ML20085N393
| ML20085N393 | |
| Person / Time | |
|---|---|
| Site: | University of Iowa |
| Issue date: | 10/29/1991 |
| From: | Danofsky R IOWA STATE UNIV., AMES, IA |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 9111150082 | |
| Download: ML20085N393 (3) | |
Text
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IOWA STATE UNIVERSITY ['"f%"1b,ge,m,,,,
OT S C I E N C E A N D T L C H N O L O G V Nudm hwnnrum IWum to4 Nudcar Digineering Lab Docket No. 50-116 Ames, Iowa Soon 223o
$is 294 5840 October 29, 1991 Regional Administrator Region III Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137
Subject:
Discoloration of Low Enrichment Uranium Fuel Cladding on Iowa State Un!versity's UTR-10 Reactor
Dear Sir:
This is a detailed report concerning the unexpected discoloration of the low enriched uranium (LEU) fuel plate cladding. The initial report of the cladding discoloration was made on October 29, 1991, via a phone conversation between John Adams, Iowa State University and Charles Cox, NRC Region III. We do not feel that a special report per 6.6.2 of the Technical Specification of license R-59 is required for the cladding discolcration. 'We have taken this position because we feel that the discoloration of the cladding is only superficial and can not be considered as a significant degradation in the fuel cladding which will result in exceeding prescribed personnel or environnental radiation exposure limits.
Recently the UTR-10 Reactor was converted from high enriched
, uranium fuel to a low enriched uranium fuel. While performing l
the required startup testing an unexpected discoloration was noticed on the dummy fuel plates which wcre being removed from the core as gradual addittora of f.el were made to achieve the desired excess reactivity. An investigation to determine the l
! cause was commenced and startup testing was continued. During subsequent fuel additions, it was noticed that the disculoration
! process was continuing. The Reactor Manager issued an order which prohibited further operation of the reactor. This order was given on the afternoon of September 20, 1991. ISU's Reactor Use
!- Committee, EG&G Idaho (the LEU conversion contractor) and Babcock and Wilcox (the fuel fabricator) were notified of tne problem.
A dummy plate which exhibited advanced discoloration was removed from the reactor core during the last addition of fuel. This l plate provided two samples which were sent to Iowa State University's Materials Analysis and Research Laboratory (MARL) for analysis using their scanning electron microscope (SEM). An 91ii160082 911029
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- olemental' analysis of the discolored materials was performed using Energy Dispersive X-Ray Spectroscopy (EDS). The EDS !
analysis indicated the presence of two elements, aluminum and oxygen. It should be noted at this time that elemental :i l
identification using-EDS techniques is limited to those elements with atomic numbers greater than or equal ta six (carbon or above).
A visual inspect *Sn wes also conducted on the SEM samples. The SEM-revealed both pitting and raised imperfections. The pitted area analyzed contained two pits approximately the same size and _,
shape.. Deth.had irregular boundaries and the pits length measured 55 microns with a width of 25 microns and an estimated depth of 10 microns. EDS analysis of the pitted areas indicated the presence of only aluminum and oxygen. The pitted area analyzed was typical of others observed on thp sample and appeared to be randomly distributed. The visual inspection was mado-at a magnification of 1000X.
The SEM visual inspection also revealed raised imperfections as mentioned earlier. A typical raised imperfection was selected and analyzed at a magnification of.500X. It measured 80 microns x 50 microns (length and width). *!eight can be estimated as 10 to 20 microns. The imperfection's surface was irregular and the EDS analysis indicated the presence of aluminum and oxygen.
Polaroid photographs were taken of the_ raised imperfection and pitted areas analyzed. These photonraphs were shown to the B&W representatives and were loaned to EG&G for analysis.
The information obtained from the SEM/EDS analysis along with another sample was provided to MARL for X-Ray Defractometer analysis. The goal of this analysis was to identify the actual compound which was causing the discoloration. The report of the X-ray diffraction analysis identified the mineral Bayerite, a form of cluminum hydroxide. The results of the X-ray diffraction was provided to EG&G.
A sample of the primary coolant has been provided to Iowa State University's Analytical Services Laboratory for chemical analysiL. In addition to our normal chemical analyses six other analyses will be performed. The results of analyses are not yet available. A fission product activity analysis performed on 10/'28/91 resulted in the following activities: alpha-beta <1.3 x 10' pci/mt and alpha = 4.3 x 10'" gci/mt. These concentrations are near the minimum detectible that our equipment is capable of measuring.
Representatives 3f B&W visited our reactor on October 15, 1991 for a fuel inspection. .The group from B&W was headed by Richard B. Chaffin and was accompanied by members of their engineering staff and quality assurance staff. Following their
-visit here they proceeded EG&G Idaho to meet with Tony Vinnola. A sample of the dummy fuel plate and photographs were sent with Mr. Chaffin to give to Mr. Vinnola.
n Questions concerning the information provided above may be directed to Dr. Richard llendrickson, Reactor Manager at (515)294-6422 or (515)233-1248, or to John Adams, Reactor Supervisor at (515)294-0539. I i
Sincerely, A
Richard A. Danofsky Facility Director l cc:' Charles Cox, NRC Regior III Theodore 11. Okiishi, Chairman, Mechanical Engineering Dept.
Richard llendrickson, Reactor Manager Thomas L. Zimmerman, Chairman, Reactor Use Committeo US NRC Document Control Desk Tony Vinnola, EG&G Idaho Ted Michales, U.S. NRC l
!