Information Notice 2005-05, Improving Material Control and Accountability Interface with Criticality Safety Activities at Fuel Cycle Facilities

Improving Material Control and Accountability Interface with Criticality Safety Activities at Fuel Cycle Facilities

ML050590234
Person / Time
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

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

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.