ML20196E344

Forwards Responses to Two Action Items from 871113 Meeting, Including Response to Evaluate Conditions Under Demineralized Reactor Coolant Storage Tank to Regenerative Holdup Tanks to Control Water Inventory Problems

ML20196E344
Person / Time
Site:	Rancho Seco
Issue date:	02/22/1988
From:	Andognini G SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Miraglia F Office of Nuclear Reactor Regulation
References
GCA-88-087, GCA-88-87, TAC-56033, NUDOCS 8803010050
Download: ML20196E344 (12)

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gSMU-EACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street. P.O. Box 15830, Sacramento CA 958521830,(916) 452 3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA GCA 88-087 FE8 2 21938 U. S. Nuclear Regulatory Commission Attn: Frank J. Miraglia, Jr.

Associate Director for Projects 11555 Rockville Pike Rockville, MD 20852 Docket No. 50-312 Rancho Seco Nuclear Generating Station License No. DPR-54 RESPONSE TO TH0 ACTION ITEMS RESULTING FROM THE NOVEMBER 13, 1987 HEETING 0F SHUD AND THE NRC ON RADIOLOGICAL EFFLUENTS

Dear Mr. Miraglia:

The attached are responses to two of SMUD's action items f om our November 13, 1987 meeting.

Attachment I is in response to the action item to "Evaluate conditions under which the DRCST will need to be pumped to the RHUTs" and to "Evaluate measures to control water inventory problems."

Attachment II addresses the action item to "Provide the NRC with the District's evaluation supporting proposed Technical Specification 3.18.5 (Gas Storage Tank Activity)."

Please contact me if you have any questions. Members of your staff with questions requiring additional infonnation or clarification may contact Harvey Story at (916) 452-3211, extension 4826.

Sincerely,

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G. Carl Andogdini Chief Executive Officer, Nuclear Attachments cc: G. Kalman, NRC, Rockville (w/atch)

A. D'Angelo, NRC, Rancho Seco ( " )

J.B. Hartin, NRC, Region V (

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0803010050 000222 DR ADOCK 05

{2 RANCHO SECO NUCLEAR GENERATING STATION D 14440 Twin Cities Road, Herald, CA 95638 9799,(2o9) 333 2935

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o ATTACHMENT I Action Ites Evaluate conditions under which the DRCST will need to be pumped to the RHUTs.

Evaluate measures to control water inventory problems.

SUBJECT:

DRCST TRANSFERS TO RHUTS INTRODUCTION This attachment identifies the major plant operating conditions which could result in the transfer of the water from the Demineralized Peactor .

Coolant Storage Tank (DRCST) to the Regenerative Holdup Tanks (RHUTs) for eventual release offsite as liquid effluent. Management of primary system water inventory involves the operation of the Primary Letdown and ,

Makeup system (PLS), Reactor Coolant Radwaste system, and the Miscellaneous Radwaste system. Each system will be briefly described to highlight the relationships between them. Their configurations determine i where water will be distributed for a given operating condition. In some r

instances it is possible to produce a surplus of t,itiated water which must be discharged offsite in a controlled manner to' preclude a storage tank overflow offsite through an unmonitored pathway.

SYSTEMS DESCRIPTION During normal operation, the letdown system (PLS) helps control the  !

Reactor Coolant System (RCS) water chemistry by continuous (y removing cool ant from the RCS and replacing it with processed watvr (Feed and i Bleed). The letdown comes from the A Steam Generator Orain line attached to the B RCS Loop at a rate of roughly 40-45 gpm. The makeup back to the RCS uses three high head injection pumps, two of which are part of the Safety Injection System. The system contains both mechanical and ion exchange filtration equipment. The Makeup Tank (V-235) provides the

, system surge capacity.

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The Coolant Radwaste system processes wastes associated with feed and bleed operations, start-up/ shutdown volume changes, draining of RCS for maintenance / refueling, and the dilution of boric acid concentration over core life. One major input is from Reactor Coolant Drain Hender which can accept coolant from a number of locations on the primary loop. The other is diversions from PLS. The Coolant Radwaste system contains mechanical filters, two sets of demineralizers, deborating ion exchangers, and an evaporator. The purified water goes to DRCST, and the concentrates are directed to the Concentrated Boric Acid Storage Tank (CBAST). Demineralized water (DRCST) and cencentrates (,CBAST) raay be recombined and returr.~1 to Makeup Tank within PLS for reintroduction into the RCS. The DRCST is sized at 450,000 gallons to accommodate the volume of both the RCS and the Coolant Radwaste systems simultaneously.

