ML23325A040
| ML23325A040 | |
| Person / Time | |
|---|---|
| Site: | BWX Technologies |
| Issue date: | 11/16/2023 |
| From: | Freudenberger R BWXT NOG-Lynchburg, BWXT |
| To: | Office of Nuclear Material Safety and Safeguards |
| References | |
| 56768, 23-059 | |
| Download: ML23325A040 (1) | |
Text
BWXTechnologies, Inc.
November 16, 2023 23-059 Attn: Document Control Desk Director, Office of Nuclear Materials Safety & Safeguards U.S. Nuclear Regulatory Commission Washington, D.C. 2055-0001
Reference:
License No. SNM-42, Docket 70-27
Subject:
30 Day Written Report of Event Notification EN-56768
Dear Sir or Madam,
Please find BWXT Nuclear Operations Group, Inc. - Lynchburg's (BWXT NOG-L) 30-Day Written Report for Event Notification (EN) 56768, enclosed. The EN was reported under 10 CFR 70.50(b)(2).
On October 16, 2023, BWXT NOG-L identified a deficiency in the Criticality Accident Alarm System (CAAS). An input parameter that was utilized in modeling the placement of criticality detectors within the BWXT NOG-L facility was questioned. Upon further examination of this parameter, it was identified that a limited number of process areas in the facility did not have adequate criticality detection capability to meet the requirements of 10 CFR 70.24(a)(1 ). BWXT NOG-L determined this condition to be reportable under 10 CFR 70.50(b)(2). The condition was reported on October 17, 2023, as EN- 56768.The enclosed report provides an event description, background information, root causes of the condition, immediate actions taken, compensatory measures, and corrective actions to prevent recurrence.
If you have any questions or require additional information, please contact Daniel Ashworth, Manager of Licensing and Safety Analysis, at dlashworth@bwxt.com or 434-522-5472.
Sincerely
-~~
Manager, Environment, Safety, Health, and Safeguards BWXT Nuclear Operation Group, Inc., Lynchburg
/\)lvj 5 S 2D Enclosure ,rE72 cc: NRC, Region II NRC, Resident Inspector f\J05.S NRC, James Downs, NMSS/DFM People Strong BWXT Nuclear Operations Group, Inc.
P.O. Box 785 Lynchburg, VA 24505 USA INNOVATION DRIVEN >
t: +1.434.522.6000 www.bwxt.com
U.S. NRC 23-059 Enclosure ENCLOSURE (4 Pages) 30 Day Written Report of Event Notification # 56768 People Strong INNDVATIDN DRIVEN >
BWXT Nuclear Operations Group, Inc.
P.O. Box 785 Lynchburg, VA 24505 USA t: +1.434.522.6000 www.bwxt.com
23-059 Enclosure BWX Technologies, Inc.
30 Day Written Report of Event Notification # 56768 Event
Description:
During development of a Nuclear Criticality Safety (NCS) Process Analysis (PA) for the Research and Test Reactor (RTR) autoclave, a modeling parameter utilized for evaluation of the Criticality Accident Alarm System's (CAAS) detector placement was questioned. Upon further examination of the base input, it was identified that the coverage of the area did not provide adequate criticality detection capability, to meet the requirements of 10 CFR 70.24(a)(1).
10 CFR 70.24(a)(1): The monitoring system shall be capable of detecting a criticality that produces an absorbed dose in soft tissue of 20 rads of combined neutron and gamma radiation at an unshielded distance of 2 meters from the reacting material within one minute. Coverage of all areas shall be provided by two detectors.
Specifically, when modeling the Minimum Accident of Concern (MAOC) described in 10 CFR 70.24(a)(1) and placing the BWXT NOG-L defined source term inside versus above the RTR autoclave, the dose rate at the nearest detectors did not meet the alarm threshold required by the analysis. Thus, CAAS coverage could not be demonstrated for the area and was not in compliance with SNM-42, Chapter 5, Section 5.6.
Background Information:
In 2011, NCS Engineering began the process of modeling the entire NOG-L Facility to determine detector placement for the new CAAS. A recently released SCALE program, MAVRIC, was used to perform the analysis. NOG-L's CAAS subject-matter-expert determined the parameters and inputs for placement of the source term, utilized in the MAVRIC model, to determine criticality detector locations. NCS completed the analysis and the results were documented as a technical reference in October of 2012.
In October of 2023, NCS engineering was completing a PA for the RTR autoclave and discovered that the input parameter for source term placement used during the original CAAS modeling was inadequate for proper detector coverage. It was identified that the source term for coverage of a MAOC in the autoclave was not actually located in the autoclave; the source term was located 2 meters above what was considered to be the surface of the "reacting vessel".
Safety Significance:
The inability to demonstrate the CAAS' compliance with the requirements of 10 CFR 70.24(a)(1) was reported under 10 CFR 70.50{b)(2).
10 CFR 70.50(b)(2): An event in which equipment is disabled or fails to function as designed when:
People Strong BWXT Nuclear Operations Group, Inc.
