ML20002E073
| ML20002E073 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 01/18/1971 |
| From: | Walke G, Wall H CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Morris P, Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101260269 | |
| Download: ML20002E073 (9) | |
Text
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Consumers i
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e General Offices: 212 West Michigan Avenue, Jackson, Michigan 49201. Area Code S17 788-050 January 18, 1971 Dr. P. A. Morris, Director Re: Docket 50-155 Division of Reactor Licensing DPR 6 ZEK United States Atomic Energy Proposed Tech Spec Commission Change 25 Washington, DC
.S 545
Dear Dr. Morris:
Attention:
Mr. D. J. Skovolt Transmitted herewith are three (3) executed and thirty-seven (37) conformed copies of a request for change to the Technical Specifications of License DPR 6, Docket No 50-155, issued to Cons-sumers Power Company on May 1, 1964 for the Big Rock Point Nuclear Plant.
This proposed change (No 25) vill enable Consumers Power Company to insert into the reactor at Big Rock Point, " Auxiliary Neutron Sources" contained in removable fuel rod positions in two fuel bundles. The additional sources vill improve the startup count rate so that it is well within current Technical Specification re-quirements. Because of lover core shutdown reactivity, lower planc load factor and longer shutdowns, the startup count rate has, on occasion, been marginal.
It is our intention to insert the sources into the Big Rock Point Reactor during our next refueling outa6e which in currently scheduled for February 1971. We would, therefore, be most appreciative of an expeditious handling of this Request for a Technical Specifications Change so that we might receive approval before March 1,1971.
Yours very truly, M /. M d 4 / + w & /~ ~
Nuclear Fuel Management Administrator 8 I I iP,p%
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Docket No 50-155 Request for Change to the Technical Specifications Change No 25 License No DPR 6 For the reasons hereinafter set forth, the following changes to the Technical Specifications of License DPR 6 issued to Consumers Power Company on May 1, 196h for the Big Rock Point Nuclear Plant are requested:
I.
Changes: Section 5 A.
Change Section 5.1.6 t'o read as follows:
Type Antimony Beryllium Quantity 2 Initial Sources up to 2 Auxiliary Sources
- Location The initial neutron sources shall be placed in Core Positions 02-59 and 09-52 as shown in Figure 5.1.
The two auxiliary neutron sources may each be contained in a removsble rod in a fuel bundle located one fuel bundle position from the outside of the core, syt:=etrically near the E-W line through the center of the "eactor core.
Physical Description The intial neutron sources shall consist of a steel jacketed antimony pin, 1 inch diameter by 12 inches long, centrally lo-cated on the vertical axis of a steel jacketed (Type 304 SS) beryllium. cylinder 5-1/2ODby16incheslong. The entire assembly,includingsupprtstructure,isacylinder79-7/16 inches long by 6 inches diameter which rests on a special i
- - With in-vessel low-le. vel neutron detectors in service, one operating source may be temporarily relocated as the operator deems appropriate.
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orifice in a standard support tube and fuel channel. / lifting
. bail shall be provided for handling purposes. The assembly de-sign shall allow adequate cooling along the surface of the source pin and the outer surface of the assembly.
The auxiliary neutron souces shall each consist of a homogeneous 50-50 mixture of antimony-beryllium first encap'ulated in a s
steel tube (Type 304 SS), then secondarily encapsulated in a circonits alloy tube. Each doubly encapsulated source vill be equipped with a spring loaded, bayonet latch locking device to permit it to be locked into a corner fuel rod position in a fuel bundle."
II. Discussion - Auxiliary Neutron Sources A. - Recent Operating Difficultics Section 7.3 2 (d) of the Technical Specifications spells out a minicum log count rate meter count rate to demonstrate in-strument operability and the presence and multiplication of fission neutrons within the reactor core. This criterion has been satisfacturily met until our last refueling outage, March 1970. At that time the minimum count rate bec:ame marginal and an in-vessel low. level neutron detector was used to establish the critical control rod configuration. Three factc rs con-trived to create the lower neutron count rate at the detector.
1.
Reload fuel currently in use included a burnable poison which reduces the core shutdown reactivity.
2.
A reduced plant load factor has resulted in a reduced equilibrium activation level of the initial neutron sources.
