ML20235K607
| ML20235K607 | |
| Person / Time | |
|---|---|
| Site: | MIT Nuclear Research Reactor |
| Issue date: | 02/14/1989 |
| From: | Bernard J, Kwok K MASSACHUSETTS INSTITUTE OF TECHNOLOGY, CAMBRIDGE |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20235K610 | List: |
| References | |
| NUDOCS 8902270181 | |
| Download: ML20235K607 (7) | |
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NUCLEAR REACTOR LABORATORY k AN INTERDEPARTMENTAL CENTER OF '8'/,Y/
MASSACHUSETTS INSTITUTE OF TECHNOLOGY O K. HARLING 138 Albany Street, Cambridge, Mass. 02139 J.A. BERNARD, JR.
Director Telefax No. (617)253-7300 Director of Reactor Operations Telex No. 921473 -MIT-CAM Tel. No. (617)253-4202 February 14, 1989 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 ATTN: Document Control Desk Subj ect : SNM Possession Limit, License R-37, Docket 50-20 Gentlemen:
The Massachusetts Institute of Technology hereby submits an application to amend its Facility Operating License No. R-37. The l
requested amendment is for a temporary increase in the possession limit for uranium-235 in paragraph 2B(2) of the license from 29 kilograms to 45 kilograms as was originally allowed under that license. The reason for this request is, as discussed in the enclosed analysis, unexpected unavailability of the MH-1A shipping cask for the transfer of spent fuel off-site. Once a shipping cask is available and once we have been able to ship out our inventory of spent fuel, the authorized possession limit would revert to 29 Kg.
This request has been reviewed and approved by the MIT Reactor Safeguards Committee.
Sincerely, u e Kwan S. Kwo Superintendent
-YW l2M John A. Bernard, Ph.D.
Director of Reactor Operations JAB /crh
Enclosures:
Safety Review #0-89-5 cc: MITRSC (with enclosures)
USNRC - Region I - Chief, Reactor Projects, Section IB USNRC - Region I - Project Inspector USNRC - Resident Inspector, p Pilgrim Nuclear Station v USNRC - Proj ect Manager, , ,
Standardization and Non-Power Reactor I 8902270181 890214 PDR P
ADOCK 05000020 PDC
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,; i Safety Review #0-89-5 i
\ms/ SNM Possession Limit for~ License R-37 (Docket 50-20)
The objective of this analysis is to provide information in sup-port of the request by the Massachusetts Institute of Technology to .
amend its Facility Operating License No. R-37 so that the possession limit for uranium-235 in paragraph 2B(2) of the license is increased from 29 kilograms to 45 kilograms, as originally allowed. This requested change would be temporary and would remain in ef fect only until it has been possible to ship out our inventory of spent fuel.
Background
Amendment No. 10 to the Facility Operating License No. R-37 for the Massachusetts Institute of Technology Research Reactor (MITR) was approved and issued by the United States Nuclear Regulatory Commission on 23 July 1975 (1]. That amendment, among other things,' authorized the possession and use of 45 kilograms of uranium-235. The USNRC requested by letter on 29 Aug. 1975 [2] that MIT voluntarily request a license amendment to reduce its possession limit for uranium-235 to the " lowest acceptable quantity" or LAQ. The LAQ was defined by the USNRC to be "the amount necessary to sustain current operations and those proj ected for the immediate future, i.e., 12 months". Given i that the MITR had at that time recently completed a major modification and was beginning a new type of fuel cycle, it was very difficult to estimate the LAQ. Nevertheless, MIT did so and by its letter of 25 O Sept. 1975 [3] requested that its SNM possession limit be reduced to 29 kilograms. This request, which was subsequently approved by the USNRC, was based on the following considerations:
(a) Unirradiated fuel would be ordered in batches of about 27 fuel elements. This fuel would be stored off-site with only the minimum required to facilitate refuelings being brought on-site. The amount on-site would always be less than a formula-quantity.
(b) The reactor core would operate with 26 elements. <
(c) The reactor's fuel management program would maximize burnup by cycling elements through each of the core's three rings.
Hence, at any given time 25 partially-burned elements would probably be in storage awaiting reuse.
(d) The burnup per element would average 25%.
(e) Shipments of spent fuel would consist of 28 elements each and be made whenever that many spent elements were accumu-lated.
Using these assumptions, it was estimated in 1975 that the MITR's fuel inventory would peak at 35 kilograms in 1981. A possession limit of 29 kilograms was requested with the understanding that MIT would, once O some operating experience was obtained with the new fuel cycle, "re-evaluate its requirements on the basis of operating experience and SR #-0-89-5 JAN 23 1989 e j
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,, subsequently' request an increase above 29 kilograms if necessary".