The third system, Miscellaneous Radwaste, covers the rest of the liquid radioactive waste generated onsite. This includes input from the Reactor Building sumps, sumps and floor drains in the Auxiliary Building, potentially contaminated system overflows, and all chemical wastes as well. In addition, the system has a cross-tie to permit processing Coolant Radwaste if necessary. While the turbine plant sumps are directed offsite through the RHUTs during normal operation, contamination resulting from primary to secondary leakage can be directed to the Miscellaneous Radwaste system. The processing includes demineralization and evaporation in much the same arrangement as the Coolant Radwaste system. The output for this system is the Miscellaneous Water Holdup Tank (T-993) which serves a variety of Reactor and Auxiliary Building needs. This vessel only holds 30,000 gallons; once it is full, the system output is routed to the DRCST.

DISCV':310N During normal operation, the primary and the associated radwaste systems are essentially closed. Losses from evaporation are made up by secondary water sources which enter the Miscellaneous Radwaste system. Generally the DRCST becomes full when a large amount of water has been removed from the primary and related systems when the reactor is not at power. In which case, the DRCST will supply the replenishing water to return the systems to their "normal" configuration. However, there are three plant configurations where the DRCST and T-993 may not provide sufficient surge capacity for the primary and its ancillaries.

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The first. is a primary to secondary leakage through the Once Through Steam Generators (OTSG). In this instance, the normally clean secondary systems become radioactively contaminated. Eventually some of this activity will end up in the Turbine Building sumps. Instead of directing this water offsite as liquid effluent, the plant may elect to pump some or all of this to the Miscellaneous Radwaste system for processing. The resulting water will have extremely low concentrations of gamma emitting nuclides (on the order of IE-7 uCi/cc) and moderate concentrations of tritium (roughly 1E-2 uCi/cc). Depending on the magnitude of the OTSG leak, the volume of sump water that gets contaminated, and the status of DRCST and T-993 with respect to other plant activities, the site storage capacity for slightly radioactive water may be exceeded. Note that if candidate effluent in the RHUTs has high levels of activity, newly installed piping permit the return of this water to the Miscellaneous Radwaste system.

The second is the break (or spill) of secondary system water inside the Containment. This water collects in the Reactor Building sumps and is pumped to the Miscellaneous Radwaste system. Even if the water is radioactively clean, it soon becomes contaminated because it mixes with other contaminants entering that system. Again the system output is a surplus of slightly radioactive water.

The third is maintenance activities which involve the draining of large secondary systems. Of particular concern are draindowns of the Component Cooling Water (CCW) and the Nuclear Service Cooling Water (NSW) both of

, which have large volumes that are potentially contaminated. Some of this water may be directed to the Miscellaneous Radwaste system through surge overflow or by Auxiliary Building drains / sumps. While this has only a remote possibility and has not contributed directly to previous CRCST transfers to the RHUT, it is included for completeness.

CONTROL MEASURES Of the three exampies, the primary to secondary leakage by far represents the largest source of potential additions to the DRCST. In 1985 it contributed the vast majority of the 800,000 gallons that were transferred from the DRCST to the RHVTs for release. Since the forced shutdown at the end of 1985, the problem of how the DRCST transfers affect the plant's standing against Appendix I have been addressed in three different ways, that is, reducing the source, recycling more of the contaminated water, and reducing the offsite impact. These measures are contained in part within the Rancho Seco Radiological Effluents Action Plan (Report EP 88-001, Revision 0, January 1988),

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During the summer of 1986, both Steam Generators underwent extensive tube integrity inspections, and many questionable tubes were either plugged or resleeved. This should lower the chances for and the effect of OTSG tube leakage which may precipitate primary water inventory difficulties. In addition, the plant has performed an effluent systems evaluation to determine the amount of primary to secondary leakage (for various degrees of failed fuel) which will jeopardize our standing against Appendix 1.

This analytical tool may also be used to evaluate maintenance options should a chronic low-level OTSG leakage return.

