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 |
This report is an independent product of the Accident Investigation Board that was appointed by Lloyd L. Piper, Deputy Manager, acting for John D. Wagoner, Manager, U.S. Department of Energy, Richland Operations Office.
The board was appointed to perform an investigation of this accident and to prepare an investigation report in accordance with DOE Order 225.1, Accident Investigations.
The discussion of facts, as determined by the Board, and the views expressed in the report do
not assume, and are not intended, to establish the existence of any duty at law on the part of the U.S. Government, its employees or agents, contractors, their employees or agents, or subcontractors at any tier, or any other party.
This report neither determines nor implies liability.
On May 16, 1997, I formally established an Accident Investigation Board to investigate the
May 14, 1997, chemical explosion at the Plutonium Reclamation Facility at the Hanford Site, Richland, Washington. The Boards responsibilities have been completed with respect to this investigation. The analysis process; identification of direct, contributing, and root causes; and development of judgments of need during the investigation were done in accordance with
DOE Order 225.1, Accident Investigations.
I accept the findings of the Board and authorize the release of this report for general distribution.
TABLE OF CONTENTS
1.0 INTRODUCTION
3.0 CONCLUSIONS AND JUDGMENTS OF NEED
4.0 BOARD SIGNATURES
5.0 BOARD, ADVISORS, STAFF AND OBSERVERS
APPENDIX A Memorandum for the Appointment of the Accident Investigation Board
APPENDIX B Performance of Barriers
APPENDIX C Change Analysis Chart
APPENDIX D Technical Aspects of the Accident
APPENDIX E References
EXHIBITS, FIGURES, AND TABLES
Exhibits
A-1. Recovered Bolts from Tank A-109 Lid
Figures
Tables
B-1. Performance of
Barriers
C-1. Change Analysis Chart
D-1. Summary of Reaction
BWHC | B&W Hanford Company |
CCX | Complexant concentrate column extractant |
CFR | Code of Federal Regulations |
DOE | U.S. Department of Energy |
ES&H | Environment, Safety and Health |
FDH | Fluor Daniel Hanford, Inc. |
FSAR | Final Safety Analysis Report |
HN | hydroxylamine nitrate |
HNO3 | nitric acid |
M | molar |
NOx | oxides of nitrogen (NO, NO2, NO3, N2O5) |
OSHA | Occupational Safety and Health Administration |
PFP | Plutonium Finishing Plant |
PRF | Plutonium Reclamation Facility |
PUREX | Plutonium Uranium Extraction (Facility) |
RL | U.S. Department of Energy, Richland Operations Office |
Autocatalytic - A self-propagating (spontaneous) reaction that does not require an external initiator.
Barrier Analysis - An analytical technique used to identify energy sources and the failed or deficient barriers and controls.
Causal Factors - Factors that had a direct role in causing the event.
Change Analysis - A review of an activity to determine the root cause, to identify less-than-adequate contributing systemic factors, and to prevent further concerns.
Contributing Causes - Factors that significantly increased the likelihood of an event, without individually causing the event.
Direct Cause - The immediate event or condition that caused the accident.
Events and Factors Charting - A method for identifying the multiple causes and triggering conditions and the events that are necessary and sufficient for an accident to occur.
Interim Standby Status - Facilities removed from active status, which are maintained or upgraded for potential future use, or for deactivation, and decontamination and decommissioning.
Key word - A word to convey related concepts or topics stated in the lesson; used to assist in sorting and locating lessons.
Lessons Learned - A good work practice or innovative approach that is captured and shared to promote repeat application. A lessons learned may also be an adverse work practice or experience that is captured and shared to avoid recurrence.
Precursors - Conditions that precede and signal the potential occurrence of an event.
Root Cause - A fundamental cause that, if eliminated or modified, would prevent recurrence of this and similar accidents.
Short-Term Exposure Limit - A 15-minute time-weighted average exposure that should not be exceeded at any time during a work day.
Weekend Shutdown - As defined in Shutdown Solvent Extraction, WHC-ZO-181-004, a shutdown used on weekends or when extended downtime will occur, usually less than 2 weeks.
INTRODUCTION
On May 14, 1997, at 7:53 p.m. (PDT), a chemical explosion occurred in Tank A-109 in Room 40 of the Plutonium Reclamation Facility (Facility) located in the 200 West Area of the Hanford Site, approximately 30 miles north of Richland, Washington (Three Video files). Walk through before the event, The Event, Walk through after the event). The inactive processing Facility is part of the Plutonium Finishing Plant (PFP). On May 16, 1997, Lloyd L. Piper, Deputy Manager, acting for John D. Wagoner, Manager, U.S. Department of Energy (DOE), Richland Operations Office (RL), formally established an Accident Investigation Board (Board) to investigate the explosion in accordance with DOE Order 225.1, Accident Investigations. The Board commenced its investigation on May 15, 1997, completed the investigation on July 2, 1997, and submitted its findings to the RL Manager on July 26, 1997.