3.
The last outa6e was about 50 percent longer than normal because of a turbine-generator inspection, and this con-sequently resulted in a greater decay of the initial souce activity.
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3 it The electronics and detector systems were tested to de-4 termine if any_ improvements could be made in their operation.
These tests and subsequent studies-indicated that the most straight-forward and expeditious solution was to increase the neutron source strength in the reactor core.
B.. Auxiliary Neutron Source Description The neutron souce material is a homogeneous mixture of 50-50 by volume antimony-beryllium compacted to a minimum packing fraction of 80 percent. Tir source material is first encapsul-ated in a 0.483 inches OD steel tube (Type 30k SS) with a 0.033 inches vall thickness.
The overall length of the source tube is 60 inches with th? source' tiaterie.1 located in the middle
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25 inches, held there by a hollow, steel tube spacer at each end. The remaining space in the source tube is void volume.
The source tube is encapsulated in a zirconium alloy fuel tube of exactly the same quality and dimensions as tubing used for fuel rods and cobalt targets. The locking mechanism and rod configuration are exactly the same as the removable cobalt rods and removable fuel rods. To distinguish the auxiliary neutron source from cobalt targets, the nut on the bayonet latch type locking mechanism is square rather than hexagonal. It is large enough to be visible through the reactor and fuel pool water.
The squarc nut is also large enough so that the hexagonal rod removal tool vill not fit it.
C.
Auxiliary Neutron Source Design The in-reactor derign life of the auxiliary neutron sources is 15 years. Sufficient void volume has been incorporated into the design to attain this objective. Based on an assumption of
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1.5.,x 1013n/cm-secforthefluxofneutronswithenergies greater than the 2.7 MEV threshold for the (n, 2n)and (n, alpha) 22 He atoms vould reactions in beryllium, approximately 2.5 x 10 be generated in 15 years. - Using 750 F as the temperature of the outer surface of the stainless steel capsule 'and assuming con-servstive conductivity values, the. peak temperatu-e in the source material vould be 911 F.
The internal capsule pressure developed then, after 15 yeers of irradiation vould be 803 psia. The nominal vall thickness of 0.033 inches is designed to be one and one-half times the minimum' thickness specified by the ASLE Pressure Vessel Code for 304 SS stressed under the above conditions of pressure and temperature.
(Rules of Construction of Pressure Vessels, Division 1,' 1968 Edition, ASSE Boiler and Pressure Vessel Code Section VIII.)
D.
Quality Assurance Program Quality assurance requirements were specified in tie original bid specifications and were adhered to throughout manufacture.
Detailed veld and manufacturing procedures were developed, re-viewed and approved. Detailed leak-test procedures were also reviewed and approved. Material certifications of the physical and chemical composition of all the source components were re-viewed and approved. In most instances, copies of these certifi-cations were sent directly to Consumers Power Company. Design calculations were also reviewed and approved. In general, the quality assurance program applied to the design, procurement and manufacture of the cources was consistent with the program, applied to nuclear fuel.
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5 E.
Naclear Characteristics Thereplacementofa35gm/ftcobalttargetwithoneofthe proposed auxiliary neutron souces would have negligible effect on the nuclear characteristics of the fuel bundle. The following chanages would occur in a typical, fresh Reload E-G fuel bundle:
1.
The two outside rods adjacent to the neutron source have approximately a 5 percent increase in the local (rod-to-rod),
peaking factor. The overall bundle maximum local peaking
~ factor is increased by approximately 4 percent.
2.
The fuel bundle reactivity is increased by approximately-0.6 percent.
Both of the above changes are caused by the lower absorption rate e.ssociated with the neutron sources. Neither change has a sig-nificant effect on the operating limits for the fuel bundle.
As designed, each auxiliary source is capable of yielding 0
1.5 x 10 n/secfollowingirradiationforsixmonthsatareactor thermal flux of 1013n/cm-sec. The current operating level of 2
the initial neutron sources is estimated to be approximately 0 n/sec. It is difficult to estimate precisely the improvement 10 in count rate that the addition of the auxiliary sources vould provide. It is estimated that the startup count rate would in-prove by about a factor of 3 to'10.
F.