Ths current configuration of the turbine plant is not ideally suited for m ating the guidelines introduced by Appendix I which are extremely restrictive for a dry site. The Environmental Protection Department has recently initiated a number of Engineering Action Requests (EARS) on the Turbine Building drain system which are designed to reduce the amount of effluent and the volume of water requiring radwaste processing. This in turn can ease inventory problems caused by the entrance of secondary water into primary sy'; ten storage.

Attention has also been directed towards reusing or disposing of slightly contaminated water in opposition to releuing it as liquid effluent. One method involves using tra recently constructed Tritium Evaporator. While some safety and oper!.ilonal problems are still outstanding on this equipment, their successful resolution may provide some relief on DRCST inventory. Another consideration which has yet to be fully evaluated is to permit the Condensate Storage Tank (CST) tu aceme contaminated as is done at some other nuclear plants. This cannot be implemented without modifications to plant equipment but shows promise for recycling water otherwise discharged down the creek.

The third type of control is to reduce the impact of DRCST transfer on the offsite dose from liquid effluents by demineralizing the DRCST water before releasing it offsite. The tritium cannot be filtered. However, demineralizers can lower the concentration of Cs-137 and Cs-134, the isotopes which historically produce well over ninety percent of the dose.

Rancho Seco has recently installed Sluiceable Demineralizer Skids near l the RHUTs. These can remove activity (particularly cesium) from candidate effluent prior to dispatch to the Retention Basins and so

' reduce the offsite dose. The DRCST also has two demineralizers (0-623A and B) located on its normal return to the plant. While the transfer route to the RRUTs bypasses this equipment, the contents of the DRCST may

be recirculated through the demins to reduce its activity prior to transfer. If necessary, portable demineralization equipment can be brought onsite on short notice to handle unexpectedly large volumes.

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CONCLUSIGI Of the three major plant configurations which may produce excessive inventory in the DRCST, the most significant source is primary to secondary leaksge through the OTSGs. The radioactive contamination of Turbine Building Sumps means that large volumes of secondary water may be processed in the Miscellaneous Radwaste System and directed to the DRCST.

If the plant demand for this water is low, some of it may be transferred to the RHUT for release offsite. The doses frota this release may influence the plant's standing against Appendix I. Efforts to reduce this impact include a major Steam Generator maintenance, plans to recycle some lurbine Plant waste water, the addition of demineralizers at the RHUTs, and the evaluation of other methods to dispose of or reuse the slightly contaminated water. Recent studies indicate that the plant can operate within the Appendix I guidance for the failed fuel and primary to secondary leakage present at shutdown.

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ATTACHMENT II Action Iten Provide the NRC with the District's evaluation supporting proposed Technical Specification 3.18.5 (Gas Storage Tank Activity).

SUBJECT:

EVALUATION OF 135,000 Ci LIMIT FOR TECHNICAL SPECIFICATION 3.18.5 Section 5.6.1 of NRC NUREG 0133, "Preparation of Radiological Effluent Technical specifications for Nuclear Plants", provides an equation for calculating the allowable curie content of a gas storage tank. This amount ensures that, in the event of an uncontrolled release of the tank contents, the resulting total body exposure (to an individual at the nearest exclusion area boundary) will not exceed 0.5 rem.

QT $ 500 mrem (3.15 E+07 sec/veari (100 uci/C1) (kxe.133) (X/Q)DBA (mrem-sec/uci yr)

' = The avantity of Xenon-133 equivalent gas in Where 07 a storage tank in curies

- The total body dose factor due to gamma kxe.133 for Xe-133 in mrem /yr per emissjons cCi/m (= 2.94E+02)

(T/Q)DBA

= The relative concentration at the exclusion I

area boundary used for evaluation of design basis accidents for ground release 1

conditions, in sec/m3 . (from USAR, '

Section 2.3.4, 2 - 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> atmospheric dispersion).

(X/0108A (Sec/ mil -2 24 hr. _QT (Ci) ,

294,348 Ci 9 400 m = 1.82E-04 787,815 C1 0 700 m = 6.80E-05 (Exclusion Area Boundary Roundup = 640 m)

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Specification 3.1.4 requires RCS activity to be less than 43/E for all isotopes > 20 minutes half-life. The equivalent RCS concentration

(< 25 uCi79) would be less than the RCS concentration at 1.0% fuel defects (USAR, Table 140-6, 9 150 effective full-power days). 1.0% fuel defects would give a gas decay tank curie content of 98,414 Ci (USAR, Table 140-23).

