United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 82-31: Overexposure of Diver During Work in Fuel Storage Pool

                                                            SSINS No.: 6835 
                                                            IN 82-31 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                          WASHINGTON, D. C. 20555 

                               July 28, 1982 

Information Notice No. 82-31:   OVEREXPOSURE OF DIVER DURING WORK IN FUEL
                                   STORAGE POOL 

Addressees: 

All nuclear power plant facilities holding an operating license (OL) or 
construction permit (CP). 

Purpose: 

This information notice is provided as a notification of a significant, 
whole-body exposure in excess of regulatory limits to a diver engaged in 
underwater work in a fuel storage pool at a pressurized water reactor. 
Licensees are using divers for an increasing number of maintenance and 
inspection tasks and have demonstrated substantial exposure savings by using
proper underwater work techniques. However, this incident demonstrates the 
potential for serious overexposures in very short time periods. Dose rates 
from LWR spent fuel assemblies and other irradiated components can be 
extremely high. A single spent fuel bundle can create a 104 - 106 R/hour 
radiation field at close proximity. Irradiated objects (e.g., BWR fuel 
channels) can read from ten to hundreds of R/hour on contact. It is expected
that licensees will review the information for applicability to their 
facilities. No specific action or response is required at this time. 

Description of Circumstances: 

On June 1, 1982 while installing fuel rack support plates in the Indian 
Point Unit No. 2 fuel storage pool, a contractor diver received an exposure 
of about 8.7 rems to the head. A second diver, also working in the pool on 
June 1, received a whole body dose of about 1.6 rems. 

Upon exiting the pool the most highly exposed diver's 500 mR and 5-R pocket 
dosimeters (worn on the head) were off-scale. The licensee suspended all 
diving operations, read the multiple TLD's (thermoluminescent dosimeters) 
worn on other body locations, and initiated an investigation of the 
incident. The fuel storage pool modification work had been ongoing for about 
three months, with daily exposures averaging about 50 millirems per diver. 

A review of the incident by licensee and NRC personnel found several factors
that contributed to the overexposure: 

(1)  An irradiated fuel assembly was mistakenly transferred to a location 
     two to four feet from the subsequent divers' work location. A 
     poor-quality copy of the fuel transfer procedures was apparently a 
     factor in the improper fuel transfer. Limited visability in the pool 
     caused by cloudy


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                                                           IN 82-31 
                                                           July 28, 1982  
                                                           Page 2 of 3 

     water and a lack of pool underwater lighting may have prevented visual 
     detection of the misplaced fuel assembly. No QA (quality assurance) 
     reviews were required or conducted of the irradiated fuel assemblies 
     locations between fuel movements and the exposure incident. 

(2)  The prior-to-work radiation survey of the pool was performed with an , 
     underwater ionization chamber connected by a long cable to the 
     detector. These surveys failed to detect the misplaced fuel assembly's 
     radiation field of several hundred R/hr within two feet of the divers 
     work area. Intermittent, erratic underwater survey instrument behavior 
     had been observed during previous dives. The licensee attributed the 
     survey instrument's erratic behavior to a buildup of moisture in the 
     underwater detector chamber housing. 

(3)  Radiation monitoring devices used during the underwater operations 
     failed to function properly. Alarming dosimeters, mounted inside the 
     divers' helmets, failed to alarm at the 200 mR set point. These 
     dosimeters were under the control of the diving contractor and were not
     source checked on the day of the incident. The licensee monitored the 
     dive with the same ionization chamber instrument used for the pre-dive 
     survey, and failed to detect any radiation fields in excess of 1 R/hr 
     in the diver work area. 

Discussion: 

The licensee increased senior management oversight for the spent fuel pool 
project and implemented the following corrective actions. 

(1)  Whenever fuel movement occurs, QA personnel will independently witness 
     and verify the new locations of the fuel assemblies. Other irradiated 
     objects greater than 1 R/hr on contact will be controlled in a similar 
     manner. After any movement of either fuel or irradiated components (>1 
     R/hr), an underwater radiation survey will be conducted before any 
     diving operations will resume. 

(2)  Daily, before any diving operation, a radiation survey of the diving 
     area will be conducted. This survey will be performed using two 
     independent radiation exposure monitoring devices. A survey map of the 
     pool will be updated to reflect current status of ongoing fuel rack 
     modification. 

(3)  Each diver will be equipped with a calibrated, alarming dosimeter; this
     dosimeter will be checked each day before diving operations begin. Each 
     diver will also be equipped with a remote-readout radiation detector 
     which will be continuously monitored by health physics technicians. The
     divers will surface and have their dosimetry checked periodically, any 
     significant deviation from the expected dive work pattern or radiation 
     levels will be grounds for dive termination. 

(4)  Fuel pool clarity and underwater lighting acceptance criteria have been
     established to help ensure adequate visability is maintained. 
.

                                                           IN 82-31 
                                                           July 28, 1982  
                                                           Page 3 of 3  

No written response to this information notice is required. If you need 
additional information about this matter, please contact the Regional 
Administrator of the appropriate NRC Regional Office. 



                                   Edward Jordan, Director  
                                   Division of Engineering and  
                                     Quality Assurance 
                                   Office of Inspection and Enforcement 


Technical Contact:  J. E. Wigginton 
                    301-492-4967 

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