The scope of the Boards investigation was to review and analyze the circumstances of the events that led to the explosion; to analyze facts and to determine the causes of the accident; and to develop conclusions and judgments of need that may help prevent a recurrence of the accident. The scope also included the application of lessons learned from similar accidents within DOE. In addition to this detailed report, a companion document has also been prepared that provides a concise summary of the facts and conclusions of this report, with an emphasis on management issues (DOE/RL-97-63).
Evaluation of emergency and occupational health response to, and radiological and chemical releases from, the explosion was not within the scope of this investigation, but has been analyzed by the RL Environment, Safety and Health organization (DOE/RL-97-62).
The Washington State Department of Ecology has conducted an independent investigation to determine whether state laws or regulations were violated. The State of Washington Department of Health has conducted an independent investigation of the potential for radioactive airborne releases from this accident.
Since October 1, 1996, Fluor Daniel Hanford, Inc., under contract to RL, manages and integrates the scope of work defined in the Project Hanford Management Contract. The B&W Hanford Company manages and operates the PFP, which includes the Facility, under subcontract to Fluor Daniel Hanford, Inc. The Westinghouse Hanford Company operated the Facility from June 1987 through September 1996, as the managing and operating contractor for the Hanford Site. During contractor change-over, the Facility line management staff remained intact.
The Facility was designed as a multipurpose facility to recover plutonium from plutonium-bearing scrap. The Facility commenced full operations in 1964 and discontinued plutonium recovery operations in 1987, when it was placed in interim standby status pending restart. In September 1992, activities were begun to prepare for and demonstrate readiness for restart of the Facility, but these activities were not completed. Tank A-109, the tank involved in the accident, was located in Room 40 of the Facility and contained an aqueous solution of hydroxylamine nitrate in dilute nitric acid, also known as complexant concentrate column extractant. Room 40 was used to mix and store non-radioactive chemicals that were transferred to, and used in, the plutonium processing areas of the Facility. The chemical solution was prepared in the tank as part of the demonstration of readiness for restart of the Facility. The final batch of 370 gallons of solution was prepared in Tank A-109 on June 17, 1993.
On December 22, 1993, the demonstration of readiness activities for restart were officially suspended and RL directed that the Facility be shut down because of mission changes. Although some of the solution had been used, the tank had not been completely drained since the solution was added to it on June 17, 1993. Contrary to the historical operating practices of the Facility, the tank was placed in a short-term, rather than long-term, shutdown basis on December 10, 1993.
Since December 1993, work activities at the Facility, including those affecting Tank A-109, have been conducted to support and maintain the facility in long-term shutdown in preparation for deactivation, and eventual decontamination and decommissioning activities.
ACCIDENT DESCRIPTION
The accident was the result of an autocatalytic chemical reaction of the solution stored in Tank A-109, in Room 40 of the Facility. The significance of this event should not be underestimated by the good fortune that no one was in or near Room 40 at the time of the explosion, nor did the energy released damage nearby rooms or release plutonium.
Some of the original 370 gallons of solution in the 400-gallon stainless steel tank had subsequently been used in Facility cleanup (e.g., flushing of process lines, etc.) activities. The unused solution had been slowly evaporating since June 17, 1993. The loss of water through evaporation concentrated the solution until conditions were reached that caused the normally unreactive solution to undergo an autocatalytic chemical reaction. The reaction created a rapid release of gases, which built up pressure inside the tank. The pressure blew the lid off the tank, severely damaged Room 40, and cut a small water line. Structural damage included deformation of a wall, and damage to interior doors and the roof above Room 40.
Environmental releases associated with the explosion included a yellow-brown colored plume emitted from the main PFP exhaust stack, and the water that was discharged from the cut water line. Laboratory studies conducted after the accident revealed that the airborne releases would likely have consisted of a mixture of gases including nitric acid, nitrous oxide (laughing gas), various oxides of nitrogen, and water vapor. Of these, only the nitric acid and oxides of nitrogen are recognized to pose a potential health hazard. Real-time measurement for concentrations of chemicals released was not possible. Therefore, dispersion modeling was performed to estimate maximum chemical concentrations at ground level. The modeling results indicated that releases from the damaged roof would have generated the highest levels of chemical concentrations, and that these levels were below applicable occupational exposure limits.
Based on extensive sampling, surveys, and stack monitoring data, no radioactivity was released from the Facility stack or the damaged area of the roof.