Therefore it is conservative to require that the online waste gas decay tank be sampled daily upon reaching the RCS activity value 436 to ensure the 135,000 curies equivalent Xe-133 is not exceeded. Once the coolant is below the limiting activity, there is no requirement to sample the waste gas decay tanks except when discharge of the tank is desired.

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17. New Soecification: . . .,

3.18.5 GAS STORAGE TANKS .

The quantity of radioactivity contained in each waste gas decay tank shall be limited to less than or equal to 135,000 curies of noble gases (considered as Xe-133).

Aeolicability At all times Action

a. When the reactor coolant s) stem activity reaches the limit of Specification 3.1.4 sample the online waste gas decay tank daily to ensure that the 135,000 curie equivalent Xe-133 limit is not exceeded.

b. Hith the quantity of radioactive material in any waste gas decay tank exceeding the above limit, immediately suspend all additions of radioactive material to the tank and within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> reduce the tank contents to within the limit, and describe the events leading to this condition in the next Semiannual Radioactive Effluent Release Report, pursuant to Specification 6.9.2.3.

B1111 Restricting the quantity of radioactivity contained in each waste gas decay tank provides assurance that in the event of an uncontrolled release of the tanks contents, the resulting total body exposure to an individual at the Exclusion Area Boundary (see Figure 5.1-1) will not exceed 500 mrem. This is consistent with Standard Review Plan 15.7.1, "Haste Gas System Failure."

Potential atmospheric releases from a waste gas decay tank are evaluated assuming design coolant activities (see page 140-25 Vol. VI FSAR). Based on primary coolant activity as shown in Table 140-7, the decay tank is assumed to hold the activity associated with the off-gas from one reactor coolant system degassing with no credit taken for decay.

Calculation of the limiting decay tank activity based on the coolant activity limit of Technical Specification 3.1.4 yields a maximum decay tank inventory of 98,414 C1 (Ref. FSAR Table 140-23). In order for the decay tank inventory to reach the limiting condition for operation, coolant activity would have to exceed the Technical Specification 3.1.4

• limit on coolant activity and this would require a reactor shutdown, thus preventing a further increase in gaseous activity.

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17. New Soecification: (Cont.) - -

• Therefore, it is conservative to require that the online waste gas decay tank be sampled daily upon reaching the reactor coolant system limiting activity value (43/E) to ensure the 135,000 curies equivalent Xe-133 is not exceeded. Once the coolant is below the limiting activity, there is no requirement to sample waste gas decay tanks except for discharging.

Discussion:

Technical Specification section 3.20 was renumbered 3.18.5 and revised in accordance with the gu! dance provided in the Standard RETS.

The Action Statement is expanded to include reporting requirements specified in Standard RETS. Action Statement a. is maintained because gas storage tank contents are limited to less than 135,000 curies by T.chnical Specification 3.1.4 as described in the Bases.

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r Appendix 14D

3. the surge tank is assumed to hold a f raction of the decay tank activity based on the volume capacity of the surge tank at 14.7 psia and 120 T.

The maximum vaste gas inventory based on these assumptions is shown in table 14D-23.

TABLE 14D-23 RADI0 ISOTOPE INVENTORY IN WASTE GAS SYSTEM Maximum Inventory, Ci Surge Tank Decay Tank Isotope 2 l 85a 5.68 x 10 l

5.68 x 10 Kr 2.14 x 10 2.14 x 10 3 Kr 1 2 Kr 3.07 x 10 ,3.07 x 10 3

2 1.00 x 10 Kr 8 1.00 x 10 2

131" 7.68 x 10 1 7.68 x 10 Xe 3

133" 1.04 x 10 1.04 x 10 Xe 133 9.02 x 10 3 9.02 x 10' Xe 2

135m 3.34 x 10 1 3.34 v. 10 Xe 3

15 1.87 x 10 2 1.87 x 10 Xe 138 1.87 x 10 1.87 x 10 Xe Total 98,414 curies B. Radiometive 1.iquid Waste System Major Components Potential atmospheric releases f rom rupture of major liquidactivity radwaste as system components are evaluated based on maximum coolant shcvn in table 14D-5. Isotopic activities in each component are shown in table 14D-24 6-