P.O. Box 785 Lynchburg, VA 24505 USA INNOVATION DRIVEN >
t: +1.434.522.6000 www.bwx1.com
U.S. NRC 23-059 Enclosure (i) The equipment is required by regulation or license condition to prevent releases exceeding regulatory limits, to prevent exposures to radiation and radioactive materials exceeding regulatory limits, or to mitigate the consequences of an accident; The likelihood of a criticality accident occurring at BWXT NOG-L remained highly unlikely; all Items Relied on For Safety {IROFS) credited in the prevention of a criticality accident were available and reliable. The performance requirements of 10 CFR 70.61 were maintained.
Immediate Actions:
- Operations with similar conditions were identified (e.g., vertical vessels below grade and/or tanks containing water, which could shield a MAOC).
- The RTR autoclave and the potentially affected areas/processes were safely shut down.
- A 24-hr. notification was made to the NRC {EN- 56768).
- Corrective Action CA202301287, Level 1, was initiated.
- The affected areas were returned to operation with the implementation of compensatory measures, per BWXT NOG-L's Conduct of Operations Procedure.
- An investigation was initiated.
Compensatory Measures in Place:
Compensatory measures were systematically implemented in accordance with BWXT NOG-L's Conduct of Operations Procedure, SNM-42 Chapter 5, and internal Radiation Protection Procedures. Personal Electronic Dosimeters (PED) are being used to monitor employees working in areas where criticality coverage is not adequate. The PEDs contain visual and audible alarms that activate at a limit of 15 mR/hr. In addition, these units are placed at the entrance and exit to these work areas. If one (1) PED is in alarm, employees are to notify their FLM or Radiation Control. If two (2) PEDs are in alarm, employees are to evacuate the area and immediately notify Security. Security's Alarm Stations will immediately activate the CAAS and evacuate all facility personnel.
Full compliance was achieved on October 27, 2023, with the implementation of these Compensatory Measures.
A capital improvement project has been initiated to upgrade the CAAS and install additional detector capability, as defined by the ongoing NCS analyses of the identified vessels and tanks.
Funding has been allocated and additional detector equipment has been ordered from the manufacturer. Field implementation of the new equipment will be executed as materials and parts arrive in 2024.
Investigation Summary:
An investigation was started shortly after the event was identified. The investigation team had representation from NCS and Licensing & Safety Analysis. The team was led by a representative from Quality Engineering. Formal investigation tools, including the Nuclear Work People Strong BWXT Nuclear Operations Group, Inc.
P.O. Box 785 Lynchburg, VA 24505 USA INNOVATION DRIVEN >
t: +1.434.522.6000 www.bwxt.com
U.S. NRC 23-059 Enclosure Model Critique and a 5 Why's Analysis, were utilized to identify Root Causes and Corrective Actions; a Safety Culture Implications Review was also performed.
Root Causes of the Event:
BWXT NOG-L has identified the following root causes leading to this situation:
- Human Error: The original NCS Engineer incorrectly interpreted the requirements leading to an inadequate selection of input parameters to the CMS program.
- Complexity/Timing: Having a single calculation preparer and a single calculation reviewer, performing First of a Kind (FOAK), large, and complex analysis resulted in a human error situation for the self and peer reviews.
- Communication/FOAK: The lack of communication and periodic oversight before, during, and after the implementation of the CMS system reduced the opportunity to prevent/detect the application of incorrect input parameters.
The investigation team acknowledged that the work associated with modeling the detector placement for the new CMS was performed by a NCS subject-matter-expert, operating in a knowledge-based mode, and this situation was caused by human error.
Extent of Cause Reviews:
BWXT NOG-L has identified the following extent of cause reviews to be performed in parallel with the implementation of corrective actions, in order to bound the reported problem:
- Review the inputs of the original CMS analysis completed in 2012 to validate that these inputs meet the requirements of SNM-42, Chapter 5, Section 5.6.
Planned Completion Date: 04/30/2024
- Review SNM 42, Chapter 5, for requirements with infrequent NCS Engineering involvement or analysis that have the potential for inadequate interpretation and assess the adequacy of the associated NCS analyses. Planned Completion Date: 06/30/2024 Corrective Actions:
BWXT NOG-L will implement the following corrective actions to prevent reoccurrence:
- 1. Proceduralize the scheduling of periodic team meetings to discuss the design process and provide the opportunity for others to review the base input parameters for complex analyses of FOAK processes. Planned Completion Date: 01/31/2024
- 2. Proceduralize the scheduling of periodic check-in times between the project lead and management to ensure adequate support for complex analysis of FOAK processes.
Planned Completion Date: 01/31/2024
- 3. Proceduralize a peer review at the beginning of a complex analysis of a FOAK process to validate the base input parameters and technical approach. Involve a second People Strong BWXT Nuclear Operations Group, Inc.
P.O. Box 785 Lynchburg, VA 24505 USA INNOVATION DRIVEN >
I: +1.434.522.6000 www.bwxt.com
U.S. NRC 23-059 Enclosure independent peer to be the "devil's advocate" similar to internal product engineering design process(es). Planned Completion Date: 01/31/2024 People Strong INNDVATIDN DRIVEN >
BWXT Nuclear Operations Group, Inc.
PO. Box 785 Lynchburg, VA 24505 USA t: +1.434.522.6000 www.bwxt.com