Failed Gamma Beam Irradiator

Samantha L PenlandSamantha L. Penland

Francis Marion University

Savannah River Site

The SystemThe System

Chosen source is sent to the top of the source transfer tube using atransfer tube using a vacuum system

Source is secured at the top of the tube by a suction cup

The GBI was designedThe GBI was designed and manufactured by Hopewell Designs, Inc.

Hopewell Designs, Inc.

Hopewell Designs, Inc.Hopewell Designs, Inc.

Founded in 1994 by R.O. RushtonFounded in 1994 by R.O. Rushton

Alpharetta, Georgia

Designer and manufacturer of SRS irradiators andDesigner and manufacturer of SRS irradiators and transport containers

Over 60 installed irradiator systemsOver 60 installed irradiator systems

Hundreds of source transfers for this type of irradiator

First instance of this type of malfunction

The SourcesThe Sources

One dummy sourceSix radioactive sources– 3 Co‐60 sources– 3 Cs‐137 sourcesLocated in a rotating carouselCarousel rotates when operator chooses desired sourceEach source is encapsulated in a “rabbit”

So, what is the “rabbit”?So, what is the  rabbit ?

The rabbit is a small aluminum container inThe rabbit is a small, aluminum container in which the source is held

The top portion of the rabbit is held togetherThe top portion of the rabbit is held together using a tightened set screw

Th i l d i id i i l lThe source is sealed inside its stainless steel capsule

Disassembled Rabbit

A: Rabbit cappB: SpacerC: Source

What Happened?What Happened?

June 12 2007June 12, 2007

Vacuum failed to catch the source at the top of the shaft during a characterization of theof the shaft during a characterization of the beam

I h l j dIt was apparent the carousel was jammed

SuspicionsSuspicions

Suspicion 1‐The rubber suction cup had fallenSuspicion 1 The rubber suction cup had fallen into the carousel

Suspicion 2 Stacked sourcesSuspicion 2‐ Stacked sources 

Suspicion 3‐None of the above

The InspectionThe Inspection

June 18 2007June 18, 2007

The Instrument Calibration Technical Director led the inspectionled the inspection

A boroscope was used to diagnose the blproblem

Hopewell Designs, Inc. was notified of the situation prior to the inspection

Were our suspicions correct?Were our suspicions correct?

Suspicion 1Suspicion 1– When the plug was removed, it was confirmed that the rubber suction cup had indeed not fallenthat the rubber suction cup had indeed not fallen.

– Conclusion: INCORRECT

Suspicion 2Suspicion 2– A disassembled rabbit was clearly resting on top of the 39 Ci Cs 137 sourceof the 39 Ci Cs‐137 source

– Conclusion: CORRECT

Upon further inspectionUpon further inspection…

It was discovered that the rabbit which had encased the 1 Ci Co‐60 source was openThe assumption was madeThe assumption was made that the rabbit separated during capture by the vacuum plugA id tifi d bj tAn unidentified object was seen resting on the rabbit’s cap which was lodged in the shaftThis object was thought to be either the spacer or the source

A: Rabbit cap

B: Spacer

C: Source

What happened next?What happened next?

The Instrument Calibration Technical DirectorThe Instrument Calibration Technical Director notified the manufacturer

The President and CEO of HopewellThe President and CEO of Hopewell Designs, Inc. (R.O. Rushton) conducted an inspectioninspection

Rushton and HPS management met to discuss l ia solution

The SolutionThe Solution

The decision was made to lower theThe decision was made to lower the boroscope with an adhesive material on the endend

The unscrewed cap was carefully lifted out of the shaftthe shaft

The cap was smeared to test for i icontamination

The smear test was negative

Recovery of Cap

Returning the Source to the RabbitReturning the Source to the Rabbit

The source was returned to a vertical position duringThe source was returned to a vertical position during recovery of the cap

The source was lifted with the adhesive

The carousel was manually turned

The source was placed in the opened rabbitThe source was placed in the opened rabbit

The carousel was rotated to the Dummy position

Replacement of the SourceReplacement of the Source

A Rare View of the Top of Each RabbitA Rare View of the Top of Each Rabbit

Cs-137

1 Ci

Cs-137

39 Ci

Cs-137

1300 CiDummy

Co-60

1 Ci

Co-60

75 Ci

Co-60

6000 Ci1 Ci75 Ci

Recovery of the SourceRecovery of the Source

Rushton and HPS constructed a plan forRushton and HPS constructed a plan for recovery of the source

The Scope:The Scope:– Remove source from carousel and transfer it to a shielded caskshielded cask

– Remove empty rabbit from carousel

A t f ll t i i (1 2 h– Account for all parts missing (1 spacer, 2 washers, 1 set screw)

Removal of the Source Using AdhesiveRemoval of the Source Using Adhesive

Removal of the RabbitRemoval of the Rabbit

Attempt 1 ‐ Screw the cap into the rabbit

Attempt 2 ‐ Adhesive on the cap

Attempt 3 was a successp

– Adhesive was placed underneath a new rabbit

– The new rabbit was lowered to the empty rabbit

– The empty rabbit was pulled from the source transfer tubeThe missing washers spacer– The missing washers, spacer and set screw were found inside the rabbit

Path ForwardPath Forward

The 1 Ci Co‐60 source option was removed from the GBI control systemThe 1 Ci Co 60 source is temporarily being held in the shipping cask in theThe 1 Ci Co‐60 source is temporarily being held in the shipping cask in the corner of the GBI roomA 200 Ci Co‐60 source will be purchased by HPS to serve as a replacement sourceLonger set screws were installed in the rabbit caps in addition to theLonger set screws  were installed in the rabbit caps in addition to the original shorter set screws

The 6000 Ci Co‐60 source already has the longer set screws

A Special Thanks To…A Special Thanks To…

Fred Ogden and Dennis gHadlockR.O. Rushton and the 

llHopewell teamJeff Hoefs and Cindy LunsfordLunsfordMichelle Holman and Brian Arnold

Questions?Questions?