Information Notice 2002-03, 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 STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001 January 10, 2002 NRC INFORMATION NOTICE 2002-03: HIGHLY RADIOACTIVE PARTICLE CONTROL
PROBLEMS DURING SPENT FUEL POOL
CLEANOUT
Addressees
All holders of operating licenses for nuclear power reactors, holders of licenses for permanently
shutdown 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 alert
addressees 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 Electric
Station 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 to
alarm. 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 particle
control zone coverage for the entire refueling floor. Additional actions undertaken at that time
included formation of a root cause event review team. The teams 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 particle
control 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 refueling
floor. 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 during
December 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 licensees 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 licensees evaluation had failed to consider properly and account for the potential for
substantial 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 been
directly 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 a
particle on a workers 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. Discussion
During 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 licensee
had 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 improve
its 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 challenging
radiological 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 to
focus 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 eventthat 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 any
questions 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 Regulation
Technical contacts: James E. Wigginton, NRR James D. Noggle, Region I
301-415-1059 610-337-5063 E-mail: jew2@nrc.gov E-mail: jdn@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence
OFFICE REXB Tech Ed IOLB SC:REXB RORP
NAME EGoodwin* PKleene* GTracy* JTappert* Wbeckner*
DATE 12/20/2001 6/19/2001 8/20/2001 6/26/2001 01/08/2002
Attachment 1 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
_____________________________________________________________________________________
2002-02 Recent Experience with 01/08/2002 All holders of operating licenses
Plugged Steam Generator for pressurized-water reactors
Tubes (PWRs), except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor.
2002-01 Metalclad Switchgear Failures 01/08/2002 All holders of licenses for nuclear
and Consequent Losses of power reactors.
Offsite Power
2001-19 Improper Maintenance and 12/17/2001 All holders of operating licenses
Reassembly of Automatic Oil for nuclear power reactors, Bubblers except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel.
2001-18 Degraded or Failed Automated 12/14/2001 All uranium fuel conversion, Electronic Monitoring, Control, enrichment, and fabrication
Alarming, Response, and licensees and certificate holders
Communications Needed for authorized to receive safeguards
Safety and/or Safeguards information. Information notice is
not available to the public
because it contains safeguards
information.
2001-17 Degraded and Failed 12/14/2001 All uranium fuel conversion, Performance of Essential enrichment, and fabrication
Utilities Needed for Safety and licensees and certificate holders
Safeguards authorized to receive safeguards
information. Information notice is
not available to the public
because it contains safeguards
information.
2001-08, Update on Radiation Therapy 11/20/2001 All medical licensees.
Sup. 2 Overexposures in Panama
2001-16 Recent Foreign and Domestic steam Tubes and Internals
Experience with Degradation of Generator
______________________________________________________________________________________
OL = Operating License
CP = Construction Permit