Water from the cut water line flooded the building, and some of it flowed out through various Facility exit doors. Extensive surveys conducted inside and outside of the building revealed radioactive contamination on the first floor of the Facility, and a small area of slightly above background levels of radioactive contamination outside that was that was isolated and immobilized. This contamination was likely the result of water flowing across walls and floors of contaminated areas of the Facility, carrying radioactive material outside the building. An evaluation of the radiological and chemical releases from the explosion may be found in a separate report (see DOE/RL-97-62). It is also likely that some gases may have escaped through holes in the damaged roof. The investigation concluded that no other chemicals that were in Room 40 at the time of the accident or any other components were involved in the environmental releases.
No one was in, or near, Room 40 of the Facility at the time of the accident. During the initial stages of the emergency response to this accident, eight construction workers, who were on a break in a trailer outside the Facility, unknowingly passed under the plume path when directed to report to the on-scene Facility emergency center. All eight of the workers were evaluated and released from a local medical center. Later, several other employees who reported symptoms were evaluated. Ongoing occupational health evaluation is being provided as necessary. For further information, see DOE/RL-97-62.
CAUSAL FACTORS
The direct cause of the Facility 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.
The three root causes of the accident (the fundamental causes that if eliminated or modified, would prevent recurrence of this and similar accidents) were the primary reason that the chemical reaction occurred, and are discussed as follows:
Even if the hazards of storing the solution were not recognized, the normal practice was to remove the chemicals from the tank upon termination of the process that used them.
Facility standby planning resulted in long-term storage of chemicals in Tank A-109, which was outside of the safety authorization basis.
As the Facility transitioned from operations to shutdown, hazards were not identified and controlled as required by procedure. When RL line management oversight approved the contractors plan to place the Facility into standby status, it was not recognized that storing chemicals in the tank was outside the safety authorization basis.
The Board also identified six contributing causes (causes that increased the likelihood of the accident without individually causing the accident, but that are important enough to require corrective action) that are discussed as follows:
Had the standby planning procedure been adequately followed, the required safety evaluation should have identified the hazard of long-term storage, resulting in draining the tank, or providing adequate controls.
Changes in the Facility equipment parameters were not monitored and evaluated to ensure that changes over time were known and understood to ensure safety.
Non-compliance with procedures is a long-standing problem at the Facility.
Corrective actions were identified but not implemented. Tracking of corrective actions to closure was not performed.
Hazards with hydroxylamine nitrate were identified as early as 1970, and reports of various accidents were available to the facility. However, these hazards were not included in training and qualification programs to heighten awareness of the chemical hazards.
Very significant and timely lessons learned were not provided to the Facility that could possibly have led to hazard recognition and development of controls for hydroxylamine nitrate and nitric acid solutions.
Analysis of the root and contributing causes indicates that the accidents origins began with events that originated in September 1992 and, through a series of oversights and missed opportunities, continued to the date of the accident. Some of the historical problems that precipitated and contributed to the accident persist and have not been corrected by the Facility management systems of the previous or current contractors, as well as by RL. The potentially hazardous condition was overlooked and the relevance of precursors and other similar events was not recognized. Thus, the lessons learned from other events and precursors were never fully applied.
Missed opportunities include: omission of chemical tanks from the Facility interim standby plan developed in late 1993; not performing a safety evaluation of the shutdown plan as required by procedure; inadequate follow-up to the corrective actions proposed in the RL response to the 1994 DOE chemical safety vulnerability assessment; failure to list chemicals in the tank on the checklist for the March 1994 DOE Headquarters request for chemicals that react with nitric acid; and the inspections that were conducted during the Project Hanford Management Contract transition in September 1996.
CONCLUSIONS
The major conclusions and judgments of need identified by the Board for this accident are presented in the following table.
Conclusions | Recommendations |
Standby planning failed to maintain the Facility in a safe condition, consistent with the approved safety authorization documentation. | |
|
|
|
|
|
|
|
|
RL line management oversight did not ensure that the Facility was maintained within the safety authorization documentation during the transition from operations to standby/shutdown. | RL line management oversight needs to ensure that Facility line management adequately maintains, and operates within, the safety authorization documentation. |
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. | Fluor Daniel Hanford, Inc. and the B&W Hanford Company 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. |
Facility line management did not incorporate safety authorization documentation 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. |
|
Conditions necessary for a spontaneous 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 spontaneous reactions. | The DOE Office of Environment, Safety and Health 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. |
SUPPLEMENTAL CONCLUSION
Although not direct conclusions of this investigation, the Board identified a related issues that may provide information that could further enhance an overall safety management system, shown in the following table.
Supplemental Conclusion | Recommendations |
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 the 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. |
|
Continue to Section 1