ML19345E378
| ML19345E378 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 01/13/1965 |
| From: | Haueter R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Boyd R, Doan R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101150739 | |
| Download: ML19345E378 (6) | |
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CONSU AIERS POWER COAIPAF r
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Dr. R. L. Doan, Director Division of Reactor Licensing United States Atomic Energy Commission Washington, D. C.
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Dear Dr. Doan:
Attention: Mr. Roger Boyd
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Trunsmitted herewith are +hree (3) executed and nineteen (19) conformed copies of a req st for changes to the
(,,27 r c Technical Specifications of License DPR-6, Docket No. 50-155,,
issued to Consumers Power Company on May 1,1964, for thTBig Rock Point Nuclear Plant.
Your early corMderation of this request will be appreciated since the modifications to the thermal shield supports are progressing rapidly. We expect to be starting up again during the early part of February 1965 and we vill require the changes to be effective by that time.
Yours very truly, p
RLH/vl Robert L. Haueter Enc Assistant Electric Production Superintendent - Nuclear r
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For the reasons hereinafter set forth, it is requested that the Technical Specifications of License DPR-6 issued-to Consumers-Power Company on May 1, 1964, for the Big Rock Point Nuclear Plant,'be changed as follows:
1.
Section 7 3.e(d) add a new paragraph:
j In the event that the antimony-beryllium source etrength is insufficient to produce a count rate of 3 counts per second (eps) and i
a signal"-to-noise ratio of 3 to 1 on the out-of-core low-level neutron detectors, the approach to criticality for the reactor start-up following i
the September 18, 1964 shutdown and such additional start-ups as may be necessary until sufficient power operation has been accumulated to ir-
- radiate,the antimony pins to acceptable levels (but not to exceed 3 j
months from first start-up) shall be allowed with the count rate from j
-the two out-of-tore low-l'evel neutron detectors less than 3 eps and the
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rignal-to-noise ratio less than 3 to 1 provided that the following conditions are met:
a.
Critical approaches with the reactor vessel head off shall be i
j performed to evaluate the out-of-vessel low-level detector response,
)
special low'-level miniature in-core detector response and the control
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rod withdrawal sequences. Two additional low-level detectors shall be temporarily inserted in the. vessel to monitor these head-off critical approaches and these detectors must satisfy the minimum requirement of l
- 3 cps with a 3 to 1 signal-to-noise ratio with all rods in.
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b.
Evaluation of instrument responses during the head-off critical j'
approaches shall. demonstrate that by the time the estimated k,ff of the core reaches 0 990 either (1) the low-level out-of-core start-up detectors are reading at least 3 cps with a 3 to 1 signal-to-noice ratio or (2) the two special'1ow-level in-core miniature detectors are respond-ing to changes in xerf and are reading at least 10 cps.
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Critical approaches with the head on and without the temporary in-vessel low-level detectors in service shall be permitted provided that the instrument response requirements of (b) above have been demon-strated and provided that these requirements are also met during the critical approaches with the head on.
d.
The procedures in (a) and (b) above shall be repeated in the event of either a core configuration change or a significant change in the control rod withdrawal sequence.
e.
A qualified reactor engineer will be on site during the evaluations and initial head-on ctart-up.
2.
Section 7 3 2(e) revised in its entirety:
" Critical approaches shall be monitored using low-level neutron detectors.
The start-up rate shall be restricted to assure that the CIC piccammeters overlap the low-level neutron detectors in use by at least one decade and are operational before attaining criticality.
Control rod withdrawal sequence shall be specified and limited to those sequences shown by previous analysis to preserve fuel integrity in the event of accidental continuous reactivity insertion."
Review The Big Rock Point Nuclear Plant is presently undergoing modifications to the thermal-shield retainer assemblies. The reactor vessel work is expected to be completed by late January 1965 and loading to an 82-bundle core started.
Based upon start-up count rates obtained following the last 8h-bundle operation and the 60-day half-life of the antimony-beryllium neutron sources, it is expected that the start-up channel count rates at the time of the initial critical approach will be about 1 eps. The noise level of Channel 6 is currently 0 583 cps and of Channel 7 is 1.02 cps. Therefore, the requirements of 7 3 2(d) of the Technical Specifications are not expected to be attainable.
