ML20031C282
| ML20031C282 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 04/18/1969 |
| From: | Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20031C280 | List: |
| References | |
| NUDOCS 8110070019 | |
| Download: ML20031C282 (4) | |
Text
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~Cons ers Power Company Docket No. 50-155-Proposed Change No.*17
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. ATOMIC ENERGY COMMISSION SAFETY EVALUATION BY THE DIVISION OF REACTOR LICENLING BIG ROCK REMOVABLE PLUTONIUM OXIDE FUEL RODS 1
By letter dated February 11, 1969, and supplementary telegrams dated March'17 and 18, 1969, Consumers Power Company has proposed Change No.
17 to_the Technical Specifications of License.Jo. DPR-6 for the Big Rock Point Nuclear Plant. According to the proposal, approximately 16 Reload' "E" or "E-G" fuel bundles containing plutonium oxide fuel in one or two of the removable fuel bundle rods would be' inserted into the Big Rock 4
Point reactor during the next refueling outage.
Therefore, a maximum of 32 Pu0 -UO r ds could be inserted. -In a letter-dated March 20, 1969, 2
2 Consumers also requested authority to receive, possess and use 50 kilo-grams of plutonium in connection with operation of the reactor.
The irradiation of plutonium oxide fuel is part of.a program to demon-strate the economic and technical feasibility'of utilizing plutonium in
' light-water reactors, with a specific objective of obtaining sufficient performance data to design a plutonium fueled core for a' commercial ~ reactor.
The cladding and mechanical design of the mixed. oxide fuel rods is iden-tical to the design of the removable UO2 rods they will replace.
Cold Pellets! prepared from mechanically blended pressed and sintered Pu0 -UO2 2
Pellets normally used ceramic grade UO2 and Puo2 Powder replace the UO2 as fuel in the removable fuel-rods. Although the fuel density of the-mixed oxide fuel rods is varied from 92% to 957. of theoretical density and void space in some is achieved by 37. dished ends and in others by.
central pellet holes varying from 5.57. to 18*/.'of the pellet volume, the weight of plutonium in each rod is the same.
This uniform fuel weight
~
in n rmal UO I#
is achieved by adjusting the weight fraction of Pu02 2
each of the pellet types described.
The removable Puo -UO r ds are 2
2 identified by crossed grooves on che top end plug and by serial numbers on'the top retainer and lower end plug.
In the Scfety Evaluation for the centermelt -fuel, uhich was issued with Amendacnt No. 1, dr.ted Parch 12, 1960, it was concluded that a reactivity excursion reculting from dropping of a cuntrol rod with a reactivity worth
~
~
of 0.021 delta k/k was entrencly improbable but constituted a reasonable
'9110070019 690418 PDR ADOCK 05000155 P-PDR.
upper limit for the purpose of evaluating a Big Rock Point care loaded with Reload "E" and six centermelt fuel bundles.
Using the conservative assumption that all of the thermal energy from fuel rods reaching enthalpies greater than 265 cal /gm is promptly released into the coolant, the prompt energy disposition in the coolant for this accident was calculated to be about 47 Mw-sec.
Additional analyses indicated that a prompt energy burst of less than aboat o4 Mw-see would not lead to loss of the integrity of the primary coolant system. We concluded that this provides an acceptable margin of safety for the integrity of the primary system in the unlikely event of a control rod-drop accident.
Consumers Power Company states that the distribution of 32 plutonium enriched natural uranium oxide fuel rods throughout the Big Rock Point core does not significantly change the core performance characterictics.
The reactivity worth of fuel bundles will be essentially unchanged.
The void and temperature coefficients of reactivity will be slightly more negative. The Doppler coefficient is essentially unchanged.
- However, because of the heterogeneity of the plutonium fuel as a result of mechanical blending of Pu02 and UO2 powders, the Doppler coefficient of reactivity could be slightly less negative for rapid changes in power, but the expected change in the coefficient is within the uncer-tainties associateu with the value of the Doppler coefficient of reactivity previously used in accident analyses.
Therefore, the conse-quences of accidents involv* ' this core characteristic are no greater than thase previously evaluv;d.
We have also censidered the possibility of the Puo VePorizing at fuel 2
rod enthalpies significantly lower than the prompt failure threshold for homogeneously distributed U-235.
Since the 32 mixed oxide rods will be distributed throughout the core with no more than 2 Pu02 rods per bundle, only a few of these rods could be close enough to a control rod of maximum reactivity worth to reach the prompt failure threshold in the event the rod were dropped.
