ML20041G441
| ML20041G441 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 03/16/1982 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-06-01, TASK-6-1, TASK-RR NUDOCS 8203220304 | |
| Download: ML20041G441 (7) | |
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CORSumel5 Power Company General offices: 1945 West Pernail Road, Jack son, Mt 49201 * (517) 739 0550
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March 16, 1982 Y
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RECEPMD 31 Q{.
sintna tita"n tum j MAR 1'91982*
Dennis M Crutchfield, Chief Operating Reactors Branch No 5 Nuclear Reactor Regulation 6
mymt US Nuclear Regulatory Commission f
8 Vashington, DC 20555 N
DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - SEP TOPIC VI-1, ORGANIC MATERIALS & POST ACCIDENT CllEMISTRY Attatned is the Consumers Power Company evaluation of SEP Topic VI-l for the Big Rock Point Plant.
As you will note, it has been concluded that the coatings on containment floor areas below approximately the 590' elevation are marginal with respect to their ability to withstand submergence under postulated DBA conditions.
j Consumers Power Company is continuing to evaluate whether qualification testing or some corrective action might be appropriate.
In the interim, it should be ncted that the floor areas of concern represent a relatively small portion of the surface area inside containment.
In addition, the primary concern would relate to those areas which have been recoated several times such as high traffic areas which in themselves represent only a fraction of the total floor area.
If the determination is made that removal of the existing floor coatings and recoating of selected floor areas is necessary, it is anticipated that this work could be performed during plant operation.
Accordingly, we would not expect to wait for the next refueling outage or completion of the SEP Integrated Assessment prior to taking any action we conclude to be required. The NRC will be notified upon completion of any testing or corrective action performed.
CEE b
d Robert A Vincent Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point pages fm o_mla,e paaRB8aN888!h P
SEP TCPIC VI-1, ORGANIC MATERIALS AND POST ACCIDENT CHE4ISTRY March 1982 1
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BIG ROCK POINT PIE C SEP TOPIC VI-l Topic VI-1, Organie Materials and Post Accident Chemistry
1.0 INTRODUCTION
The purpose of this assessment is twofold:
1.
To ensure that organic coatings used inside the Big Rock Point containment are suitable for use under design basis accident conditions, consistent with the intent of Section 6.1.2 of the Standard Review Plan.
2.
To ensure that post-accident containment chemistry at the Big Rock Point Plant does not result in unacceptable rates of steel corrosion, or increase the volatility of dissolved iodines, consistent with the intent of Sections 6.1.1, and 6.13 of the Standard Review Plan.
2.0 CRITERIA 2.1 Criteria for Organic Materials Used Inside the Centainment Section 6.1.2 of the Standard Review Plan requires that all signif-icant coating systems used inside containment be suitable for use in the environmental conditions seen after an accident. The sta-bility of the coatings and their decomposition products must be examined to determine the potential for interacticns with engi-neered safety features. Specific areas of concern are:
1.
The possibility of coatings peeling and clogging su=p screens.
2.
The generation of volatiles from the decomposition of coatings which could interfere with the proper functioning of charcoal absorbers used to remove radio-iodine from the containment atmosphere.
3.
The generation of hydrogen and other flammable volatiles from the decomposition of coatings. These gases could adversely impact the operation of systems used for containment hydrogen control on some plants.
According to the Standard Review Plan, a coating system is considered acceptable if:
Big Rock Point Plaat 2
SIP TOPIC VI-l 1.
"It meets Regulatory Guide 1.5h or equivalent; or, the area covered with the system is a negligible fraction of the con-tainment interior surfaces.
2.
"No adverse interactions with engineered safety features are likely as a result of materials released by radiation decom-position or chemical reaction of the coating system in the containment post-accident environment.
2.2 Criteria for Post-Accident Chemistry Control Standard Review Plan Section 6.1.1, " Engineered Safety Features Metallic Materials", requires that the composition of core spray coolants be compatible with materials in the containment building, including the reactor vessel, reactor internals, primary piping, and structural and insulating materials. The intent of this re-quirement is to ensure that integrity of the reactor coolant pressure boundary is maintained, and to prevent evolution of exces-sive amounts of hydrogen in the containment, should' an accident occur. The acceptance criteria with regard to coolant chemistry in Section 6.1.1 of the Standard Review Plan read:
"The co= position of containment spray and core cooling water should be controlled to ensure a minimum pH of 7 0, as given in the Branch Technical Position METB 6-1.
