2600 lbs.  During the lift, the licensee did not 
detect the additional weight because the weight of the upper internals 
(with suspended fuel assemblies) was within the maximum allowable weight 
of 125,800 lbs, as specified by the licensee's refueling procedure.  
 
Each of the two assemblies were attached to the upper core plate by bent 
fuel assembly guide pins as shown in Attachment 1.  These guide pins 
extend down-ward from the upper core plate and insert into two holes in 
the upper nozzle of the fuel assembly when the upper core internals 
structure is properly aligned over the top of the core.  For each of the 
suspended fuel assemblies, the licensee found that one guide pin was bent 
and not inserted into the top nozzle hole (upper nozzle S-hole on 
Attachment 1) of the fuel assembly, with the other guide pin bent and 
wedged into the assembly.  In this condition, the guide pin suspended the 
assembly at an angle of approximately 7 degrees.  The licensee has 
determined that the fuel assembly guide pins were damaged during the 
previous refueling outage when the upper internals package was being 
removed from the upper internals storage stand.
 
Similar problems involving suspended fuel assemblies have occurred 
previously. Information Notice 86-58, "Dropped Fuel Assembly," describes 
a similar situation at the Haddam Neck Generating Station in which the 
licensee inadvertently lifted an assembly when removing the upper 
internals.  In this situation, the assembly dropped 2 to 4 feet onto the 
reactor core when the upper internals were moved laterally.  The dropped 
assembly and the two assemblies it impacted were damaged; however, no 
radiological release occurred.  
 
Another similar event occurred at the Palisades Nuclear Power Station (a 
Combustion-Engineering plant) on September 3, 1988.  At Palisades, the 
licensee was removing the upper guide structure (UGS) from the vessel and 
discovered a fuel bundle attached to the bottom.  The licensee freed the 
fuel bundle using a J-hook manipulated by a worker supported in a JIB 
crane while the fuel bundle was suspended over the reactor core.  The 
root cause of the fuel bundle becoming attached to the UGS was attributed 
to the bundle adhering to the UGS bundle guide pins.
 
Other licensees have identified fuel assembly guide pins that were bent 
for a variety of reasons.  At Byron Station, Unit 2, on October 8, 1990, 
the licensee inadvertently bent approximately 8 guide pins due to an 
error of a polar crane floor director.  The crane floor director gave a 
hand signal to lower the upper internals package prematurely, while 
approximately 1/4 of the upper internals were still over the upper 
internals storage stand.  As a result, the upper internals package 
impacted the storage stand and bent the guide pins. 
. 
 
                                                       IN 90-77 
                                                       December 12, 1990 
                                                       Page 3 of 3
 
 
Licensees may wish to consider reviewing their procedures and equipment 
prior to performing activities which may lead to inadvertent damage to 
fuel assembly guide pins and inspecting the guide pins before 
reinstallation of the upper internals package into the reactor vessel.  
When reviewing their procedures (to assure the ability of the reactor 
cavity seal to withstand the mechanical, thermal, and radiation impacts 
from a dropped fuel assembly) licensees may also wish to consider the 
need to carefully inspect the upper core support structure as it is 
initially raised from the reactor vessel to ensure that no core 
components are suspended.
 
This information notice requires no specific action or written response.  
If you have any questions about the information in this notice, please 
contact the technical contact listed below or the appropriate NRR project 
manager. 
 
 
 
 
                                Charles E. Rossi, Director
                                Division of Operational Events Assessment
                                Office of Nuclear Reactor Regulation
 
 
Technical Contact:  John Thompson, NRR
                    (301) 492-1171
 
 
Attachments:  
1.  Indian Point 3 Detailed View Showing Suspended
      Fuel Assembly from Bottom of Upper Internals
      Package
2.  List of Recently Issued NRC Information Notices
.ENDEND
Page Last Reviewed/Updated Tuesday, November 12, 2013