ML20128C857

Summary of 710511 Meeting W/Util Re Discussions on Possible Fuel Pellet Enrichment Mixup at Plant

ML20128C857
Person / Time
Site:	Monticello
Issue date:	05/20/1971
From:	Benaroya V US ATOMIC ENERGY COMMISSION (AEC)
To:	Boyd R US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9212040551
Download: ML20128C857 (5)

Text

_ -- . . <-.,r ,, s . . ._

~

)

p4*, UNITED STATES p ATOMIC ENERGY commission y a

4 j*

f 1 ) Y.l'-

W AsHINGTON, D C. 20l49

% < A -)'

?

' s,,, [ , May 20, 1971 Roger S. Boyd, Assistant Director, BWR, Division of Reactor Licensing THR nald T. Knuti, Chi f. BWR-1, Division of Reactor Licensing W.44.Y h MEETINr. ITH NORTilERN STATES POWER COMPANY (NSP) - MONTICELLO GENERATING PLANT (E-5979), CONCERNING FUEL ENRICHMENT MIXUP, DOCKET NO. 50-263 Summarv A meeting was held on May 11, 1971, with NSP to discuss possible fuel pellet enrichment mixup at the Monticello plant, and the probabic consequences of such an occurrence. An attendance list is enclosed.

This meeting was held as a result of a previous meeting with General Elcetric (GE) held on April 20, 1971, to discuss fuel pellet enrichment mixup at its Wilmington facility on reactors presently under review and those with operating licenses (See memo from Mark J. Wetterhahn to Roger S. Boyd,

" Meeting with the General Electric Company Concerning Fuel Enrichment Mixup," dated May 3, 1971.) This was a generic meeting, and GE stated that they would recommend that NSP discuss with DRL the Monticello fuel problem more specifically. GE believed that this meeting should take place before Monticello exceeds 50% power.

Monticello fuel was f abricated at GE's Wilmington facility. GE has taken the position that mixups in fuel enrichments occurred during high volume production which started after March 1, 1970. Most of the Monticello fuel (392 assemblies out of 494) was fabricated during the early days of Wilmington, prior to March 1, 1970, when the output was low. Only a i small number of assemblies (92) were fabricated after March 1, 1970.

According to GE's evaluation, the consequences of fuel pellet mixup in a small portion of the core is small enough to continue the power ascen-tion testing now in progress.

Discussion NSP first Icarned of possible enrichment mixup in the fuel during March 1971, from a member of the Safety Audit Committee who works for Commonwealth Edison (Dresden 3 and Quad Cities plants). NSP had a series of meetings with GE, and as a result of these discussions it was concluded that test-ing up to 50% power would not create a safety problem.

i GE claims that as production increased at Wilmington, the number of different I fuci enrichments present at the plant increased. Until March 1, 1970, cabinets were segregated so that all trays in a cabinet contained the same enrichment; however, after that date, due to lack of storage space, trays 9212040551 710520 ~~ ~~~~~~

PDR ADOCK 05000263 P PDR

l Roger S. Boyd 2 I

with different enrichments were housed in the same cabinet. GE has con-

cluded that the most likely cause for fuel enrichment mixup has been pellets with a different enrichment in the same cabinet getting mixed.

GE became aware of fuel enrichment mixup in November,1970.

According to GE, fuel of incorrect enrichments probably started in March 1,1970, and probably continued untti complete gamma scanning of the fuel rods was initiated early in 1971. Based on the fuel examined thus far, approximately 1% of the fuel rods fabricated during that period is suspected of having wrong enrichments. Based on the observations of the fuel that has been gamma scanned, strings of up to 25 pellets in a rod may have the wrong enrichment. A few rods have more than one error in enrichment. Based on the assumption that 93 assemblies of Monticello were fabricated during the critical period and on the statistics of fuel that has been gamma scanned thus far, GE is of the opinion that 12.1 rods of the Monticello fuel may be affected. Of these, only 0.2 rod would have a power density of greater than 20.5 kW/f t, where the fuel could melt.

We brought to GE's attention that according to the " tray mixup" theory, the probability of having more than one type of enrichment in any specified enrichment should be extremely small. Ilowever, inspections to date show that more than 107 of the pellets have more than one enrichment error.

