ML20117A205
| ML20117A205 | |
| Person / Time | |
|---|---|
| Site: | University of Missouri-Columbia |
| Issue date: | 11/23/1992 |
| From: | Bolon A MISSOURI, UNIV. OF, ROLLA, MO |
| To: | |
| Shared Package | |
| ML20117A204 | List: |
| References | |
| NUDOCS 9211250157 | |
| Download: ML20117A205 (8) | |
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IUitt0RT_0R_TillilODDESS10N Ol' LON._ImRICilliDJIMN1DM.135 IR EXCESS._Q1LLLCIWSE . LIMITD AT TillL11HLVERSITY OLMISS01?RI-ROLIA IIIMCTRILI%CILITY (November 23, 199.7)
.t Approvedt NJA - c M- !
Dr. Albert E. Bolon UMR Reactor Direct.or -
9211250197 921123 -
PDR ADOCK 05000186.-
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1.0 lixcqutivolutn!stry on July 18, 1992, the University of liissouri-Rolla (UMR)
Reactor received a partial shipment of twenty LEU (19.8 w/o enriched) elements totaling 3,982 grams of U-235 as part of t a LEU conversion. On August 27. 1992, the UMR Reactor it :eived the remaining eight LEU clements totaling 1,261 grams l of U-235. ,
On Octci,vr :.8, 1992, the UMR Reactor staff identified that tho i sum total of LEU U-235 on site was (3,982 grams + 1,261 grams) ,
5,243 grams. This was immediately recognized as being in '
violation of Operating License R-79 that limited on-site LEU ;
fuel to 4.95 kg. The Reactor Director was immediately not.lfied. The NRC was nromptly notified that same day-by _
phone. .
, s
! On October 29, 1992 (the next day) through conference calls with the NRC, it was agreed that no safety problem existed and that the UMR Reactor staff would quickly apply for a license amendment requesting an increase in the limit of LEU U-235 from 4.95 kg to 5.5 kg. The request for a license amendment was prepared and sent to the NRC by " Pax" and by registered mail on October 29, 1992. On November 10, 1992, the NRC issued Amendment Number 10 of the Operating License increasing ,
the LEU limi' to 5.5 kg as requested.
This report presents an analysis of the root cause of the license .l i mi t violation. Additionally, corrective actions taken and recommendations to preclude recurrence of this or similar situations are presented.
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2 2.0 ADitlyrd H_Q f_RQQL_Qtu B C_ll nd_CQIltr_lbutlIIG _l'iLGLQui In October or 1979, the UMR Staff submitted documents for the license renewal of Facility opo ating License R-79. Several years lapsed prior to issuance of the new facility license.
During this time (in the early 1980s), the LEU conversion project was initiated at UMR. The renewal license was finally issued in 1985 as Amendment Number 8. In an of fort - to eliminate the need to amend the license again as a result of the impending LEU conversion, the authors of Amendment Number a had the f oresight to include a possession and use clause for LEU fuel. As it turned out, the license would again be amended as a result of the LEU fuel conversion. Ironically, -
Amendment Number 9 did not revise LEU related issues, but
. rather dealt solely with possession limits of HEU material -
in particular with Iission chamber and flux foil possession 5
limits.
The LEU possession and use clause of License Amendment Number 8 was incorporated in Paragraph 2.B.2 which stipulated:
... to receive, possess, and use up to a maximum of 9.9 ,
kilograms of Uranium-235 at various enrichments ... the maximum limits on specific enrichments of U-235 are as follows:
Maximum
_U-235 % Enrichment 4.95 kg < 20 4.95 kg > 20 " =
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b At the time of the license renewal (1985), the LEU fuel design
, was still in its early stages.
It is unclear what the exact motivation was to set the 4.95 kg limit of LEU fu91 in the old license.. Most likely, because the f uel element design phase was in it ; infancy in 1985, the 4.95 kg value was cnosen because that was the existing HEU limit and we were expecting to esGentially convort on a "one-to-one"_ element basis. Under this rationale, the fact that
, such a-high loading of LEU per element would-be required-to compensate for the less potent (reactivity wise) LEU fuel had not yet been thoroughly analyzed.