Planned Operating Procedu: es Current plans call for the auxiliary neutron sources to be inserted into the core positions 03-52 and 08-59 during the February 1971 refueling outage. The neutron source activity vill build up to a useful level by the end of the next operating cycle.
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6 When the fuel bundle containing an auxiliary neutron source is to be discharged from the reactor or moved to another core location, it vill be placed in the fuel transfer cask and moved to the spent fuel pool.- The source vill then be transferred to another fuel bundle,- then returned to the reactor via the fuel transfer cask. The fuel bundle with the source vill be located in a fuel bundle or channel position one row from the out. ide of the core, symmetrically near the E-W line through the center of the reactor core.
G.
Hazards Considerations The main hazards considerations relate chiefly to the effect the auxilia y neutron sources vill have on startup count rates.- Ex-c tensive testing of this effect was performed at the initial start-up. Technical Specifications Change Request No 1, submitted November lo,1962 and subsequent additional information reported the results cf these tests. Table VI, copy attached, from the additional information submitted on November 18, 1962 shows clearly that with sources in locations 03-52 and 08-59, the neutrons seen at the startup detector are fission neutrons and not source neutrons. This measurerent supports an analysis of the source-detector geometry which indicates that it is unlikely that source neutrons of approximately 30 Kev could penetrate the large water gap and other shielding.
Other hazards considerations related to the dose rates at the surface of the fuel transfer of the fuel transfer operations.
Calculations at the fuel transfer cask surface, assuming no shielding effect of the cask material, show a dose rate of 180 mrem /hr and at 3 ft from the cask surface, 20 mrem /hr. This
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is well within normal dose rates occuring during normal fuel handling operations.
The possibility of inadvertently inserting a fuel bundle con-taining a neutron source into the center of the core has also been considered. Peaking factors for the bundle are not sufficien-tly different to have a substantial effect on the operating limits.
Additionally, because of the conservative mechanical design, there vould be no adverse effects on the integrity of the source, III. Conclusions Considering the analyses presented herein, we have concluded:
1.
The mechanical and physics design of the auxiliary sources is conservative and compatible with other core components.
2.
The addition of the auxiliary neutron sources vill improve the startup count rate and hence improve the operability of the reactor.
Based upon this, we have concluded'that the use of the " Aux-iliary Neutron Sources" in the Big Rock Point Nuclear Plant does not present a change in the hazards considerations described or implicit in the Final Hazards Su - y Report.
CONSUMERS POWER COMPANY By e
Senior Vice President i
Date: January 18, 1971 Sworn and subscribed to before me this 18th day of January 1971.
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Notary Public, Jackson County, Michigan My Commission. Expires January 15, 1972
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'TABLB'VI - IEUTRON ORIGIN DE:0NSTRATION Operating Sources In 0352 & 0o:59
~ Channel Readings (Nornalized).
No.l' No.2 No.3 No.4 No.5 No.6 No.7 Instrument Channel Nunber 0157 (a) 1054 0651 0560. (a)
(a)
Chamber Locations - All at core midplane 1-
'(b) 1 1
1 1
1 Initial Readings,'all rods in 56 bundles in nomal location.
l'.7 (b) 31 1
.83 5
13 Bundle moved from 0858 to 0156:
1 bundle displaced 17
. (b)
.28 13
.83
.2 1
Bundle moved from 0958 to 0451:
Tuo bundles displaced 4
17 (b)
.23 13 5
.1 13 Bundle moved from 0759 to 1055:
Three bundles displaced
-17 (b)
.23 1.4 -
37
.1 15 Bundle removed from 0758:
Four bundles displaced 17 (b)
.27 1.4 53
.1 15 Blade F3: Four bundles displaced, blade next to sources pulled
-(a) Out of vessel (b) Not sufficiently sensitive The above set of data demonstrate that the neutrons seen by Channel 6 originate with fission in the bundles adjacent to the sources. These
-fissions, of course, can be caused by neutrons from the sources or other portions of the core.
The rather strance behavior of Channels 1, 3 and 4 during the unloadinn test results from the use of positions adjacent to some of these chambers as storage locations for bundles from the source re61ons. Channel 5 shows the effect of removing the fuel brid e between it and the source.
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