ML20002C409
| ML20002C409 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 07/20/1972 |
| From: | Haueter R, Lamley R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101100265 | |
| Download: ML20002C409 (7) | |
Text
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L CORSumBTS p
L Power Company
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Genera' Offices: 212 West Machigan Avenue, Jackson, Michigan 49201. Area Code 617788-0550 July 20, 1972 Regulatory
'FBe Cy'.'
Mr. John F. O' Leary, Director Re: Docket No 50-155 Directorate of Licensing License No DPR-6 United States Atomic Proposed Tech Speci-Energy Commission fication Change 33 Washington, DC 20545
Dear Mr. O' Leary:
Transmitted herewith are three (3) executed and thirty-seven (37) conformed copies of a request for change to the technical specifi-cations of License No DPR 6, Docket No 50-155, issued to Consumers Power Company on May 1,1964 for the P4 g Rock Point Nuclear Plant.
This proposed change (No 33) stems frcm the in-depth review of ' 4e Big Rock Point Plant liquid poison system which was conaaleted er a result of the recent difficulties encountered when performing annual testing of the explosive valves. These difficulties were re-ported by letter to the Directorate of Licensing, dated May 11, 1972.
Yours very truly, N&
RBS/vl Robert L. Haueter Electric Production Superintendent -
CC: BHGrier, USAEC Nuclear o
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Regulatory IF% cy; CONSUMERS POWER COMPANY Docket No 50-155 Request for Change to the Tech:lical Specifications Change No 33 License No DPr,_6 g, g; g., gggyy_ ya
.~.......w For the reasons hereir.after set forth, the following changes to the technical specifications of License No DPR-6 issued to Consumers Power Company on May 1, 19614 for the Big Rock Point Nuclear Plant are requested:
I.
Changes Change the law, sentence of Section 5 2 3 to read as follows:
"One squib primer and trie,ger assembly from the equalizing line shall be rt moved and test-fired at least every 12 months. These shall be tested on an alternate basis insuring valve replacement every two years. One squib primer and trigger assembly from the remaining five units shall be removed and test-fired at least every 12 months. These shall be tested on an alternate basis insuring valve replacement every five years. The tests will consist of monitoring of the input firing current and shear-ing of the integral inlet cap."
II.
Discussion The poison system consists of a spherical phenolic lined 850-gallon stcrage tank containing a solution of sodium pentaborate (19%-% by 5 eight), an injection line from the tank to the reactor primary system, a pressure equalizing line from the steam drum to the tank and a pressurization line between the bank of 2,000 psig nitrogen bottles and the tank.
The pressurization line and equalizing line each have two full capacity valves in parallel, and the injection line has three half-capacity valves in parallel. This valve arrangement provides redundancy for all valves, reducing the probability of system failure due to valve i
failure.
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2 The explosive charge is provided with two electrically fired primers per valve, each of which is energized from a different d-c circuit, and either of which is designed to shear the integral inlet cap. Two parallel circuits supply all of the seven explosive valves so.,uat an external failure or internal breaking of a circuit due to staggered firing will not prevent all valves from being energized. Also, each individual line to the 14 primers is fused so that a short circuit in an element during firing v'11 not disturb the remainder. In the normal position, all elements ar connected in series, including the control relays and each circuit is 'onitored continuously. An open circuit failure in any part of a circui-causes an alarm to be annunciated in the main control room. Also in the procurement of the valves, destructive tests are per-formed in which the energy output of sample primers is monitored and checked against a standard. This insures that the energy output is sufficient to shear the integral cap. In addition, the Big Rock Point Plant vill test-fire and shear an integral cap before any primers from a new lot of primer charge materials are installed into the system.
1herefore, the probability of system failure due to valve failure becomes infinitesimally small.
The poison tank is not pressurized during normal system oper-ation to allow easy access for sampling and chemical additions (if required) to keep the sodium pentaborate solution (poison) within the specified limits. Upon initiation of the poison valves admitting full 2,000 psig, nitrogen pressure to the poison tank, poison is forced into the reactor within a few seconds; however, if the primary system is at full operating pressure, the nitrogen volume will be insufficient for forcing out more than a few gallons of solution. The driving force for the remaining volume is achieved from the static head due to the elevated position of the tank and the head across the recirculating pumps. If both recirculating pumps are down, a valve on the injection line into the pump suction is closed by an interlock on the pump motor breakers and poison is forced directly into the reactor through a check valve.