One of the goals _ of the LEU element design was to prnvide similar core geometries. Thus a design that would allow for the direct "one-to-one" replacement of HEU fuel elements was sought. Consistent with this philosophy, a decision was made early on to have 28 LEU elements fabricated to replace the 28
3 IIEU elements originally f abricated f or our f acility in 1961.
(The 28 IIEU elements consisted of 22 standard elements, 4 control elemei.. , and 2 half olements. The 28 LEU elements include 18 standard elements, 5 control elements, 4 half elements, and one " irradiation facility" element.)
In the early design phases of the LEU element, a 16 plate standard element was proposed. Possibly, the 16 plate element was used as a basis for calculating the LEU limit in the 1985 license amendment. The U-235 inventory for the 28 LEU elements based on the 16 plate element model would have been about 4.67 kg - in such an instance the selection of 4.95 kg for a license limit would have been appropriate.
In 1989, work presented in a Master's Thesis' investigated both 16 plate and 18 plate LEU elements. Based on information :
presented, it was decided that 18 plate elements would provide superior performance and the 16 plate design was dropped.
Whatever the exact basis was behind the 4.95 kg LEU possession limit in the 1985 license, it is clear that specifying such a limit several years 1. flor to finalization of the element design was premature. Ilad this issue not been addressed prematurely, then certainly an appropriate possession limit (i.e. 5.5 kg) wou?d have been negotiated based on the finalized fuel element design.
The license was amended again (Amendment Number 9) to accommodate the LEU conversion. License Amendiaent Number 9 was solely a result of NRC concerns that the possession and use clause of Paragraph 2.B.2 should be revised to specifically address fission chambers and flux foils.
Although we had verbal conversations concerning the revision,- ,
the first time the Reactor staff saw the license revision was when it was issued with the modifying order to convert. When we received the license revision, we reviewed it against the-existing license (Amendment S). The revision concerning fission chambers and flux (foils) appeared acceptable. The 4.95 kg limit on LEU had not been altered.
This fact is pointed out to emphasis that a- complete administrative license review was not perfirmed upon the issuance of Amandment 9 occause the scope - of the license revision was limited to addressing p o s s e s s i o n --l i m i t s - f o r--
fission chambers and flux foils. In fact, the entire license -
was not reissued by the modifying order -
only those
'Covi ngton , Lorne, J, "Neutronice Study of the Conversion-of the University cf Missouri-Rolla Reactor to Low Enriched Fuel",
UMR, 1989.
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paragraphs that were revised were reissued. Only the revised
, portions of the license issued with the modifying order were reviewed by the UMR Reactor administration.
It appears that no one on the UMR Reactor staff independently calculated the total amount of U-235 contained in the 28
.ements and compared that total to the 4.95 kg limit in the license until after the fuel was onsite. Had this simple calculation and comparison been performed and documented, a j revision to our possession limit could have been initiated and obtained prior to receiving the LEU fuel onsite. ;
It should be noted, however, that the problem was identified in a relatively timely fashion. The problem was identified during the very next semi-annual material inventory. Thus, the system of checks and balances already in place allowed for the identification of the discrepancy.
One of the f actors that contributed to our not identif ying the discrepancy immediately upon receipt of the LEU fuel was the fact that the fue' was shipped to us in two aeparate shipments. The shipper lacked the shipping containers required to ship the entire inventory. Thus, a compromise was reached and we received 20 elements on July 18, 1992 (totaling 3,982 grams of U-235) and the remaining 8 elements were received on August 27, 1992 (totaling 1,261 grams of U-235).
Because of the partial shipments, both DOE /NRC 741 forms .
showed U-235 inventories well beneath our limit. The problem was not immediately identified upon receipt of the second shipment boccuse we did not immediately sum the amounts raceived on the two 741 forms. Had all 18 elementa been shipped 11 the same shipment, we and the shipper would have immediately identified that the U-235 inventory was-over our limit by inspecting the DOE /NRC 741 Material Transfer Form.