Discussion and Hazards Considerations The Big Rock Point reactor had been completely unloaded by September 30,196k for the modification work. Heloading the core to 82 bundles is expected to begin in late January 1965 upon completion of the installation of six thermal-shield retainers (stilts).
In-vessel fission chambers (dunkers) will be utilized to load the core. An
3 82-bundle core configuration will be used to provide two empty channels (02S2 and 0959) for temporary instrumentation to be utilized during a short initial run to confirm the stress levels in the modified components and to check for unexpected movement of reactor vessel internals.
At the initial head-off critical approach, the core con-ditions will be as follows:
(a) 82 fuel bundles, all loaded in zircaloy channels.
(b) Core Positions 06-51 and 05-60 or other similar symmetrical positions will contain fission chambers in dunker cans. These will have readouts located in the control room.
(c) Core Positions 02-52 and 09-59 will be vacant to allow for exit of the instrument leads from the temporary instrumentation.
(d) The -eutron sources will be located in Positions 02-59 and 09-52.
(e) In-core strings located at Locations 15 and 17 vill contain special low-level fission chambers with readout in the control room.
(f) All normal seven channels of out-of-core instrumenta-tion will be installed and in service.
(g) The count rate from the in-vessel dunkers (fission chambers) shall be 3 cps or greater.
(h) The 82-bundle core kerr with all blades in will be about 0 93 The initial critical approach will utilize a prescribed centr 71 rod withdrawal pattern designed to meet normal Technical Specifi-cations' limits. The in-vessel fission cha=bers as well as the two special in-core chambers at Locations 15 and 17 will be monitored closely to insure multiplication is being observed.
It is expected that the in-core Chamber 15A and the in-vessel fission chambers will have increased by a factor of 10 - 20 as the core keff approaches o.990. The exact performance of the special in-core in location 17 is unknown since it has not been used to date at Big Rock Point but the response is expected to equal in-core 15A.
4 The out-of-core start-up instrumentation is expected to respond before a core keff of 0 990 is reached and,at k,ff of 0 990,the start-up channels will meet the 3 cps and 3 to 1 signal-to-noise ratio requirement. Records will be maintained of the correlation between the in-vessel and out-of-vessel instrumentation to provide adequate knowledge to perform the critical approaches with the dunkers removed and the vessel head installed.
It is expected that, with the knowledge gained through the head-off testing plus the special low-level in-cores, the start-up with the head installed can proceed with complete confidence that the neutron population is being monitored at all times.
The out-of-core instrumentation will provide all normal scram protection before and after the reactor is critical.
The initial lower operation will be a test run of several days to gather informstion from the special stress and vibration instrumen-tation installed in the reactor vessel. Upon completion of this run, the head will be removed and portions of the core unloaded to remove temporary instrumentation. The second approach to power is expected to take place 2 - 3 weeks after the initial operation and will uti'.1ze 84 fuel bundles; otherwise, conditions will be the same.
The requested changes to Section 7 3 2(e), Item 2, are not directly concerned with the source level difficulties, but rather with our difficulty in meeting a strict interpretation of the "lO-I% of rated power" requirement. We believe that the apparent confusion with respect to this number was brought about by an inadvertent error by us in our submittal of May 21, 1964 in which we supplied further supporting informa-tion to requested changes to the Technical Specifications, submitted March 26,1964.
You will note from the sketch of instrument response on Page 9 of the May 21, 1964 submittal that 125 x 10-7% of power is specified as the approximate minimum sensitivity while the line would lead one to believe that 1 x 10-I% of power is the minimum sensitivity. The lO-I% line was drawn in error and is considerably below the minimum sensitivity that can be achieved even under the most ideal circumstances.
5 Since the requirements for overlap and minimum sensitivity are somewhat redundant, we would propose that the sensitivity requirement be deleted and a one decade overlap requirement be substituted.
If the minimum sensitivity requirement must be continued, the "10 %" should be changed to "10" %."
Based upon the above information, we have cone]uded that the requested chances to the Technical Specifications do not present significant hazards considerations not described or implicit in the Hazards Summary Report.
ColiSUMERS POWER COMPAh By H. R. Wall Vice President Date: January 13, 1965 Sworn and subscribed to before me this 13th day of January 1965 W.O S. 'Lb &
t!otary Public, Jackson County, Michigan My commission expires February 16, 1968
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