DEFENSE NUCLEAR FACILITIES SAFETY BOARD

February 16, 2024

TO: Katherine R. Herrera, Acting Technical Director

FROM: B. Caleca, P. Fox, N. Huntington, and P. Meyer, Resident Inspectors

SUBJECT: Hanford Activity Report for the Week Ending February 16, 2024

Tank Farms: In support of future tank farm missions, WRPS plans to remediate double shell 

tank SY-103, which is currently classified as a Waste Group A tank because of its potential for 

buoyant displacement gas release events (BDGRE) that could result in the headspace reaching 

the hydrogen lower flammability limit. Waste disturbing activities in Waste Group A tanks are 

currently not authorized in the tank farms documented safety analysis. The remediation includes 

first decanting the supernatant from the tank then dissolving the remaining soluble waste solids

prior to transferring out the waste. Resident inspectors observed a meeting where the control 

strategy for decanting was presented. The strategy involves monitoring for hydrogen releases 

during decanting and is based on a previous analysis by Pacific Northwest National Laboratory

that concluded any BDGREs induced by the decanting process will be bounded by historical 

behavior, and therefore will not challenge headspace flammability limits. 

To support retrieval operations, two hoses were connected to a hydraulic power unit (HPU) that 

will transfer waste from double shell tank AP-101 to AP-104. Per the Technical Safety 

Requirements (TSRs), this condition requires an administrative lock to prevent inadvertent waste 

transfers. Operations verified an upstream breaker that provides power to the HPU was

administratively locked open to implement the control. Later, a separate maintenance activity on 

a different portion of the HPU required the breaker to be shut to power the unit’s electronics. 

Contrary to TSR requirements, a different control was not implemented prior to removing the 

lock from the breaker. When the condition was discovered, operations declared multiple TSR 

violations. WRPS has issued a timely order that requires level one management approval prior to 

removing administrative locks as it investigates the event.

High Level Waste (HLW): A resident inspector observed a field office Senior Review Board 

(SRB) meeting held to review a safety basis review team recommendation to approve revision 

12A of the HLW preliminary documented safety analysis. This revision is focused on revising 

hazard analyses for events involving facility cranes to support downgrading them from safetysignificant to defense-in-depth controls. The new waste acceptance criteria reduced the 

consequences of crane drop events below the threshold to consider safety-significant controls. 

However, during a seismic event, cranes were postulated to fall on safety systems in the facility. 

In place of crediting the crane’s components, a load drop design feature was added to the 

revision demonstrating that the geometry of facility cranes prevents them from falling off their 

supports and impacting facility systems. The SRB voted to recommend approval of the revision.

Central Waste Complex: The Mission Need Statement supporting a new contact handled 

mixed low-level waste and transuranic waste processing capabilities project was approved by 

DOE last June (see 8/26/2022 report). The needed capabilities include characterization, 

treatment, repackaging, storage, and shipping functions. The project is currently working to 

identify and analyze alternatives to develop the conceptual design. The Safety Design Strategy 

document is under development and expected to be submitted to DOE in March 2024.