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3 The primary purpose of nitrogen pressurization is to insu: e positive displacement of poison solution only when the reactor recircu-lation system is static; that is, both recirculation pumps off such as
-during refueling when there is no initial driving head to establish a siphon throagh the discharge dip tube in the poison tank. Sufficient pressurized nitrogen is available to displace the entire poison solution from the tank without benefit of siphon for system operating pressures up '.> 350 psig. 'However, at any operating pressure with natural or pumped recirculation flow, a minimum of nine feet friction loss through the reactor will establish siphon through the injection line and empty the poison tank even without benefit of nitrogen pressurization.
The top outlet arrangement of the poison injection connection was selected to avoid precipitation of sodium pentaborate in contact with external piping and valves.
Tht. resulting siphon required is three feet when the tank is full and nine feet when the tank is empty. Integrity of this siphon, once established, is assured by the small size of the in-jection line (three inches). Air in-leakage is improbable under any circumstances as the associated piping and flanges are designed for 2,000 psig pressure.
Within the first five minutes, cufficient solution is intro-duced into the primary system to produce a boron concentration of 1,300 ppm.
Thisisequivalentto-16%Ak/le, which is more than adequate to reduce power level to zero by offsetting the effect of decreasing voids.
In-jection of the remaining solution raises the boren level to 2,000 ppm which produces -25% Ak/k and is sufficient to hold the core subcritical even after it has cooled completely and with all control rods removed.
The test firing of one primer and trigger assembly from the equalizing line every 12 months will provide a maximum in-service l
inspection period of two years for the equalizing line units. The units installed in the equalizing line experience the highest ambient tempera-tures of the seven assemblies installed. The remaining five units will be tested on a one-per-year basis. This testing program will insure that r.o units exceed an in-service life of five years, whip is well
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within the manufacturer's recommended life for the service conditions experienced. The test firing will include shearing of an integral ini This will demonstrate that the force developed by the charge is cap.
sufficient to actuate the poison system.
The life of the primers is conservatively based on the l
attached chart provided by the Conan Corporation. The values on this chart were developed, based on short life span testing of primers, and extrapolated to predict lower temperature - longer life relation-ships. A temperature monitoring program is in progress at Big Rock Point to determine the precise environmental temperatures that the primers experience. Current results show that the primers in the 0
equalizing line experience a temperature of about 101 F while the warmest of the other five squib valves experiences a temperature of,
about 95 F.
In the event a primer were to fail if it were called on i
to operate, it could be replaced with a new unit during plant opera-tion in a short time period. These primers are accessible during plant operation.
III. Conclusions Based on our review, which is summarized above and in our letter of May 11, 1972, we have concluded that the liquid poison system I
is now a capable and reliable system and meets all criteria of initial plant design and the Final Hazards Summary Report. The testing programs implemented will ensure continued adherence to these criteria.
CONSUMERS POWER COMPANY By A
VicePresidentg Date: July 20, 1972 Sworn and subscribed to before :se this 20th day of July 1972.
l 7n a zl7L R L Notary Public, Jacksc,p County,Idchigan My Commission ExpireV October 14, 1974
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i AEC DISTRIBUTIO?i FOR PART 50 DOCIET MATERIAL 4039 (TEMPORARY FORM)
CONTROL NO:
FROM: Consumers Power Co.
"DATE OF DOC:
DATE REC'D LTR MEMO RPT OfHER Jackson, Michigan 49201 Robert L. Haueter 7-20-72 7-24-72 X
TO:
> RIG CC OTHER SENT AEC E"JR N
Mr. John F. O' Leary 1 signed 39 SEhT LOCAL PDR hPROPINFO CLASS:
INPUT NO CYS REC'D DOCKET NO:
X 40 50-155 DESCRIPTION: Ltr trans the following:
ENCLOSURF.S:
Request for Change No. 33 to Tech Specs for Lic. DPR-6 notarized 7-20-72 w/attchmt......
(3 Orig & 37 confd cys enc 1 rec'd)
PLANT NAIES:
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