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Yo ho ho and a Cask of leaking fuel
#1
NOBLE FISSION GAS RELEASES DURING SPENT FUEL CASK LOADING OPERATIONS
https://www.nrc.gov/docs/ML1723/ML17234A705.pdf
February 21, 2018

[ large primary doc Kr-85 releases detected at Milestone, Calvert Cliffs, Arkansas. Some snips ]

Millstone Power Station, Unit 2
On May 12, 2015, [...] dry shielded canister (DSC) being loaded with Unit 2 spent fuel.  
During the blowdown evolution, the licensee received local radiation alarms
and observed a spike in activity with the spent fuel pool (SFP) ventilation radiation monitor.   

[...] detectable krypton (Kr)-85 results from a sample taken directly from the DSC [...]

[...] 15 of the loaded assemblies originated from cycles that experienced grid-to-rod fretting (GTRF).

Calvert Cliffs Nuclear Power Plant, Unit 1
On September 17, 2015 and October 8, 2015, the Unit 1 wide range noble fission gas monitor detected Kr-85 releases.
The investigation concluded the probable cause to be latent near-through-wall failure sites which fully opened when subjected to the vacuum environment.  

Arkansas Nuclear One, Units 1 and 2
September 2014
On September 12, 2014, the control room emergency ventilation system at Arkansas Nuclear One (ANO) was unexpectedly triggered, placing both Unit 1 and 2 control rooms on emergency recirculation because of increased radiation levels.
[ https://www.nrc.gov/reading-rm/doc-colle...ml#en50454 ]
 
The licensee cited both the prevalence of GTRF in the operating cycles of the subject assemblies, which may produce breaches larger than a pinhole, and the limitations of ultrasonic testing in accurately identifying leaking fuel.

As a corrective action, the licensee elected to conservatively reclassify the fuel loaded into the
MPC as damaged and submitted an exemption request from the requirements in
IN 2018-01 Page 4 of 9 10 CFR 72.212(a)(2) and 10 CFR 72.212(b)(11), as the loaded MPC had not been approved for
damaged fuel.

August 2015
On August 21, 2015, the licensee’s process radiation monitor for Unit 2 spent fuel area alarm was activated, which tripped the exhaust system. [ Unclear if 'tripped' means the exhaust system was activated or deactivated. ]

The licensee characterized the sample and identified fission product gas Kr-85

Reactor Operating Records

Licensees may assess whether any missing records from early reactor operation, such as those
lost because of changes in plant ownership, may impact conclusions made about fuel discharged from a given cycle.

[ This statement illustrates how non chalant they are in record keeping, convieniently able to claim lost records, everyone shrugs, nice plausible deniability in case a fuel bundle casked causes a prblem in the future. ]

Visual Inspection

NUREG-1536, Revision 1, states that a visual examination of a breached rod can be used to determine if a breach is gross (i.e., cladding breaches greater than 1 mm).

------------

[ From the Reactor Status data ]

   

[ I thought there was another unit that had leaking fuel problems (Columbia?) but haven't been able to verify yet. ]
[ I think that the three bundles meet the definition of the gross damage. ]  
[ So we know that at least RiverBend has breached (leaking) fuel assemblies in the spent fuel pool. ]

---------

A new method to predict Grid-To-Rod Fretting in a PWR fuel assembly inlet region | https://www.sciencedirect.com/science/ar...9311005024
Nuclear Engineering and Design | Volume 241, Issue 8, August 2011, Pages 2974-2982

[ from the abstact ]
Grid-To-Rod Fretting (GTRF) is one of the main causes of leaking fuel in a Pressurized Water Reactor (PWR). GTRF is caused by grid-to-rod gap, secondary flow, and axial/lateral turbulence caused pressure fluctuations within the fuel assembly, which produces rod vibration and wear.

---------

[ Dry casks are air cooled, meaning they have vents in them for air flow, the vents have to be free of blockage. ]


[ This EN involves WI_Zion - snow blocked vents in casked fuel ]

SAFETY EQUIPMENT DISABLED DUE TO SNOW     
http://www.nrc.gov/reading-rm/doc-collec...ml#en50787

---------

March 1, 2018
NRC - NRC Begins Technical Review of Holtec Application for New Mexico Spent Nuclear Fuel Storage Facility
https://www.nrc.gov/reading-rm/doc-colle...18-007.pdf

The Nuclear Regulatory Commission has formally docketed an application by Holtec Inc. to
construct and operate a consolidated interim storage facility for spent fuel from commercial nuclear
power reactors in Lea County, New Mexico.
In docketing the application, the NRC has determined the application is sufficiently complete
for the staff to begin its detailed safety, security and environmental reviews.

Docketing does not indicate approval of the application.Holtec submitted its application on March 30, 2017,
and supplemented it in October and December in response to NRC staff questions.
Holtec seeks to store up to 8,680 metric tons of uranium in commercial spent fuel
in the Holtec International Storage Module Underground “MAXimum Capacity (HI-STORM UMAX) Storage System
for a 40-year license term. [ What do you think international means? ]

The NRC staff informed Holtec of its docketing determination in a letter dated Feb. 28, 2018.
The NRC will publish a notice of docketing in the Federal Register in coming days.

The application and other documents related to the NRC’s review are available on the NRC website.
https://www.nrc.gov/waste/spent-fuel-sto...ional.html
[ There's a picture showing what they mean by undergrund storage. ]
[ it's a giant cncrete pad with the canisters sunkintothe ground and only the top showing. ]
[ Bet that will absorb some heat. ]

[ If they were smart they would shade the pad with solar panels. ]


[ So possible leaking fuel, stored in air cooled casks in the desert. What could go wrong? ]

----------

[ Here's a couple vids showing what happens to spent fuel. ]

3 mins | Spent fuel composition by Ace Hoffman (based on Sorensen) | https://www.youtube.com/watch?v=2m2sr78g9uI

45 mins | Is Nuclear Waste Really Waste? | https://www.youtube.com/watch?v=rv-mFSoZOkE
 
Reply
#2
Staup,

Thanks for providing these reports.

It is very interesting that snow can block the cooling vents in casked fuel, and the safety equipment was disabled due to snow.
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