Experience has shown that maintaining the pH of borated solutions at this level vill inhibit initiation of stress-corrosion cracking of austenitic stainless steel components for periods of more than seven months.
" Hydrogen release within the containment because of corrosion of materials by the sprays in the event of a loss-of-coolant accident should be controlled as described in Regulatory Guide 1.7, " Control of Combustible Gas Concentrations in Contain-ment following a Loss-of-Coolant Accident". As the pH increases over 7.5, the rate of corrosion of aluminum increases. The amount of aluminum within the containment should, therefore be controlled' and the amount of hydrogen that could be generated within the containment should be calculated as recommended in Regulatory Guide 1.7".
Standard Review Plan 6.1.3, " Post-Accident Chemistry", requires that the pH of spray and emergency coolant solutions be controlled.
The purpose of controlling the pH is to reduce the probability of chloride stress corrosion cracking leading to equipment failure or loss of containment integrity, and to ensure low volatility of dis-solved radio-iodines. The acceptance criteria stated in Section 6.1.3. of the Standard Review Plan are stated as follows:
Big Rock Point Plant 3
SEP TOPIC VI-l "The procedures and methods which the applicant proposes to use to raise or, maintain the pH of the solutions expected to be recire-ulated within containment after a DBA should be straightforward and reliable. The chemistry of the post-accident environment in the contain=ent should not result in significant deterioration of engineered safety features".
3.0 DISCUSSION 3.1 Organic Materials The design basis for selection of paints for the Big Rock Point Plant is not documented. Topic VI-l is intended to review the Plant design to assure that organic materials such as the organic paints and coat-ings used inside contain=ent do not tehave adversely during accidents (LOCA & DBA) and also when they are exposed to high radiation fields in conjunction with the accident. In particular, the possibility of coatings clogging the emergency spray system especially the sump screens and sprey nozzles should be minimized. The assessment of the suitability of the paint coatings inside containment included in this review is based on a review of the coating schedule for the Plant along with the specified coating materials applied to surfaces under unknown conditions and also questionable materials as to the exact manufacturer and catalogue numbers. However, generically these are being reviewed.
Protective coatings systems in the containment comprise the bulk of the materials (outside of the electrical cable insulation) for concern in the containment in case of a design basic accident (DBA) or a loss of coolant accident (LOCA) and the subsequent safe shutdown of the facilities. Three generic-type coatings were scheduled used inside containment for coating surfaces, both steel and concrete. See draw-ing No OTh0G10219 Rev A dated 9/65 The inside of the sphere is coated with a system consisting of a zine dust metal primer and an alkyd semi-gloss enamel topcoat except for an area from the floor to 6' above the flocr which was coated with the epoxy system. Other systems used on steel consisted of an epoxy block filler or concrete filler plus epoxy topcoats. Some of the concrete floors were sealed with Sonneborn-sona=ar sealer in a light gray or a clear color.
These materials are of a urethane type. All coating materials inside of containment are being reviewed against current criteria for mater-ials for the same type of application to assure that any degradation of the paint =aterials under accident conditions vill not interfere with the operation of the engineered safety features, such as exces-sive flaking, peeling of the paint from the containment surfaces following a LOCA which night plug safety-related screens, filters, pumps, and valves and nozzles. Excessive generation of volatile
Big Rock Point Plant 3
SEP TOPIC VI-l organic compounds which saturate the charcoal filters in the contain-ment purge system and thereby interfere with the trapping of radioactive organic iodines is also being investigated.
Generically, the coatings of the inorganic zines and epoxy types have been subjected to DBA test exposure in combination with radiation at Oak Ridge National Laboratories. In evaluating the resistance of the coatings during DBA, ve used the results of recent DBA tests run at Oak Ridge National Laboratories on coatings for the Midland Project.