V On :17 Nov. 1975, Amendment No. 11 to the Facility Operating license was issued. As noted, it reduced the allowed inventory of contained U-235 to 29 Kg [4).
Operatina Experience with Fuel Cycle The MITR's' fuel management program has been extremely successful.
'The salient features ares (a) Unirradiated fuel is ordered, inspected for compliance with quality assurance requirements, and installed in the core.
MITR policy is to keep the inventory of fresh fuel at zero to the maximum extent possible. Fresh fuel is ordered only when needed.
(b) The reactor core operates with 24 or 25 elements.
(c) There are frequently as many as 27 partially-spent fuel ele-ments awaiting reuse.
(d) The burnup per element averaged 40-43% for the original 445 gram MITR elements made by Gulf Atomic. It is averaging 35-37% for the more heavily loaded 506 gram MITR elements that are now in use. These were made by AI.and more recently by Babcock & Wilcox. .,
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(e) Shipments of spent fuel have not been possible because of the lack of a suitable cask.
Other relevant information is that (f) The reactor normally generates 875 MWD of energy per operat-ing year. Assuming 1.25 grams of U-235 per MWD, the reactor therefore consumes about 1100 grams of uranium-235 per year.
This is slightly more than the equivalent of two fresh 506 gram MITR fuel elements. (Note: In terms of actual fuel elements, this amounts to a discharge rate of [(875 MWD)
(1.25 gr/MVD)]/[(0.35)(506 gr/ element)) or 6.2 elements per year when at equilibrium.
(g) The actual rate of addition of fresh fuel elements to the core is shown in Table One. l (h) The MITR's core is reactivity, not burnup-limited. 1 Fuel Management Policy l
The MIT Research Reactor's core is a hexagon consisting of three rings which are labeled 'A', 'B', and 'C'. The 'A' ring is the center one and contains three element positions. The 'B' ring is the inter-mediate one with nine positions. The 'C' ring is the outer one with O. fifteen positions. The standard fuel management plan calls for:
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-Table One
' Rate of~ Introduction of Fresh Elements to MITR Core Year # Fresh Elements Introduced f, . 1978- 8 1979 8 1980 4
'1981 8 1982 10 1983 9 1984- 7 1
1985 3 19E6- 0 1987 3 1988 3 l
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~ (a). Insertion of fresh. fuel in the A or B-rings.where the pcwer
-( N peaking !s least.
(b) Placement'of partially spent fuel that has been removed from the A or B-rings in temporary storage.
(c) Once sufficient' partially-spent fuel has accumulated, it is placed in the C-ring where the. peaking is more severe because of the surrounding heavy water reflector.
Fuel depletion is maximized by rotating elements in place to negate radial gradients and by inverting elements to negate axial enee. De-tails are given in [5,6]. As noted, this policy has been extremely successful. In particular, average fuel burnups of 178-190 grams per element for all types of MITR fuel have been obtained while still observing the technical specification limit on fission density. In fact, this policy was so successful that is was assumed that the 29 Kg limit would be acceptable and that the originally forecasted need to revise it upwards to 35 Kg or more would not be necessary. Of course, all this presupposed the capability to ship out spent fuel.
As the Commission is aware, the U.S. Department of Energy sought to make the MH-1A shipping cask available to the research reactor com-munity for the shipment of epent fuel. The MIT Research Reactor assumed that this cask would in fact be available and predicated its fuel management planc accordingly. Starting in 1985, the MH-1A sched-f-s ule began to slip. Accordingly, the MITR-II's fuel policy was adjust-ed. This is evident from Table One which shows a marked decrease in the number of fresh elements received for that and subsequent years.
Instead of relying on the insertion of fresh fuel to provide suffi-cient reactivity, the inventory of partially spent elements was drawn down. The U.S. Department of Energy repeatedly tried to obtain license approval from the U.S. Nuclear Regulatory Commission for the MH-1A. Each time additional questions were cenerated and each time there was a further delay. Accordingly, the MITR policy of acceler-ated reuse of partially spent fuel was continued. In retrospect, this was unwise but repeated assurances were given of the cask's ultimate availability. Late in 1989, MIT was informed that the U.S. Nuclear Regulatory Commission had again denied a license for the MH-1 A cask and that no further efforts would be made to license it. The MIT Research Reactor then initiated contact with General Electric for use of the GE-700 cask.