If it is conservatively assumed that 2
2 fuel fails promptly at enthalpies in excess of 150 cals/gm,the Pu0 -UO additional prompt energy deposition in the water, considering the power profiles of all 32 pug -UO2 rods, would be 10.5 th-sec.
For this 2
assumption, less than 30% of the mixed oxide fuel would promptly deposit its therani energy in the water.
The total combined energy rclease to water from centermelt fuel and mixed oxide fuel would then be 57.5 th-sec.
We conclude that the margin of safety for the integrity of the primary system is sufficient to accommodate the additional calculated prompt energy release from the Pu0 -U0g fuel rods in the event of the control 2
rod drop accident.
o
( -Consumers Power Company has noted that the plutonium rods will be depleted almost twice as fast as the neighboring rods or the 2.5 a/o U-235 rods which they replace, and that annular pellets will be used in some of the plutonium fuel rods.
Neither of these fuel characteristics increases the probability or consequences of accidents as long as maximum fuel temper-atures are maintained well below the melting temperature. Experience with Pu0g-UO, fuel rods in the PRTR, SAXTON, and SENN reactors and annular pellets in ETR and GETR supports this conclusion.
The p%cposed Pu0 -UO f el rods will operate with a 1.3 power peakir; 2
2 factor within the fuel bundle thereby requiring a slight reductica oc the average bundle power to stay within the existing technical specifi-cation limits for minimum critical heat flux ratio (MCEFR) and rod power.
We agree.with Consumers that this reduc of average bundle power can be accomplished by placf ag the bundles
.aining plutonium oxide rods into radial core positions of lower than average power density.
On this basis, the peak fuel temperatures encountered during the design basis accident would be no greater than those which have been accepted previously.
Based on these comparative evaluations, we have concluded that 32 mixed oxide, pug -UO, fuel rods distributed throughout.the core do not signif-i 2
2 icantly change the magnitude of the accidents which we have previously evaluated and found ac captable for the Reload "E" and "E-G" cores.
Furthermore, the probability of an accident which could release fissica products from the primary system or which could impair the effectiveness of the installed engineered safety features beyond conditions previously analyzed would not be increased by the presence of 32 plutonium fuel rods.
Enrichment of 32 fuel rods with plutonium changes the total Big Rock Point core plutonium inventory by less than 4% at the beginning of a fuel cycle and even less at the end of a fuel cycle.
The results of previous calculations, as reportca in the Safety Analysis Report (Final Hazards Summary Report), indicate that the lifetime dose to the bone at any off-site location and for any exposure time or diffusion is c1vays less than 0.1 rem.
Since analysis indicates that most of the bone dose would be due to the long-lived radioisotopes of strontium, yttrium, zirconium, barium and cerium, we agree that a 4% increase in the plu-tonium inventory at the beginning of the fuel cycle would not cause significant change in the internal bone dose at off-site locations.
A
e 1
Corsumers Power Company has stated that because of the toxic nature of int,ested plutonium, unirradiated plutonium bearing rods will be handled with extra caution to prevent damage which might expose the fuel. To minimize the daaage possibility, experienced General Electric personnel will remove the fuel rods from the shipping containers when they arrive at the Big Rock Point site and the GE personnel will be available during all handling and loading operations.
Appropriate respiratory protection and alpha counting instrumentation will be available at all times during these operations.
Special emergency procedures have been prepared to cc pe with accidents involving the plutonium enriched fuel rods.
The difference in plutonium concentration between irradiated mixed oxide rads and irradiated U-235 enriched fuel rods is insignificant insofar as paysiological effects are concerned; therefore, the handling of irradiated mixed oxide rods will be in accordance with existing procedures for han-dling irradiated fuel.
Reactor water and waste discharge which are routinely analyzed for certain radioisotopes will be further analyzed for alpha contamination and for a change in fission product content. We are natisfied that the extra handling precautions for the new fuel rods
-ontaining plutonium are adequate and agree that existing handling procc-dures for irradiated fuel rods are suitable also for depleted plutonius fuel rods.
Based on our evaluation of the proposed substitas*0n of Pu0 -UO2 fuel rods for thirty-two 2.; a/o U-235 remavable fuel rods in Reload E" or "2-G" fuel bundles, we have concluded that Proposed Change No. 17 does net represent significant hazards considerations not described or implicit in the safety analysis report and that there is reasonable assurance that the health and safety of the public will not be endangered by operation with the plutonium fuel rods.
Accordingly, the Technical Specifications of License No. DPR-6 may be revised as indicated in Attachment A.
pfk U h ll Donald J.
novholt Assistant Director for Reactor Operations Division of Reactor Licensing Date: April 18, 1969 f