Information Notice 2000-02, Failure of Criticality Safety Control to Prevent Uranium Dioxide Uo2 Powder Accumulation
| ML003685215 | |
| Person / Time | |
|---|---|
| Issue date: | 02/22/2000 |
| Revision: | 0 |
| From: | Weber M F NRC/NMSS/FCSS/FCOB |
| To: | |
| Burrows S A | |
| References | |
| IN-00-002 | |
| Download: ML003685215 (6) | |
UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDSWASHINGTON, February 22, 2000NRC INFORMATION NOTICE 2000-02:FAILURE OF CRITICALITY SAFETY CONTROL TOPREVENT URANIUM DIOXIDE (UO2) POWDERACCUMULATION
Addressees
- All Nuclear Regulatory Commission (NRC) licensed fuel-cycle conversion, enrichment, andfabrication facilities.
Purpose
- The NRC is issuing this information notice to alert addressees to a problem recently noted withsafety-significant level probes that are not self-checkin A level probe in a uranium dioxide (UO2) powder hopper failed without indicating a failed condition due to a broken connector inthe level-probe circui This allowed UO2 powder to accumulate in a hopper and approach thecriticality safety mass limit before discover Recipients are expected to review this information for applicability to their facilities and consider actions, as appropriate, to avoid similar problem Suggestions contained in this information notice are not NRC requirement Therefore, no specific action nor written response is required.
Description of Circumstances
- On August 5, 1999, a fuel cycle facility operator noticed that dry UO2 powder was not comingout of a granulator while the granulator was operatin Powder was being automatically fed to the equipment at the time and a level probe was monitoring the powder level in the feed hopper as a primary nuclear criticality safety contro The licensee determined that powder had blocked the compaction section of the granulator and an unusual amount of dry UO2 powder hadaccumulated in the powder hoppe The powder accumulation was not detected by the level- probe on the feed hopper because the probe had failed due to a broken connector in the level- probe circuit.Discussion:A fuel cycle licensee achieves uniform fuel particle size with equipment that compacts UO2powder into a ribbon and then grinds up the compacted powder. Powder is added to theequipment from safe-geometry containers called polypack A known difficulty with this ML003685215Template: NRR-052 IN 2000-022000-02 equipment is that the ribbon of compacted UO2 can jam and block the material flo The safetyof the operation was assured by limiting mass and moderator in the equipmen Primary criticality safety controls on mass included operator monitoring of the equipment, an interlock system limiting the number of polypacks that can be added, and a level-probe in the powder hopper that feeds the compactor.An operator assigned to the compactor/granulator equipment observed that powder was notcoming out of the granulator while the equipment was in operation and powder was being automatically fed to the compacto The operator subsequently discovered that an unusual amount of dry UO2 powder had accumulated in the hopper that feeds the compacto Licenseeinvestigation revealed that the powder hopper level-probe, which was intended to detect this type of failure, did not work due to a broken connector in the level-probe circui Additionally, the licensee determined that the limit on the number of polypacks that could be added to the powder hopper was set too high to prevent the mass limit in the hopper from being reache Also the licensee determined that required visual checks for powder accumulation were set at twice per shift without specific instructions on the required interva Operators were allowed to perform the checks at the beginning and end of a shift which was too long an interval to ensure that the mass of UO2 powder did not exceed the mass limit in the hopper.The primary contributing factor to the event was that the level-probe on the compactor/granulator powder hopper did not self-indicate failure and alert the licensee to a lost contro A properly functioning level probe would have indicated the powder accumulation in the hopper before the powder approached safety limit A self-indicating circuit would have informed the licensee of probe failure so that corrective actions could be taken to restore the control.Additional contributing factors were that the limit on the number of polypacks automaticallyadded to the hopper was set too high to protect against exceeding the mass limit and that the interval between required visual checks was allowed to be too long to assure that accumulations would be seen before the mass limit was exceeded.This event highlights the need to establish the availability and reliability of safety-significantcontrols involving nuclear criticality safety under all credible upset Licensees should evaluate the need for safety-significant electronic equipment to be self-checkin Licensees should also establish that supporting criticality safety controls will actually perform their intended functio IN 2000-022000-02 It is expected that addressees will evaluate the above information for applicability to licensedactivitie This information notice requires no specific actions nor written respons If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate regional office. Michael F. Weber, DirectorDivision of Fuel Cycle Safety and Safeguards Office of Nuclear Material Safety and Safeguards