Current Situation Regarding Fuel Supplies The MIT Research Reactor currently has about 27.7 Kg of SNM on site. Therefore, under the present license limit of 29 Kg, only one additional element can be brought in. Also, the inventory of partial-ly spent fuel has been reduced to eight elements, four of which will be reinserted within the core during the next month. Accordingly, un-less additional fresh fuel can be brought in, it will not be possible to continue reactor operation for more than four-six months. (The
'~' exact figure depends on experiment schedules and is difficult to I determine precisely.) The earliest date for which use of the GE-700 l
cask can be expected is September 1989. Hence, the Massachusetts SR #-0-89-5 JAN 23 1989
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Institute of Technology is hereby requesting a temporary increase in the SNM possession limit. Specifically, it is requested that the (V~'} possession limit for uranium-235 in paragraph 2B(2) of Facility Operating License No. R-37 be increased f rom 29 Kg to 45 Kg as was origir. ally allowr.d under MITR License Amendment No. 10. MIT would, of course, strive to maintain its inventory as low as possible and would order fresh fuel only as needed to maintain uninterrupted reactor operation. Also, this request is temporary. The possession limit would revert to 29 Kg once the reactor's spent fuel was shipped.
(Note: It is currently estimated that this will require three ceparate shipments in the GE-700 cask. The temporary increare would therefore probably have to remain in effect through the remainder of 1989 and possibly part of 1990.)
Arguments Supporting a Temporary Increase in the Possession Limit (a) MIT received a uranium-235 possession limit of 45 Kg on 23 July 1975 as part of Amendment No. 10 to Facility Operating License No. R-37.
(b) MIT voluntarily requested a reduction in its possession lim-it to 29 Kg on 25 Sept. 1975. No safety system or safety-related procedure or regulatory requirement was relaxed or eliminated as a result of this reduction.
(c) Several safety improvements relative to the storage of fuel have been made at MIT since 1975. Physical security, never
[ a problem, has been increased in accordance with revised NRC
\-- regulations. The criticality analyses of all fuel storage locations were redone using the latest calculational methods. The results which confirmed the safety aspects of the fuel's storage were reported to the NRC in License Amendment No. 21 to Facility Operating License No. R-37.
(d) Storage facilities for spent fuel are well below capacity.
Also, the fuel in those facilities is well above the self-protection Euideline.
(e) The proposed increase will be temporary.
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(f) No changes will be needed or made to procedures for fuel receipt, Q/A, storage, handling, or security as a result of this request.
(g) No unreviewed safety question exists because this limit (45 Kg) was previously in effect. Since receipt of that approv-al, only conservative changes have been made that affect any facet of the handling of fresh fuel. In particular, (1) There is no increase in the probability of occurrence or the consequences of an accident that was previously evaluated. In particular, the requirements of MITR j g-s
(,) Technical Specification 3.10 concerning the security, storage, and handling of unirradiated fuel remain un-I l
changed.
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(ii) No new type of accident is created.
(iii) No margin of safety as defined in any technical speci-fication is decreased.
Proposed Wording of Change If approved, it is proposed that Facility License No. R-37 be amended by revising in its entirety paragraph 2.B(2) thereof to read ar follows:
(2) Pursuant to the Act and 10 CFR Part 70, "Special Nuclear Material", to receive, possess, and use in connection with operation of the reactor up to 29 kilograms of contained uranium-235 and 2 one-curie plutonium-beryllium neutron sources subject to the following exceptions (a) The limit for possession, receipt, and use of contain-ed uranium-235 may be exceeded on a temporary basis fo the purpose of maintaining uninterrupted reactor or,eration pending the establishment of a capability for the off-site shipment of spent fuel and the actual shipment of the spent fuel accumulated prior to the establishment of that capability. In no case shall the possession limit exceed 45 Kg. The Facility I shall, as part of its annual reporting requirements, report the status of the establishment of the shipping O capability and other activities relevant to the use of this temporary increase in the possession limit.
References
[1] Amendment No. 10 to Facility Operating License R-37.
[2] USNRC letter to Mr. L. Clark, Jr. dated 29 Aug. 1975.
[3] MITR letter to USNRC dated 25 Sept. 1975.
[4] Amendment No. 11 to Facility Operating License R-37.
[5] Bernard, J.A., Lanning, D.D., and L. Clark, Jr., "Use of Element Rotation / Inversion to Increase MITR-II Fuel Depletion,"
Transactions of the American Nuclear Society, Vol. 38, Suppl. 1, Aug. 1981, pp IP-18.
[6] Bernard, J.A., Kwok, K.S., Lanning, D.D., and L. Clark, Jr.,
" Calculational Procedures Used to Extend MITR-II Fuel Burnup,"
Transactions of the American Nuclear Society, Vol. 44, Suppl. 1, Aug. 1983, pp 14-15.
Copies of all references are attached.
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