This discrepency __J not resolved.

GE re:alculated the cladding temperatures resulting from a LOCA making the following assumptionst

1. 12 fuel assemblies (1 rod in each fuel assembly) are affected, t

2. The complete rod has the wrong enrichment.

3. No end effects.

4. The rod is located in the worst condition in the bundle.

i

5. All assumptions per NED0-10329 The calculated cladding temperatures are as follows:

3 LPCI 2 CS i FSAR case (17.5 kW/ft) 1900'F 1520*F 4

NEDO-10329 (17.5 kW/ft) 2130'F 1970'F 1

(20 kW/ft) 2025'F

, (25 kW/ft) 2650'F 2

e T

4

, , - . , - ~ - - , - - , - . - - - - - - . . v,,- . - -, -

i Roger S. Boyd 3 4

4 e i i

GE has concluded that based on very conservative assumptions, very few pellets would melt, the change in temperature for the bulk of the core j

is negligible, therefore the hazards associated with fuci enrichment mixup for the Monticello core can be ignored.

NSP and GE concluded that since the fuel mixup for Monticello is hypo-thetical and not yet proven, and the consequences are negligibic and should not affect the health and safety of the public, the possibility of having enrichment mixup in the Monticello fuel need not be reported to DRL. We informed NSP that we were of the opinion that the fuel problem is not a hypothetical case but an existing one, and therefore i we would prefer to see something in the docket which would explain I

a) the logic that only 92 of the 494 assemblies are affected:-

b) the basis of determining the probability that 12.1 rods may have enrichment mixups; c) the consequences of the accidents analyzed assuming the fuel 4

'nrichment mixup.

NSp agreed to look into the matter further.

1

\U Victor Benaroya, Project Leader Boiling Water Reactors Branch No. 1 l

' Division of Reactor Licensing

Enclosure:

j Attendance List 1

J I i

b 4

1 (

e - ,--,- - -,, , y y w- - , , . , -

,, -,y- <-, -- ,

ATTENDANCE LIST l

F10NTICELLO NUC1 EAR GENERATING PLANT Hay 11. 1971 4

DRL NSP i R. S. Boyd E. Ward D. F. Knuth R. Jensen V. Benaroya C. Larson J. Thie

, po, C1 J. llenderson-C.-D. Feierabend A. Suasek E. Nichols Shaw Pittman, C. liills J. Power G. Charnoff A. Rogers R.-Ketchel-

,- GE San Jose C. Miller A. Bram J. Barnard

i Roger S. Boyd 3 MAY 2 01971 cc has concluded that based on very conservative assumptions, very few pellets would melt, the change in temperature for the bulk of the core is negligible, therefore the hazards associated with fuel enrictment mixup for the Monticello core can be ignored.

HSP and GE concluded that since the fuel mixup for Monticello in hypo-thetical and not yet proven, and the consequences are negligible and should not nffect the health and safety of the public, the possibility of having enrichment mixup in the Monticello fuel need not be reported to DRL. We infotued NSP that we were of the opinion that the fuel problem is not a hypothetical case but an existing one, and therefore we vould prefer to see something in the docket which would explaint a) the logic that only 92 of the 494 assemblics are affected; b) the basis of determining the probability that 12.1 rods may have enrichment mixups; c) the consequences of the accidents analyzed assuming the fuel enrichnent mixup.

NSP agreed to look into the matter further.

Victor Benaroya, Project Leader Boiling Water Reactors Branch No. 1 Division of Reactor Licensing Distribution:

Enclosures Docket Attendance List DRL Reading BWR-1 File PAMorris, DRL FSchroeder, DRL Asst. Directors, DRL EGCase, DRS RRMaccary, DRS llDenton, SERSG

-< .- Br. Chiefs. DRL/DRS Compliance (2)

BGrimes, DRL SMKari, DRL VBenaroya, DRL Attendees DRL/C0 DRL ,: B,WR ,1 omet > ... DRL : Bh'R- 1,,, ,

VBenaroya:ks y

$URNWE> X.7 7 91,. Qk, . b bI. l . . . . . . .. ,

iwm ac.$UT)

~ $~JJCL,.6Jf.;%.4 == ="

_ _ __ j