Information Notice 2005-05, Improving Material Control and Accountability Interface with Criticality Safety Activities at Fuel Cycle Facilities
ML050590234 | |
Person / Time | |
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Issue date: | 03/10/2005 |
From: | Pierson R NRC/NMSS/FCSS |
To: | |
References | |
IN-05-005 | |
Download: ML050590234 (5) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, DC 20555 March 10, 2005 NRC INFORMATION NOTICE 2005-05: IMPROVING MATERIAL CONTROL AND
ACCOUNTABILITY INTERFACE WITH
CRITICALITY SAFETY ACTIVITIES AT FUEL
CYCLE FACILITIES
ADDRESSEES
All licensees authorized to possess a critical mass of special nuclear material.
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform
addressees of a safety concern related to criticality safety at fuel fabrication and other facilities
processing, storing, or handling critical masses of fissile material. The safety concern arises
when licensees fail to establish and maintain a communication process between criticality
safety staff and material control and accountability (MC&A) staff, in order to support timely
identification of fissile material-related process upsets that challenge the criticality safety basis
for the facility. It is expected that licensees will review this information and consider actions, as
appropriate, to avoid similar problems. Suggestions contained in this IN are not NRC
requirements; therefore, no specific action nor written response is required.
DESCRIPTION OF CIRCUMSTANCES
Under 10 CFR Parts 70 and 76, certain licensees processing, storing, or handling critical
masses of fissile material are required to analyze accident scenarios leading to criticality and
provide reliable controls to assure that inadvertent criticality events are highly unlikely.
Recently, a licensee reported an event, to the NRC, concerning operation of an incinerator
outside of the approved safety basis. The licensee had performed a criticality safety evaluation
of the incinerator approximately 8 years previously and had concluded that criticality was not
credible outside of the primary combustion chamber.
The licensee nuclear criticality safety (NCS) analysis focused on accumulation of sufficient
mass in the incinerator system to support criticality. Licensee NCS engineers concluded that
very limited amounts of ash would carry over from the incinerator primary combustion chamber
to the remainder of the incinerator system and that mass controls on the primary combustion
chamber would limit uranium concentration in the ash to less than 21.6 percent throughout the
incinerator system. This led the licensees NCS engineers to conclude that criticality outside
the primary combustion chamber was not credible due to normal operations and
expected upsets.
At the time that this NCS analysis was approved, licensee MC&A staff possessed sampling
data showing concentration levels above 21.6 percent uranium in some parts of the incinerator
system. In addition, licensee MC&A staff were aware, from approximately 15 years of
operational experience, that substantial amounts of fissile material routinely accumulated in
parts of the incinerator system where criticality analysis assumed minimal accumulation.
The material accumulation event was identified initially when a licensee criticality safety
engineer reviewed MC&A sampling data. Subsequent investigation of the event by the licensee
revealed that ash deposits at various locations in the incinerator routinely exceeded the
21.6 percent uranium concentration assumed to be bounding for ash and that the mass of ash
deposited also exceeded expectations. Licensee review of MC&A sampling records confirmed
that both concentration and deposit information were known prior to approval of the original
NCS analysis.
The amount of fissile material that accumulated in the uncontrolled parts of the incinerator
system exceeded a critical mass. Extensive investigation by the licensee and the NRC
revealed a poor interface between licensee criticality safety and MC&A staff. This poor
interface, resulting from failing to require routine interaction, apparently was a factor in the
failure to identify the process upset before the event occurred.
Discussion
Two issues from this event are of concern to the NRC. The first issue is that licensee NCS staff
had not ensured that MC&A staff were familiar with the criticality safety basis for the incinerator
system. Specifically, MC&A staff were not aware of the basic assumption that fissile material
would not accumulate in the upper chamber or flue. Had MC&A staff been made aware of this
assumption, they would likely have identified the reality of incinerator ash deposition and
caused the NCS staff to place additional criticality controls on at least those two sections of the
incinerator system.