Test results showed that epoxy-type coatings used in containment re-mained serviceable even after being exposed to large radiation doses and subsequent exposure to a DBA test. On this basis, we conclude that the radiation damage to these types of coatings does not propose a signifi-cant hazard to the operation of the engineered safety features during a DBA. The alkyd enamel coatings which vere used on steel and much of the concrete have an unknown serviceability during and immediately after a DBA. Also, the urethanes are questionable as to their adequacy during DBA conditions. Another factor that enters into the evaluation concerns coatings applied over the original floor coatings for sealing in contaminLtion and also for repairing large areas where the coating had been damaged. It is believed that alkyd enamel coatings frcm several manufacturers were used in these instances, and as many as two and three additional coats have been applied in some floor areas.
It is likely that these floor coatings would not successfully pass the DBA and radiation exposure tests.
This does not happen to be the case on the valls. They do not appear to have had additional coatings applied subsequent to the original painting of the facility. Because of original application with no subsequent coating applied on the valls and the tenacity by which the vall coatings are adhering to the substrate surface, it is expected that these coatings vould successfully withstand a DBA test under the time, temperature and pressure conditions of the plant (signifi-cantly less severe than standard coating test conditions under ANSI N 101.2).
3.2 Post Accident Chemistry The acceptance criteria in Standard Review Plan 6.1.1 are concerned with limiting the corrosion of stainless steel following an accident.
The corrosion resistance of stainless steel is reduced in strong acid solutions or in the present of chlorides. The acidity or pH that would result following core and/or containment spray would be approximately 8.0 with or without injection of 850 gallons of sodium-pentaborate poison. The chloride concentration of the post LOCA water is less than 20 mg/L. The post LOCA t'e=perature envelope indicates a peak temperature of 223 F and containment temperature less than 212 F coincident with initiation of containment spray system at 800 seconds into the transient. This condition vill cause minimal corrosion from either a pH and/or chloride standpoint.
The production of hydrogen frcm zine or aluminum vill be insignifi-c ant. The basicity of the pcst LOCA solution is not high enough to break down the oxide layer formed after the initial reaction.
Big Rock Point Plant 5
SEP TCPIC VI-1 h.0 CONCLUSIONS h.1 Coating Materials It is concluded that the epoxy-type coatings were applied under a good commerical practice and following the specifications that were available at that time. Therefore, it is expected that these coatings vill function in the same manner as those generic types presently being used. The original coatings of the alkyd and urethanes were also applied using the best commercial practices at that time. However, it is likely that these types of coatings will not successfully pass a DBA test under ANSI N101.2 criteria and radiation exposure. With respect to the vall coatings, this is not considered to be cignificant because the existing coatings would be expected to withstand DBA test conditions representative of the Big Rock Point Plant. Coatings on some floor areas, however, could be marginal.
It should be noted that the only plant areas of significance within the scope of this topic are those below approximate elevation 590' since they could be submerged during recirculation following a LOCA.
h.2 Post Accident Chemistry The post accident chemistry and temperature conditions vill not measureable accelerate corrosion of the reactor materials. The chemical composition of the recirculated fluid vill not reduce con-tainment integrity. The post accident chemistry at the Big Rock Point Plant vill nct degrade or reduce the efficiency of any engi-neered safety features.
5.0 REFERENCES
A.
Final Hazards Summary Report for Big Rock Point Plant, November ik, 1961 B.
ANSI N101.2-1072, " Protective Coatings (Paints) for Light Water Nuclear Reactor Containment Facilities" C.
Perry's Chemical Engineer's Handbook, Perry, Chilton, and Kirkpatrick ed., McGraw-Hill, New York, Fourth Edition D.
Mesmer, Baes, and Sweeton: BorF. Acid Equilibria and pH in PWR Coolants, 32nd Internation1 Water conference E.
Big Rock Point Plant Facility Operating License, Appendix
'A',
Technical Specifications F.
DPHoffman letter to DLZiemann, dated July 12, 1979 G.
SPDonner memo to WSSkibitshy, dated March 15, 1978, DCC A200-09*09*06
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