Ideally, we should have had a procedure in place that required inventory review prior to receipt of a shipment. Such a procedure would have lead to the early identification of the discrepancy prior to receipt of the material.
Anothcr f actor was due to the fact that this is the first fuel changa we have ever experienced at the UMR neactor. Due tv our low burnup, we were still ope ating with the original 28 HEU elements provided to us in 1961. Therefore, it is by no-means " routine" for us to receive incoming fuel. As such, we ,
had no standard operating Procedure in place to receive the LEU fuel. Wo did pr epare, review and approve a "special procedure" to cover receipt of the new f uel prior to receiving the shipment; however, the need to keep a " running inventory" of incoming fuel 1was not for seen. ->
l To summarize the analysis, the following contributing f actors ,
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are identified:
- 1. Amendment Number 8 of License R-79 prematurely addressed LEU possession limits -
years before the fuel element design was finalized.
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- 2. The. fuel element design was changed from 16 fuel plates ;
to 18 fuel plates as the conversion project progressed. ;
- 3. Once the LEU fuel element design was f j nalized, there was i a failure to calculate the total-inventory of U-235 in 1 the 28 elements to be fabricated to assure that the license limit would be met.
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- 4. The LEU fuel was receivnd in two separate shipments.
Although each shipment was verified to be less than_the -
license limit, no " running total" was calculated hence the violation was not immediately identified. -
The root cause is believed to be due to the fact that-no prescedure was in place requiring the assessment of anticipated ;
onsite inventories prior to the receipt of a shipment of licensed materials, llad such a procedure been in-place, the problem would have been identified prior to receiving the material and could have been mitigated through normal channels ,
without violating our license limits.
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3.0 Currentiv1 lac 11onn_and. Recommendations _t9_Provent Rooncurrence It should be noted that presently, there are no plans to receive any more fuel at the UHR Reactor. The LEU fuel now in-house is expected to last for the next 30 to 100 years. As J such, recurrence of this problem is not expected with respect to fuel. However, it is quite possible that additional fission chambers and flux foils will be acquired at some time in the future. Thus, it is important to implement a corrective action to assure that license limits are always met with respect to incoming licensed material. The proposed corrective actions are as follows:
- 1. Establish a written procedure that requires the projected onsite inventory of licensed material to be assessed and I compared with licensed limits prior to the receipt of any licensed material.
- 2. Fully brief each UMR Reactor staff member on this incident at a special staff meeting to make sure that I cach person understands exactly what happened and why and to present measures to prevent recurrence.
A new Standard Operating Procedure 311 " Receipt of Licensed Material" will establish a protocol that will require that the projected inventory onsite be assessed prior to receiving a i planned shipment of licensed me terial. .This procedure will assure the prior review and authorization of anticipated incoming shipmento against licensed quantity limits.
The staff briefing will serve as important training making sure everyone learns as much as possible from this incident.
It is believed that the above corrective actiotis will prevent recurrence of. this type of problem at the UMR Reactor-facility.
4.O S y m a r y.
On August 27, 1992, the UMR _ _ Reactor Facility vio M its licensed limit of 4.95 kg of_ LEU fuel by receiving a stal of 5.24 kg of LEU U-235. The violation was identified by the UMR Reactor Staff- on October 28, 1992. The violation _ was identified through procejures in place at the facility
-(specifically, the semi-a.inual completion of the DOE /NRC Material Balance Reports). The NRC was prompt'y notified-on the same day that the problem was identified. On November 10, 1992, the NRC issued Amendment Number 10 increasing our LEU license limit to 5.5:kg, thus bringing us-into complitace.
The incident did not-compromise the safety of any individual
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7 or of the reactor system. -The incident did show a failure by the reactor staf f to identif y the discrepancy prior to receipt of the fuel.
The root cause of this incident and several- contributing i factors have been identified. !
Corrective actions implemented include establishing a new SOP l directly addressing receipt of incoming material, and a full ;
staff briefing of the incident. These corrective-actions .
should preclude recurrence of this type nf problem.
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