The second issue is that the MC&A sampling data routinely reported mass and concentration
values that challenged the criticality safety basis, and this fact was not recognized by criticality
safety engineers because the data were not routinely provided to them.
Licensee NCS staff are familiar with the criticality safety basis and underlying assumptions.
MC&A staff have a general knowledge of where material is currently located and where process
hold-up is likely to occur. Communication between these two organizations is necessary to
assure that the criticality safety basis is not violated.
Failure to establish appropriate interactions between criticality safety and MC&A staff exposes
fuel cycle licensees to this type of programmatic failure. Licensees should consider actions, as
appropriate, to mitigate this vulnerability. NCS staff should be familiar with MC&A sampling
methodology and data reporting and should routinely review MC&A reports for location of
material in relation to the criticality safety basis. MC&A staff should be trained on the criticality safety basis, particularly bounding assumptions about fissile material accumulation, and should
routinely review new or changed NCS analyses.
This IN requires no specific action nor written response. If you have any questions about the
information in this notice, please contact the technical contact listed below.
/RA/
Robert C. Pierson, Director
Division of Fuel Cycle Safety
and Safeguards
Office of Nuclear Material Safety
and Safeguards
Technical Contact:
Dennis Morey, NMSS
301-415-6107 e-mail: dcm@nrc.gov
Attachment: List of Recently Issued NMSS Generic Communications safety basis, particularly bounding assumptions about fissile material accumulation, and should
routinely review new or changed NCS analyses.
This IN requires no specific action nor written response. If you have questions about the
information in this notice, please contact the technical contact listed below.
/RA/
Robert C. Pierson, Director
Division of Fuel Cycle Safety
and Safeguards
Office of Nuclear Material Safety
and Safeguards
Technical Contact:
Dennis Morey, NMSS
301-415-6107 e-mail: dcm@nrc.gov
Attachment: List of Recently Issued NMSS Generic Comminications
ML050590234 OFC TSG FCFB Tech ED TSG NSIR
NAME DMorey:dw JMuszkiewicz Ekraus: by fax MGalloway MWilliams
DATE 2/ 22 /05 3/ 01 /05 2/ 28 /05 2/ 28 /05 3/ 09 /05 OFC FCSS
NAME RPierson
DATE 3/ 10 /05
Attachment Recently Issued NMSS Generic Comminications
Date GC No. Subject
Addressees
12/16/2004 RIS-04-020 NRC Regulatory issue All holders of, and applicants for, Summary 2004-20: a (1) 10 CFR Part 71 certificate
Lessons Learned from of compliance for a radioactive
Review of 10 CFR Parts 71 material transportation package;
and 72 Applications (2) 10 CFR Part 72 cretificate of
compliance for a spent fuel
storage cask; and (3) 10 CFR
Part 72 specific license for an
independent spent fuel storage
installation (ISFSI).
12/01/2004 RIS-04-018 NRC Regulatory Issue All holders of U.S. Nuclear
Summary 2004-18: Regulatory Commission (NRC)-
Expiration Date for 10 CFR approved 10 CFR Part 71 Quality
Part 71 Quality Assurance Assurance Programs (QAPs).
Program Approvals
11/23/2004 RIS-04-017 NRC Regulatory Issue All licensees regulated under 10
Summary 2004-17: CFR Parts 30, 32, 33, and 50.
Revised Decay-in-Storage
Provisions for the Storage
of Radioactive Waste
Containing Byproduct
Material
10/26/2004 IN-04-018 Recent Safety-Related All licensees authorized to
Event at Panoramic possess and use sealed sources
Wet-source-Storage in panoramic wet-source-storage
Irradiator irradiators, and irradiator
vendors.
07/19/2004 IN-04-014 Use of less than Optimal All licensees authorized to
Bounding Assumptions possess a critical mass
in Criticality Safety Analysis of special nuclear material
at Fuel Cycle Facilities
Note: NRC generic communications may be found on the NRC public website, http://www.nrc.gov, under Electronic Reading Room/Document Collections.