ML20002C541
| ML20002C541 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 05/26/1976 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML20002C531 | List: |
| References | |
| NUDOCS 8101100436 | |
| Download: ML20002C541 (4) | |
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I CONSUIERS POWER COMPANY Docket No 50-155 Request for Change to the Technical Specifications License No DPR-6 For the reasons hereinafter set forth, the following change to the Techni-cal Specifications of License No DPR-6 issued to Consumers Power Company on May 1, 1964 for the Big Rock Point Plant is requested:
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Change Change Section 6.h.3(a) to read as follows:
"(a) At least one of the two air ejector off-gas monitoring systems shall be in, service during power operation and set to initiate closureofffhioff-gasisolationvalveasdescribedbelow.
Alarms normally shall be set to annunciate in the control room if the off-gas radioactivity reaches a level that corresponds to a stack release of 0.1 curie per second. At stack releases above 0.1 curie per second, the alarm shall be set approximately a factor of two above the expected off-gas release rate but in no event above that level corresponding to a stack release of 0.h7]p-- curie per second where E is the average gamma energy per disintegration (MEV/ dis).
S1 If the limit of p curie per second is exceeded, reactor power shall be immediately reduced such as to meet the limits. The monitors shall be set to initiate closure of the off-gas isolation valve (after a time adjustable from 0 to 15 minutes) if the off-gas radio-activity reaches a level that would correspond to a stack release rate of ten curies per second. Off-gas samples 4.nall be taken monthly during power operation and analyzed for calibration of the off-gas radiation monitors. The automatic closure function of the f
monitors shall be tested monthly during power operation."
II.
Discussion
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The air ejector off-gas monitoring system for the Big Rock Point Plant is provided to continuously audit the re1<.ase to the enviro 9s.
In 3(a 82oiioolpg35 i
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s addition, an isolation feature was thought to be provided by initial-plant design which would close the release path when the activity level
' approached an instantaneous limit for allowable discharge. The system 4
is also considered to be a fuel rupture detection system. The fore-going is described in Section 7 2.1 of the FHSR.
In addition, in Section 7 5 10.2'of the FHSR high condenser pressure is discussed. Among other things, one of the causes of high condenser vacuum identified in this section is the automatic closing of the off-gas valve from a high activity signal. Also included in the discussion in this section relating to high condenser pressure is the fact that a reactor trip will occur on high condenser pressure.
Section 6.h.1(a) and Section 6.h.3(a) of the existing Big Rock Point Technical Specifications describe the purpose and operating requirements of the air ejector off-gas monitoring systems. The function of the system is to provide a continuous audit of off-gas release rates, to provide an alarm which will annunciate in the Control Room if release rates become excessive and to provide an, automatic isolation function if release rates become extremelf high. No reactor trip is required by the exist-ing Technical Specifications. Based on consideration of the foregoing, we have concluded that there was no intent that an isolettion of the off-gas system result in a reactor trip. Rather, it was noted in the FHSR that an isolation of the off-gas system could result in a loss of con-denser vacuum which could result in a reactor trip.
By letter dated June 26, 1972, Consumers Power Company reported '4a results of a test conducted to the term in the isolation capability of the off-gas isolation valve. This test showed that operation of the valve to the closed position for 30 minutes failed to cause any change in the condenser vacuum of approximately 29 inches of Hg.
Further in-vestigation revealed that the design of the valve did not allow for tight closure of the valve because of a lack of proper seating surfaces. At that time and during the interim period until a new valve could be ob-(
tained and installed and made to work properly, operating procedures were revised to require manual operator action to reduce off-gas release rates in the event that they exceeded certain values.
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Our letters of January 21, April 23 and May 3,197h and February 21, 1975 reported the installation of a new valve and the results of testing of the system including corrective maintenance that was performed to attempt to achieve operation of the system such that it vill have a substantial impact on condenser vacuum and, thits, cause a plant trip.
In addition, testing was performed with the reactor st power on January 31, 1976.
With respect to achieving a reactor trip because of a loss of condenser vacuum on off-gas isolation valve closure, the testing has been totally unsuccessful.
As stated previously, the January 31, 19T6 test was performed with the reactor at power. During this test we achieved the best results so far toward demonstrating the integrity of the off-gas system by achieving a back pressure in the holdup system of 22 psia after about one hour time period but there was still not reduction of condenser vacuum.
In theory, the automatic closure of the off-gas isolation valve should cause a buildup of pressure in the holdup pipe which, in turn, should cause a reduction of the effectiveness of the air ejector and a subse-quent loss of condenser vacuum. However, it appears that the numerous fittings, gaskets and valves in the system have a combined leakage at the 22 psi which precludes a timely loss of condenser vacuum. We feel that the extensive maintenance performed over the past two years in attempting to achieve performance such that a loss of condenser vacuum vill occur has resulted in a mere optimum performance of the system as designed.
The stack gas release rates during the January 31, 1976 test showed an initial si6nificant decrease to a low value following off-gas isolation valve actuation.
It remained at that lov value until pressure built up significantly in the off-gas holdup pipe and then the stack gas release rate increased to a value which was slightly in excess of that previously observed prior to off-gas valve actuation. The increase was likely due to leakage through the numerous fittings, gaskets and valves in the off-gas system. There was no indication that unmonitored releases occurred
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during this test. The ventilation design is such that no unmonitored l
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release should occur.
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In hindsight, it appears that this mechanism identified as a possible loss of condenser vacuum in the FHSR is not feasible.
