DOE/RL-97-59
Revision 0

FINAL REPORT JULY 26, 1997
ACCIDENT INVESTIGATION BOARD REPORT ON THE MAY 14, 1997, CHEMICAL EXPLOSION AT THE PLUTONIUM RECLAMATION FACILITY, HANFORD SITE, RICHLAND, WASHINGTON

3.0 CONCLUSIONS AND JUDGMENTS OF NEED

This section identifies the conclusions and judgments of need developed by the Board using the accident analysis methods described in Section 2.0. Conclusions drawn by the Board were based on significant facts relative to the accident and pertinent analytical results. Judgments of need are managerial controls and safety measures believed to be necessary to prevent recurrence of the accident. The judgments of need are derived from the causal factors and conclusions, and are directed at assisting managers in developing corrective action plans to prevent future accidents.

The Board concluded that this accident could have been prevented if Facility line management had taken reasonable steps to understand and control the storage of HN and HNO3 in Tank A-109 or if RL line management oversight had ensured that the Facility was maintained within the safety authorization basis. Based on the results of the barrier analysis, there were physical, management, and administrative barriers that failed, which allowed the accident to occur; any one of these barriers, if properly implemented, could have prevented the accident from occurring. The change analysis identified changes that contributed to the accident including the failure to remove the HN and HNO3 solution from Tank A-109 in accordance with the long-term shutdown procedure, and failure to maintain the HN and HNO3 solution in its original dilute concentration during the storage period. Both the change and barrier analyses techniques confirmed the conclusions that were identified by the Boards causal factor analysis. The investigation revealed that conditions necessary for an autocatalytic reaction of the HN and HNO3 solution are not well known, or documented, during long-term storage. Thus, important lessons learned exist that need to be disseminated to the DOE Complex regarding this information.

The Board concluded that the direct cause of the accident was the concentration by evaporation of the dilute solution in the tank to the point where a spontaneous reaction occurred, creating a rapid gas evolution that over-pressurized the tank beyond its physical design limitations. Table 2 contains other conclusions and corresponding judgments of need identified by the Board.

Table 2. Conclusions and Judgments of Need.

Conclusions Judgments of Need
Standby planning failed to maintain the Facility in a safe condition, consistent with the approved safety authorization basis.  
  • The procedure, Perform Long-term Shutdown of PRF Chemical Prep (room 40), was not implemented by Facility line management after the demonstration of readiness activities were suspended in 1993. This procedure required that the solution in Tank A-109 be drained into plastic drums, for later use or disposal, at the time that the Facility was placed in long-term shutdown.
  • FDH and BWHC need to ensure that procedures for long-term shutdown of their facilities are adequate and implemented.
  • Facility line management standby planning, with RL approval, deferred addressing Room 40 chemicals to a later, unspecified, time. This decision eventually led to long-term storage of chemicals in Tank A-109, an activity that was outside of the safety authorization basis.
  • FDH and BWHC need to ensure that only activities within the scope of the safety authorization basis are conducted.
  • Facility line management failed to comply with the site contractor management standby planning procedure requirements for safety evaluations, written guidance on safe shutdown by safety organizations, and requirements to revise the safety authorization basis documents.
  • FDH and BWHC need to ensure that corporate management procedures for standby planning are adequate, and are implemented by Facility line management.
  • Facility line management failed to maintain the chemical solution contained in Tank A-109 in a known, safe configuration.
  • BWHC needs to define safe concentrations and conditions of process chemical solutions on a periodic basis, with appropriate documentation to ensure that changes over time are known and hazards are
RL line management oversight did not ensure that the Facility was maintained within documented and authorized safety parameters during the transition from operations to shutdown/standby. RL line management oversight needs to ensure that Facility line management operates within and adequately maintains the safety authorization basis.
Facility line management did not adequately implement lessons learned from previous events with similar chemicals into the staff training and qualification process; therefore, the hazards were not sufficiently recognized and controlled. FDH and BWHC need to ensure that a system is in place to ensure lessons learned are effectively developed (as applicable), identified for applicability, and addressed in operations. Additionally, corrective action tracking and trending processes should be enhanced to ensure that concerns identified during occurrences, and as a result of assessment and evaluation activities are tracked, monitored for progress, and closed expeditiously.
Facility line management did not incorporate safety authorization basis hazard information and lessons learned from previous accidents involving the chemicals that reacted in this accident into the training and qualification process for Facility technical and operations staff.
  • BWHC needs to incorporate information obtained from previous incidents/accidents, as well as hazard information from these events, into its operational training and qualification program; this information should be specifically directed at its applicability to Facility operations.
  • DOE Headquarters (EH-1) needs to enhance the Occurrence Reporting and Processing System to ensure that it will provide sufficient summary information to allow the users to accurately determine the applicability of occurrence data to specific facilities and operations.
Conditions necessary for an autocatalytic reaction of the stored hydroxylamine nitrate and nitric acid solution are not well documented. The roles of temperature and catalysts are not well understood with respect to how they promote autocatalytic reactions. DOE Headquarters (EH-1) needs to ensure that, if hydroxylamine nitrate and nitric acid solutions will continue to be used by the complex, a study is conducted to define safe use and storage parameters, and that this information is distributed to the DOE complex.

3.1 SUPPLEMENTAL CONCLUSION

Although not directly a result of this investigation, the Board identified a supplemental conclusion that may provide information to further enhance an overall safety management system, shown in Table 3.

Table 3. Supplemental Conclusion and Judgments of Need.

Supplemental Conclusion Judgments of Need
Explosions may be preceded by abnormal facility conditions, such as smoke, heat, vibration, and unusual sounds. Fortunately, no one was in the room when the explosion occurred. However, if someone would have been in the room, unusual conditions such as the sounds of gas escaping, or the sight of smoke, might have led a worker to investigate the cause, putting the worker in harms way. A review of Facility worker training indicated that clear guidance is not provided for worker response upon observing unusual facility conditions. There is a need for RL to ensure that worker training programs provide adequate consideration of appropriate response to observation of unusual facility conditions.

There is a need for RL to evaluate worker training and emergency preparedness to ensure that procedures and training exist on:

  • when to report abnormal facility conditions to supervisors,
  • the need for protective equipment when investigating, and
  • when urgently exiting the building may be appropriate.

Continue to Section 4