Technical Contact:
Sheryl A. Burrows, NMSS301-415-6667 E-mail: sab2@nrc.gov
Attachments:
List of Recently Issued NMSS Information Notices List of Recently Issued NRC Information Notices IN 2000-022000-02 It is expected that addressees will evaluate the above information for applicability to licensedactivitie This information notice requires no specific actions nor written respons If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate regional office. Michael F. Weber, DirectorDivision of Fuel Cycle Safety and Safeguards Office of Nuclear Material Safety and Safeguards
Technical Contact:
Sheryl A. Burrows, NMSS301-415-6667 E-mail: sab2@nrc.gov
Attachments:
List of Recently Issued NMSS Information Notices List of Recently Issued NRC Information NoticesFILE NAME: a:\in2000-02.wpd*See previous concurrencesOFCTECH EDFCOBFCOBFCOBIMNSFCSSNAMEEKrauss*SBurrows*WSchwink*PTing*KRamsey*MWeber*
DATE01/21/0001/310002/4/0002/7/0002/4/0002/14/00C = COVERE = COVER & ENCLOSUREN = NO COPYOFFICIAL RECORD COPYAttachment1 IN 2000-02February 22, 2000 LIST OF RECENTLY ISSUEDNMSS INFORMATION NOTICES_____________________________________________________________________________________InformationDate of Notice N SubjectIssuanceIssued to_____________________________________________________________________________________99-33Management of WastesContaminated With Radioactive Materials12/28/99All medical licensees99-32The Effect of the Year 2000Issues on Medical Licensees12/17/99All NRC medical licensees99-31Operational Controls to GuardAgainst Inadvertent Nuclear Critically11/17/99All NRC licensed fuel cycleconversion, enrichment and fabrication facilities99-30Failure of Double ContingencyBased on Administrative Controls Involving Laboratory Sampling and Spectroscopic Analysis of Wet Uranium Waste11/8/99All fuel cycle licensees andcertificates performing laboratory analysis to determine uranium content, in support of administrative criticality safety controls99-29Authorized Contents of SpentFuel Casks10/28/99All power reactor licensees andspent fuel storage licensees and applicants99-28Recall of Star Brand FireProtection Sprinkler Heads9/30/99All holders of licenses for nuclearpower, research and test reactors, and fuel cycle facilities99-27Malfunction of SourceRetraction Mechanism in Cobalt-60 Teletherapy Treatment Units 9/2/99All medical licensees authorizedto conduct teletherapy treatments99-26Safety and EconomicConsequences of Misleading Marketing Information 8/24/99All Distributors and/orManufacturers of Generally Licensed Products99-24Broad-Scope Licensees'Responsibilities for Reviewing and Approving Unregistered Sealed Sources and Devices7/12/99All medical licensees' of broad-scope and master materials licensees
____________________________________________________________________________________OL = Operating License CP = Construction PermitAttachmentIN 2000-02 February 22, 2000 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICES_____________________________________________________________________________________InformationDate of Notice N SubjectIssuanceIssued to_____________________________________________________________________________________2000-01Operational Issues Identified inBoiling Water Reactor Trip and Transient2/11/2000All holders of licenses for nuclearpower reactors99-34Potential Fire Hazard in theuse of Polyalphaolefin in Testing of Air Filters12/28/99All holders of licenses for nuclearreactors and fuel cycle facilities99-33Management of WastesContaminated With Radioactive Materials12/28/99All medical licensees99-32The Effect of the Year 2000Issues on Medical Licensees12/17All NRC medical licensees99-31Operational Controls to GuardAgainst Inadvertent Nuclear Criticality11/17/99All NRC licensed fuel cycleconversion, enrichment and fabrication facilities99-30Failure of Double ContingencyBased on Administrative Controls Involving Laboratory Sampling and Spectroscopic Analysis of Wet Uranium Waste11/8/99All fuel cycle licensees andcertificates performing laboratory analysis to determine uranium content, in support of administrative criticality safety controls99-29Authorized Contents of SpentFuel Casks10/28/99All power reactor licensees andspent fuel storage licensees and applicants99-01, Rev. 1Degradation of PrestressingTendon Systems in Prestressed Concrete Constrainments10/7/99All holders of operating licenseesfor nuclear power reactors99-28Recall of Star Brand FireProtection Sprinkler Heads9/30/99All holders of licenses for nuclearpower, research and test reactors, and fuel cycle facilities