Further, it appears that the mechanism of off-gas isolation valve closure to stop extremely large release rates is not feasible. Thus in the proposed Technical Specifications we have incorporated permanent administrative action limits to control off-gas radioactivity releases in the event that they far exceed releases experienced to date during plant operations.
Off-gas release rates experienced during the previous four or five years of operation have seldom, if ever, exceeded 50,000 microcuries per second. Typically, at the start of a cycle releases are on the order of 1,000 microcuries per second and at the end of the cycle they approach 20,000 to 30,000 microcuries per second. In the early days of Big Rock Point operation when stainless steel and inconel clad fuels were installed on a research and development basis and when center melt fuel was utilized on a research and nevelopment basis, releases did, on three occasions, exceed h0,000 microcuries per second. The highest activity was 78,000 j
microcuries per second in 1966. These releases never approached the limit of one curie per second imposed by the Technical Specifications.
It is our experience that increases in of f-gas release rate which would result from going from normal operating levels to levels of 100,000 microcuries per second cr larger do not occur rapidly and that increases, when they occur, are easily controlled by reduction in reactor power level. Thus, we have concluded that administrative control of the off-gas releases as defined in the proposed Technical Specifications will preclude instantaneous releases in excess of allovable limits and can be effectively substituted for the off-gas isolation function that ras thought to be provided in initial plant design.
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III. Conclusion Based on the foregoing, both the Plant Review Committee and the Safety and Audit Review Board have concluded that this proposed change does not constitute an unreviewed safety question.
CONSUMERS P0' C0b' ANY By
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R. C. Youngdahl hecutiv 'Vice President Sworn and subscribed to before me this 26th day of May 1975 s _i h t.b ba !U
....Sylvid B. Ball, Hotary Public
...... Jackson County, Michigan My comission expires April 13, 1980.
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i Limiting Conditions for Operation Surveillance Requirement 3.5 1 STATION PROCESS EFFLUENTS (Contd).
h.5 1 STATICN PROCESS EFFLUENTS "Contd) longer than eight. days shall be gases shall be adjusted to determine 4
limited in accordance with the.
total gaseous release rate. Gaseous y
following:
- release of tritium shall.be calculated on a monthly basis from measured data.,-.
j Limiting Release
-Tritium shall be-measured'at least 4
Nuclide Rate pCi/s every 6 months,-
25%.
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I-131 0.2 2.
Station records of stack release of 2
I-133 h.h lodines and particulates with half-Particulates 2.8 lives greater than eight days shall be maintained on che basis of all filter 3
At least one of the two air ejector cartridges analysed. ihese cartridges off-gas monitors shall be operable to shall be analyzed at-least weekly.
administratively control the stack gan release rate as specified in Specifi-3 Each Six Months cation 3.5..l.A.
a.
Conduct off-gas density test.
B.
Liquid Effluent b.
Conduct off-gas holdup time test.
5 1.
The concentration of gross beta radio-activity above background in the con-k.
Monthly
i denser cooling water discharge canal shall not exceed the limits stated Off-gas samples shall be taken monthly below unless the discharge is controlled and analyzed for calibration of the on an identified isotopic basie in off-gas radiation monitors.
accordance with Appendix B, Table.II, Column 2 of 10 CFR 20 and Note 1 thereto.
I Maximum concentration (excluding a.
tritium) - 1 x 10-I pCi/ml.
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i Limiting Conditions for Operation Surveillance Requirement 3.5 1 STATION PROCESS EFFLUENTS (Contd) h.5 1~
STATION PROCESS EFFLUENTS (Contd) b.
Maximum tritium concentration B.
Liquid Effluent 4
3 x 10-3 pCi/ml.
1.
Station records shall be maintained of c.
The liquid process monitor in the the radioactive materials concentration discharge line from the waste dis-and. volume before dilution.of each proposal tanks to the discharge canal batch of liquid effluent released and shall be operative.
of the average dilution flow and length.
of time over which each discharge occurs.
C.
If the limits of 3 5 1.A are not met as indicated by the stack-gas monitor or.a 2.
Each batch of radioactive liquid efflu-normal routine surveillance. check, reactor ent shall be sampled and analyzed prior powar shall be immediately reduced to meet to release, t h<.
limits.
3 Isotopic analysis of a representative D.
If the limits of 3 5 1.B are not met fol-batch of radioactive liquid waste shall loving a routine surveillan'e check, normal be performed at least once per quarter.
orderly shutdown of the liqu Ad w % dis-Each batch shall be analyzed for gross charge equipment shall b'e' initiated within beta radioactivity and wnen released on one hour and discharge shall not be resumed an identified radionuclide basis, the until the cause of the excessive discharge analysis shall also include a gamma rate is identified and corrected.
spectral analysis.
E.
Waste Storage k.
Monthly composite samples shall br col-lected from the discharge canal and 1.
The inventory of liquid radioactive analyzed for gross beta radioactivity.
vastes in the liquid radioactive vaste disposal system shall not exceed 5,000 curies.
2.
The inver. tory of solid radioactive wastes shall not exceed h0,000 curies.
This total does not include radio-1 active material such as spent fuel, l
Cobalt-60,' control rods and in-core j
flux measurement tievices which are stored in the spent fuel pool.
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t Limiting Conditions for Or,eration Surveillance Requirement 351 STATION PROCESS EFFLUENTS (Contd)
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General It is expected that releases of radio-active material in effluents be kept at s=all fractions of the limits specified in 10 CFR 20.106. At the same time, the license is permitted the flexibility of operation, compatible with considerations of health ani saf ety, to a sure that the public is provided a dependable source of power even. under unusual operating condi-tions, which may temporarily result in releases higher than such small frac-tions but still within the
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