Information Notice 2002-03, Highly Radioactive Particle Control Problems During Spent Fuel Pool Cleanout

Highly Radioactive Particle Control Problems During Spent Fuel Pool Cleanout

ML011790547
Person / Time
Issue date:	01/10/2002
From:	Beckner W Operational Experience and Non-Power Reactors Branch
To:
References
TAC MB1382 IN-02-003
Download: ML011790547 (7)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555-0001January 10, 2002NRC INFORMATION NOTICE 2002-03:HIGHLY RADIOACTIVE PARTICLE CONTROLPROBLEMS DURING SPENT FUEL POOL

CLEANOUT

Addressees

All holders of operating licenses for nuclear power reactors, holders of licenses for permanentlyshutdown facilities with fuel onsite, and holders of licenses for non-power reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alertaddressees to recent issues involving evaluation and control of radioactive particles generated

during removal of material from a spent fuel pool prior to shipping the material offsite for

disposal. The issue emphasized in this notice is that highly radioactive (hot) particles represent

a radiological hazard not just in terms of shallow dose to the skin or an extremity but also as a

deep or whole-body dose. 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 are not NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances

Toward the end of a 5-month spent fuel pool cleaning project, the Susquehanna Steam ElectricStation completed compacting irradiated components that had been temporarily stored in the

pool. Working under water remotely, the licensee had used an "advanced crusher and shearer"

(ACS) unit to compact control rod blades and local power range monitors. On October 12,

2000, the ACS was removed from the cask storage pit with a crane after apparently inadequate

cleaning with a high-pressure spray Hydrolazer. The ACS was moved over the refueling floor

and into the reactor head washdown area for further decontamination prior to shipment offsite.

The ACS was not totally wrapped or sealed during this movement. Also, access to the ACS

pathway over the refueling floor was not radiologically controlled during the move. During the movement of the ACS, the refueling floor local area radiation monitor began toalarm. The cause was a previously unidentified highly radioactive particle which had fallen from

the ACS. The particle was later determined to be a 2.78 gigabecquerel (Gbq) [75 millicuries

(mCi)] Co-60 particle, reading approximately 8 sievert/h (Sv/h) (800 rem/h) at contact. The licensee stopped work, shielded and captured the particle, and initiated radioactive particlecontrol zone coverage for the entire refueling floor. Additional actions undertaken at that time

included formation of a root cause event review team. The team's work led to upgraded

controls, surveying, more management oversight and more detailed planning and work

procedures for handling high specific activity particles.A search was then begun for additional hot particles on the refueling floor. Workers in particlecontrol zones were surveyed for particles every 15 minutes, and more protective clothing (PC)

was required for certain work activities. The 15-minute control was a default stay time, and not

based on dose calculations for the high-activity particles known to be present.During the cleanup activities, more than 30 radioactive particles were found on the refuelingfloor. Two high activity radioactive particles found on September 9 and December 6, 2000, had

resulted in shallow-dose equivalent (SDE) exposures of 0.12 and 0.17 Sv (12 and 17 rem),

which is below the annual SDE limit of 50 rem. The licensee discovered two more high-activity

particles, a 0.78 Gbq (21 mCi) particle on November 28, and a 0.7 Gbq (19 mCi) particle on

December 4, 2000; these particles did not result in significant exposure to personnel. No actual

exposures in excess of any annual dose limits occurred during the cleanup activities.During a scheduled NRC health physics, rad-waste transportation, baseline inspection duringDecember 11-15, 2000 (Inspection Report Nos. 05000387/2000-009 and 05000388/2000-009, ADAMS Accession No. ML010250469), the NRC inspector identified significant weaknesses in

the licensee's particle control program. The inspector noted that the licensee had failed to

identify that conventional hand-held survey instruments using standard survey methods were

underestimating the contact dose rates of the particles, thus underestimating the radiological

hazards not just to the skin but in terms of whole body exposure. The licensee's evaluation had failed to consider properly and account for the potential forsubstantial dose to personnel from the high-activity particles. Specifically, the 15-minute worker

stay time was not adequate to prevent potential overexposures from the particles known to be

present in and around the refueling floor. The stay time would have allowed both SDE and total

effective dose equivalent (TEDE) annual exposure limits to be exceeded.Four of the particles found ranged from 0.7 to 2.78 Gbq (19 to 75 mCi). Had the particles beendirectly on the workers' PCs, the TEDE annual limit of 0.05 Sv (5 rem) could have been

exceeded in 25 seconds to 2 minutes, and the SDE limit exceeded in 6 to 21 seconds, depending on the activity of the individual particle.In response to the NRC findings and a 0.17 Sv (17 rem) SDE exposure on December 6 from aparticle on a worker's boot, licensee management stopped all high-risk work, initiated a

comprehensive events evaluation, requested on-site assistance by an industry expert team, and

implemented improved training and communication of lessons learned in this area. DiscussionDuring previous similar processing of irradiated components at Susquehanna in 1991,radioactive particles had been identified with external gamma dose rates greater than

100 rem/hr. However, the plant failed to incorporate fully this previous experience and industry- wide experience into the planning for the 2000 fuel pool clean out project. (NRC Information

Notice No. 90-33, "Sources of Unexpected Occupational Radiation Exposures at Spent Fuel

Storage Pools," also concerns highly radioactive particles.)Prior to the NRC baseline inspection, after the initial event, the work controls that the licenseehad implemented were not sufficient under the circumstances to evaluate and control the

potential radiological challenges posed by these extremely high activity particles. A Notice of

Violation (failure to conduct adequate evaluation and survey) associated with a White finding

(using the Significance Determination Process) was issued. These actions were taken because

of the substantial potential for exposure in excess of the annual limit for TEDE even though no

worker dose limits were exceeded.During the regulatory conference for this violation, the licensee stated that it needed to improveits hot particle surveying, identification, handling, and control. The improvements included

more effective use of remote handling techniques, proactive staging of particle control zones, and aggressive treatment of potential sources of particles by using decontamination and

filtration on systems that communicate with the spent fuel pool.The licensee noted that in cases like this where a contractor was used for a challengingradiological evolution, plant management oversight was essential. That oversight must focus

on, and have sufficient resources to implement and maintain a sense of an acceptable radiation

culture and acceptable practices and standards for radiation work. According to the licensee, this can best be accomplished by direct ownership for significant, high-risk projects

demonstrated by the visible presence and direct oversight of the work by utility managers.Most importantly, this occurrence demonstrated a need to strengthen procedural controls tofocus attention on the large potential doses from these challenging radiological work

environments. The worker training program and job oversight must emphasize the most

important lesson learned from the event-that radioactive particles can present not only

shallow-dose risks but, at higher activity levels, whole body dose risks, which can be much

more significant. This information notice requires no specific action or written response. If you have anyquestions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager./RA/William D. Beckner, Program Director

Operating Reactor Improvements Program

Division of Regulatory Improvement Programs

Office of Nuclear Reactor RegulationTechnical contacts: James E. Wigginton, NRRJames D. Noggle, Region I301-415-1059610-337-5063 E-mail: jew2@nrc.govE-mail: jdn@nrc.govAttachment: List of Recently Issued NRC Information Notices

ML011790547*See previous concurrenceOFFICEREXBTech EdIOLBSC:REXBRORPNAMEEGoodwin*PKleene*GTracy*JTappert*Wbeckner*DATE12/20/20016/19/20018/20/20016/26/200101/08/2002

______________________________________________________________________________________OL = Operating License

CP = Construction PermitAttachment 1 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICES

_____________________________________________________________________________________InformationDate of

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